Re: [RCSE] Re: TX RF output? Long!
From: Doug McLaren <[EMAIL PROTECTED]> For desense to occur, the signals don't even have to be in the same band. For example, in my car the FM radio (88-108 MHz) signal gets noticibly quieter when I transmit on my 144 MHZ ham radio. Same thing happens in my car. It's almost certainly due to rectification of the super-loud signal at an emitter-base diode somewhere in the IF strip, putting a bias on the AGC line or biasing one of the transistors toward cutoff. RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
Re: [RCSE] Re: TX RF output? Long!
As it would have Bill...if indeed a PCMm RX was employed, as the communications protocol would have been different (except in the unlikely case the offending TX was identical and on the same frequency). A PCM RX would immediately have gone into hold, and then would have either returned to normal communications if the proper signal returned or entered falisafe after a set period of time. In some cases depending on manufacturer this delay can be altered. Sorry to Randy for calling him Pat Randy claims to be be the tall good looking one (trust me...I have no desire to find out but maybe Gordy could comment for the edification of all :^) Some may recall me posting on testing I did on versions of a neat RX (Sky & Technology) which employ rather complex algorythms which dissect a specific transmitter's signal O/P looking at (and remembering) anomalies which make that TX unique. The result is you can turn on another TX (identical make/model in some circumstances), and it will not interfere. Pretty extraordinary! In fact their particular system touted that you could have two TX's on precisely the same frequency, program the RX to uniquely identify both of them, and then use "both" TX's simultaneously in a student/instructor environment. The neat idea being that the RX would know which TX is master and which was slave. When the student got into trouble with his slave TX, the instructor would turn on his master TX, all on the same frequency, and take over. There were a few fly's in the ointment though; - the TX's had to pretty simple units, such that when they turned on they outputed a valid signal immediately. Not something you can do with today's microprocessor-driven TX's (start-up delays, etc). - there were times when on two identical TX's were employed, the slave OR master could still overrule the other. I still operate a few of these RX's, as they are IMO as good if not better than PCM for precisely the reasons poor Randy got bad juju. Quoting Bill Swingle <[EMAIL PROTECTED]>: > A PCM signal is no better than PPM. The only benefit would have been if the > PCM Rx went into fail safe. Obviously could have been quite helpful. If it > did go into failsafe. > > Bill Swingle > Janesville, CA > > > > RCSE-List facilities provided by Model Airplane News. Send "subscribe" and > "unsubscribe" requests to [EMAIL PROTECTED] Please note that > subscribe and unsubscribe messages must be sent in text only format with MIME > turned off. Email sent from web based email such as Hotmail and AOL are > generally NOT in text format > Simon Van Leeuwen PnP Systems - The E-Harness of Choice Radius Systems Cogito Ergo Zoom RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
Re: [RCSE] Re: TX RF output? Long!
>Imagine trying to hear a whisper across a crowded room. Nearby louder voices drowned out the one familiar voice you are trying to hear. All radio receivers face the same issues. (Jon Stone) This is where the magic of the newer receivers comes into play. Like any other radio they also have a hard time listening for the whisper across the crowded room but they use their knowledge of what the whisperer is saying to build an adaptive filter that picks out the whisper from the junk. Current techniques are not perfect because the radios are all saying the same thing -- its like everyone's repeating the same phrase -- but they try to pick up on slight differences in inflexion to distinguish between the talkers. Conventional radio, the sort we've grown up with, distinguishes between information by sending carrying in different parts of the R/F spectrum -- that is, we 'tune' the receiver to pick up the transmitted information stream that we want to receive. This kind of selection is technically straightforward, its the only sort that could be envisaged using the technology available to us when radio was first invented, but its got the problem that the filters that select one stream from an adjacent one are always going to be imperfect -- no matter how well we design them some unwanted signal's going to get into the receiver if the interference is strong enough or close enough in frequency. The trick has been to design the receiver so that the filtering's adequate for the intended use, and to do within a size and price point that's realistic. There are other ways of putting streams of information out, possibly the earliest common example is how television got adapted to first carry the sound signal (it started as essentially two distinct transmissions, video and sound) and then to put color information into the same signal. Things gradually got more exotic but we were unaware of it (I was, certainly) because the applications were things like receiving information from spacecraft or satellites (there's a limit to how sensitive you can make a receiver even if you cool it) but gradually they started turning up in everyday stuff such as cellphones and digital radio and TV. Our R/C radios are very crude by comparison but they're still adequate for what they do (anyway, modern technology doesn't render old stuff useless per se -- you can still use a CB radio to talk to someone instead of a cellphone). Conventional radio is essentially obsolete, it'll eventually go the same way as spark gap or R/F alternator technologies, but it will take some time before it fades away. Martin Usher RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
Re: [RCSE] Re: TX RF output? Long!
