Receiving ATV
Connect your TV to an outside 70cm antenna with the same polarity as used by your areas ATVers. It does not get any cheaper than this to check out the ATV action. The 75/50 Ohm miss match is negligible and we stock a F to N connector adaptor. Set your digital or old analog TV tuner to cable channel 57, 58, 59 or 60 depending on what frequency is used in your area - cable channels are on different frequencies than the old analog over the air broadcast channels. Cable channel 60 is 439.25 MHz and each channel is spaced by 6 MHz. The TV tuner should lock on, even if off a MHz. Have a local ATVer transmit a picture to you while you talk back on two meters - usually 144.34 or 146.43 simplex. You will hear them on the sound subcarrier coming out of your TV speaker. Antennas are the key, so good coax and mounted as high as possible to get line of sight will work best. You can build an antenna or buy one like in the antenna section below.

Front view with ATV channel knob,
power on toggle switch and LED.
Built in a rugged Hammond 1590C diecast aluminum enclosure - 3.7 x 4.7 x 2.2 in.

Rear view with N antenna jack, F output jack
to TV and DC power jack.

Channel 3 receiver with A/V outputs

Want to check out ATV in your area but don't have a cable ready TV (cable ch 57-60) or need to be right on frequency and with more sensitivity? Then this downconverter is for you. The TVC-4S downconverts the 5 standard USA ATV frequencies - 421.25, 426.25, 427.25, 434.0 and 439.25 MHz - in the 420 to 450 MHz ham band down to your TV receiver on ch 3 or 4 - what goes in at 70cm, comes out on the TV channel. The frequency is locked to a crystal referenced synthesizer for accuracy and no temperature drift. 70cm Analog ATV will be around for a long time due to the high cost and complexity of transmitting Digital ATV and the fact that new TV's must also have analog cable tuners in them per FCC Rule 15.118(b). However, this downconverter will work for both analog or digital ATV - which ever mode goes in, comes out at the downconverted channel.

The rear of the downconverter has a N connector 50 Ohm antenna input and 75 Ohm F to the TV set. A DC power jack is used with the supplied 12Vdc wallplug power supply, or you can make a cable for portable battery or mobile operation. We stock a variety of 70cm antennas - download our catalogue page 3 on this downconverter, antennas and ch 3 receiver. The frequency is selected by a rotary switch tuning knob on the front.

This ready to go downconverter contains the sensitive TVCX-4S board with a low noise HJ-FET (less than .4 dB noise figure device) preamp and GaAsfet mixer stage in a die cast aluminum box with 120vac to 12Vdc wall plug power supply. You can run it on external +11 to 14 Vdc at 120 ma by your own DC power cable with a 2.1 x 5.5 DC power plug - Radio Shack 274-1569 - to connect to a battery or other supply. We also have the TVC-9S 33cm band downconverter for $159 and TVC-12S 23cm band version for $159.

Downconverters by definition, change one frequency down to another frequency. What ever signal or no signal goes in at that one frequency, comes out at the lower frequency. There is no signal processing or detection done or remodulation on to a carrier. Your TV is the receiver which does all the signal processing and detection. Our downconverters provide a lower noise figure preamp stage and mixer than can be found in a TV tuner which results in greater DX and less snow in weaker signals.

If you want video and line audio (A/V) outputs to drive a monitor, computer, camcorder, etc., that have this kind of input, add the Rch3 channel 3 receiver...$89. Infact, if you want both types of output, you can put a splitter - Radio Shack 15-1234 or 15-1235 - on the 70 or 33cm downconverter output and drive a TV or TV's as well as a monitor through the Rch3. The Rch3 receiver has a F jack ch 3 input, RCA jack A/V outputs and comes with wallplug AC power supply. Download the Rch3 app note to add squelch, S-meter or external 12Vdc power for portable or mobile applications.

It is best to select a TV that does not go to blue screen or automatic shut off when there is a snowy picture or no signal present. You dont want the TV to shut off while monitoring a local ATV repeater, searching for DX or aligning your beam. Some TV's require reprogramming the active channel memory so that you can use the open channel 3 or 4 in your area. The best way to do this is to connect the TV to your Cable TV service, then push the channel program button in the CATV mode. This should set the TV up to select most all VHF channels (catv and over the air channels 2-13 are the same frequency) even when no signal is present as is the case when connected to the downconverter and no one is on the air at that instant. New TV's will contain an analog NTSC cable channel tuner in addition to digital channels per FCC Rule 15.118(b) to accomodate all cable TV systems, but it is a good idea to keep your old analog only TV's for ATV work rather than trash them when you buy a new digital TV.

A net can greatly benefit getting ATVers by video to show and tell rather than trying to describe something by voice only - "Pictures are worth a thousand words." With ATV you can have full duplex audio - while one transmits and talks on the ATV sound subcarrier, everyone else can watch and listen on their cable ready TV set (cable ch 58, 59, 60) or TV with our downconverter, and at the same time talk back on a two meter FM voice frequency (better interaction and eliminates the long winded). How about setting ATV up at your ham club and transmitting the meeting live or by tape later to those members who cannot attend. The possibilities are endless - see our ATV application notes web pages.

