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#31
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On Sun, 27 Jul 2003 22:33:48 +0100, Paul Burridge
wrote: How did you go with Win's soft start motor controller? Currently under construction... -- Hello Paul, you are dragging the anchor a bit. That was months ago! :-) Have a look here http://www.ife.tugraz.at/datashts/nsc/h7912.pdf Page 9. Application hints, has some good reading on how to play around with the input transformer. Is Henry's Radio still around? They used sell sets of IF coils for hobbyists and experimenters. My Henry's catalogue is a bit old. A nice Indian gent in an electronics junk shop in Edgeware Road gave it to me in 1973. I should come over there and get a more up to date copy. Are the electronic disposal shops still there? Maybe rob some 455 KHz IF coils out of a dud transistor radio if necessary. Save some dosh. Get that Dalo etch resist pen out, bottle of ferric chloride and sharpen your old soldering iron. You have a good Tek CRO and a Signal Generator. Do I sound like I am pushing you? Heh heh heh.... Regards, John Crighton Sydney |
#32
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![]() 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 |
#33
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![]() 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 |
#35
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On 28 Jul 2003 07:13:56 GMT, (Michael Black)
wrote: John Crighton ) writes: Maybe rob some 455 KHz IF coils out of a dud transistor radio if necessary. Save some dosh. It would be interesting to have some tests done on the original receiver. If I remember the start of the thread, the receiver is not sensitive enough. I can't help but wonder if it's insensitive or it's too sensitive, leading to overload in the front end. That would be just as bad (in terms of operational range) as an insensitive receiver. Likewise, if one had an idea of the IF bandwidth, it would be easier to know if the problem really needs fixing, or there is some other issue. If the thing is using some sort of ceramic filter, looking at the board would hopefully say what type (unless the markings have been sanded off), and then the specs could be found. Assuming it's a standard IF frequency, maybe one could find a narrower filter that would drop right in. For all we know, it may have too wide an IF, and that's causing the initial problem. Knowing the bandwidth of the existing filter would also make it easier to figure out a complete replacement for the receiver. In this day and age, ceramic or crystal filters are the way to go, not a bunch of IF transformers. Pull parts out of a cordless phone, at least the 49MHz type, and you'll get a filter suitable for narrow deviation FM and a crystal for converting from 10.7MHz to 455KHz. If FM happens to be the operating mode, then pull out the whole IF strip. If that filter is too wide, pull the 455KHz ceramic filter out of a am BCB radio, or for something narrower, a CB set. The possibilities are endless. Michael VE2BVW Hello Michael, you are correct, there are many possibilities. I would like him to do some tests also. The main stumbling block for Paul is no information on the present Sanwa receiver and an understandable reluctance to poke around and then kill it accidentally, especially if it is borrowed or belongs to a mate. I suggested building a new Rx that is physically big so that experiments and mods are easily done by Paul. If the CRO probe slips.....no big deal. :-) We know of this LM1872 http://www.ife.tugraz.at/datashts/nsc/h7912.pdf that we can all look at and help out with suggestions. Do you know of anything else we can all see on a website? Regards, John Crighton Sydney |
#36
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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 |
#37
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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 |
#38
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#39
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#40
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On Mon, 28 Jul 2003 07:02:53 GMT, (John Crighton)
wrote: On Sun, 27 Jul 2003 22:33:48 +0100, Paul Burridge wrote: How did you go with Win's soft start motor controller? Currently under construction... -- Hello Paul, you are dragging the anchor a bit. That was months ago! :-) Have a look here http://www.ife.tugraz.at/datashts/nsc/h7912.pdf You'll have to forgive me here, John, as i'm battling with a duff display on the computer I'm using at the moment and I was only able to glimpse the data for a few seconds, but this chip doesn't seem to be suitable for 40Mhz FM, does it? I'm sure your general solution to the problem is an excellent one, though, if a suitable chip can be found. -- "I believe history will be kind to me, since I intend to write it." - Winston Churchill |
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