From: Rick Eckel <[EMAIL PROTECTED]> But how about if all the other conversations are being held above 20khz or below 20hz?? Does sheer power on other frequencies swamp the front end of a receiver? Shouldn't we see more evidence of this at the launch area? === Up or down 20 khz doesn't mean anything if the desensing happens in a stage that lets through a range that's 1 mhz wide. And that is indeed the case for r/c receivers, the front end lets through every signal on the whole 72 mhz band. If an unwanted signal is 60 db above the desired signal, it can impair the receiver's ability to respond to the desired signal. And of course the IF of a little r/c radio doesn't have a lot of selectivity either. What Randy experienced wouldn't happen at the launch area, because all the signals are strong. But in Randy's case, his signal was weak because his plane was low and far away from his transmitter, and the other guy's transmitter was right under the plane. The effect of such desensing is the same whether the desired signal is PPM or PCM, but a PCM radio might have saved him via the fail-safe feature. The plane might have continued on its course until the desired signal reappeared in the passband. RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
Re: [RCSE] Re: TX RF output? Long!
On Fri, Mar 10, 2006 at 11:08:42AM -0500, Rick Eckel wrote: | Hmm. Of course this is true when all are speaking in the same | frequency range. But how about if all the other conversations are | being held above 20khz or below 20hz?? Yes, whispered voices aren't the best analogy, as they all use the same frequency range. But consider somebody near you speaking in a low voice, as you try to understand somebody far away speaking in a high voice -- the low voice will make it harder to understand the weaker high frequency voice. However, in this case, the confusion happens in our brain, not our ear. Our ears really don't work that much like a typical radio receiver. | Does sheer power on other frequencies swamp the front end of a | receiver? Yes. | Shouldn't we see more evidence of this at the launch area? The reason that we don't is that all the signals are of similar strengths, since all the pilots are near to each other. For desense to occur, the signals don't even have to be in the same band. For example, in my car the FM radio (88-108 MHz) signal gets noticibly quieter when I transmit on my 144 MHZ ham radio. However, the effect is much much stronger when the signals are very close to each other, as they would be with two R/C TX's, or a R/C TX and a pager tower (possibly with hundreds of watts) also in the 72 MHz band. Exactly how much a RX is affected by desense and how close the other signal has to be depends on it's design. Unfortunately, our gear is generally made to be small and cheap, and so it's difficult to add too much protection. As for PPM vs. PCM, PCM uses exactly the same sort of RF stage as PPM -- all that differs is what the signal looks like and how it's decoded. If you've lost control with PPM, you'll also have lost control with PCM, it's just that PCM should handle the loss of control better (going to failsafe or position hold rather than random glitching.) -- Doug McLaren, [EMAIL PROTECTED] All theoretical chemistry is really physics; and all theoretical chemists know it. RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
Re: [RCSE] Re: TX RF output? Long!
A PCM signal is no better than PPM. The only benefit would have been if the PCM Rx went into fail safe. Obviously could have been quite helpful. If it did go into failsafe. Bill Swingle Janesville, CA RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
RE: [RCSE] Re: TX RF output? Long!
