TV DXing from the transmitting side of the hobby

[Capt. Radio]

While this post is not about the reception and logging of commercial TV stations from a distance, it is about the transmitting and reception of UHF analog signals over a good distance considering the power levels used.

I hope some of the forum members that are interested in TV dxing might like to read about this activity from another perspective... the transmitting side.

I participated in the transmission and reception of UHF analog TV signals (439.25Mhz) over fairly long distances to other similarly equipped stations, here in the midwest, back in the '80's. Back then, most stations were equipped with tube-type transmitters. Solid-state had just begun to be available, but it was expensive and fairly low powered. Cameras were mostly B&W, color was used but was sure a lot more expensive.

Summertime was best for the long distance shots... sending our comparatively weak signals across state lines for several hundreds of miles. Summertime brought the temperature inversions we used to skip our signals to far away receivers. We patiently waited for the hot summer days to cool off towards nightfall... hopefully without winds that would ruin the forming of the inversion layers.

To make up for power levels far less than commercial TV stations used, we made very directional, high gain yagis and placed them as high in the air as possible. We fed the antennas with very low loss runs of heliax. We tried to squeeze as much power as we could from our tube amplifiers to go the distance.

On the receive side, most of us used very low noise "gaasfet" preamps before the TV monitor to extract the most signal we could get from the station at the other end.

We co-ordinated our activities between each other using 2 meter FM, because we could always be heard at a distance at a stronger level than the TV signal we were sending at UHF.

When conditions were good, we were able to send live (fast scan) TV over several states to other operators here in the midwest region. It was a lot of fun getting to see the person you were talking to live on your own TV set!

From my location in Indiana, conditions permitting, I had my signals viewed from and received:

downstate Indiana, Illinois, Iowa, Wisconsin, Michigan, Ohio, and St. Louis Missouri.
 
That's "quite a haul" for a transmitted signal... roughly 50 watts of wide bandwidth UHF!

I kept a record of all that activity back then by taking a screen shot of every station that appeared on my TV. I still have those pictures in a photo album. Many of those ops have (sadly) passed away.

I'm glad I had participated in that group back then. Some of the "mentors" that got me started were "old-timers" that pioneered the mode (ATV) from "day one". They built all of their own equipment from scratch... even down to the machining of amplifier hardware. Of course, most of them were either electronics engineers or military radio operators. I was fortunate to know them.

Well, times have changed with the digital age of TV. Just like every other phase of the wireless hobby.

Still... best dx to you!

[atrainradio]

I'd love to do that!! Isn't that called ATV? (Amature Television)

[Capt. Radio]

Yes, it is atrain.

Our group was a very small minority as far as numbers of hams participating. Most ham activity was, and still is, HF orientated. A few hams used the UHF bands back then, but only for FM repeaters.

I wonder what the ATV activity "looks like" today in 2013. I would bet that basically the same percentage of hams are doing ATV now as then.     

[redhat]

If there is one good thing the conversion to digital TV has done for the ATV community, its flooded the surplus market with translators and analog video gear.  I picked up a UHF 1KW tube type translator by TTC for about 200 bucks, complete with a few tubes.  I had to modify it to accept a cable modulator for drive, but otherwise is fully functional.  Audio and video processing gear can also be had quite inexpensively.  I've also got some PA modules from VHF transmitters kicking around, but those are more for local "tom foolery" than anything else.  I thought it might be fun to run movies late at night, but with memory scan tuners, those days are probably gone forever.

+-RH

[Capt. Radio]

Redhat,

Since I left the ATV scene many years ago, I have no idea what the "state of the art" is now, it's current level of activity, or how well its supported (if at all) by the commercial ham outlets. Back then, there wasn't much in the way of commercial products available. Mostly it was homebrew and you found an "elmer" on the air (2 meters) to help you make a workable station.

I can see what you are saying about the digital age helping out with making lots of analog equipment available. That 1KW translator sounds like an excellent buy. I guess if one is technically savvy enough, one could put a very nice station together rather inexpensively nowdays if you knew where to look for the equipment.

You mentioned running movies... one time I hooked up an Atari 5200's video to my transmitter and sent a few games of "pac-man" over the air.    (That shows you how long ago it was that I was on ATV).

-------------------

Atrain,

I think the most memorable time I had in ATV (besides working the DX), was with a co-worker who wasn't a ham or radio enthusiast at all. He lived about 5 miles from me, so one day I told him to turn on his regular home TV set at a certain time in the evening after work and that I would give him a call on the telephone. That evening, I called him on the phone... he had his TV on. Since he had a small tower for his TV antenna, and a rotor, I told him to rotate the antenna towards my town.

I told him to rotate the TV tuner on the set as far as it would go (the tuners were mechanical and manually operated back then). He said that the picture was just "snow". As I was speaking to him on the phone, I turned the transmitter on, the snow went away, and there I was on his TV set, sitting in a chair, looking at him holding the phone's reciever to my ear with the transmiting gear alongside the chair !

It was great hearing his "Wow" over the phone. I wish I could have seen the look on his face!

Yes, many TV's were able to just catch our ATV freq. if you "maxed out" the tuner and had a decent UHF antenna that could be rotated towards the transmitter.

What fun that was!

