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! Num~ 21 on your FHdback eard ABOVE AND BEYOND C.L. Houghton WB61GP San Diego Microwave Group 6345 Badger Lake San Diego CA 92119 10GHzARRL Contest Preparations In April, I covered the construction of a tripod and microwave dish antenna for use on 10 GHz. This month I would like to continue with local involvement and where to get equipmenttooperate on the microwave bands. The prime goal is to prepare for the 10 GHz ARAl contest later this summer. This month.ret's cover some of the things that you can do in your own area to enhance operation on microwave . At first I thought San Diego was dormant until N61ZW and I started to talk abOut cceraucne on the l0 cal repeater and at swap meets. This resulted in quite a few fellow amateurs forming a common interest forum, the San Diego Microwave Group. Through discussions, we began forming a common bond , which has grown and spread quite widely. Participation in a local group stimulales interest and helps us sort out data from other parts of the country. This as· sists us in experimenting. As to equipment, you have bastcally two choices : bUy the very fine MIA COM Gunnptexer, or obtain surplus microwave equipment at swap meets or even possibly for free. SCrounging for Equipment By scrounging, you can get QRV on the 10 GHz microwave band for next to nothing, The quality is not as good as the MIA COM nunnpiexers. but it will work well. Go to your local burglar alarm and electric door companies and try to obtain some of the otder mi crowave control units they no longer use, since they're switch· ing to I.R optical units , Pat AA6EG wrote to me questioning the use of a peculiar type of alarm unit and detector diode current. see Figure 1 fOf details. You can check the detector for in- jection with a meter (0 to 1 rnA) in series with the detector diode and ground. With the transmit source on, you should observe a DC current flowing in the detector. About VHF and UHF Operation the frequency of the transmi t source to the ham band, usually about 10.250 GHz, by lowering the frequency adjust screw further into the cavity about 1 to 2 turns. The microwave unit is set in the factory to around 10,525 GHz. The only limiting factors with surplus devices are the system sensitivity and any gains associated with detector noise and antenna types. Rememberthe SOLFAN types were intended to be short range devices, but they work very well for the small cost of obtain ing them. Transmitter output power is a consideration , but you may be surprised with what you can do with 10 mW. Usually, with modest transceivers and small horns, 25 miles is the limit. With larger dish antennas, 200-mile contacts are possible. By the way, I still have a quantity of 50 to 100 mW 10 GHz Gunn devices availabte lor $5 each postpaid. Success Stories Sieve KA0ZIl from Plymouth, Minnesota, writes: " I had some time off from work, so I called some local automatic door companies. I picked two out 01 the severallisted because they were local companies. I struck paydirt with both calls. At one, the tech is going to clean up the shop next week and set aside all microwave units he would otherwise toss out. The other shop had two units for me! One was an old SOlFAN with a detector, and the other was a small black box, like the ones above the doors at the grocery store. The kicker is that they bolh work!" ,,,... ...fOC". - ,.... - I .~ . c ,. ."- _/ Steve KAIZll goes on to say that with two units, he WIll probably rope Rusty NIHVW, a good friend, into 10 GHz operation. Figure 2 is a sketch Steve provided of one of his units, This unit is very similar to the SO l FA N devices. Power to the Gunn diode is positive. With 5 volts positive on the Gunn, Steve was able to measure about 1 rnA on the detector diode. A little much, but still OK for a transceiver . Connecting the detector to a monitor receiver, Pat was able to detect his fing er movement in front of the cavity while monitoring on the receiver. For a Doppler radar device, connect your detector diode to a small audio amplifier. The low trequency sound you hear is the microwave Doppler signals returning, As a mailer of fact, the radar devices the police use are very similar. They have circuits that measure only the low frequency audio tone (Doppler) to indicate your speed. It's a direct corretalion. For a speed of about 35 miles per hour, the audio Doppler returned is about 1085 Hertz. This works out to about 31 Hertz per mile per hour. Se«ing the Frequency The biggest problem remaining is to set the frequency so that your coeraucn is within our amateur bands. I have received letters from seve ral amateurs without test equipment, who are trying to set the frequency. Without test equipment, it can be quite bothersome. I am willing to set up cavities sent to me in the mail (provided return postage is included) to the frequency desired, and I will