In Pat's case I would suspect he was not employing PCM given that the person who was present under the aircraft at the time stated that he could here the servos acting erratically prior to full down (exibited behavior of PPM interference). Add to this, and I won't bother surmising why, is that it went full down (I could call in Murphy's law here - as this seems to be the flight maneuver of choice during bad ju-ju). If the operating system had employed PCM, the event in question would have the sailplane continue flying in the direction of the last good framerate before entering hold/FS...whatever that position was, possibly not noticed anyhting unusual. If memory serves, he was level flight... As far as incursions from operating systems outside of the 20KHz spacing, yes, this is entirely possible... Quoting Rob Davis <[EMAIL PROTECTED]>: > So if the far is PCM and the near is PPM does using PCM mitigate this > problem? What about the opposite situation i.e. PCM near and PPM far? > > Rob > > -Original Message- > From: Jon Stone [mailto:[EMAIL PROTECTED] > Sent: Friday, March 10, 2006 8:38 AM > To: EXT-McCleave, Howard R > Cc: soaring@airage.com > Subject: Re: [RCSE] Re: TX RF output? Long! > > From: "Doug McLaren" <[EMAIL PROTECTED]> > > > Of course it's a real phenomenon. The technical term is `desense'. > > > > http://users3.ev1.net/~medcalf/ztx/desense.html > > > It's also called the "near-far" problem. > > Imagine trying to hear a whisper across a crowded room. Nearby louder > voices drowned out the one familiar voice you are trying to hear. All radio > receivers face the same issues. > > Jon > > RCSE-List facilities provided by Model Airplane News. Send "subscribe" and > "unsubscribe" requests to [EMAIL PROTECTED] Please note that > subscribe and unsubscribe messages must be sent in text only format with > MIME turned off. Email sent from web based email such as Hotmail and AOL > are generally NOT in text format > > RCSE-List facilities provided by Model Airplane News. Send "subscribe" and > "unsubscribe" requests to [EMAIL PROTECTED] Please note that > subscribe and unsubscribe messages must be sent in text only format with MIME > turned off. Email sent from web based email such as Hotmail and AOL are > generally NOT in text format > Simon Van Leeuwen PnP Systems - The E-Harness of Choice Radius Systems Cogito Ergo Zoom RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
Re: [RCSE] Re: TX RF output? Long!
Hmm. Of course this is true when all are speaking in the same frequency range. But how about if all the other conversations are being held above 20khz or below 20hz?? Does sheer power on other frequencies swamp the front end of a receiver? Shouldn't we see more evidence of this at the launch area? Inquiring minds and all that. ;-) Rick At 09:37 AM 3/10/2006, Jon Stone wrote: From: "Doug McLaren" <[EMAIL PROTECTED]> > Of course it's a real phenomenon. The technical term is `desense'. > > http://users3.ev1.net/~medcalf/ztx/desense.html It's also called the "near-far" problem. Imagine trying to hear a whisper across a crowded room. Nearby louder voices drowned out the one familiar voice you are trying to hear. All radio receivers face the same issues. Jon RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
RE: [RCSE] Re: TX RF output? Long!
So if the far is PCM and the near is PPM does using PCM mitigate this problem? What about the opposite situation i.e. PCM near and PPM far? Rob -Original Message- From: Jon Stone [mailto:[EMAIL PROTECTED] Sent: Friday, March 10, 2006 8:38 AM To: EXT-McCleave, Howard R Cc: soaring@airage.com Subject: Re: [RCSE] Re: TX RF output? Long! From: "Doug McLaren" <[EMAIL PROTECTED]> > Of course it's a real phenomenon. The technical term is `desense'. > > http://users3.ev1.net/~medcalf/ztx/desense.html It's also called the "near-far" problem. Imagine trying to hear a whisper across a crowded room. Nearby louder voices drowned out the one familiar voice you are trying to hear. All radio receivers face the same issues. Jon RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
Re: [RCSE] Re: TX RF output? Long!