[redhat]

I believe most "cable ready" TV's these days will pick up a few of the ATV channels.  I had an onboard on a race bike one upon a time and used a VCR to pick the video up off air and record it.  At those speeds, multipath was a bit of a problem.  I think ATV will be around for a while, as long as the FCC doesn't auction off more of the 70CM band.

+-RH

[Capt. Radio]

I do believe that our freq of 439.25mhz is exactly on one of the cable channels, now that you mention it. The only problem is the TV is looking for a digital video signal instead of analog.

That's cool how you had a transmitter on a race bike! I can see that multi-path would enter into the "picture" (pun intended) and cause some problems though.

About the FCC...

You know, I always thought that things revolved around the "public" being the owner of the RF spectrum. So how is it that the Fed can sell it off to corporations, pocket the money, and leave us the poorer for it?

Inquiring minds wish to know...  

[redhat]

Last I checked, all off the shelf TV's still have analog tuners in them as well.  A LOT of small cable systems all over the country are still analog.  In addition, there are still a few analog broadcasters out there.  There is no current "analog sunset" for low power stations.

+-RH

[ChrisSmolinski]

There was (maybe is, not sure if it is around anymore or not) an ATV repeater in Baltimore. I recall trying several times in the past to pick up ATV transmissions, but never was able to. It's possible that I picked the wrong random times to see if there was any activity.

[Capt. Radio]

I'll have to check my TV for the analog tuner! If nearly all have analog, that's a "plus".

Chris, yes, you may have just looked when there was no activity. I'd bet activity is still real sparse. I would assume, like everything else radio related, weekends and/or weekend evenings would probably bring the best chances of seeing something.

Back then, Indianapolis Indiana had a rptr, but I never saw anything from it.

[n2avh]

I remember that in the 1970s/80s a lot of ATV stuff came from a single supplier, that was called ATV (something) and had a small advertisement in QST every month.

[uhf35]

Well... mine is a little different story, but not too much.

From 1987 to around 1994 I was a "gatekeeper" for the TV rebroadcast station in the city where I lived at the time. In a province in the interior of Argentina. With resources and property from the local council, we operated three signals placed on channels VHF 11, UHF 29 and UHF 35 respectively PAL-NC (German PAL mode but with NTSC line ratio, due to the need to provide compatibility -at the time of the arrival of color -, with the previous 525-line technology of monochrome televisions imported from the USA and our 50 electric cycles)
All with tree national "Ditel" transmitters of 500 watts each, in video, and a lower power ratio for the FM channel of the audio carrier.

In the first case, the station linked by air from the "previous" retransmitter in channell VHF 9, about 55 km away, suffered from continuous fading and saturation events in the summer "tropo" periods. I remember that the transmitter was prepared to turn off one minute after the start of the overload episode, which always caused a period of negative image and synchronization interruption that was quite undesirable to be transmitted.

On the other hand, the case of the two UHF stations was noticeably more stable.

Channel 29 was operated with satellite downlink and generally had no problems.
Channel 35 lasted for a while, remaining on "delayed program" (yes, even well into the '80s.) For years they sent me by bus an S-VHS cassette -recorded at the slowest possible speed with the "yesterday program without news segments."  -, which I plays when I arrived to do my daily revision of the station, after leaving high school, around 7 pm. And it auto power off when tape ends and video carrier dissapear. During the last three years of attendance, they put on a satellite disc also for this station.

The VHF channel antennas were simple bidirectional crossed yagis (without a reflector) were at the top on about 48 meters of mast, while the UHF panels (without plastic cover, it didn't snow there or anything like that), a little further down.

I remember that the VHF performance was better towards the surrounding towns up to about 40 kilometers with fairly low receiving antennas, but much more unstable due to the multiple interferences and atmospheric abnormalities of the band, while UHF had less performance (needing directional corner reflect antennas placed at greater height, but with a much more stable and "clean" signal. There were also many fewer complementary services and signal-based appliances generating spurious radioelectric radiation in urban plants.

Around 1995, when I started university in this other city, I passed the work to friend. Today the station is fully automatic with hardly any periodic inspection, but with many more errors and outages.

[criker]

is this still a thing? i would love to catch these

[shadypyro]

is this still a thing? i would love to catch these

All of the tv stations are digital now.

[RobRich]

There are UHF analog TV transmitters popping up on AliExpress and similar.

https://www.aliexpress.us/w/wholesale-TZT-Analog-TV-Transmitter.html
https://www.aliexpress.us/w/wholesale-UHF-200mW-Video-Wireless-Transmitter-UHF.html

Various listings suggest 200mW output, which is YMMV for Part 15 compliance assuming that is a concern.

Some professional wireless microphones and 'low power auxiliary' stations (including those labeled as "UHF") are licensed under Part 74, Subpart H of the FCC's rules. However, as of January 2010, many professional wireless microphones, and other Part 74 certified 'low power auxiliary' stations with a 50 mW output or less, can be operated in the "core TV band" (TV channels VHF 2-13 and UHF 14-51, except 37) frequencies without a license under a waiver of Part 15 rules. This waiver is expected to become permanent.

Source: https://en.wikipedia.org/wiki/Title_47_CFR_Part_15

Not much power as these are close-range devices, but FWIW, high-gain UHF yagis and similar tend to be rather compact. Another YMMV.