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Radio control transmitter - interference problem
This is somewhat off topic; I apologize, but it seems like the people
that hang out here might actually be able to help me with my problem. I fly radio control gliders. I recently purchased a new transmitter (a Royal Evo 9 with synth module, for those that might care). I'm in the US so this broadcasts on 72MHz. I have problems with this transmitter at one particular flying site that's right next to a military base. The xmitter is fine at other locations, and all the gliders respond just fine to my 'old' xmitter at this site. I've done a bunch of things and it really is just the new xmitter at this particular flying site. It seems like there must be an interference problem with some signal being broadcast from the military base. I've tried to shield the transmitter without much improvement. That makes me think the offending signal may be coming in through the antenna. Being relatively naive electronically, it seems like I could simply insert a filter between the antenna and the rest of the transmitter that passes through the 72 MHz signal but blocks everything else. However, I'm smart enough to know I'm not that smart. That's why I'm here. Is it as simple as finding a filter that passes 72 MHz along and splicing it in to the wire going to the antenna? Is that likely to cause other problems (transmitting on the wrong frequency, overheating the RF module due to impedance mismatch, sudden death)? Assuming I can't find a filter that passes along precisely the frequency I want, is it OK to put filters in series (like a high-pass plus a low-pass)? And finally, am I just totally missing the boat here with this idea? I'm open to other suggestions. |
P. Venkman wrote:
This is somewhat off topic; I apologize, but it seems like the people that hang out here might actually be able to help me with my problem. I fly radio control gliders. I recently purchased a new transmitter (a Royal Evo 9 with synth module, for those that might care). I'm in the US so this broadcasts on 72MHz. I have problems with this transmitter at one particular flying site that's right next to a military base. The xmitter is fine at other locations, and all the gliders respond just fine to my 'old' xmitter at this site. I've done a bunch of things and it really is just the new xmitter at this particular flying site. It seems like there must be an interference problem with some signal being broadcast from the military base. I've tried to shield the transmitter without much improvement. That makes me think the offending signal may be coming in through the antenna. Being relatively naive electronically, it seems like I could simply insert a filter between the antenna and the rest of the transmitter that passes through the 72 MHz signal but blocks everything else. However, I'm smart enough to know I'm not that smart. That's why I'm here. Is it as simple as finding a filter that passes 72 MHz along and splicing it in to the wire going to the antenna? Is that likely to cause other problems (transmitting on the wrong frequency, overheating the RF module due to impedance mismatch, sudden death)? Assuming I can't find a filter that passes along precisely the frequency I want, is it OK to put filters in series (like a high-pass plus a low-pass)? And finally, am I just totally missing the boat here with this idea? I'm open to other suggestions. First, you can really mess things up by playing the filter game, so don't do it unless you need to. Second, it may be that the transmitter has a weaker signal, or that it is a bit off frequency. Since your average military base has about a gazillion different transmitters it's likely that there is some spur being generated at 72MHz, or a valid signal at your RX's image frequency. If your transmitter is a bit weak than such a signal from the base would have an easy time getting into your RX. If you can get the receiver out of the plane (or if you can get to the antenna) do a range check with the RX antenna rolled up but with the TX antenna extended. I'd do this at some _other_ flying site. Check the range with the suspect TX and with a known good one. If it's significantly lower with the suspect TX then you can do all the filtering in the world and it won't help you -- but having the new TX fixed (or selling it and getting another brand) may help a lot. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com |
P. Venkman wrote:
This is somewhat off topic; I apologize, but it seems like the people that hang out here might actually be able to help me with my problem. I fly radio control gliders. I recently purchased a new transmitter (a Royal Evo 9 with synth module, for those that might care). I'm in the US so this broadcasts on 72MHz. I have problems with this transmitter at one particular flying site that's right next to a military base. The xmitter is fine at other locations, and all the gliders respond just fine to my 'old' xmitter at this site. I've done a bunch of things and it really is just the new xmitter at this particular flying site. It seems like there must be an interference problem with some signal being broadcast from the military base. I've tried to shield the transmitter without much improvement. That makes me think the offending signal may be coming in through the antenna. Being relatively naive electronically, it seems like I could simply insert a filter between the antenna and the rest of the transmitter that passes through the 72 MHz signal but blocks everything else. However, I'm smart enough to know I'm not that smart. That's why I'm here. Is it as simple as finding a filter that passes 72 MHz along and splicing it in to the wire going to the antenna? Is that likely to cause other problems (transmitting on the wrong frequency, overheating the RF module due to impedance mismatch, sudden death)? Assuming I can't find a filter that passes along precisely the frequency I want, is it OK to put filters in series (like a high-pass plus a low-pass)? And finally, am I just totally missing the boat here with this idea? I'm open to other suggestions. First, you can really mess things up by playing the filter game, so don't do it unless you need to. Second, it may be that the transmitter has a weaker signal, or that it is a bit off frequency. Since your average military base has about a gazillion different transmitters it's likely that there is some spur being generated at 72MHz, or a valid signal at your RX's image frequency. If your transmitter is a bit weak than such a signal from the base would have an easy time getting into your RX. If you can get the receiver out of the plane (or if you can get to the antenna) do a range check with the RX antenna rolled up but with the TX antenna extended. I'd do this at some _other_ flying site. Check the range with the suspect TX and with a known good one. If it's significantly lower with the suspect TX then you can do all the filtering in the world and it won't help you -- but having the new TX fixed (or selling it and getting another brand) may help a lot. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com |
Tim Wescott wrote in message ...
