Re: revija ATV

[s58ru]

TV Rptrs Rptr-147.doc ( 11/22/23, kh6htv) p. 1 of 12
Boulder Amateur
Television Club
TV Repeater's
REPEATER
November, 2023
3ed edition, issue #147
BATVC web site: www.kh6htv.com
ATN web site: www.atn-tv.com
Jim Andrews, KH6HTV, editor - kh6htv@arrl.net www.kh6htv.com
NEW, Hi-Des 13cm DTV
LINEAR RF POWER AMPLIFIER
TV Rptrs Rptr-147.doc ( 11/22/23, kh6htv) p. 2 of 12
We have just received this communciation from Darko, OE7DBH
"We ( HiDes and OE7DBH ) are currently developing a new 2-stage power amplifier for the 13cm
(2.4 GHz) amateur radio band, also good for DVB-T operating mode. Expected DVB-T performance
is around 5 Watts output in hardware configuration with HV320. Gain around 45 dB. Here are a few
pictures from the first test version."
Editor's Note: Looking carefully at these photos we can gain some additional info about this new
amplifier being developed. The interior photo shows two gain blocks, U2 & U3 in cascade. U2 is
the driver MMIC. U3 is the final power amplifier block with heat sinking. J3 (lower right) is the
SMA input. J4 (upper left) is the SMA output. J3 (top upper left) is an rf output signal sample port
SMA. U4 (upper left) is a circulator with a 50 Ω termination on it's 3ed port. It is used for VSWR
isolation to protect the final amp. Reading the hand written labeling on the prototype amplifier we
see that the DC power supply is 27 Vdc. The test rf input power was 0.15mW (-8dBm). The rf
power output was 44 Watts (+46dBm). Thus implying a gain of 54dB. The J4 test port is labeled as
33mW (+15dBm)
=========================================================================
Free Space Laser Communications Q ?
Mario, KD6ILO
The San Diego ATV Society and myself are experimenting and using Free Space Optics [Laser]
Communications for our 2024 project. WE have one(1) working system at our Carlsbad lab sending a
beam 13 miles line-of-sight to our Ramona site {voice, video and data at Gigabit speeds.
TV Rptrs Rptr-147.doc ( 11/22/23, kh6htv) p. 3 of 12
Q? 1: I was asked why use lasers for Amateur TV and cost?
You can assemble a simple test system using form factor
computer(s) such as the Raspberry pi 5 for example and other
models of similar cost. Using low cost effective laser
transmitter/receiver assemblies on the market. Knowing how to
write basic code helps.
Q? 2: Yes AREDN MESH can benefit from this too, especially when data from sources which send
heavy message traffic, video streaming technology from multiple venues, there's endless possibilities.
--Advantages of using laser communications over radio waves, increased bandwidth, enabling the
transfer of more data in less time and quicker, sharper, video images. The improved technology of
today is much smarter, smaller, lighter, and takes up lass space to assemble as I've found out first hand.
That's why our team will bring it into our amateur radio lab in Carlsbad, CA with the help of grant
funding and will acquire products from the Mitsubishi products lab in Japan. Optical-Data modems
help as a gateway {light to binary data} and vice versa speeds 1- 7.2 Gbit/s flawless and to achieve
100% throughput at all times. No bandwidth or RF challenges, just free space communications.
Laser KD6ILO laser comms work bench
Q? 3; How are aiming the laser over a long distance to the receiver unit?
Answer: As for alignment, for me I don't bother with a gimbal to point the laser beam. Instead, I used a
custom error-signaling system that adjusts the entire LCT itself to point precisely towards the receiver
optical lens. Like I said earlier, knowing coding helps. This allows the optical components to be
miniaturized.
My home built system uses surplus parts and buying some new components such as for my receiver
makes for a less costly mistake on my part budget wise. It works, I'm just getting my laser modem
setup with a special router, a LinkStar H68K. then put everything in a nice package unit.
Q? 4: Can you give us a project that your STEM students use for Laser communication?
Answer: Sure! here is the link information;
https://electroniqueamateur.blogspot.com/Optical receiver prototype for laser communication terminal (LCT)
TV Rptrs Rptr-147.doc ( 11/22/23, kh6htv) p. 4 of 12
In conclusion we must also keep up with technology as it takes hold over us and time this is not new
but improvements over time. Amateur Radio must keep pace so we can educate our younger hams in
our community {STEM} as we have in our classes on a weekly basis. We have moved forward from
analog, digital DVB-T,S, ATSC and now newer laser upgraded technologies. 2024 will be a big step
forward. I will see NASA's new space Internet DSN grow with improvements. I know what's
coming...do you?
73 de Mario, KD6ILO
LCRT Optics - Ramona, CA
KD6ILO Test Station LCT Platform
Carlsbad, CA
Mobile, Portable LC Transceiver Station
=========================================================================
Editor Reminisances about Laser Comms: Mario's recent notes above about his new
interest in optical communications, caused me to reflect upon my early career. While working for
the National Bureau of Standards (NBS, now NIST) in Boulder, Colorado -- they sent me and my
family on a one year assignment in 1971-72 to work in the French national telecom labs (CNET) in
Lannion, Brittany, France. CNET was the French equivalent of our Bell Labs. There I was assigned to
work with some other engineers on the birth of fiber optics for telecom. In particular, I was measuring
TV Rptrs Rptr-147.doc ( 11/22/23, kh6htv) p. 5 of 12
laser pulse dispersion in the picosecond region in glass fibers. During that year, we and others made a
couple of major break-throughs which were land marks in proving fiber optics could eventually replace
conventional wired telecom. First was a dramatic improvement in optical fiber attenuation. In 1971,
we were working with fibers which had 1,000dB/km loss ! Right -- I said 1000 dB ! That year,
glass chemists were able to get the loss down dramatically to 20dB/km. That showed it was suddenly
feasible to send comms over long distances. Today, optical fiber losses are even much lower. The
second major break through was the development of a laser diode which would work continuously
(CW) at room temperature. Previously the only laser diodes which would work CW had to be cooled
to cryogenic temperatures.
After returning back to Boulder and NBS a couple of years later, I designed and built a couple of
complete, working fiber optic telecom demonstration set-ups to send full band-width (4.2 MHz),
baseband, NTSC, color TV signals over a fiber optic cable. The first one was analog. I AM
modulated an IR LED with the TV signal. At the receive end I had an avalanche photo diode detector
followed by a wide-band video amplifier with AGC.
The second, much more complicated one was a 100 Mbps digital system. I designed and built all of
the various component pieces with one exception. The only commercial piece of gear I used was a
then state-of-the-art 8 bit, A/D converter running at 10 MHz clock rate. The A/D was in a full 3" high,
19" rack mount cabinet ! A real dinosaur by today's standards ! My fiber optic telecom system ran
at an overall data rate of 100 Mbps. We didn't do any data compression in those days. Simply sent
the raw, un-compressed video signal as an RZ serial data train. My 100 Mbps data package consisted
of the first bit always being a "1" as sync, followed by the 8 bits of video from the A/D, plus 1
additonal data bit for another lower speed data channel. 100 MHz ==> 10 ns long data with each data
bit occupying 1 ns. The digital transmitter included a 100 MHz xtal clock, the 8 bit, BCD, A/D
converter, parallel BCD data to serial converter, etc. All done in ECL.
