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Getting Started On ATV
How Do I Get Started On ATV?
The first thing you will want to do is build a suitable receiving station. This can be done quite cheaply, depending on what quality
images you want to be able to view. About the cheapest receiving setup you can come across is the use of a cable ready TV or
convertor box tuned to channels 58-60 (depending on the signal frequency), attached to an outside antenna. This is not the best
setup, however, since it is designed to handle cable level inputs, it suffers from some S/N and sensitivity problems, making the
usable range somewhat small. The use of a directional antenna for 420 Mhz will help somewhat, but this setup will probably only
pickup the stronger local stations. The classic DX station setup would use a downconverter in front of the TV or cable box, which
would be tuned to channel 3 or 4. This setup usually adds a pre-amplifier upmast (at the antenna) to increase the system's S/N
ratio. To maximize the station S/N ratio, the downconvertor should be located upmast as well, with the preamplifier. Power for
the downconvertor and Preamp is usually DC, supplied through a seperate shielded cable.
What kind of Antenna do I need to work ATV
First! Find out what polarization the local guys are using. Here in south Okaloosa county we are currently using VERTICAL
polarization because we are scattered around and vertical is the easiest omni-directional antenna to find. Eventually we will
switch to horizontal polarization, when enough people are online to make it worth while. Use the wrong polarization and you
will suffer an additional 20 dB loss in your setup (this would be a very bad thing). Directional antennas are best, with yagis
and corner reflectors leading the pack. There are plans floating around to make various forms of the coner reflector or even
Alford slots. A UHF TV yagi might work in the local area (mounted vertically of course) but since the UHF band is just above
the 440 band, the effeciency of this antenna would probably be low. Once you have your antenna installed, don't comprimise
the installation by using cheap coax. Use the BEST, lowest loss cable you can afford between the masthead installation and
the station receiver. I cannot begin to enumerate the troubles you will experience with using RG-8X or RG-58 at these
frequencies! Belden 9913 or similar style, low loss, 1/2" cables should suffice.
Where do I find ATV gear?
There are several manufacturers of downcovertor/preamplifier assemblies currently in business. PC Electronics, in Pasadena
CA, has manufactured ATV transcievers, downconvertors and transmitters for many years. I have used both their
downconvertors and transceivers and found them workable units. Be aware that the PC electronics series of transcievers
don't put the downconvertor upmast, so these units, while quite functional, are not well suited to DX work. Ham fests and
tailgaters are also good places to pick up used units. A list of manufacturers of ATV gear appears at the end of this report.
How do I send out an ATV signal!
Well abviously you need an ATV transmitter. Again, as with receivers, there are several manufacturers of transmitters
available. The same rules apply here, as with receivers, use the best quality coax cable you can afford between transmitter
and antenna (I can't stress this point enough). If you have a mast mounted preamp/downconvertor assembly, you will need
a transfer relay to pass the signal around the receive portion of the setup during transmit. Users of the PC Electronics
transceivers will not have this problem as the preamp/downconvertor and exciter are all in one unit.
How much power do I need?
As much as you can afford! Using a power amplifier with your ATV exciter is a good idea, but remember that sync levels will
need to be adjusted to maintain linearity in the signal (most ATV exciters include a sync stretcher which is used for this purpose).
You will probably need to do on the air checks with another station to get the levels set right. 100 Watts is about the limit of
commercially available 440 amplifiers, make sure the one you buy has an SSB position on the switch. A Class C ampilifier is NOT
acceptable for use.
Do I need a TV camera to transmit on ATV?
NO NO and more NO! You can use any NTSC video source, such as a VCR. PC's with NTSC outputs are very common these days,
as many of the newer 3D video cards now include video out to play games on the big screen in your den. I will write another
column on this subject next time!
Well I guess that about does it for now. For those of you with internet access, you can subscribe to several ATV mailing lists.
The closest is in Tallahassee, see the lists at the end. There is also the HATS (Houston Area Television Society) mailing list,
as well. Here in the local area, I have given the unofficial name ECATS (Emerald Coast Amateur Television Society) to the
few of us hangin' out. We don't have scheduled meetings, although if I get enough email response, we can start a net or
ATV Resources List
|PC Electronics||2522 Paxson Lane||Arcadia CA,91007||(818) 447-4565|
|CCI||508 Millstone DR.||Xenia OH,45385||(513) 826-8600|
- ATV Quarterly - was published by ????. Look for back issues, good source for goodies.
- Spec-Com - Published by WB0QCD, now defunct (I think), but look for back issues at ham fests.
- Amateur Television Workbook, First Edition - Published by the Spec-Com group.
There are a couple of good mailing lists to belong to. Try subscribing to either the HATS
list (out of the Houston area) or the Tallahassee list.
|List||List name||Mail reflector Hostname||Additional info|
|Houston Area||HATSemail@example.com||yourname yourcall|
|Phoenix AZAATVfirstname.lastname@example.org|| |
Subscription instructions: To subscribe to a mailing list above, send an email message to the mail reflector host with the first
line of the body : subscribe
Note: If you would like your club listed here, please send me email: email@example.com
TNX, 73 and SEE YOU ON THE RADIO! DE KB4OID, Steve>
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