P. Venkman wrote: SNIP Is it as simple as finding a filter that passes 72 MHz along and splicing it in to the wire going to the antenna? Is that likely to cause other problems (transmitting on the wrong frequency, overheating the RF module due to impedance mismatch, sudden death)? Assuming I can't find a filter that passes along precisely the frequency I want, is it OK to put filters in series (like a high-pass plus a low-pass)? And finally, am I just totally missing the boat here with this idea? I'm open to other suggestions. First, you can really mess things up by playing the filter game, so don't do it unless you need to. Second, it may be that the transmitter has a weaker signal, or that it is a bit off frequency. Since your average military base has about a gazillion different transmitters it's likely that there is some spur being generated at 72MHz, or a valid signal at your RX's image frequency. If your transmitter is a bit weak than such a signal from the base would have an easy time getting into your RX. If you can get the receiver out of the plane (or if you can get to the antenna) do a range check with the RX antenna rolled up but with the TX antenna extended. I'd do this at some _other_ flying site. Check the range with the suspect TX and with a known good one. If it's significantly lower with the suspect TX then you can do all the filtering in the world and it won't help you -- but having the new TX fixed (or selling it and getting another brand) may help a lot. When I first had the problem I sent the transmitter back for service - they didn't find anything wrong, but tuned it anyway and sent it back. The problem still existed, so I got them to replace the transmitter. Still the same problem. At other flying sites the new transmitter actually range checks better than the old transmitter when checked against multiple different receivers. For these two reasons I don't think it's that this TX has a weaker or off-frequency signal. Lots of other people fly at the same location with a variety of equipement with no trouble. I've flown a variety of different gliders there with my old transmitter and never had a problem. I really don't think there's a conflicting 72 MHz signal. It really is just this transmitter at this particular site - other transmitters at the same site are fine, and this transmitter at other sites is just fine. Is there any way to make this work? |
Tim Wescott wrote in message ...
P. Venkman wrote: SNIP Is it as simple as finding a filter that passes 72 MHz along and splicing it in to the wire going to the antenna? Is that likely to cause other problems (transmitting on the wrong frequency, overheating the RF module due to impedance mismatch, sudden death)? Assuming I can't find a filter that passes along precisely the frequency I want, is it OK to put filters in series (like a high-pass plus a low-pass)? And finally, am I just totally missing the boat here with this idea? I'm open to other suggestions. First, you can really mess things up by playing the filter game, so don't do it unless you need to. Second, it may be that the transmitter has a weaker signal, or that it is a bit off frequency. Since your average military base has about a gazillion different transmitters it's likely that there is some spur being generated at 72MHz, or a valid signal at your RX's image frequency. If your transmitter is a bit weak than such a signal from the base would have an easy time getting into your RX. If you can get the receiver out of the plane (or if you can get to the antenna) do a range check with the RX antenna rolled up but with the TX antenna extended. I'd do this at some _other_ flying site. Check the range with the suspect TX and with a known good one. If it's significantly lower with the suspect TX then you can do all the filtering in the world and it won't help you -- but having the new TX fixed (or selling it and getting another brand) may help a lot. When I first had the problem I sent the transmitter back for service - they didn't find anything wrong, but tuned it anyway and sent it back. The problem still existed, so I got them to replace the transmitter. Still the same problem. At other flying sites the new transmitter actually range checks better than the old transmitter when checked against multiple different receivers. For these two reasons I don't think it's that this TX has a weaker or off-frequency signal. Lots of other people fly at the same location with a variety of equipement with no trouble. I've flown a variety of different gliders there with my old transmitter and never had a problem. I really don't think there's a conflicting 72 MHz signal. It really is just this transmitter at this particular site - other transmitters at the same site are fine, and this transmitter at other sites is just fine. Is there any way to make this work? |
P. Venkman wrote:
Tim Wescott wrote in message ... P. Venkman wrote: SNIP Is it as simple as finding a filter that passes 72 MHz along and splicing it in to the wire going to the antenna? Is that likely to cause other problems (transmitting on the wrong frequency, overheating the RF module due to impedance mismatch, sudden death)? Assuming I can't find a filter that passes along precisely the frequency I want, is it OK to put filters in series (like a high-pass plus a low-pass)? And finally, am I just totally missing the boat here with this idea? I'm open to other suggestions. First, you can really mess things up by playing the filter game, so don't do it unless you need to. Second, it may be that the transmitter has a weaker signal, or that it is a bit off frequency. Since your average military base has about a gazillion different transmitters it's likely that there is some spur being generated at 72MHz, or a valid signal at your RX's image frequency. If your transmitter is a bit weak than such a signal from the base would have an easy time getting into your RX. If you can get the receiver out of the plane (or if you can get to the antenna) do a range check with the RX antenna rolled up but with the TX antenna extended. I'd do this at some _other_ flying site. Check the range with the suspect TX and with a known good one. If it's significantly lower with the suspect TX then you can do all the filtering in the world and it won't help you -- but having the new TX fixed (or selling it and getting another brand) may help a lot. When I first had the problem I sent the transmitter back for service - they didn't find anything wrong, but tuned it anyway and sent it back. The problem still existed, so I got them to replace the transmitter. Still the same problem. At other flying sites the new transmitter actually range checks better than the old transmitter when checked against multiple different receivers. For these two reasons I don't think it's that this TX has a weaker or off-frequency signal. Lots of other people fly at the same location with a variety of equipement with no trouble. I've flown a variety of different gliders there with my old transmitter and never had a problem. I really don't think there's a conflicting 72 MHz signal. It really is just this transmitter at this particular site - other transmitters at the same site are fine, and this transmitter at other sites is just fine. Is there any way to make this work? Not without more information, which was why I suggested a test. Did you do the range check against the other transmitters with the TX antenna collapsed? If so, then you've done a fine test of how well your TX will work compared to others -- with everyone's antennas are collapsed. If you normally fly it with the antenna _out_ then you need to test it that way, and find some other way of attenuating the signal to the receiver -- like rolling up _it's_ antenna. You obviously have a problem with that particular TX, which is why I'm suggesting a look at the TX first. Another question you can ask is does the TX have the same problem with other receivers? On other frequencies? Do you have another plane with a different brand receiver, or a buddy with same, that you can try at the problem site? This may be a valid thing to try. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com |