I then pulse modulated on & off a semiconductor laser diode with the 100 Mbps data steam. The
laser's light beam was launched into a muli-mode fiber optic cable. At the other end of the fiber cable
was an avalanche photo diode detector followed by a broad-band amplifier. This then went to my
digital receiver which included a clock recovery circuit, data detector, serial to parallel converter, then
an 8 bit D/A converter, and video amplifier. The digital receiver was again done in ECL plus discrete
components for my D/A design. Surprise ! It all worked !
When I gave a live demo of the system to the NBS staff, it blew them away at the time. They hadn't
seen such digital tech before. What was especially an eye-opener to them was digital quantization.
My live demo included disabling one or more of the 8 data bits and seeing what it did to the resultant
TV image on the video monitor.
What Mario is proposing is really nothing new. It is just that technology has improved a whole lot
since my early attempts in the 70s (50 years ago !). Here in Boulder by the late 70s, some E.E.
professors at the University of Colorado were experimenting with exactly what Mario wants to do. i.e.
send video data though the atmosphere using lasers and optics. Yes, they worked, but not without
issues. And Yes, it will work for Mario, but some of the same issues now as then. A couple of
Biggies that everyone will encounter are:
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1. Antenna Pointing -- If you think it is difficult to align your 30dBi dish antenna for 10 GHz at a
target 10 miles away, try doing that with an infinitely narrower beam-width from a laser ! Not
impossible, but damm hard to do. Now try to stabilize it and keep it on target.
2. Atmospheric Effects --- We all know what happens to visibility on a foggy day. Light
propagation drops to very short distances. Plus even on a clear day, have you noticed wavy lines on
the horizon due to thermal effects ? i.e. all sorts of propagation issues to attenuate, scatter, distort
and bend our laser beams. For NASA and space laser comms -- not an issue, but here on Mother
Earth a big issue.
73 your editor, Jim, KH6HTV, Boulder, Colorado
=========================================================================
DVB-T Digital Parameters --
How do they impact system performance ?
Jim, KH6HTV
This is a report on some experiments performed to determine the impact of chosing various DVB-T
digital parameters upon the sensitivity of a DVB-T receiver. The tests were performed in a perfect
lab environment with a coaxial cable connection between the transmitter and receiver. They
obviously did not cover all of the nasty issues encountered out in the real world with radiated signals.
Issues such as multi-path, mobile flutter, RFI, etc. rear their ugly heads out there. Some of the digital
parameters are intended to deal with those but don't necessarily impact receiver sensitivity. To test
them, would require additional field testing.
The digital parameters considered are those which can be selected on the Hi-Des HV-320 modulator
using the windows PC program called AV-Sender. They include:
Media Configuration:
Video Encoding Type: MPEG2 or H.264
Video Encoding Resolution: 15 choices from Auto, 360x480 up to 1920x1080
Max Bit Rate: any arbitrary value may be entered up to the calculated theoretical upper limit
Video Encoding GOP (Group of Pictures) Length: any integer value. typical is 30 or 60
Video Encoding Frame Rate: we use 30 fps for the USA
Audio Encoding Type: MPEG2, AAC, or AC3, most common is MPEG2
Audio Encoding Rate: 96, 128, 192, or 384 Kbps
Transmission Configuration:
Center Frequency: 100 MHz to 2.6 GHz, in 1 kHz increments
Band-Width: 1.5, 2, 2.5, 3, 4, 5, 6, 7 or 8 MHz
Modultation Method (Constellation): QPSK, 16QAM, or 64QAM
Number of Sub-Carriers (FFT): 2K, 4K, or 8K
FEC - Forward Error Correction (Code Rate): 7/8, 5/6, 3/4, 2/3, or 1/2
TV Rptrs Rptr-147.doc ( 11/22/23, kh6htv) p. 7 of 12
Sync (Guard Interval): 1/32, 1/16, 1/8, or 1/4
Modulation Data Rate: Based upon the choices made in the above Trans. Config. parameters,
the computer then calculates a theoretical max. possible data rate. This is then taken into
consideration when selecting the video encoding data rate in the Media Config. Hi-Des
reccommends that it be set no higher than 80% of the theoretical max. This is to allow for the
audio data plus other overhead data to also be transmitted. For very low band-widths, an
even lower % should be used.
"Standard" Parameters: These are the values typically used by the Boulder ATV hams, plus they
are used in the Boulder, W0BTV repeater transmitter.
Media Configuration: HDMI, H.264, 1920x1080, 5.5 Mbps, 60 GOP, Audio = MPEG2, 96 Kbps
Trans Configutation: 6 MHz BW, QPSK, 8K sub-carriers, 5/6 FEC, 1/16 sync
Receiver Parameter Requirements: Fortunately, the DVB-T receivers are "smart". They work
automatically with any combination of the above parameters, except for band-width. They will even
switch seamlessly if the transmission parameters are changed abruptly mid-steam. The transmitter
sends out a meta-data header informing the receivers what it will be using.
Receiver Sensitivity Test Proceedure: The transmitter was a Hi-Des model HV-320E modulator. A
live HDMI video source was a DVD player playing a live action video with constant motion and audio.
The receiver was a Hi-Des model HV-110. Some tests also placed a low noise, pre-amplifer in front of
the receiver. The pre-amp was a KH6HTV model 70-LNA. The transmitter and receiver were
connected via a long coaxial cable permitting adequate seperation between the two units to minimize
any residual rf leakage coupling. The internal attenuator in the HV-320 was adjusted to provide
exactly 0 dBm rf average power at the far end of the coax cable. Additional attenuation was inserted
in front of the receiver with fixed 20dB & 30dB SMA attenuators plus a rotary step attenuator (0 -
69dB in 1 & 10 dB steps). The step attenuator was adjusted to determine the weakest possible signal
which still gave perfect P5 / Q5 video and audio. The signal level and resultant signal / noise ratio
were then recorded. An additional 1 dB of attenuation caused either freeze framing or complete loss of
signal. This state was also indicated by the Signal LED on the front panel of the HV-110. It flickered
red/green. The LED was solid green when receiving a P5 picture. The LED was solid red when no
signal was present at all.
TEST RESULTS -- RECEIVER SENSITIVITY for
VARIOUS DIGITAL PARAMETERS
QPSK vs. 16QAM vs. 64QAM: All were measured with "standard" parameters. Only items
changed were modulation method and video data rate. The "max" values are the calculated theoretical
max. possible encoding data rates. Hi-Des recommends we never exceed 80% of the max. The
measured receive sensitivities and resultant signal to noise ratios were:
QPSK (5.5 Mbps 7.32 max) = -94dBm / 8dB s/n (max s/n = 23dB)
16QAM (11.5 Mbps, 14.64 max) = -88dBm / 14dB s/n (max s/n = 26dB)
64QAM (16 Mbps, 21.96 max) = -80dBm / 22dB s/n (max s/n = 32dB)
TV Rptrs Rptr-147.doc ( 11/22/23, kh6htv) p. 8 of 12
conclusion: 16QAM is 6 dB worse and 64QAM is 14 dB worse compared to QPSK
QPSK - vary the Code Rate (i.e. FEC): measured with standard parameters. Only items changed
were FEC and video data rate. The measured receiver sensitivities were:
7/8 (6.0 Mbps, 7.68 max) = -93dBm / 9dB s/n 5/6 (5.5 Mbps, 7.32 max) = -94dBm / 8dB s/n
3/4 (5.0 Mbps, 6.59 max) = -95dBm / 7dB s/n 2/3 (4.5 Mbps, 5.85 max) = -96dBm / 6dB s/n
1/2 (3.5 Mbps, 4.39 max) = -98dBm / 5dB s/n
conclusion: Each step increase in FEC adds about 1dB improvement in sensitivity and required s/n.