provide a voltage vs. frequency spread calibration chart for the unit. Ron Wicker WA5VJS has take n me up on lhis offer and shipped me two SOl FAN units. I set both units on 10,250 GHz , " c " Figure t, so GHz dual cavity from AA6EG, Each cavIty couples to its own horn 0.5 to 0.7 rnA is optimum. Adjust antenna, Anlenna gain is 1G- 12 dB. 70 73 Amateur Radio • June, 1989 , with my HP counter. It remains to be seen just how much bouncing around the units will take for a change in frequency in the postal system. They were well-packed and shoutd survive. Postage cost less than I'd anticipated, at $2 for a one-pound package . The rates go up very quickly for a package over two pounds. The lnjector, described in the January 1989 issue of 73 Magazine, is an alternative to verifying lrequency. Take a detector mount and replace the normal detector (1N23 diode) with a surplus varactor and a 3 dB pad for DC return. Inject your 2 meter HT on low power (100 mW) in to the moont. The varaetor should produce energy radiating on 10 GHz. 146 MHz times the 70th harmonic - 10.220 GHz, a good marker. Experiment with surplus varactors for best results on output. It will be very low po wer, and close coupl ing i s needed, but it works well. So. cal. Microwave Weekend News There was quite a " urry of microwave activity on 10 GHz narrow band FM and SSB here in southern California over our most recent microwave weekend. The contacts were from a location in the L a k e Arrowhead , San Bernardino mountains at Heaps Peak. Phil W6HCC was operating his 10 GHz system with about 1 Watt of power output, and had a very noticeable signal. You could turn your antenna some 20 degrees away from the true path and still copy him at a distance 01 over 100 miles with no troubte. There were several other stations operating remote to Phil W6HCC at Heaps Peak. Chuck WA6EXV was operating In the desert to the east checking out locat ions. Kerry N6I ZW , Ed W60YJ, Art WA60YS, and l eon WA5BNH from the San Diego Microwave Group were operating on Mt. Soledad in San Diego proper, anchoring the southern end of the 100 mile test path. The signals from W6HCC's rig with 1 Watt output were so strong they were pinning the s-meter on the narrow band systems at Mt. Soledad, 153 km distant. Kerry N61ZW made contacts with both FMand SSB over the 10GHz path to Heaps with relative ease. His system uses a two stage MGF 1402 preamp with about 18 dB gain and 4 dB noise figure. Provisions are made in N6IZW's rig to reverse the amplifier and use it in the transmit mode, as it is linear
and gels about + 5 dBm output on transmit (approxima tely 3 mW power). The S-meter indicated full peg on both SSB and FM. Leon WASBNH was using his system which places the mixer directly on Ihe antenna without a preamp. His output power (transmit) is about 100 ~W. leon was able to make contact with Phil W6HCC on Heaps Peak who was still full peg on WA5BNH 's rig. W6HCC decided 10 redu ce his power to about 100mW, and leon WA5BNH saw the S-meter come just off the peg. Further reducing W6HCC's power to 20 mW gave WA5BNH 's s-meter an 8-7. The copy at Heaps was j ust above marginal during Ihe test, using 5 kHz FM for the contact on 2 meter HTs. Kerry decided to try another test. He replaced the 2 meter FM transceiver wilh a Santec lS-202 multimode 2 meter HT capable of FM and SSB with the same transmitter power. He switched the mode 10 SSB on both ends of the path. The resulting copy went to full Q-5 copy on SSB at Phil W6HCC's location. Going back 10 FM again led to marginal copy. JI's often very handy 10 be able to switch to SSB from FM Figure 2. KAIZIL '5 10GHzunit. With 5 V to ground, the d6tector diod6 gives about J rnA DC. to improve copy on a long path. Eq uipment Detail A brief outline of the equipment is in order so that you can see just what is pieced together. The parts are not all identical, and they depend on what is available through scrounging or swap meets. The heart of the unit is the phaselocked oscillator that provides about + 10 to + 20 dBm output on 10 GHz. The units that we have been able to obtain have come from many different sources. The prime source seems to be the surplus disposal section at Collins Microwave in Richardson, Texas. They hold monthly auctions 10 dispose of out-o f-spec equipment, and the hams in that area pick up the material and make it available through newsrettere and swap fests. The phase-locked oscillator is basically a high power microwave oscillator run ning in the 1.2 to 2 GHz range, depending on Ihe model. You tune it with a varactor controlled by a 97 to 100 MHz crystal reference. Some crystal oscillators are internal and some are external. The internal types usually demand a higher price, about $35 to $50 dollars each , depending on condition. The less desirable units run about 5 to 10 dollars less. In future _ '" 0(
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