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On Mon, 28 Jul 2003 10:19:13 +0100, "Hans Summers"
wrote: Back to your interference problem. Is your operating channel frequency smack in the middle of the 40 Mhz band? If so, maybe you could try a different set of crystals, so that you operate as far away from everyone else as possible. Or simply just borrow a different set of crystals in case there is a weird mix going on, just to eliminate that possibility. We've recently got wise to that one and I've ordered a pair of xtals from the *last* channel of the band. That's what we'll be running with come the last week in August, when we're due up for the next filming. Not necessarily the solution, I got bitten by that one once some 9 or 10 years ago when I used to fly radio controlled aircraft (in the UK on 35MHz). It bothered me when someone else at the flying field had the same crystal as I did and I had to wait for them to finish flying before I could fly. So bought another pair of crystals, the highest I could find, if I recall that was channel 83 (35.230MHz). Everything was fine for a while but a few weeks later I crashed after losing radio contact with my plane. A little investigation (in between gluing the aircraft bits back together) found the cause. A channel vs frequency listing, compared with the MHz printed on the crystal case revealed that the receivers were single conversion superhets with 110KHz IF. Channel separation was 10KHz. Clearly with that setup, image rejection is practically negligible. So someone transmitting on channel 61, 220KHz away, interferes with channel 83. After that I went back to my crystals on 76 smack in the middle of everyone elses, learnt to be patient if someone was already using the channel, and had no more problems ;-) Hans G0UPL http://www.HansSummers.com Hello Hans, what brand/make was that R/C set that you had? You have reminded me of a silly incident at my model flying club decades ago. One of the wealthier club members was having all sorts of trouble with his model, engine and radio gear so he flung heaps of money at a ready made, ready to fly model with an expensive four stroke engine, and a new expensive all singing and dancing radio control set. First day out with the new model and everything is going well for him, he was doing stunts all over the sky. My models were el cheapo sticks and tissue construction, I couldn't afford nice covering film/material. I was more interested in home built radio control gear. Radio assisted free flight was more my style. When the fuel ran out in my models I didn't mind walking a few hundred yards if necessary to retrieve my model. So I am off for a long walk with my transmitter still switched on as one would. (The receiver gets switched off first then the transmitter.) The rich guy is stunting around and decides to buzz me at low level about 20 feet above the ground. His model flies over me and then nose dives into the ground near by. I could here his servos twitching away as I walked past the wreckage. After I retrieved my model and switched off my transmitter, I stopped by the little gathering at the wreck site. The rich guy was operating his servos OK and scratching his head. " I spend thousands on my model and that ******* John Crighton comes here every weekend with 50 dollars worth of homebuilt junk and flies. It just isn't fair." "Moan...grumble..moan." I didn't try to explain that his receiver got swamped. His mates put the crash down to pilot error at low level, and that was that. Fun and games, eh! :-) Regards, John Crighton Sydney |
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