But at the expense of considerable reduction in encoding data rate.
QPSK - 6 MHz BW vs. 2 MHz BW: measured with standard parameters. Only items changed were
band-width and video data rate. The measured receiver sensitivities were:
6 MHz BW (5.5 Mbps, 7.32 max) = -94dB / 8dB s/n
2 MHz BW (1.5 Mbps, 2.39 max) = --98dB / 8dB s/n
conclusion: Going from 6 to 2 MHz band-width buys 4 dB improvement in sensitivity, but at a
considerably lower data rate.
MPEG-2 vs. H.264 Video Encoding: No change was noted.
# Sub-Carriers - 8K vs. 2K: No change was noted
Guard Interval (i.e. Sync): Only items changed were guard interval and video data rate. No
change was noted.
Video Encoding Resolution: No change was noted.
Parameters for Best Sensitivity:
6 MHz BW = -98dBm Trans. Config = QPSK, 8K FFT, 1/2 Code (FEC), 1/16 Guard
Media Config = H.264, 1080P, 2.5 Mbps
2 MHz BW = -102dBm Trans. Config = QPSK, 8K FFT, 2/3 Code (FEC), 1/16 Guard
Media Config = H.264, 640x480, 1.2 Mbps
Add a Low-Noise PreAmp: measured with standard parameters.
6 MHz BW: HV-110 = -94dBm 70-LNA + HV-110 = -98dBm
2 MHz BW: HV-110 = -99dBm 70-LNA + HV-110 = -102dBm
Ultimate Performace: Best Sensitivitity Parameters + plus low noise preamp
6 MHz BW = -102 dBm / 5 dB s/n
2 MHz BW = -105 dBm / 6 dB s/n
LNA Conclusion: adding a low noise (NF < 1 dB) pre-amplifier improves HV-110 receiver
sensitivity by about 3-4 dB.
ATN-California, Recommended 2 MHz Parameters with 16QAM:
see the July, 2023, ATV newsletter, issue #135, page 5
TV Rptrs Rptr-147.doc ( 11/22/23, kh6htv) p. 9 of 12
Trans. Config = 2 MHz BW, 16QAM, 8K FFT, 3/4 Code (FEC) & 1/16 Guard
Media Config = MPEG2, 1280x720, 2.6 Mbps, & 30 GOP
HV-110 = -93dBm / 14 dB s/n 70-LNA --> HV-110 = -97dBm / 13 dB s/n
ADDITIONAL READING: If you want to find out a lot more about the various digital parameters,
or anything else about DVB-T (or DVB-S, DVB-C, etc.), I suggest the book I consider the "Bible"
for DTV. ------ "Digital Video and Audio Broadcasting Technology --- A Practical
Engineering Guide" by Walter Fischer (TV engineer at Rhode & Schwartz, Munich, Germany).
Springer, 3ed edition, 2010
=========================================================================
Another Mid-West ATV
Band Opening !
Photos are WB8LGA's analog ATV signal
from 90 miles to AH2AR's hamshack, along
with W8URI's distant 85+ mile DVB-T signal
also being received at AH2AR's shack in
Vandalia on Sunday, Nov.18th. ATV DX
continues to be alive and well within the
Midwest region. W8URI has built a 1 KW
70cm pallet amplifier, and was transmitting
about 130 watts on DVB-T. Two way DVB-T
and analog, A5 contacts were accomplished
with both stations. 73 de Dave, AH2AR
analog ATV digital ATV
FEEDBACK:
ATV Trivia: Alan, AD6E writes --- "Yes, it's
an amazing job of deep research by someone at
ARRL to find that photo. It makes me wonder what
else they could dredge up. I'm sure it's the only
one in existence of me standing next to an ARRL
banner. Here's another, but of Jim this time.
Kent, KH6CJJ writes --- "Nice picture of you and
Alan, Jim. Gee that seems so long ago! I am
reading this in Japan nearing the end of a 24 day
visit. Unfortunately, no ham radio contacts here
although a near miss. I need to wear a hat with my
call on it on future trips. Aloha, Kent"
TV Rptrs Rptr-147.doc ( 11/22/23, kh6htv) p. 10 of 12
Feedback on Remote Receivers: Mike, WA6SVT, writes --- "Great newsletter Jim! BTW,
you can set up the remote receiver for a 5 MHz bandwidth or the main receiver that way with the
remote at 6 MHz. Having a different bandwidth will allow the selection to take place and the users
would set up each bandwidth on a different channel but same center frequency. Simular way as using a
different PL tone for NBFM voice receivers." 73, Mike
W0BTV Repeater Status Update:
Recently Don, N0YE, made yet another trip up the hill to service
our repeater. This time he made a trip to the roof top to tighten up
the bolts on our receive antenna. He also replaced the Video ID
media player with a new unit and new USB memory. Once back
home, he tested the media player and decided that the problem
with the tearing of the video images was due to a defective USB
memory stick, thumb drive and not the media player itself.
We also still are having "flaky" issues with the repeater controller. Toning up the Quad Display mode
leads to unpredictable behaviour. Sometimes it works properly, other times not. Most recently it has
been dropping out of quad mode after a few minutes and then hanging up the repeater transmitter. The
only way out is to then tone in the control code for a System Master Reset-Boot. Never a dull
moment when you have a repeater ! ! !
=========================================================================
Disturbing RFI Products found on AliExpress !
On a recent Boulder ATV net, Colin, WA2YUN, showed us a new, Chinese, low cost, 23cm amplifier
he had found on Ali-Express. Looking at the link to it Colin sent me I also noticed some other items
advertised. I was really troubled by their presence. But considering the current world situation with
wars being fought in the Ukraine and Israel/Gaza with a proliferation of war drone aircraft, I guess I
shouldn't be surprised. So just what did I find ? Under the banner "Frequency Shield" were some
low cost frequency jamming equipment marketed as "Frequency Control". Here is directly from the
AliExpress ad ---- "Module overview -- Used to generate a sweep frequency suppression signal in a
certain frequency band to shield and interfere with the equipment in the corresponding frequency band.
It is widely used in WiFi signal shielding, 433M signal, GPS positioning, UAV countermeasures and
other application scenarios. --- available for 315MHz, 300-400MHz, 433MHz, 840-960MHz, 1200-
1400MHz, GPS 1575MHz, 2400-2500MHz, 5160-5320MHz & 5725-5850MHz"
If we here in Boulder thought our 70cm RFI issue was bad for our W0BTV repeater, just imagine what
it will be like if enough bad guys start using this *^%%#*$ stuff from China which is so cheap and
readily purchased over the internet !