Transmitting ATV
Very few multimode UHF transmitters and transceivers support the broad band ATV mode. Most all ATVers use transmitters specifically made for video. Sending video is easy by plugging in your camcorder, video camera, digital camera, VCR, or any device with Video outputs that can output on an A/V cable and be normally seen in a video mointor, VCR or TV sets A/V inputs. Most camera mic's are amplified and output line audio which can be plugged into the ATV transmitters line audio input. Any Technician class licensed Radio Amateur can transmit live action black and white or color video along with audio in the 70cm and above bands to other hams simplex or through ATV repeaters.

This transmitter comes ready to plug in your 70cm antenna, 12-14 Vdc @ 2A, video camera with or without line audio or optional separate dynamic mic and get on the air right away. The unit contains antenna and DC power T/R relays to turn your TV or downconverter off while in transmit - connecting cables included. The transmitter uses the adjustable 0-5W pep 4 channel 70cm Videolynx VM-70X ATV Transmitter module. The channel selector shows 5 channels, however, channel one is not used in the transmitter but corresponds to the same numbered channels as the TVC-4s downconverter - Ch 2= 426.25, 3=427.25, 4=434.0, 5=439.25 MHz. Sound subcarrier has automatic gain control limiter. Manual

As an alternative, you can build your own transmitter from the modules. Download and see our application note which contains a parts list and sources (about $360), Hammond 1590D die cast aluminum chassis drill template, wiring schematic and more information. Basically you will be drilling the enclosure, mounting the modules, connectors, switches, etd., and doing the interconnect wiring. We stock all the Videolynx 70cm ATV transmitter modules: the 50mW 434, 50mW 4 ch w/audio Z70A for hat cams, R/C, and demo applications for up to a half mile line of sight, and the 0-5W VM-70X as shown in the photo on the left for home stations, portable at public service events, balloons and rockets. You can even operate the VM-70X as it comes out of the box at 1/2 Watt out by soldering RCA jack to pig tail A/V cables and 11 to 13.8 Vdc power wires to the solder pads. The RF out SMA jack goes to the antenna - we have SMA to N jack adaptor. Download our VM-70X Quick Start page. If you want to adjust up the power, the module will need to be connected to a heat sink or fan as shown in this application note download.

More Power - If you start out with the 50-100 mW 434 or Z70A transmitter module, for higher power you can add a Downeast Microwave 7025PA linear amplifier for over 20W, or build your own using one of our PA5 boards and a RA30H4047M module from RF Parts. The TX70-5s/VM-70X can be adjusted down to drive the Mirage amplfiers - D26N, D1010 or D100 ATV versions - to over 50 Watts within their linear range. Downeast Microwave linear amplifiers can also be added to our TX33-.1s 33cm and TX23-.1s 23cm band transmitters.

Over the years we have gone back and forth between having available a transceiver or a transmitter that would pair up with a downconverter. The demand has always been about 50-50. So now we will go back to Transmitter plus downconverter. The advantage of using a separate downconverter is that you dont have to get a downconverter to use at the receive end of a public service event as you might if you only owned a transceiver. Also some areas may only operate through a crossband repeater and very little simplex. Separate units also offer a lower entry cost to 70cm ATV since a cable ready TV can be used initially to receive.

You might still be able to obtain one of our TC series 1, 10 or 20 Watt Transceivers on eBay, QRZ.com On Line Swapmeet or other used ham gear internet web sites. If you do, and it does not come with a manual, email us requesting one giving model number and any revision letter or date etched on the exciter board inside - always include your call letters when emailing us. If you need trouble shooting advice, contact us with your questions. Any of the older transmitters or transceivers may be repaired by us - assuming we have the parts - for $80 plus parts cost. See our repair policy.

70cm Antennas
DX running 4 Watts with a TX70-5s transmitter, 100 ft Belden 9913 or Times LMR400 coax can be snow free up to 60 miles if line of sight using the Directive Systems DSFO-25ATV antennas at both ends. They are one of the best designed (specifications) high gain and broadband beams for ATV. With this antenna, 4 Watts is plenty for most all line of sight applications. The hard part, however, is getting line of sight between the two antennas given the curvature of the earth, trees, buildings, etc. Non-line of sight cannot easily be predicted, but how strong a signal is on 2 meter simplex is a good indication that you might have a path - See ATV DX and ATV DX Records. For temperature inversion tropo skip usually in early summer, you can often get over the horizon snow free DX of 60 miles and even further with an added amp, or some snow in the video decreasing one P unit for each doubling of distance.

Good antennas up high as possible and line of sight are the most important part of any ATV system for best DX.

Directive Systems DSFO-25ATV 16 dBd gain broadband Yagi antenna on a 17 foot boom. Designed for the serious ATV DXer......$229

The Olde Antenna Lab 5 element 5L-70cm - 8 dBd on a 31 inch boom. End mounted horizontal or vertical...$85.

OAL 7CP-70cm, 7 element circular polarized beam can be hand held for manually tracking balloons, rockets, R/C aircraft, ham satellites, or mounted to a mast...$160.

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