P. Venkman wrote:
Tim Wescott wrote in message ... P. Venkman wrote: SNIP Is it as simple as finding a filter that passes 72 MHz along and splicing it in to the wire going to the antenna? Is that likely to cause other problems (transmitting on the wrong frequency, overheating the RF module due to impedance mismatch, sudden death)? Assuming I can't find a filter that passes along precisely the frequency I want, is it OK to put filters in series (like a high-pass plus a low-pass)? And finally, am I just totally missing the boat here with this idea? I'm open to other suggestions. First, you can really mess things up by playing the filter game, so don't do it unless you need to. Second, it may be that the transmitter has a weaker signal, or that it is a bit off frequency. Since your average military base has about a gazillion different transmitters it's likely that there is some spur being generated at 72MHz, or a valid signal at your RX's image frequency. If your transmitter is a bit weak than such a signal from the base would have an easy time getting into your RX. If you can get the receiver out of the plane (or if you can get to the antenna) do a range check with the RX antenna rolled up but with the TX antenna extended. I'd do this at some _other_ flying site. Check the range with the suspect TX and with a known good one. If it's significantly lower with the suspect TX then you can do all the filtering in the world and it won't help you -- but having the new TX fixed (or selling it and getting another brand) may help a lot. When I first had the problem I sent the transmitter back for service - they didn't find anything wrong, but tuned it anyway and sent it back. The problem still existed, so I got them to replace the transmitter. Still the same problem. At other flying sites the new transmitter actually range checks better than the old transmitter when checked against multiple different receivers. For these two reasons I don't think it's that this TX has a weaker or off-frequency signal. Lots of other people fly at the same location with a variety of equipement with no trouble. I've flown a variety of different gliders there with my old transmitter and never had a problem. I really don't think there's a conflicting 72 MHz signal. It really is just this transmitter at this particular site - other transmitters at the same site are fine, and this transmitter at other sites is just fine. Is there any way to make this work? Not without more information, which was why I suggested a test. Did you do the range check against the other transmitters with the TX antenna collapsed? If so, then you've done a fine test of how well your TX will work compared to others -- with everyone's antennas are collapsed. If you normally fly it with the antenna _out_ then you need to test it that way, and find some other way of attenuating the signal to the receiver -- like rolling up _it's_ antenna. You obviously have a problem with that particular TX, which is why I'm suggesting a look at the TX first. Another question you can ask is does the TX have the same problem with other receivers? On other frequencies? Do you have another plane with a different brand receiver, or a buddy with same, that you can try at the problem site? This may be a valid thing to try. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com |
Lots of other people fly at the same location with a variety of
equipement with no trouble. I've flown a variety of different gliders there with my old transmitter and never had a problem. I really don't think there's a conflicting 72 MHz signal. It really is just this transmitter at this particular site - other transmitters at the same site are fine, and this transmitter at other sites is just fine. Is there any way to make this work? You didn't say, but if that "military site" is an airport, there's a localizer beacon that's probably just off the end of the runway and is on 75 MHz. Could readily be strong enough to give your receiver trouble. W4ZCB |
Lots of other people fly at the same location with a variety of
equipement with no trouble. I've flown a variety of different gliders there with my old transmitter and never had a problem. I really don't think there's a conflicting 72 MHz signal. It really is just this transmitter at this particular site - other transmitters at the same site are fine, and this transmitter at other sites is just fine. Is there any way to make this work? You didn't say, but if that "military site" is an airport, there's a localizer beacon that's probably just off the end of the runway and is on 75 MHz. Could readily be strong enough to give your receiver trouble. W4ZCB |
In article ,
P. Venkman wrote: | I have problems with this transmitter at one particular flying site | that's right next to a military base. The xmitter is fine at other | locations, and all the gliders respond just fine to my 'old' xmitter | at this site. I've done a bunch of things and it really is just the | new xmitter at this particular flying site. You haven't actually told us what the problem is. Is the computer in your transmitter crashing? (interfering with the transmitter) Are the servos in your plane jittering? (interfering with the receiver) Are you seeing reduced range or something? (interfering with the receiver) | It seems like there must be an interference problem with some signal | being broadcast from the military base. I've tried to shield the | transmitter without much improvement. That makes me think the | offending signal may be coming in through the antenna. We'll need to know what the actual problem is. Shielding your transmitter isn't going to do much unless the interference is actually affecting your transmitter (possible, but unlikely) rather than your receiver. | Being relatively naive electronically, it seems like I could simply | insert a filter between the antenna and the rest of the transmitter | that passes through the 72 MHz signal but blocks everything else. If the problem is interference to your receiver, doing this at your transmitter won't help at all. You'd need to do it at the receiver. Some people have had good luck simply wrapping their receiver (just the receiver, not the antenna) in tin foil. Twisting the servo and power wires round and round can also help reduce interference to the receiver as well, and you can get chokes to wrap your servo wires around as well. Very very few people put additional filters on their R/C receivers. Are there any pager towers nearby? Pager companies use the spaces between the R/C channels to talk to pagers, and can use hundreds of watts -- this has definately been known to overload R/C receivers and crash planes. (In that case, the fix would be to 1) do the tin foil/choke thing and 2) try a different frequency. (Your transmitter is synthesized, so all you need is a new receive crystal.) | However, I'm smart enough to know I'm not that smart. That's a pretty good sort of smart to be! :) | Is it as simple as finding a filter that passes 72 MHz along and | splicing it in to the wire going to the antenna? Probably not, unless your problem really is with the transmitter computer crashing. Which receiver are you using? The cheap park flier ones don't handle interference well at all. Do other people fly at this site? Your radio should be able to talk to any plane, so try switching frequencies and picking the proper shift and see if you can do a proper range check with their plane. (Or another plane if you have more.) You might also try asking in rec.models.rc.air, though they'll probably tell you the same things I did. (And yes, I fly R/C too.) -- Doug McLaren, Reserve your bear to right arms. |