Disgusted ! -- de Jim, KH6HTV
========================================================================
TV Rptrs Rptr-147.doc ( 11/22/23, kh6htv) p. 11 of 12
W0BTV Details: Inputs: 23 cm Primary (CCARC co-ordinated) + 70 cm secondary
all digital using European Broadcast TV standard, DVB-T 23cm, 1243 MHz/6 MHz BW
(primary), plus 70cm (secondary) on 441 MHz with 2 receivers of 6 & 2 MHz BW
Outputs: 70 cm Primary (CCARC co-ordinated), Channel 57 -- 423 MHz/6 MHz BW, DVB-T
Also, secondary analog, NTSC, FM-TV output on 5.905 GHz (24/7 microwave beacon).
Operational details in AN-51c Technical details in AN-53c. Available at:
https://kh6htv.com/application-notes/
W0BTV ATV Net: We hold a social ATV net on Thursday afternoon at 3 pm local
Mountain time (22:00 UTC). The net typically runs for 1 to 1 1/2 hours. A DVD ham travelogue is
usually played for about one hour before and 1/2 hour after the formal net. ATV nets are streamed live
using the British Amateur TV Club's server, via: https://batc.org.uk/live/ Select ab0my or n0ye. We
use the Boulder ARES (BCARES) 2 meter FM voice repeater for intercom. 146.760 MHz ( -600 kHz,
100 Hz PL tone required to access).
Newsletter Details: This is a free newsletter distributed electronically via e-mail to
ATV hams. The distribution list has now grown to over 500+. News and articles from other ATV
groups are welcomed. Permission is granted to re-distribute it and also to re-print articles, as long as
you acknowledge the source. All past issues are archived at: https://kh6htv.com/newsletter/
ATV HAM ADS -- Free advertising space is offered
here to ATV hams, ham clubs or ARES groups. List here amateur
radio & TV gear For Sale - or - Want to Buy.
DVB-T Receiver for Sale: I have a brand new Hi-Des model HV-110 that I don't plan
to use. It comes with everything shown - HV-110 receiver, software CD, power supply, video cable,
and remote control. I purchased it a few weeks ago after seeing a talk at Pacificon but decided I'm not
ready to get into this part of the hobby yet. I plugged it in to confirm it works (it does). Price is US$90
shipped. Contact me at chancekp@yahoo.com if you are interested. Kevin, KN6WKM
(editor's comment -- the new price from Hi-Des is $119, so you can save $29 buying it from Kevin)
===================================================
TV Rptrs Rptr-147.doc ( 11/22/23, kh6htv) p. 12 of 12
HV-320 DVB-T Modulator 70-7B Amplifier 70-9B or 23-11A Amplifier
Your NEW DVB-T 70cm or 23cm Transmitter
What is required to put a digital ATV signal on the air ? 1. Video source, such as a cam-corder camera 2. A
DVB-T modulator 3. A Linear RF Power Amplifier & 4. An Antenna. KH6HTV Video can supply you
with a "Turn-Key" DVB-T Transmitter. No building DIY, nor programming required, just "plug-n-play". The
transmitter would consist of a Hi-Des model HV-320B Modulator and one of the above Amplifiers. The
modulator would come pre-programmed to work on the amateur ATV channels. I am offering to purchase the
modulator for you, program it, and resell it to you at cost. The catch is you also need to purchase an amplifier
from me.
For base station, or repeater use, I offer the larger amplifier package shown on the right in the above photo. For
the 70cm band, it is my model 70-9B. It is a 70 Watt amplifier (FM/CW service) which puts out 10 Watts
average power in digital TV service. It operates from a +12Vdc supply and pulls 8 Amps. For the 23cm band,
it is my model 23-11A. It is a 30 Watt amplifier (FM/CW service) which puts out 4.5 Watts average power in
digital TV service. It operates from a +12Vdc supply and pulls 6.5 Amps.
For out in the field, portable ATV operations, we run on batteries. There conserving battery capacity is very
important. So we need to use equipment with much lower current requirements. The 70cm, model 70-7B
amplifier was designed specifically for these applications. It is the ideal choice if your local ARES group is
considering adding ATV capability to the services they offer to the public safety agencies. For example, the
Boulder, Colorado ARES group (BCARES) has 4 complete DVB-T portable pack sets, all using the 70-7B
amplifier. The 70-7B is a 25 Watt amplifier (FM/CW service) which puts out 3 Watts average power in digital
TV service. Operating from a 12Vdc battery it pulls 2.6 Amps at full power. The RF power can also be
lowered with a front panel rotary switch by -5dB & -10dB. The respective current draws are thus: high power
= 3 W @ 2.6 A, medium power = 1W @ 1.2A and low power = 300 mW @ 700 mA. www.kh6htv.com
If you are interested, contact KH6HTV for a detailed quote at 303-594-2547 or kh6htv@yahoo.com

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TV Rptrs Rptr-148.doc ( 11/28/23, kh6htv) p. 1 of 16
Boulder Amateur
Television Club
TV Repeater's
REPEATER
December, 2023
issue #148
BATVC web site: www.kh6htv.com
ATN web site: www.atn-tv.com
Jim Andrews, KH6HTV, editor - kh6htv@arrl.net www.kh6htv.com
(from K0DVB)
SPECIAL ISSUE on
DVB-T Digital Parameters
Jim, KH6HTV
Note: several figures used in this article came from K0DVB, Matt Holiday's slide show talk given as ATV training classes to members of the Boulder,
CO ARES (BCARES). https://k0dvb.org/ https://bouldercountyares.org/our-tool- ... mateur-tv/
TV Rptrs Rptr-148.doc ( 11/28/23, kh6htv) p. 2 of 16
In our previous issue, #148, we discussed some experiments to demonstrate the effects of adjusting the
various digital parameters for a DVB-T signal upon the ultimate weak signal capability of a receiver.
So just what are these parameters ?
I consider the "Bible" for DTV. ------ "Digital Video and
Audio Broadcasting Technology --- A Practical
Engineering Guide" by Walter Fischer (TV engineer at Rhode
& Schwartz, Munich, Germany). Springer, 3ed edition, 2010
Much of the material for this article comes from this book. I denote
this material using quotes.
SOURCE CODING--MEDIA CONFIGURATION:
Video Encoding: For DVB-T, we have a choice of two
methods, either MPEG2 or H.264.
"In 1992, MPEG-1 was created as the first standard for encoding
moving pictures accompanied by sound. The aim was to achieve a
picture quality close to that of VHS (352x288) at CD data rates (<
1.5 Mbit/s)." MPEG-2 then followed in 1996 with higher resolution,
better quality, and supported transmission, not just
data storage. Then in 2003 a still more improved
system was released. It goes by several names,
H.264, AVC (Advanced Video Coding) or MPEG-
4, part 10. "Compared with MPEG-2, H.264 is
more effective by a factor of 2 to 3 and thus allows
data rates which are lower by a factor of 2 to 3,
often even with improved picture quality."
Video Encoding Resolution: With Hi-Des
modulators, we have the ability to then select our
desired resolution. They range from a low of
360x480 to a hi-def high of 1920x1080 pixels. For
some other brands, this is not an option.
(from K0DVB)
Max. Bit Rate: For Hi-Des, this is a user selectable value, while for some other brands it is fixed.
It can never be set higher than a calculated theoretical maximum called the Modulation Data Rate.
Hi-Des recommends it never be set any higher than about 80% of the Modulation Data Rate. This is to
allow space for audio encoding and other over-heads. For very low RF band-widths, the percentage
should be set considerably lower than 80%.