From: "Doug McLaren" <[EMAIL PROTECTED]> > Of course it's a real phenomenon. The technical term is `desense'. > > http://users3.ev1.net/~medcalf/ztx/desense.html It's also called the "near-far" problem. Imagine trying to hear a whisper across a crowded room. Nearby louder voices drowned out the one familiar voice you are trying to hear. All radio receivers face the same issues. Jon RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
Re: [RCSE] Re: TX RF output? Long!
On Thu, Mar 09, 2006 at 10:28:37AM -0600, EXT-McCleave, Howard R wrote: ! What do you think experts, is "swamping" a real phenomenon or did | he have a lousy TX?? Plane's gone but I would still be interested to | know what y'all think. Of course it's a real phenomenon. The technical term is `desense'. http://users3.ev1.net/~medcalf/ztx/desense.html talks about it in some detail, at least from a ham radio point of view. In our case, all we can really do is not let the plane get really far from our TX and yet really close to somebody else's TX. This can happen even if all TX's and RX's are correctly tuned, and even if there's no signal bleeding over into other channels (of course, in the real world there's always some `bleeding', but if the radios are properly tuned it's very weak.) -- Doug McLaren, [EMAIL PROTECTED] How is education going to make me smarter? --Homer Simpson RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
Re: [RCSE] Re: TX RF output? Long!
- Original Message From: "EXT-McCleave, Howard R" <[EMAIL PROTECTED]> I was flying at about 50 feet of altitude along the tree line at the west end of the field when the plane did an immediate vertical dive into the ground with no possibility of recovery. When I walked out to get the trashed plane I found a gentlemen standing at the base of the trees with his transmitter on (not visible when the incident happened) doing a range check on the plane he had just crashed. A friend was walking back to the landing area with it. He explained as my Icon flew over his head he heard the servos "go nuts" and it went straight in. .. What do you think experts, is "swamping" a real phenomenon or did he have a lousy TX?? == Randy, when your signal is weak and there is an adjacent signal that is very strong, bad things can happen. Our receivers have little selectivity, of course, because they have little IF filtration, usually just a couple of 455 khz IF cans. It's not so much that an adjacent signal actually splatters into the passband; what is more likely is that a strong adjacent signal will depress the gain of the receiver on the desired frequency. There are various AGC techniques used by RC receivers, but most will be affected to some extent by strong adjacent signals. This effect is felt even in multi-thousand dollar ham receivers weighing 50 pounds, and obviously it's much more serious in a minimalist receiver like those in an RC plane. Your misfortune was that you were a long way from the plane, and he was right under it. The strength of his signal may have been 60 db or more above yours, which is the kind of thing that presents problems for much more elaborate receivers. This normally isn't the case, since usually all the flyers are standing together, and the signals reaching the plane are of similar strength. In that case, the desired signal still fills up the passband. His transmitter could have been working perfectly legally, right on its freq, no spurious radiation, and still caused such a thing. Sad but true. RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
[RCSE] Re: TX RF output? Long!