In article ,
P. Venkman wrote: | I have problems with this transmitter at one particular flying site | that's right next to a military base. The xmitter is fine at other | locations, and all the gliders respond just fine to my 'old' xmitter | at this site. I've done a bunch of things and it really is just the | new xmitter at this particular flying site. You haven't actually told us what the problem is. Is the computer in your transmitter crashing? (interfering with the transmitter) Are the servos in your plane jittering? (interfering with the receiver) Are you seeing reduced range or something? (interfering with the receiver) | It seems like there must be an interference problem with some signal | being broadcast from the military base. I've tried to shield the | transmitter without much improvement. That makes me think the | offending signal may be coming in through the antenna. We'll need to know what the actual problem is. Shielding your transmitter isn't going to do much unless the interference is actually affecting your transmitter (possible, but unlikely) rather than your receiver. | Being relatively naive electronically, it seems like I could simply | insert a filter between the antenna and the rest of the transmitter | that passes through the 72 MHz signal but blocks everything else. If the problem is interference to your receiver, doing this at your transmitter won't help at all. You'd need to do it at the receiver. Some people have had good luck simply wrapping their receiver (just the receiver, not the antenna) in tin foil. Twisting the servo and power wires round and round can also help reduce interference to the receiver as well, and you can get chokes to wrap your servo wires around as well. Very very few people put additional filters on their R/C receivers. Are there any pager towers nearby? Pager companies use the spaces between the R/C channels to talk to pagers, and can use hundreds of watts -- this has definately been known to overload R/C receivers and crash planes. (In that case, the fix would be to 1) do the tin foil/choke thing and 2) try a different frequency. (Your transmitter is synthesized, so all you need is a new receive crystal.) | However, I'm smart enough to know I'm not that smart. That's a pretty good sort of smart to be! :) | Is it as simple as finding a filter that passes 72 MHz along and | splicing it in to the wire going to the antenna? Probably not, unless your problem really is with the transmitter computer crashing. Which receiver are you using? The cheap park flier ones don't handle interference well at all. Do other people fly at this site? Your radio should be able to talk to any plane, so try switching frequencies and picking the proper shift and see if you can do a proper range check with their plane. (Or another plane if you have more.) You might also try asking in rec.models.rc.air, though they'll probably tell you the same things I did. (And yes, I fly R/C too.) -- Doug McLaren, Reserve your bear to right arms. |
Tim Wescott wrote in message ...
P. Venkman wrote: Tim Wescott wrote in message ... P. Venkman wrote: SNIP Is there any way to make this work? Not without more information, which was why I suggested a test. Did you do the range check against the other transmitters with the TX antenna collapsed? If so, then you've done a fine test of how well your TX will work compared to others -- with everyone's antennas are collapsed. If you normally fly it with the antenna _out_ then you need to test it that way, and find some other way of attenuating the signal to the receiver -- like rolling up _it's_ antenna. You obviously have a problem with that particular TX, which is why I'm suggesting a look at the TX first. Another question you can ask is does the TX have the same problem with other receivers? On other frequencies? Do you have another plane with a different brand receiver, or a buddy with same, that you can try at the problem site? This may be a valid thing to try. I've done the range check with the antenna in; under normal circumstances the range is further than I can see with the antenna out. I can try rolling up the receiver antenna. I've tried the transmitter with 5 different receivers (4 different brands) on 5 different frequencies, all with the exact same problem. At one point I had two different receivers (different brands) on the same frequency turned on, and when they glitched they both glitched in exactly the same way (rudder went hard right on both models, for example). This isn't proof, but in general you wouldn't expect two receivers to glitch in exactly the same way if the problem is interference at the receiver. |
Tim Wescott wrote in message ...
P. Venkman wrote: Tim Wescott wrote in message ... P. Venkman wrote: SNIP Is there any way to make this work? Not without more information, which was why I suggested a test. Did you do the range check against the other transmitters with the TX antenna collapsed? If so, then you've done a fine test of how well your TX will work compared to others -- with everyone's antennas are collapsed. If you normally fly it with the antenna _out_ then you need to test it that way, and find some other way of attenuating the signal to the receiver -- like rolling up _it's_ antenna. You obviously have a problem with that particular TX, which is why I'm suggesting a look at the TX first. Another question you can ask is does the TX have the same problem with other receivers? On other frequencies? Do you have another plane with a different brand receiver, or a buddy with same, that you can try at the problem site? This may be a valid thing to try. I've done the range check with the antenna in; under normal circumstances the range is further than I can see with the antenna out. I can try rolling up the receiver antenna. I've tried the transmitter with 5 different receivers (4 different brands) on 5 different frequencies, all with the exact same problem. At one point I had two different receivers (different brands) on the same frequency turned on, and when they glitched they both glitched in exactly the same way (rudder went hard right on both models, for example). This isn't proof, but in general you wouldn't expect two receivers to glitch in exactly the same way if the problem is interference at the receiver. |
"Harold E. Johnson" wrote in message news:vIbic.12068$IW1.760683@attbi_s52...
Lots of other people fly at the same location with a variety of equipement with no trouble. I've flown a variety of different gliders there with my old transmitter and never had a problem. I really don't think there's a conflicting 72 MHz signal. It really is just this transmitter at this particular site - other transmitters at the same site are fine, and this transmitter at other sites is just fine. Is there any way to make this work? You didn't say, but if that "military site" is an airport, there's a localizer beacon that's probably just off the end of the runway and is on 75 MHz. Could readily be strong enough to give your receiver trouble. W4ZCB It's not an airport, but who knows what they have blasting away on any number of frequencies. I don't have the equipment to check it out. |
"Harold E. Johnson" wrote in message news:vIbic.12068$IW1.760683@attbi_s52...