TV Rptrs Rptr-148.doc ( 11/28/23, kh6htv) p. 3 of 16
Video Aspect Ratio: This is the ratio of the screen width to height. Older TVs used 4:3.
Newer wide screen TVs use 16:9.
Video Encoding Frame Rate: This is the number of video frames transmitted per second.
We ususally try to adhere to the old NTSC (30 fps) or PAL (25 fps) standards.
Video Encoding GOP Length: GOP stands
for Group of Pictures. Successive frames of
video are sent as various types of data. First there
is the "I" or "Key" frame. It sends all the data
required to create a complete picture in a frame.
Each GOP begins with this "I" frame. The "I" is
then followed by "B" and "P" frames which only
send partial data, mainly dealing with motion
compensated differences from the "I" frame. The
GOP length parameter determines how many video
frames are sent before starting over again with a
new "I" - Key frame. Typical GOP length values
are 30 or 60, i.e. every 1/2 second or full second.
(from K0DVB)
CHANNEL CODING -- TRANSMISSION CONFIGURATION:
Modulation: The choices for DVB-T are:
QPSK, 16QAM or 64QAM. QPSK stands for
Quadrature Phase Shift Keying. It is similar to FM
in that there is no change in the amplitude of the rf
signal, only shifting of 90, 180, 270 or 360 (0)
degrees of the phase. It is usually graphically
displayed as a Constellation diagram with I & Q
axis ( I = in phase, Q = quadrature, or 90 deg ).
QPSK is the simplest with 4 possible logic states
and 2 Bits/symbol. QAM stands for Quadrature
Amplitude Modulation. It starts out with QPSK,
but then adds discreate amplitude levels for higher
amounts of logic. 16QAM adds 2 more
amplitude levels of 25% and 75%. It is best
shown in the I/Q constellation drawing to the right.
It now has 16 logic states an 4 Bits/symbol.
64QAM adds even more amplitude levels with 64 ( from K0DVB)
logic states and 6 Bits/symbol. Using higher levels of QAM allows more data to be transferred within
a fixed band-width rf channel. There will be some compromises required however to be discussed
further. With the newer DVB-T2, they have added an even higher choice of 256QAM.
TV Rptrs Rptr-148.doc ( 11/28/23, kh6htv) p. 4 of 16
Is QAM better than QPSK in a noisy rf channel ?
What does this I/Q QAM picture tell you ? For
the same amount of added rf noise to each logic
state, we see that with 16QAM, the various logic
states now are interfering with each other.
We reported some experimental results in our last
ATV newsletter, issue #147 comparing these.
16QAM required a 6 dB stronger signal than QAM,
while 64QAM required a 14 dB stronger signal.
Clearly going to 256QAM with DVB-T2 would
require an even stronger rf signal with attendent
improvement in required S/N.
(from K0DVB)
# of Sub-Carriers: DVB-T uses a system called Coded Orthogonal Frequency Division Multiplex
or COFDM for short. Basically it means the data is split up and transmitted over many sub-carriers.
For DVB-T the choice is either 2K or 8K. Newer DVB-T2 adds more choices. For our USA
standard 6 MHz TV channels, the sub-carrier spacings are: 840 Hz (8K) or 3.35 kHz (2K).
"Due to multi-path reception, fading occurs which is frequency- and location-selective. In terrestrial
radio transmission, narrowband or wideband sinusoidal or impulse-type interferers must also be
expected which can adversely affect reception. Plus Doppler shift in mobile operations." --- "Single
carrier methods have a relatively high symbol rate, often within a range of more than 1 MS/s up to 30
MS/s. This leads to very short symbol periods of 1 μs and shorter (inverse of the symbol rate).
However, multi-path echo delays can easily be within a range of up to 50 μs or more in terrestrial
transmission rf channels. Such echoes would lead to inter-symbol interference between adjacent
symbols or even far distant symbols and render transmission more or less impossible. An obvious
trick would now be to make the symbol period as long as possible in order to minimize inter-symbol
interference and, in addition, pauses could be inserted between the symbols, so-called Guard intervals.
However, there is still the problem of the location- and frequency selective fading phenomena. If then
the information is not transmitted via a single carrier but is distributed over many, up to thousands of
subcarriers and a corresponding overall error protection is built in, the available channel bandwidth
remaining constant, individual carriers or carrier bands will be affected by the fading, but not all of
them. If, however, many thousands of subcarriers are used instead of one carrier, the symbol rate is
reduced by the factor of the number of subcarriers and the symbols are correspondingly lengthened
several thousand times from < 1 μs up to a millisecond. The fading problem is solved and, at the same
time, the problem of inter-symbol interference is also solved due to the longer symbols and the
appropriate pauses between them. It is now only necessary to see that the many adjacent carriers do
not interfere with one another, i.e. are orthogonal to one another. Hence COFDM."
For DVB-T, there is a choice of using either 2K or 8K sub-carriers. Thus "the symbol lengths are
either 250 μs (2K) or 1 ms (8K). The 2K mode has greater subcarrier spacing of about 4 kHz but the
symbol period is much shorter. Compared with the 8K mode with a subcarrier spacing of about 1 kHz,
TV Rptrs Rptr-148.doc ( 11/28/23, kh6htv) p. 5 of 16
it is much less susceptible to spreading in the frequency domain caused by doppler effects due to
mobile reception and multiple echoes but much more susceptible to greater echo delays caused by
doppler effects due to mobile reception and multiple echoes." DVB-T2 adds more choices of the
number of sub-carriers.
Actually not all of the many thousand sub-carriers are dedicated to carrying our A/V data. DVB-T
also contains: Inactive carriers with fixed positions, Contiuous Pilots with fixed position, Scattered
Pilots with changing positions and Transmission Parameter Signalling (TPS) carriers with fixed
positions. The TPS carriers represent virtually a fast information channel via which the transmitter
informs the receiver about the current transmission parameters. The Pilot Carriers are used in the
receiver for rf channel degradation effects estimation and subsequent correction to remove multi-path.
Guard Interval: The purpose of the guard interval is to introduce immunity to propagation
delays, echoes and reflections, to which digital data is normally very sensitive. In OFDM, the
beginning of each symbol is preceded by a Guard interval. As long as echoes fall within this interval,
they will not affect the receiver's ability to safely decode the actual data, as data is only interpreted
outside the guard interval. The guard interval is not left empty, but contains a fixed data pattern
which helps the receiver acquire sync lock. In DVB-T, the choices for Guard are: 1/32, 1/16, 1/8
and 1/4 of the data symbol length.
Forward Error Correction - Code Rate: The previous parameters discussed concerned how
the data was arranged in the COFDM signal to compensate for rf channel degradation. The Code Rate
deals with adding Forward Error Correction (FEC) to help the receiver decode corrupted data. In
DVB-T, the choices for Code Rate are: 7/8, 5/6, 3/4, 2/3 and 1/2. What this ratio means is how much
of a symbol is devoted to real video data and how much is error correction info. For example 5/6
means a video data symbol is split into 6 pieces with 5 being real video data and the last piece being
error correction data.
