NC output

(HtrmiHu con

NC output


(RSi? 270-224 or 270-232) {See Photo C J Connect a Hamtronics preamp between the TV set's antenna jack and the DPDT antenna switch on the top of the box next to ihe BNC antenna jack. Jusl above the TV receiver mount the smalt B/W TV camera with ils case removed Thss particular model was the Mitchell Industries Micro-Video camera (The GBC CCO-lOO is a similar sized camera and could be usee as welt.) Mount a P C Electronics KPA-5 transmitter to the back of the project box

Figure 1 Ten minute timer schematic, just above the 1.2 Ah gel celt battery,

The DPDT switch on the top of the box is used to switch the antenna jack from transmit to receive, as well as to supply power to turn the ATV transmitter on and off. OptionaJ switches can be mounled for external audio or video inputs as well. Button i* up and you should be ready for some real portable ATV action.

Waging around Phoenix with the "Lookte/" Earl can watch the local ATV repeater with a P3 or better picture from over 20 mites away He has taken

11 up on several Nights on board a research jet for some realty wild OX. His most recent flight took him from Arizona to Italy on a Cessna Citation jet at 42,000 feet, During ihis flight he used the "Lookie Talkie" to make aeronautical ATV contacts in Arizona, Minnesota and Great Britain!

Now that the video HT is a reality, who be the first with a Dick Tracy style ATV wristwatch?

Phoenix ATV

The AAA5 of Phoenix (Arizona Amateurs on A5) have quite an active group. Their local ATV repeater (KS8J/ r) is about 2100 feet above the city on top of Shaw Butte, (See Photo D.) Shaw Butte is centrally located and provides coverage over a wide area Of greater Phoenix. P5 quality reception has been consistently seen over 40 miles away. The repeater is vertically polarized with an input on 434 MHz

(923.25 MHz alternate receive) Ouiput is on 421.25 MHz Most stations in the area need only 1 watt to access the repeater, so amplifiers are used only for distant simplex contacts or for mobile use. if you are in the Phoenix area, look for their weekly ATV net every Wednesday night at 7:30 p.m. The 2 meter talk frequency is via the 145.17 repeater (-600) or 145.17 MHz simplex, They can also be found on the 147.28 ( + 600) repeater during net nights as weiL No need to wait for the net, however, since there is tons of activity most any night!

Ten Minute ID Timer

This little circuit (Figure 1J solves the problem of identifying your ATV system every 10 minutes. You can use it to automatically switch in another source of video via the onboard relay (computer or identifier}, or use it to switch 12 volt power to another relay or device. There are spaces for two different kinds of relays on the board (onty one relay is necessary}. \ prefer the Arom^ relay since it draws less current. This circuit will drive both relays, however, if you'd Nke to control more than one device (see Figures 2 & 3}, The 555 (use the standard 555, not the CMOS version) timer charge and discharge paths are Independently controllable via the 1 MEG control pots. I usually set it up to ID for 5 seconds every 10 minutes, I've used this same circuit in my Jive camera balloon flights to kick in the video ID board for 30 seconds every two or three minutes (using a 22 or 33 nF capacitor lor C3). It's been a reliable performer and fits in a small space. You should use a high quality tantaJum or low leakage electrolytic for the timing capacitor To set up the on/ Off ratio initially, use a capacitor that is 10 times less than your final vatue That way you can make your adjustments without having to wait a full 10 minutes! Then just replace the small capacitor with Ihe final value If you can t achieve the desired delay interval wtih the adjustment pot R6r try varying the values of C3 and R4. f¥\

Figure 2. Timer PC foil pattern.

s'ET B3M3T

Figure 3 Trme r parts place men t. 78 73 Amateur Radio Today * February, 1991

s'ET B3M3T

Figure 3 Trme r parts place men t. 78 73 Amateur Radio Today * February, 1991

Parts List (Ten Minute Timer)


1K ohm V4 watt resistor

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