Lots of other people fly at the same location with a variety of equipement with no trouble. I've flown a variety of different gliders there with my old transmitter and never had a problem. I really don't think there's a conflicting 72 MHz signal. It really is just this transmitter at this particular site - other transmitters at the same site are fine, and this transmitter at other sites is just fine. Is there any way to make this work? You didn't say, but if that "military site" is an airport, there's a localizer beacon that's probably just off the end of the runway and is on 75 MHz. Could readily be strong enough to give your receiver trouble. W4ZCB It's not an airport, but who knows what they have blasting away on any number of frequencies. I don't have the equipment to check it out. |
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P. Venkman wrote:
Tim Wescott wrote in message ... P. Venkman wrote: Tim Wescott wrote in message ... P. Venkman wrote: SNIP Is there any way to make this work? Not without more information, which was why I suggested a test. Did you do the range check against the other transmitters with the TX antenna collapsed? If so, then you've done a fine test of how well your TX will work compared to others -- with everyone's antennas are collapsed. If you normally fly it with the antenna _out_ then you need to test it that way, and find some other way of attenuating the signal to the receiver -- like rolling up _it's_ antenna. You obviously have a problem with that particular TX, which is why I'm suggesting a look at the TX first. Another question you can ask is does the TX have the same problem with other receivers? On other frequencies? Do you have another plane with a different brand receiver, or a buddy with same, that you can try at the problem site? This may be a valid thing to try. I've done the range check with the antenna in; under normal circumstances the range is further than I can see with the antenna out. I can try rolling up the receiver antenna. I've tried the transmitter with 5 different receivers (4 different brands) on 5 different frequencies, all with the exact same problem. At one point I had two different receivers (different brands) on the same frequency turned on, and when they glitched they both glitched in exactly the same way (rudder went hard right on both models, for example). This isn't proof, but in general you wouldn't expect two receivers to glitch in exactly the same way if the problem is interference at the receiver. If two receivers are receiving exactly the same interference at exactly the same time they may glitch the same way. Since it's a synthesized module and should be easy to do, have you tried it on a different frequency (with appropriate RX, of course)? Obviously something screwy is going on, if it's limited to one frequency you may be able to just switch to a more benign frequency and have fun. You could switch to flying control line, but that gets difficult with gliders. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com |
P. Venkman wrote:
Tim Wescott wrote in message ... P. Venkman wrote: Tim Wescott wrote in message ... P. Venkman wrote: SNIP Is there any way to make this work? Not without more information, which was why I suggested a test. Did you do the range check against the other transmitters with the TX antenna collapsed? If so, then you've done a fine test of how well your TX will work compared to others -- with everyone's antennas are collapsed. If you normally fly it with the antenna _out_ then you need to test it that way, and find some other way of attenuating the signal to the receiver -- like rolling up _it's_ antenna. You obviously have a problem with that particular TX, which is why I'm suggesting a look at the TX first. Another question you can ask is does the TX have the same problem with other receivers? On other frequencies? Do you have another plane with a different brand receiver, or a buddy with same, that you can try at the problem site? This may be a valid thing to try. I've done the range check with the antenna in; under normal circumstances the range is further than I can see with the antenna out. I can try rolling up the receiver antenna. I've tried the transmitter with 5 different receivers (4 different brands) on 5 different frequencies, all with the exact same problem. At one point I had two different receivers (different brands) on the same frequency turned on, and when they glitched they both glitched in exactly the same way (rudder went hard right on both models, for example). This isn't proof, but in general you wouldn't expect two receivers to glitch in exactly the same way if the problem is interference at the receiver. If two receivers are receiving exactly the same interference at exactly the same time they may glitch the same way. Since it's a synthesized module and should be easy to do, have you tried it on a different frequency (with appropriate RX, of course)? Obviously something screwy is going on, if it's limited to one frequency you may be able to just switch to a more benign frequency and have fun. You could switch to flying control line, but that gets difficult with gliders. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com |
Tim Wescott wrote in message ...
P. Venkman wrote: Tim Wescott wrote in message ... P. Venkman wrote: Tim Wescott wrote in message ... P. Venkman wrote: SNIP I've tried the transmitter with 5 different receivers (4 different brands) on 5 different frequencies, all with the exact same problem. At one point I had two different receivers (different brands) on the same frequency turned on, and when they glitched they both glitched in exactly the same way (rudder went hard right on both models, for example). This isn't proof, but in general you wouldn't expect two receivers to glitch in exactly the same way if the problem is interference at the receiver. If two receivers are receiving exactly the same interference at exactly the same time they may glitch the same way. Possible; however, they were different brands and different circuits, and it's less likely that some random interference would cause them to act the exact same way. The same brand wouldn't surprise me. Since it's a synthesized module and should be easy to do, have you tried it on a different frequency (with appropriate RX, of course)? Obviously something screwy is going on, if it's limited to one frequency you may be able to just switch to a more benign frequency and have fun. I've tried 5 different frequencies; all act the same way. You could switch to flying control line, but that gets difficult with gliders. I think at that point it becomes a kite! |
Tim Wescott wrote in message ...