Channel Band-Width: The sizes of many other parameters are determined based upon how
much frequency is allocated to the actual rf channel. In the USA, the standard TV channel band-width
is 6 MHz. Standard TV channels vary from 5 to 8 MHz world-wide. 7 MHz in Europe being the
most common. With the transition from analog TV to digital TV, these channel band-widths were
usually retained. Radio amateurs have been recently experimenting with narrower band-widths. Hi-
Des DVB-T equipment supports band-widths down to 2 MHz. An actual DVB-T signal does not
occupy the entire channel allocated band-width. It is actually a bit narrower to allow some guard band
for the steep skirts of the digital signal to roll-off to an acceptable lower dB level. For 6 MHz BW,
DVB-T, the actual signal band-width is 5.71 MHz.
Modulation Data Rate: This is NOT a parameter which can be programmed by the user.
Instead it is a theoretical, calculated value based upon the selection of all of the above transmission
parameters. This is the number which should be consulted when setting the video encoding data rate.
As an example for: 6 MHz BW, QPSK, 8K sub-carriers, 5/6 Code Rate, and 1/16 Guard Interval, the
calculated Modulation Data Rate is 7.16 Mbps. Going from QPSK to 64QAM ups this to 21.96
Mbps.
TV Rptrs Rptr-148.doc ( 11/28/23, kh6htv) p. 6 of 16
AN-39 DVB-T Recommended Parameters -- This app. note was written in 2017,
but is still very relevant today. Therefore, I am re-printing it here in our ATV newsletter. It
discussed some lab bench tests comparing various digital parameters, much like we recently repeated
and reported in the last newsletter, issue #147. Of particular interest is the inclusion of some actual, in
the field, mobile tests which compared results using both analog FM-TV, analog NTSC VUSB-TV,
with DVB-T, and on both 70 cm and 23 cm bands.
Application Note
AN-39c
June, 2017
rev. Jan. 2021
rev. Nov. 2021
rev. Jan. 2023
DVB-T Recommended Parameters
Jim Andrews, KH6HTV
I am often asked what parameters are recommended for DVB-T, amateur, digital Television (DTV).
The commonly used modulators, such as the Hi-Des model HV-100EH, HV-310 or HV-320E, allow a
wide adjustment range in many of the parameters. The selection of the proper values can have a
dramatic impact on the system performance. The table below lists my recommendations.
Common Parameters: Media Configuration = HDMI input, H.264 Video Encoding, CBR Data
Rate Control, 29.97fps Frame Rate, 16:9 Aspect Ratio, 30 GOP Length, 0 B Frame Number,
MPEG2 Audio Encoding, 96Kbps Audio Encoding Rate, and HDMI HDCP = on
Transmission Configuration = 8K FFT, 1/16 Guard (sync) Interval
TS Info Configuration = PMT PID 0x640, Video PID 0x641, Audio PID 0x642, Service Name = your
station's call sign
PARAMETER Perfect
Channel
Normal
Channel
Poor
Channel
Weakest
Signal
Bandwidth 6 MHz 6 MHz 6 MHz 2 MHz
Modulation 16-QAM QPSK QPSK QPSK
Resolution 1080P 1080P 720P 480i
lines 1920x1080 1920x1080 1280x720 720x480
Forward Error
Correction
(Code Rate)
5/6 5/6 1/2 3/4
Bit Rate 11.5 Mbps 5.5 Mbps 3.5 Mbps 1.2 Mbps
Receiver
Sensitivity
-91dBm -96dBm -100dBm -103dBm
with Pre-Amp -94dBm -100dBm -104dBm -108dBm
TV Rptrs Rptr-148.doc ( 11/28/23, kh6htv) p. 7 of 16
RECEIVER SENSITIVITY: The values reported in the table for receiver performance were
measured at 423 MHz on a Hi-Des model HV-110, DVB-T receiver. The measurements were made in
a controlled lab environment on a well shielded, closed coaxial circuit, using an HV-100EH modulator
and calibrated coaxial fixed and step attenuators The modulator was located 75ft. away from the
receiver to minimize any leakage signals. Thus the only effect altering the transmission channel was a
progressively weaker, attenuated signal. There was no multi-path, RFI, etc. present to distort the
signal. The pre-amp values were measured using an ARR model P432VDG amplifier (0.5dB NF,
18dB gain). Adding the low noise, pre-amp in front of the Hi-Des receiver improved the sensitivity by
3 to 5dB.
Fig. 1 Transmission Configuration page of AVSender --- shown with recommended settings for
normal 1080P, 6 MHz BW, QPSK operation -- note: a custom channel table was used.
TRANSMISSION PARAMETERS: The parameters of Bandwidth, FFT, FEC and Guard
Interval are extremely important in determining how well your TV signal will propagate and be
decoded at the receiver under real world, multi-path conditions. These are set on the Transmission
Configuration page of AVSender, Fig. 1. AVSender is the Windows computer program supplied by Hi-
Des for setting the modulator's digital parameters. The normal bandwidth used is 6 MHz in the USA,
which is the same as used by commercial broadcast TV stations. For extremely weak signal
performance, going to the lowest possible bandwidth of 2 MHz with lower, 480i, standard definition
resolution buys several dB in receiver sensitivity. The Constellation parameter selects the modulation
method of either QPSK, 16QAM or 64QAM. The best video performance (in very strong signal
conditions) is obtained using 64QAM and the highest possible bit rate. For weak signal, amateur
useage, QPSK is recommended. Very acceptable, high-definition, video performance with normal
scenes is obtained using QPSK. The Guard Interval is used to synchronize the receiver. It is the same
as sync pulses used in the old analog NTSC system. The Guard ratio determines how much of the
total data frame is devoted to "sync". The Code Ratio, also called FEC or Forward Error Correction
ratio determines how much data is devoted to error correction, versus the true live video data. 5/6 FEC
TV Rptrs Rptr-148.doc ( 11/28/23, kh6htv) p. 8 of 16
means for every 5 bits of real data, one extra bit is added for error correction. The FFT determines
how many subcarriers are used within the channel bandwidth. The choice is either 2000 or 8000. (2K
or 8K). I selected using an FFT of 8K based upon the recommendation in reference [1] which stated
"An 8K system allows reception with longer multi-path echos." 2K is supposed to be a better choice
for Doppler shift corrections for mobile operations. I have found that 8K works fine with mobile
doppler shift at speeds of at least 75 mph.
Fig. 2 Media Configuration page of AVSender --- shown with recommended settings for normal
1080P, 6 MHz BW, QPSK operation
MEDIA PARAMETERS: Another key parameter is the encoding data rate, called "Max Bit Rate."
This is found on the Media Configuration page of AVSender, Fig. 2. To follow rapidly changing
scenes, the highest possible data rate should be used. The max. theoretical possible data rate is a
function of Bandwidth, modulation type, FEC and Guard Interval. Ref [2] tabulates all of the various
possible options. AVSender also displays the theoretical maximum for any setting. It is on the
Transmission page, Fig. 1, and called "Modulation Data Rate". It is grayed out indicating that you can
not alter it. For a 6 MHz bandwidth, the theoretical maximum is 23.75Mbps for 64QAM with 7/8 FEC
and 1/32 Guard Interval. For QPSK the maximum is a much lower 7.92Mbps with 7/8 FEC & 1/32
Guard.
The older Hi-Des HV-100EH will not operate above 16 Mbps. Trying to set any data rate too high, the
Hi-Des HV-100EH defaults back to 8 Mbps. Thus there is not much to be gained by using 64QAM
over 16QAM with the HV-100. The newer HV-320E does work with 64QAM at the highest data rate
(suggest limit to 18 Mbps).