Ok, great thread and to some degree, educational. While I have absolutely no technical background on this subject, I have been the victim of a very expensive and unavoidable, on my part, "shoot down". I basically considered it a "swamping" incident, another term for you experts to butcher. This happened at the '05 SWC and cost me a nearly new Icon. Those of you that have flown with me know that this plane had been flown to limits of vision many times with nary a glitch. I was flying at about 50 feet of altitude along the tree line at the west end of the field when the plane did an immediate vertical dive into the ground with no possibility of recovery. When I walked out to get the trashed plane I found a gentlemen standing at the base of the trees with his transmitter on (not visible when the incident happened) doing a range check on the plane he had just crashed. A friend was walking back to the landing area with it. He explained as my Icon flew over his head he heard the servos "go nuts" and it went straight in. The good news is it didn't hit him, the bad was a totaled $2000.00 plane! What do you think experts, is "swamping" a real phenomenon or did he have a lousy TX?? Plane's gone but I would still be interested to know what y'all think. Thanks, Randy (Supra # 21) McCleave RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
Re: [RCSE] Re: TX RF output? and urban legends
- Original Message From: [EMAIL PROTECTED] Cc: Soaring@airage.com Actually Tony, what I stated are actual...heaven forbid...facts, as I prefer to speak from a position of first-hand knowledge and experience rather than hearsay. == Yep. The guesswork Gordy was referring to was his own post. I was just quoting the most correct part of his post, which was when he said he was only guessing. RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
Re: [RCSE] Re: TX RF output? and urban legends
Actually Tony, what I stated are actual...heaven forbid...facts, as I prefer to speak from a position of first-hand knowledge and experience rather than hearsay. The anecdotal evidence put forth by John D. is a great real-world indicator of how prevelant this problem can be. I have personally been on the receiving end of a TX that turned out to be bleeding horrendously into adjacent (lower in this case) bandwidth O/P at the same dBm as my TX (next outing I brought an SA to the field). Not pleasent I assure you...for the other chap in question. Seems he (like others) believed you can merrily replace the XTAL (in the bloddy module) as he saw fit...without the benefit of proper tuning by folks who know what they are doing... Quoting tony estep <[EMAIL PROTECTED]>: > > From: [EMAIL PROTECTED] > The above is of course only a guess... > > > Yep. Perhaps some of the engineers in the group could provide some factual > info. > > > > > Simon Van Leeuwen PnP Systems - The E-Harness of Choice Radius Systems Cogito Ergo Zoom RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
RE: [RCSE] Re: TX RF output? and urban legends
Ever wonder why someone's plane works fine at home field and contest, but gets all kinds of hits/holds at major contests with lots of people. -Original Message-From: tony estep [mailto:[EMAIL PROTECTED]Sent: Thursday, March 09, 2006 10:34 AMTo: Soaring@airage.comSubject: Re: [RCSE] Re: TX RF output? and urban legends From: [EMAIL PROTECTED] The above is of course only a guess...Yep. Perhaps some of the engineers in the group could provide some factual info.
Re: [RCSE] Re: TX RF output? and urban legends
From: [EMAIL PROTECTED]The above is of course only a guess...Yep. Perhaps some of the engineers in the group could provide some factual info.
[RCSE] Re: TX RF output? and urban legends
I hope you're right. Wasn't always like that, and I suspect with park flyers, or any such single conversion (ugh! and yes, I've heard there are other solutions than dual conversion) receivers it still isn't. Back in 1990 or so, I conscientiously got a "1991" system on channel 20. I could shoot down almost anyone at will.* Anyway, if I'm not mistaken, if you're flying hand launch or something so that the other guy's transmitter is one tenth the distance to your plane as yours is, then you're operating at almost a 20db handicap. So his signal had better drop by more than that by the time it gets to be one channel over. Or if you're flying any other event where pilots aren't all in one place. Of course, it's remarkable how much less often the really experienced pilots get "shot down". I think dumb thumbs must somehow interfere with clean radio signals. Real shootdowns are a real bummer. I was at a mismanaged contest once that had slope and thermal components. They handed me my tx, I turned on, heard the commotion, saw the plane diving, figured out what was happening and turned off just before the unfortunate guy had his plane slam into the ground. Or the time my plane started jumping all over and then I heard a bzSMACK! because of a guy who hadn't bothered to look around or range check at the uncontrolled field. (Am I showing my age if I admit that that was on brown and white?) *(Except I didn't know that's what was happening, all I knew was that I'd had my tx tested on [nice