P. Venkman wrote: Tim Wescott wrote in message ... P. Venkman wrote: Tim Wescott wrote in message ... P. Venkman wrote: SNIP I've tried the transmitter with 5 different receivers (4 different brands) on 5 different frequencies, all with the exact same problem. At one point I had two different receivers (different brands) on the same frequency turned on, and when they glitched they both glitched in exactly the same way (rudder went hard right on both models, for example). This isn't proof, but in general you wouldn't expect two receivers to glitch in exactly the same way if the problem is interference at the receiver. If two receivers are receiving exactly the same interference at exactly the same time they may glitch the same way. Possible; however, they were different brands and different circuits, and it's less likely that some random interference would cause them to act the exact same way. The same brand wouldn't surprise me. Since it's a synthesized module and should be easy to do, have you tried it on a different frequency (with appropriate RX, of course)? Obviously something screwy is going on, if it's limited to one frequency you may be able to just switch to a more benign frequency and have fun. I've tried 5 different frequencies; all act the same way. You could switch to flying control line, but that gets difficult with gliders. I think at that point it becomes a kite! |
"P. Venkman" wrote in message om... This is somewhat off topic; I apologize, but it seems like the people that hang out here might actually be able to help me with my problem. I fly radio control gliders. I recently purchased a new transmitter (a Royal Evo 9 with synth module, for those that might care). I'm in the US so this broadcasts on 72MHz. I have problems with this transmitter at one particular flying site that's right next to a military base. The xmitter is fine at other locations, and all the gliders respond just fine to my 'old' xmitter at this site. I've done a bunch of things and it really is just the new xmitter at this particular flying site. It seems like there must be an interference problem with some signal being broadcast from the military base. I've tried to shield the transmitter without much improvement. That makes me think the offending signal may be coming in through the antenna. Being relatively naive electronically, it seems like I could simply insert a filter between the antenna and the rest of the transmitter that passes through the 72 MHz signal but blocks everything else. However, I'm smart enough to know I'm not that smart. That's why I'm here. Is it as simple as finding a filter that passes 72 MHz along and splicing it in to the wire going to the antenna? Is that likely to cause other problems (transmitting on the wrong frequency, overheating the RF module due to impedance mismatch, sudden death)? Assuming I can't find a filter that passes along precisely the frequency I want, is it OK to put filters in series (like a high-pass plus a low-pass)? And finally, am I just totally missing the boat here with this idea? I'm open to other suggestions. Here's an idea. How about talking to the senior radio technician on the military base? Just maybe he/she would have the answer. 73 Roger ZR3RC |
"P. Venkman" wrote in message om... This is somewhat off topic; I apologize, but it seems like the people that hang out here might actually be able to help me with my problem. I fly radio control gliders. I recently purchased a new transmitter (a Royal Evo 9 with synth module, for those that might care). I'm in the US so this broadcasts on 72MHz. I have problems with this transmitter at one particular flying site that's right next to a military base. The xmitter is fine at other locations, and all the gliders respond just fine to my 'old' xmitter at this site. I've done a bunch of things and it really is just the new xmitter at this particular flying site. It seems like there must be an interference problem with some signal being broadcast from the military base. I've tried to shield the transmitter without much improvement. That makes me think the offending signal may be coming in through the antenna. Being relatively naive electronically, it seems like I could simply insert a filter between the antenna and the rest of the transmitter that passes through the 72 MHz signal but blocks everything else. However, I'm smart enough to know I'm not that smart. That's why I'm here. Is it as simple as finding a filter that passes 72 MHz along and splicing it in to the wire going to the antenna? Is that likely to cause other problems (transmitting on the wrong frequency, overheating the RF module due to impedance mismatch, sudden death)? Assuming I can't find a filter that passes along precisely the frequency I want, is it OK to put filters in series (like a high-pass plus a low-pass)? And finally, am I just totally missing the boat here with this idea? I'm open to other suggestions. Here's an idea. How about talking to the senior radio technician on the military base? Just maybe he/she would have the answer. 73 Roger ZR3RC |
Here's an idea. How about talking to the senior radio technician on the military base? Just maybe he/she would have the answer. ================ Or borrow a handheld scanning receiver. It could well be that a nearby transmitted signal ,not necessarily on or near 'your ' transmitted frequency affect the RC receiver (which probably has limited immunity in respect of strong harmonics/mixing sigs.) Frank GM0CSZ / KN6WH |
Here's an idea. How about talking to the senior radio technician on the military base? Just maybe he/she would have the answer. ================ Or borrow a handheld scanning receiver. It could well be that a nearby transmitted signal ,not necessarily on or near 'your ' transmitted frequency affect the RC receiver (which probably has limited immunity in respect of strong harmonics/mixing sigs.) Frank GM0CSZ / KN6WH |
Might be kind of tough to pin down. IF they're using H.F. and probably up
into the GHz region and maybe even as low as the L.F. area to transmit, any one of those transmitters OR a harmonic OR a clashing of all or any - could be causing the problem. Given he said Crystal control planes work there but not Synthesized units and given he said the planes operate ok elsewhere, leads me to believe that the synthesized receiver (all of those he has tried) is coming unlocked due to RF overload from something. Synthesized receivers are nice, but they do have their draw backs. I've had battles with them too in tight RF areas. Some places, a crystal IS better. Antiquated maybe, but if it works, what the hell........ Just my opinion. I'm not an RF engineer, but work around RF a lot. I've seen lots of weird stuff. Lou "Roger Conroy" wrote in message ... "P. Venkman" wrote in message om... This is somewhat off topic; I apologize, but it seems like the people that hang out here might actually be able to help me with my problem. I fly radio control gliders. I recently purchased a new transmitter (a Royal Evo 9 with synth module, for those that might care). I'm in the US so this broadcasts on 72MHz. I have problems with this transmitter at one particular flying site that's right next to a military base. The xmitter is fine at other locations, and all the gliders respond just fine to my 'old' xmitter at this site. I've done a bunch of things and it really is just the new xmitter at this particular flying site. It seems like there must be an interference problem with some signal being broadcast from the military base. I've tried to shield the transmitter without much improvement. That makes me think the offending signal may be coming in through the antenna. Being relatively naive electronically, it seems like I could simply insert a filter between the antenna and the rest of the transmitter that passes through the 72 MHz signal but blocks everything else. However, I'm smart enough to know I'm not that smart. That's why I'm here. Is it as simple as finding a filter that passes 72 MHz along and splicing it in to the wire going to the antenna? Is that likely to cause other problems (transmitting on the wrong frequency, overheating the RF module due to impedance mismatch, sudden death)? Assuming I can't find a filter that passes along precisely the frequency I want, is it OK to put filters in series (like a high-pass plus a low-pass)? And finally, am I just totally missing the boat here with this idea? I'm open to other suggestions. Here's an idea. How about talking to the senior radio technician on the military base? Just maybe he/she would have the answer. 73 Roger ZR3RC |
Might be kind of tough to pin down. IF they're using H.F. and probably up
into the GHz region and maybe even as low as the L.F. area to transmit, any one of those transmitters OR a harmonic OR a clashing of all or any - could be causing the problem. Given he said Crystal control planes work there but not Synthesized units and given he said the planes operate ok elsewhere, leads me to believe that the synthesized receiver (all of those he has tried) is coming unlocked due to RF overload from something. Synthesized receivers are nice, but they do have their draw backs. I've had battles with them too in tight RF areas. Some places, a crystal IS better. Antiquated maybe, but if it works, what the hell........ Just my opinion. I'm not an RF engineer, but work around RF a lot. I've seen lots of weird stuff. Lou "Roger Conroy" wrote in message ... "P. Venkman" wrote in message om... This is somewhat off topic; I apologize, but it seems like the people that hang out here might actually be able to help me with my problem. I fly radio control gliders. I recently purchased a new transmitter (a Royal Evo 9 with synth module, for those that might care). I'm in the US so this broadcasts on 72MHz. I have problems with this transmitter at one particular flying site that's right next to a military base. The xmitter is fine at other locations, and all the gliders respond just fine to my 'old' xmitter at this site. I've done a bunch of things and it really is just the new xmitter at this particular flying site. It seems like there must be an interference problem with some signal being broadcast from the military base. I've tried to shield the transmitter without much improvement. That makes me think the offending signal may be coming in through the antenna. Being relatively naive electronically, it seems like I could simply insert a filter between the antenna and the rest of the transmitter that passes through the 72 MHz signal but blocks everything else. However, I'm smart enough to know I'm not that smart. That's why I'm here. Is it as simple as finding a filter that passes 72 MHz along and splicing it in to the wire going to the antenna? Is that likely to cause other problems (transmitting on the wrong frequency, overheating the RF module due to impedance mismatch, sudden death)? Assuming I can't find a filter that passes along precisely the frequency I want, is it OK to put filters in series (like a high-pass plus a low-pass)? And finally, am I just totally missing the boat here with this idea? I'm open to other suggestions. Here's an idea. How about talking to the senior radio technician on the military base? Just maybe he/she would have the answer. 73 Roger ZR3RC |
"Highland Ham" wrote in message ...
Here's an idea. How about talking to the senior radio technician on the military base? Just maybe he/she would have the answer. ================ Or borrow a handheld scanning receiver. It could well be that a nearby transmitted signal ,not necessarily on or near 'your ' transmitted frequency affect the RC receiver (which probably has limited immunity in respect of strong harmonics/mixing sigs.) Frank GM0CSZ / KN6WH I appreciate the replies, but the problem is NOT with the receiver, it's with the transmitter. I admit this was more or less the response I expected, but I really hoped someone would say 'oh, I had the exact same problem and designed and built a filter for my transmitter that fixed everything, and I'd be happy to show you how to do the same'. But thanks for the replies, I do appreciate it. |
"Highland Ham" wrote in message ...
Here's an idea. How about talking to the senior radio technician on the military base? Just maybe he/she would have the answer. ================ Or borrow a handheld scanning receiver. It could well be that a nearby transmitted signal ,not necessarily on or near 'your ' transmitted frequency affect the RC receiver (which probably has limited immunity in respect of strong harmonics/mixing sigs.) Frank GM0CSZ / KN6WH I appreciate the replies, but the problem is NOT with the receiver, it's with the transmitter. I admit this was more or less the response I expected, but I really hoped someone would say 'oh, I had the exact same problem and designed and built a filter for my transmitter that fixed everything, and I'd be happy to show you how to do the same'. But thanks for the replies, I do appreciate it. |
"P. Venkman" wrote in message
om... "Highland Ham" wrote in message ... Here's an idea. How about talking to the senior radio technician on the military base? Just maybe he/she would have the answer. ================ Or borrow a handheld scanning receiver. It could well be that a nearby transmitted signal ,not necessarily on or near 'your ' transmitted frequency affect the RC receiver (which probably has limited immunity in respect of strong harmonics/mixing sigs.) Frank GM0CSZ / KN6WH I appreciate the replies, but the problem is NOT with the receiver, it's with the transmitter. I admit this was more or less the response I expected, but I really hoped someone would say 'oh, I had the exact same problem and designed and built a filter for my transmitter that fixed everything, and I'd be happy to show you how to do the same'. But thanks for the replies, I do appreciate it. Look, if the transmitter is "synthesized" i.e. not crystal bound, and it is suffering the problem only near the Military base, then it is pretty obvious that the transmitter is being overwhelmed by a stronger signal. IT CAN AND DOES HAPPEN! The minute signal of your transmitter milliwatts to a watt or so is most likely being swamped out by the mega watts they are using or the mixing of the signals is doing it. Either use a crystal controlled transmitter there, or quit flying there! They're not going to shut down for you to fly your model plane. You claim that is the only place it happens.... Sooooooo! Maybe no one else flys in RF bombarded fields to have experienced the same problem that you're looking for the answers to. The answer is obvious. Crystal controlled or stop flying there. Lou |
"P. Venkman" wrote in message