Caution: Operation at or near the theoretical maximum sometimes gave unacceptable breakups the
picture. In their instruction manual, Hi-Des recommends that the "Max Bit Rate" be set no higher than
TV Rptrs Rptr-148.doc ( 11/28/23, kh6htv) p. 9 of 16
80% of the theoretical max. "Modulation Data Rate." The values listed in the above table are set
approximately at 80%.
Another important parameter to be set is that of HDMI-HDCP. The HDMI protocol allows for
motion picture copyright security to be implemented. Normally this prevents the use of certain HDMI
equipment with others if copyrighted media would be compromised. This means that under some
circumstances a video source such as a DVD player can only be connected to a video monitor and not a
transmitter. If this parameter is set to OFF, you will not be able to connect a DVD player to your Hi-
Des modulator. It will not accept the source and give you instead a screen with the test "No Input
Video". It will only accept a TV camera input. To avoid this situation, you should thus set this HDCP
parameter to ON. This does not mean it is thus OK or legal as an amateur to transmit copyrighted
movies. But we may want to transmit our own DVD home movies, such as family events or travels. It
is legal for us to do this.
Fig. 3 TS Info configuration page of AVSender
TS INFO PARAMETERS: Don't change most of the parameters on this page, Fig. 3. The
PIDs (Packet Identifiers) shown are the normal factory presets and normally shouldn't be changed. All
DTV amateurs in your local area should use the same PIDs. If the PIDs of different stations do not
match, the Hi-Des receivers will lock up when receiving a signal with different PIDs than those it was
originally trained with.
Do however change the Service Name. Enter here your own stations's call sign. It will then be
transmitted automaticaly with the data header and make your station IDing automatic to comply with
FCC ID regulations.
NORMAL CHANNEL: Under normal conditions, to obtain the highest video definition possible
of 1080P, a 6 MHz bandwidth is used. Most amateur operations are done with far lower rf power
TV Rptrs Rptr-148.doc ( 11/28/23, kh6htv) p. 10 of 16
levels than commercial broadcast ( watts vs. kilowatts ! ). Thus, the preferred modulation method is
QPSK. QPSK gives considerable improvement in receiver sensitivity (-96dBm vs. -91dBm for
16QAM and -82dBm for 64QAM). 8K FFT was chosen to handle longer multi-path echos. I chose to
use the factory presets of 5/6 FEC and 1/16 Guard Interval. Jim White, NC0JW, has confirmed that
they are the same settings which CBS found in early DTV propagation experiments to work best in
most situations [3]. These settings have been found to give very acceptable video performance for
most all, but the very, fastest moving sports scenes.
POOR CHANNEL: For marginal channel conditions, with either weak signals and/or severe
multipath(s), operation with the "Normal" parameters will be impossible. Oftentimes, perfect P5
video/audio can again be achieved by lowering the video resolution and using much more aggressive
forward error correction. High definition, 720P, performance can still be achieved with very good
picture quality. Using the much more aggressive FEC than for the Normal channel resulted in a 4dB
improvement in receiver sensitivity for a multi-path free, closed circuit channel. Even better
sensitivity improvements have been observed in real world, over the air conditions. A test run by
Colin, WA2YUN, and Jim, KH6HTV on 23cm, DVB-T using loop yaggi antennas on a clear, line of
sight, 5.6 mile path showed an impressive, 10dB improvement in weak signal reception using the 720P,
1/2 FEC over the 1080P, 5/6 FEC parameters.
2 MHz BANDWIDTH: In many parts of the USA, in particular large metro areas, there is too
much other RF activity on the amateur 70 cm band to allow use of the full, broadcast standard, 6 MHz
bandwidth. The Hi-Des modulators and receivers are capable of operating at much lower bandwidths,
down to 2 MHz. Hi-definition, 1080P resolution does not work well at 2 MHz BW, QPSK. However,
excellent video performance with standard definition, 480i is possible at 2 MHz BW, even using very
aggressive FEC. Going to a lower bandwidth also buys us a considerable increase in receiver
sensitivity (-108dBm, 0.9μV with a pre-amp). High definition, 720P, is possible at 2 MHz BW
however using 16QAM or 64QAM.
DVB-T RECEIVERS: Fortunately, the available receivers are smart and do not need to be
retrained when most of the transmitter's digital parameters are changed, even on the fly. As long as the
center frequency, bandwidth and PIDs remain unchanged, the receiver will automatically track changes
in parameters such as Constellation, FEC, Guard ratio, FFT, etc.
TV Rptrs Rptr-148.doc ( 11/28/23, kh6htv) p. 11 of 16
Fig. 4 TV Repeater Field Survey Route through city of Boulder & Boulder Valley
FIELD TESTS: In May and June, 2017, several Boulder, Colorado ATV amateurs did a series of
field tests to compare various TV modulation methods, including DVB-T. Hams participating were:
Don, N0YE, Colin, WA2YUN, Jack, K0HEH and Jim, KH6HTV. The Boulder TV repeater, W0BCR,
was used. It is capable of receiving on both 23cm and 70cm bands. On 23cm, it receives either 6
MHz bandwidth, DVB-T, or 4 MHz deviation FM-TV. On 70cm, it receives either 6 MHz bandwidth,
DVB-T, or 6 MHz bandwidth, NTSC, VUSB-TV. The repeater's ability to receive TV signals on all of
these modes/bands was tested in controlled experiments. For DVB-T, the 1080P, 5/6 FEC and 720P,
1/2 FEC modulation parameters were tested and compared.
The first tests were performed by driving a mobile TV transmitter on a fixed, 30 mile route, Fig. 4. A
camera was set up on a tripod in the passenger seat looking out the front windshield giving a live view
of the current location of the transmitter. A TV receiver at the qth of KH6HTV was monitoring the
relayed video from the TV repeater and it was recorded permanently on a DVD for later review and
analysis. Also during some of the tests, N0YE and WA2YUN monitored the TV repeater's relayed
images.
For the tests, the mobile transmitters and antennas used were very comparable for both bands. The
digital, DVB-T, transmitters and the 23cm FM-TV transmitter all put out about 3 Watts (+35dBm). The
70cm, VUSB-TV transmitter put out 10 Watts (PEP). The mobile transmit antenna was a Diamond,
TV Rptrs Rptr-148.doc ( 11/28/23, kh6htv) p. 12 of 16
tri-band, model NR-2000NA with 9 dBi gain on 70 cm and 7 dBi on 23 cm. The TV repeater's receive
antenna, a Diamond X6000A, had essentially the same gain of +7 dBi on both 70 cm and 23 cm.
There was a 14 dB difference between 23cm vs. 70cm tests, which consisted of the 10 dB extra path
loss, 2 dB difference in transmitter antenna gains and about 2 dB additional coax feedline loss.
Fig. 4 shows the route driven for each of the six tests in the city of Boulder and the surrounding
Boulder valley. This was almost a 30 mile route and typically took about 1 3/4 hours to traverse. The
route chosen included rural, residential, urban canyons (among tall buildings), light industrial, open
rolling hill prairie, high ridges, wooded areas, flat highways for high speeds (55mph), etc. It included
several areas where BCARES has operated in the past for major police operations including the
University of Colorado campus, Uni-Hill district, downtown Boulder, etc. Also included were the
QTHs of several active ATV amateurs. The farthest distance tested from the repeater was about 6
miles.