to have] the club scanner/frequency analyzer and it was very clean. A beat frequency between channel 20and a TV signal was the problem, I'm told. What finally convinced me was that I could repeatedly lock up a Futaba 5 channel PCM with my signal. ) Gordy wrote: This is mostly just that .splatter, not RF but conversation. Our RX's have a huge problem...they are sooo selective they barely listen to their own frequencies, so the idea of them being bothered by some sort of close emission from a grey tuned TX, while 'possible' fact is the offending TX's emission would have to be as powerful as your own TX's correct output so as to 'slur' your TX's frequency.. snip However stories about getting shot down are reinforced by reports of off tune TX's makes them more dramatic which equals 'real'. When in fact seldom is a 'shoot down' a shoot down, usually the cause is a faulty on board power connection...switch, or connector. Cases like the Nats problems are more likely due to on board antenna situations., or then there is the assumption that the pilots TX must be working just fine at the time of the glitches. Dirty antenna, a funky rubber ducky install or it's sloppy BNC connector connection or some other mechanical shortcomingcouldn't be :-) It is a lot easier and more fun to put the blame on the other and his probably out of tune module, the mysterious 'them' are always the culprit.. snip RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
[RCSE] Re: TX RF output? and urban legends
the receiving end of splatter. This is mostly just that .splatter, not RF but conversation. Our RX's have a huge problem...they are sooo selective they barely listen to their own frequencies, so the idea of them being bothered by some sort of close emission from a grey tuned TX, while 'possible' fact is the offending TX's emission would have to be as powerful as your own TX's correct output so as to 'slur' your TX's frequency.. The reason for tuning your TX is so that YOUR RX can hear it, not to avoid someone else's RX from hearing it. However stories about getting shot down are reinforced by reports of off tune TX's makes them more dramatic which equals 'real'. When in fact seldom is a 'shoot down' a shoot down, usually the cause is a faulty on board power connection...switch, or connector. Cases like the Nats problems are more likely due to on board antenna situations., or then there is the assumption that the pilots TX must be working just fine at the time of the glitches. Dirty antenna, a funky rubber ducky install or it's sloppy BNC connector connection or some other mechanical shortcomingcouldn't be :-) It is a lot easier and more fun to put the blame on the other and his probably out of tune module, the mysterious 'them' are always the culprit.. The above is of course only a guess based on ..oh about a million hours of flying on sites all over the world, conversations with guys like Steiner and Marks on the subject, so take it all with a grain of, any way you want :-) Gordy Los Angles tonite
Re: [RCSE] Re: TX RF output?]
Actually without being as smart as some of you I can still disagree with this. Most radios do get out of alignment. I have been on the receiving end of splatter. A tuneup couldn't hurt. Receivers do emit RF. An ESL member has come up with a way of tracking a receiver based on its emission. He started with duplicating the Walston receiver using a Yasu and other Scanners. Then by playing around he noticed he didn't need a walston transmitter in the plane, that with many RX's he could actually see their output on scanners. While true not all receivers emit, most emit enough that he was able to pick them up. I received a couple of bumps at the nats, but I remember 2 guys being out of shift enough that they caused I think it was Daryl to go in.. about 6-7 years ago. When the scanners looked at their frequencies they were obviously off of their channel... enough to be a problem. Gotta run... my 2 cents.. probably all it is worth... Martin Usher wrote: What a novel and smart suggestion. Makes one wonder how many TX's out there have never experienced a tune-up... They don't have any moving parts. Older radios may have parts like descrete coils (sometimes with slugs) that can can change their size slightly over time (mechanical, maybe due to just moving the radio around) so its possible that the output spectrum could get misshapen (i.e. "splash over to adjacent channels"). Its even possible for crystals to age or get damaged. But in general what you buy should be what you'll use until the mechanical parts wear out. That's not to say that it wouldn't help to look at the output spectrum from time to time, but (IMO) suggesting to people that radios somehow require regular servicing like a car is an application of FUD. Martin Usher (time for the flameproof suit) PS. Receivers don't emit R/F -- actually they could but they shouldn't -- but if the transmitter is prone to drifting around then the receiver would be as well, they've got the same kinds of internals as the Tx. RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format -- Jeff Steifel RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
Re: [RCSE] Re: TX RF output?]