om... "Highland Ham" wrote in message ... Here's an idea. How about talking to the senior radio technician on the military base? Just maybe he/she would have the answer. ================ Or borrow a handheld scanning receiver. It could well be that a nearby transmitted signal ,not necessarily on or near 'your ' transmitted frequency affect the RC receiver (which probably has limited immunity in respect of strong harmonics/mixing sigs.) Frank GM0CSZ / KN6WH I appreciate the replies, but the problem is NOT with the receiver, it's with the transmitter. I admit this was more or less the response I expected, but I really hoped someone would say 'oh, I had the exact same problem and designed and built a filter for my transmitter that fixed everything, and I'd be happy to show you how to do the same'. But thanks for the replies, I do appreciate it. Look, if the transmitter is "synthesized" i.e. not crystal bound, and it is suffering the problem only near the Military base, then it is pretty obvious that the transmitter is being overwhelmed by a stronger signal. IT CAN AND DOES HAPPEN! The minute signal of your transmitter milliwatts to a watt or so is most likely being swamped out by the mega watts they are using or the mixing of the signals is doing it. Either use a crystal controlled transmitter there, or quit flying there! They're not going to shut down for you to fly your model plane. You claim that is the only place it happens.... Sooooooo! Maybe no one else flys in RF bombarded fields to have experienced the same problem that you're looking for the answers to. The answer is obvious. Crystal controlled or stop flying there. Lou |
In case anyone cares I have an update on this. I was able to get a
crystal controlled RF module for the transmitter and that took care of the problem. It's definitely the synth RF module that's experiencing the interference. I'm still interested in findind a way to deal with this aside from just not using the synth module at that site. Now that I've more or less isolated the problem, is there anything I can try? I did make an attempt at sheilding just the RF module with no luck, but are there other options? Thanks. |
In case anyone cares I have an update on this. I was able to get a
crystal controlled RF module for the transmitter and that took care of the problem. It's definitely the synth RF module that's experiencing the interference. I'm still interested in findind a way to deal with this aside from just not using the synth module at that site. Now that I've more or less isolated the problem, is there anything I can try? I did make an attempt at sheilding just the RF module with no luck, but are there other options? Thanks. |
"P. Venkman" wrote in message om... I'm still interested in findind a way to deal with this aside from just not using the synth module at that site. Now that I've more or less isolated the problem, is there anything I can try? I did make an attempt at sheilding just the RF module with no luck, but are there other options? As long as it's at the transmitter, you could try a bandpass filter. Chances are the interference is coming from outside the RC band. There are programs available for free that will give you the numbers you need. I use one called AADE Filter Design from AADE.com . Ask if you need info on making the inductors etc. "PM" |
"P. Venkman" wrote in message om... I'm still interested in findind a way to deal with this aside from just not using the synth module at that site. Now that I've more or less isolated the problem, is there anything I can try? I did make an attempt at sheilding just the RF module with no luck, but are there other options? As long as it's at the transmitter, you could try a bandpass filter. Chances are the interference is coming from outside the RC band. There are programs available for free that will give you the numbers you need. I use one called AADE Filter Design from AADE.com . Ask if you need info on making the inductors etc. "PM" |
"Paul_Morphy" wrote in message ...
"P. Venkman" wrote in message om... I'm still interested in findind a way to deal with this aside from just not using the synth module at that site. Now that I've more or less isolated the problem, is there anything I can try? I did make an attempt at sheilding just the RF module with no luck, but are there other options? As long as it's at the transmitter, you could try a bandpass filter. Chances are the interference is coming from outside the RC band. There are programs available for free that will give you the numbers you need. I use one called AADE Filter Design from AADE.com . Ask if you need info on making the inductors etc. "PM" That's very useful, thanks! I downloaded the program and think I understand it well enough to plug in the numbers. I do have one big question though. How do I measure the impedance? I've got a basic VOM but that's it as far as test equipment, and my knowledge of things electronic is pretty basic. |
"Paul_Morphy" wrote in message ...
"P. Venkman" wrote in message om... I'm still interested in findind a way to deal with this aside from just not using the synth module at that site. Now that I've more or less isolated the problem, is there anything I can try? I did make an attempt at sheilding just the RF module with no luck, but are there other options? As long as it's at the transmitter, you could try a bandpass filter. Chances are the interference is coming from outside the RC band. There are programs available for free that will give you the numbers you need. I use one called AADE Filter Design from AADE.com . Ask if you need info on making the inductors etc. "PM" That's very useful, thanks! I downloaded the program and think I understand it well enough to plug in the numbers. I do have one big question though. How do I measure the impedance? I've got a basic VOM but that's it as far as test equipment, and my knowledge of things electronic is pretty basic. |
"P. Venkman" wrote in message om... That's very useful, thanks! I downloaded the program and think I understand it well enough to plug in the numbers. I do have one big question though. How do I measure the impedance? I've got a basic VOM but that's it as far as test equipment, and my knowledge of things electronic is pretty basic. Oh, yeah, I didn't consider that your antenna is not 50-ohms. How long is the antenna, and what frequency band are you using? 72 MHz? When it comes to calculating what your antenna looks like impedance-wise, there are others here more knowledgeable than me and I hope they jump in! I wonder how well shielded the transmitter is, also. If not well shielded the interference could just get in directly and the BP filter wouldn't help. There are devices that allow you to measure an antenna's impedance, but they cost about what your transmitter cost. "PM" |
"P. Venkman" wrote in message om... That's very useful, thanks! I downloaded the program and think I understand it well enough to plug in the numbers. I do have one big question though. How do I measure the impedance? I've got a basic VOM but that's it as far as test equipment, and my knowledge of things electronic is pretty basic. Oh, yeah, I didn't consider that your antenna is not 50-ohms. How long is the antenna, and what frequency band are you using? 72 MHz? When it comes to calculating what your antenna looks like impedance-wise, there are others here more knowledgeable than me and I hope they jump in! I wonder how well shielded the transmitter is, also. If not well shielded the interference could just get in directly and the BP filter wouldn't help. There are devices that allow you to measure an antenna's impedance, but they cost about what your transmitter cost. "PM" |
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