CONCLUSION: In summary, the following list prioritizes the overall performance of the six,
various modes/bands tested from best to worse.
1. 70cm, digital, DVB-T, 720P resolution, 1/2 FEC aggressive digital parameters.
2. 70cm, digital, DVB-T, 1080P resolution, 5/6 FEC, normal digital parameters
3. 70cm, analog, VUSB-T, 480i resolution
4. 23cm, digital, DVB-T, 720P resolution, 1/2 FEC, aggressive digital parameters
5. 23cm, analog, FM-TV, 480i resolution
6. 23cm, digital, DVB-T, 1080P resolution, 5/6 FEC, normal digital parameters.
Fig. 5 below shows an example of the video images received and recorded on DVDs for later review.
This example was retrieved from three separate field test runs at the same identical location, but with
different different modulation methods of FM, VUSB and DVB-T. At this particular location, the
transmitter vehicle was shielded from the repeater by the highway overpass and berms.
Clearly, the best performance was found using DVB-T on the 70cm band with a lower 720P
resolution and the best possible, most aggressive, Forward Error Correction (FEC) of 1/2. Perfect
P5 reception by the repeater was achieved from well over 90% of the total 30 mile route tested.
None of the other modes/bands came anywhere close to this performance. The 23cm coverage was
particularly poor with coverage from much less than 30% of the areas tested.
TV Rptrs Rptr-148.doc ( 11/28/23, kh6htv) p. 13 of 16
Fig. 5a 23cm DVB-T with aggresive coding of 720P and 1/2 FEC
Fig. 5b 23cm FM-TV, 4 MHz deviation, 480i standard definition
TV Rptrs Rptr-148.doc ( 11/28/23, kh6htv) p. 14 of 16
Fig. 5c 70cm VUSB-TV, normal analog NTSC standard definition
Fig. 6 Radio Mobile RF path prediction from DIA site to TV repeater
TV Rptrs Rptr-148.doc ( 11/28/23, kh6htv) p. 15 of 16
DIA TESTS: In June, N0YE and K0HEH drove out to the Denver International Airport (DIA) to
perform repeater coverage tests from a remote, fringe area where BCARES might be called upon in the
future for an airplane crash disaster. Fig. 6 shows the computer predicted, 70cm, rf path profile for the
tests from DIA to the Boulder TV repeater, using the on-line program Radio Mobile [4]. The path was
clear, unobstructed, line-of-sight over rolling prairie, but over a long distance of 32 1/2 miles. The
70cm predicted path margin was 13dB. They tested both 23cm and 70cm bands and all modes. For
DVB-T, they only used 720P, 1/2 FEC. They used yaggi antennas (11dBi on 70cm & 18dBi on 23cm)
on a telescoping mast. They were able to put perfect P5 pictures (except P3+ for 70cm, VUSB-TV)
into the repeater from antenna heights of at least 10ft. They were unsuccessful with a mag. mount
mobile, tri-band,NR-2000NA antenna.
REFERENCES:
1. "Digital TV - DVB-T", h ttp://digitaltvbooks.com/cofdm.pdf
2. "Digital Video and Audio Broadcasting Technology - A Practical Engineering Guide", W.
Fischer, Springer-Verlag, Berlin & Heidelburg, DE, 3ed Edition, 2010, ISBN 978-3-642-11611-7
3. Jim White, NC0JW, retired KCBS rf broadcast engineer, private conversation 10 July 2014.
4. "TV Propagation", Jim Andrews, KH6HTV Video Application Note, AN-33a, Oct. 2016.
Note: Revision "A", Jan. 2021 -- only change made was lowering the bit rates in table 1, page 1 to
agree with Hi-Des recommendation they be no higher than 80% of max.
Revision "B", Nov. 2021 -- added comments about HDMI-HDCP.
Revision C, Jan. 2023 -- added info about HV-320E, corrected table I for weak signal FEC from 1/2 to
3/4
============================================================
FEEB-BACK:
Digital Parameters: Thanks for sharing your test results with the Hi-Des gear. I may do some more
“tweaking” of our parameters based on your results. As some one said, “What a difference a dB can
make.” 73/Happy Thanksgiving, Mel, K0PFX, St. Louis, MO
Nostalgia: Another excellent newsletter Jim! I especially enjoyed your reminisces about the early
days of fiber optic communications. I think that was about the time I was pushing modulation format
up to 90 state QPR and stuffing 45 Mb/s (T3) data into a 10 MHz FCC allocation at 6 GHz. It was sure
frustrating back then but thinking back now it was also a lot of fun.
Aloha, Alan AD6E / KH6TU, Maui, Hawaii
Laser Comms: Jim, I really love this newsletter. Did I ever mention that I've also been working with
LASER Diode transmitter/receivers there in Panama City, Florida ? I like that BATC and So Cal are
also doing it. One of the things I'd like to do now that I'm up and running on AREDN is to be able to
use LASER for short range field deployments for disaster sites and events. This would be the ticket for
our Mesh Chat, PBX systems, our mailbox servers "WINLINK" and for live streaming or video
TV Rptrs Rptr-148.doc ( 11/28/23, kh6htv) p. 16 of 16
cameras. I've been at it for right at 5 years and I get a good amount of pointers and assistance from
Mike Collis in LA. Didn't know if you mentioned my name, call sign and location would help to bring
more interest in this High Speed communications. Feel free to mention me in any article or news letter.
Hope your Thanksgiving was a great one.
73 de Wolfgang, KV4ATV, Panama City, Forida
==================
W0BTV Details: Inputs: 23 cm Primary (CCARC co-ordinated) + 70 cm secondary
all digital using European Broadcast TV standard, DVB-T 23cm, 1243 MHz/6 MHz BW
(primary), plus 70cm (secondary) on 441 MHz with 2 receivers of 6 & 2 MHz BW
Outputs: 70 cm Primary (CCARC co-ordinated), Channel 57 -- 423 MHz/6 MHz BW, DVB-T
Also, secondary analog, NTSC, FM-TV output on 5.905 GHz (24/7 microwave beacon).
Operational details in AN-51c Technical details in AN-53c. Available at:
https://kh6htv.com/application-notes/
W0BTV ATV Net: We hold a social ATV net on Thursday afternoon at 3 pm local
Mountain time (22:00 UTC). The net typically runs for 1 to 1 1/2 hours. A DVD ham travelogue is
usually played for about one hour before and 1/2 hour after the formal net. ATV nets are streamed live
using the British Amateur TV Club's server, via: https://batc.org.uk/live/ Select ab0my or n0ye. We
use the Boulder ARES (BCARES) 2 meter FM voice repeater for intercom. 146.760 MHz ( -600 kHz,
100 Hz PL tone required to access).
Newsletter Details: This is a free newsletter distributed electronically via e-mail to
ATV hams. The distribution list has now grown to over 500+. News and articles from other ATV
groups are welcomed. Permission is granted to re-distribute it and also to re-print articles, as long as
you acknowledge the source. All past issues are archived at: https://kh6htv.com/newsletter/
ATV HAM ADS -- Free advertising space is offered
here to ATV hams, ham clubs or ARES groups. List here amateur
radio & TV gear For Sale - or - Want to Buy

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