There are many public service applications or for ATV demos where a simple portable ATV transmitter can come in handy. This app note describes putting a small 50-100 mW 4 channel Videolynx Z70A transmitter in a Husky 4" belt pouch with a 9V battery pack that makes it easy to grab and go much like you would for voice with an HT. You can use it to make a hat cam so others can see what you see at emergency operations where the on site commanders must remain in an emergency operations vehicle but would love to see what others are seeing. This is especially true when decisions must be made quickly and cannot wait for a voice description or interpretation - if you also carry a 2 meter HT you can have full duplex audio like a telephone. The ATV Pouch is great for transmitting to the EmComm vehicle or to a portable repeater back to an emergency operations center.

At public service events like races and parades, video of approaching runners, bikes or floats a quarter to a half mile away from the finish, aid station or critical traffic corner can be of great help as an early warning to anticipate traffic volume, physical conditions and other factors.

Snow free line of sight DX is over a 1 mile using the Videolynx Z70A transmitter connected to a small Olde Antenna Lab 5L-70cm beam and received on a 8 dBd omni or 5 element beam connected to a TV on cable channel 58, 59 or 60. Both the Videolynx ATV transmitter and mini color camera are powered by a 9V alkaline battery pack with 7 AA cells in series giving about 2 hrs of continuous operation. If you don't want sound or need to use one of the 3 other frequencies, you could use the Videolynx 434 transmitter module instead and operate continuously for 8 hours.

I purchased a 4 inch Husky belt clip pouch Model # 65507-1N09 for about $6 at Home Depot. There are other pouches and tool belts one could use if you wanted to carry other items like an HT or spare batteries, etc., but this one I used to keep it small and light for fixed portable operation at public service events. This pouch comes with a bungee loop which can be used to hang it from its belt clip to the antenna mast for fixed portable work. The pouch has two inner pockets and the larger one makes a nice fit for the transmitter. The battery pack is placed in the outside front pocket which has a velcro fastened flap and makes it a little easier to get at the plugs hanging out the side for T/R. It also provides some insulation from connector bodies accidently shorting out the batteries. There are two outer side pockets, one of which can store a rubber duck antenna and the other to attach the camera with a small clothes pin for fixed portable applications. The Z70A transmitter, camera and cable are stuffed inside the zippered pouch for transport, but the antenna coax is separate. When in use, the pouch pocket is unzipped and the power, camera and antenna coax cables are run outside.

DC power to the camera and transmitter for portable can come from a 9V battery pack using 8 AA rechargeable NiMH batteries - Radio Shack 23-746 - as shown above in the system photo, or 7 alkaline AA batteries - Radio Shack 23-849. Only 7 AA alkaline batteries can be used in series in the battery pack to keep the voltage below the 11.0 Vdc maximum the transmitter can safely handle. I used a 1/4-20 1-3/4" round head screw and nut on the end to jumper the 8th battery slot as shown on right. The 8 NiMH AA size batteries gives about an hour of continuous transmit time and double that for the alkalines. The camera will drop out before the transmitter at around 8.4Vdc. The DC power wires from the Z70A transmitter are soldered to male size M (2.1x5.5mm) coaxial DC power plug - red wires are + and go to the center solder lug, and the 9V battery clip wires to a female DC plug. A DC cable harness is made up with two female and one male coaxial DC power plugs. A ready made 1 ft long DC power splitter is also available - MCM 24-5355. In areas where AC is available a 9V1000MARS regulated wall plug power supply can be used. Another alternative is a 7809 3 terminal regulator on a heat sink to drop the voltage from a car battery or other 12Vdc system or a DC/DC switching power adaptor - MCM 29-3340, requires changing to a 2.1x5.5mm plug. The total current draw varies from 250mA to 330mA depending on applied voltage.

To transmit, the 9V battery pack is plugged into the cable harness. You could put a spst toggle switch in series with the 9V battery red postive wire, but most ATV transmissions are long and you would need to insulate the switch and connections well so as to not accidently short out the battery on the coax connectors or antenna mast. So plugging and un-plugging the DC connector vs. adding a switch may be determined by your application and usage. in any case, make sure the battery pack DC plug is not connected when you snap on the 9V battery clip to the pack so as not to accidently reverse voltage to the transmitter and camera.

Parts list and sources:
Videolynx Z70A transmitter - P. C. Electronics $149
  or Videolynx 434 transmitter - P. C. Electronics $99
OAL 5L-70cm beam antenna - P. C. Electronics $85
  and/or Diamond RH519 whip antenna - favorite ham store
Mini color camera - ATV Research
15 ft CNT-240 coax N Male to BNC Male - Cable X-Perts

Adapter, BNC/Phono - Radio Shack 274-254 or P.C. Elect.
3 Coaxial DC Power Plug(F) size M - Radio Shack 274-1569
2 Coaxial DC Power Plug(M) size M - Radio Shack 274-1577
9V battery clip - Radio Shack 270-324
8 AA battery holder - Radio Shack 270-387
9Vdc 1A AC adaptor - P.C. Electronics 9V1000MARS $15

For home station ATV, mobile or other applications you can use the ATV pouch to drive the Downeast Microwave 7025PA amp or package your own 25W amp using a RA30H4047M power module and our PA5 board. The ATV DX Variables application note will explain how to make the distance you want and the ATV DX Chart will give you the expected line of sight distances for various transmitted power and antenna gains with examples.

ATV in general is very useful for medical and search and rescue volunteers at trail races to remotely evaluate runners at distant aid stations with limited accessability. See the web page describing ATV at the Angeles Crest 100 Mile Trail Race.

P5 video was received at the Mt. Disappointment trail 33 mile run Shortcut Saddle aid station from a 434 ATV transmitter in a hat cam 4/10 of a mile away. This section of the course is a full sun exposed tough climb out of a valley run in mid August and the video can show the condition and number of the runners well before they arrive. The 50 milliwatt 434 MHz signal was received on cable channel 59 using an Insignia 7" battery portable TV and small 70cm beam at the aid station to test the path. A 19 to 26 inch LCD flat screen TV is good for fixed portable operations if AC is available from mains or battery and inverter. In day time, the TV should be placed in the shade, like under a push-up canopy, and screen facing away from the sun for best viewing. Be familiar with how to adjust the brightness and contrast controls on the TV. 2 or 3 five foot antenna mast sections can be lashed to one of the canopy legs or use an adjustable speaker stand for the antenna as is done with the ATV pouch system at the transmit end. The antennas need to be a few feet above head, car or any obstacle heigth to minimize multipath ghosts and drop outs, and stay line of sight.

S-meter Cam - The ATV pouch is a handy tool for aligning a fixed beam antenna toward a repeater or link on the tower. Aim the camera at the S-meter in the repeater receiver then climb up the tower and move the antenna back and forth looking for a peak on a portable TV. For an ATV repeater and you don't have an S-meter, aim the camera at the TV screen in the shack and adjust for minimum snow in the portable TV picture. This application qualifies as one of the few legal one way transmissions under FCC Rule 47 CFR 97.111(b)(1) - Brief transmissions necessary to make adjustments to the station. Most legal transmissions must be directed to at least one other ham. You still have to ID with your call every 10 minutes and at the end of the transmission, and with ATV, you can do that by speaking into the mic if running a sound subcarrier with the Z70A transmitter and/or something in plain view in the picture with your call if running the 434 transmitter.

(c)12-2012 W6ORG

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