You might consider asking a repair depot about how many TX's come in that are indeed emanating into adjacent channels. Secondly, RX's have interfered with each other in dual installations causing a loss of range, which on some installations has been severe. Using isolation techniques, the problem has been solved consistantly... Martin Usher wrote: What a novel and smart suggestion. Makes one wonder how many TX's out there have never experienced a tune-up... They don't have any moving parts. Older radios may have parts like descrete coils (sometimes with slugs) that can can change their size slightly over time (mechanical, maybe due to just moving the radio around) so its possible that the output spectrum could get misshapen (i.e. "splash over to adjacent channels"). Its even possible for crystals to age or get damaged. But in general what you buy should be what you'll use until the mechanical parts wear out. That's not to say that it wouldn't help to look at the output spectrum from time to time, but (IMO) suggesting to people that radios somehow require regular servicing like a car is an application of FUD. Martin Usher (time for the flameproof suit) PS. Receivers don't emit R/F -- actually they could but they shouldn't -- but if the transmitter is prone to drifting around then the receiver would be as well, they've got the same kinds of internals as the Tx. RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format -- Simon Van Leeuwen RADIUS SYSTEMS PnP SYSTEMS - The E-Harness of Choice Cogito Ergo Zooom RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
RE: [RCSE] Re: TX RF output?]
No flame, just fact. Radios/RF decks (modules) still have tuning coils and the like. Just open up your radio or module and look at all the little parts with wax on them, that's what gets adjusted. We, Horizon Hobby and JR service center tune about 30-40 radios a day. John -Original Message- From: Martin Usher [mailto:[EMAIL PROTECTED] Sent: Wednesday, March 08, 2006 4:01 PM To: soaring@airage.com Subject: Re: [RCSE] Re: TX RF output?] >What a novel and smart suggestion. Makes one wonder how many TX's out there have never experienced a tune-up... They don't have any moving parts. Older radios may have parts like descrete coils (sometimes with slugs) that can can change their size slightly over time (mechanical, maybe due to just moving the radio around) so its possible that the output spectrum could get misshapen (i.e. "splash over to adjacent channels"). Its even possible for crystals to age or get damaged. But in general what you buy should be what you'll use until the mechanical parts wear out. That's not to say that it wouldn't help to look at the output spectrum from time to time, but (IMO) suggesting to people that radios somehow require regular servicing like a car is an application of FUD. Martin Usher (...time for the flameproof suit) PS. Receivers don't emit R/F -- actually they could but they shouldn't -- but if the transmitter is prone to drifting around then the receiver would be as well, they've got the same kinds of internals as the Tx. RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
Re: [RCSE] Re: TX RF output?]
What a novel and smart suggestion. Makes one wonder how many TX's out there have never experienced a tune-up... They don't have any moving parts. Older radios may have parts like descrete coils (sometimes with slugs) that can can change their size slightly over time (mechanical, maybe due to just moving the radio around) so its possible that the output spectrum could get misshapen (i.e. "splash over to adjacent channels"). Its even possible for crystals to age or get damaged. But in general what you buy should be what you'll use until the mechanical parts wear out. That's not to say that it wouldn't help to look at the output spectrum from time to time, but (IMO) suggesting to people that radios somehow require regular servicing like a car is an application of FUD. Martin Usher (time for the flameproof suit) PS. Receivers don't emit R/F -- actually they could but they shouldn't -- but if the transmitter is prone to drifting around then the receiver would be as well, they've got the same kinds of internals as the Tx. RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
[RCSE] Re: TX RF output?
What a novel and smart suggestion. Makes one wonder how many TX's out there have never experienced a tune-up... John Diniz wrote: Food for thought. With all the talk about batteries and redundancy in the terms of saving your expensive RC model I wonder how many people are concerned about their Tx condition and RF output. When was the last time you had your radio in for service and to check the output freq? We've used scanners at events like the USRA Race Over Rantoul to check Tx output. The biggest issue is old radios that are splashing over onto adjacent freq's. This usually more of an issue for the guy on the adjacent channel as the guy with the offending radio say's it works fine. We'll probably be checking radio's at the LSF Soaring Masters to keep this from happening. If its been more than a couple years you might want to get that radio in for a check up. John -- Simon Van Leeuwen RADIUS SYSTEMS PnP SYSTEMS - The E-Harness of Choice Cogito Ergo Zooom RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
