<div>Wayne,</div> <div> </div> <div>Thanks for that report!!! I always like to hear real-world data.</div> <div> </div> <div>I was not saying that I advocate PPM over PCM. I like the idea of failsafe. I only use the PPM receivers in my smaller planes. Nothing but the PCM goes in my competition or giant scale planes.</div> <div> </div> <div>However, the Berg RX shows that you can have PCM-like features with a PPM signal. I would love it if you could test the Berg 7 under the same scenario that you performed your previous tests.</div> <div> </div> <div>It would also be good to subject the RXs you tested to other interference sources, such as on-board ignition noise. Not sure how you would do that, however.</div> <div> </div> <div>Bob R.</div> <div> </div> <div> </div> <div><BR><B><I>Wayne <Whinkle1024@msn.com></I></B> wrote:</div> <BLOCKQUOTE class=replbq style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT:
#1010ff 2px solid">Bob, I understand how it works. The Carrier signal is still FM and I<BR>understand that. The fact that the signal is digitally encoded and how it is<BR>encoded rejects bad signal or noise or what ever you call it better than<BR>straight PPM. I spoke to a semi local Team JR guy at a contest and he told<BR>it was like a little email package with PCM to simplify it. If the email was<BR>formatted properly then the RX said OK you are my daddy. If the signal was<BR>not formatted properly it would reject it in favor of the proper format and<BR>if none was found it would do what the Failsafe setting told it to do. In<BR>some cases that is Hold the last input on the channel and if you program it<BR>to go to a specific position it would. In the case of straight PPM if the RX<BR>sees the signal it passes it through after its been filter and so on. This<BR>is why you see a glitch in FM(PPM) and not in PCM<BR><BR>Am I right?<BR><BR><BR>I know that F/S doesn't right
the model but in reality if you are getting<BR>radio interference would you rather have the model do something predictable<BR>like low throttle and hold other controls or do something totally<BR>unpredictable. I have played with F/S in the air by turning my TX on and<BR>off. The return of the signal is very very fast like a second or so. My<BR>thinking is that if you have enough interference to make the model go into<BR>hold "Lockout" for long enough to crash then I think its reasonable to<BR>assume this interference is bad enough that the model may very well not be<BR>controllable?<BR><BR>We did some testing last fall at my local club as guys had questions about<BR>this subject. This followed a serious accident in which a 40% model at a<BR>Giant Scale fly-in was controlled by a little $60 FM RX and went to full<BR>power and cut through the pits and into another modeler. This guy almost<BR>died. A tragic event for sure but a $3000 or $4000 model controlled by a $60<BR>RX?
one of our club members was a witness to the event and came home with a<BR>major agenda for our club to implement. Our club was looking at a PCM or<BR>aftermarket F/S device requirement to help mitigate issues. Our big concern<BR>is as with all flying sites the homes are getting closer and we don't want a<BR>model heading off to meet the local neighborhood.<BR><BR>We flew some trainers and foamy models. We took models high and simulated<BR>PCM F/S and shoot down situations. For our tests we only used Futaba and JR<BR>radios. These were higher end TX's as we used the synth capabilities on some<BR>of the systems to create the issues (JR 9303, 8103, 10X and Futaba 9C'S and<BR>9Z's also a 14MZ). We tried lots of different frequencies throughout the<BR>band. We used everything from little hitec foamy size rx's to the top of the<BR>line 14MZ 2048 stuff. In the cases of the PCM system we found that in most<BR>cases the Futaba and JR PCM stuff was pretty bullet proof even in a
shoot<BR>down. It took a very close TX of the same brand to cause a PCM HOLD<BR>condition (our test had engine go to Idle so we could hear it go in and out)<BR>If the radio brands were mixed JR flying and Futaba as the shoot down it was<BR>a rare blip of throttle and the longest hold was on the order of maybe a<BR>couple seconds. In the case of same brand shoot down the model would go into<BR>PCM hold for longer until the shoot down TX was off. Then immediately the<BR>model was in full control again. Sometimes we could not even tell the shoot<BR>down TX was on until its antenna was extended or the primary antenna was<BR>collapsed partially. If the primary was PCM and the shoot down TX was in FM<BR>mode it was almost a non existent problem. A very very rare blip of power<BR>when the shoot down TX was closer to the model than the primary. And this<BR>was only with the shoot down antenna extended more than about 1/3 to 1/2<BR>way. In other rare cases the shoot down TX
actually became the primary and<BR>started controlling the model. This was rare but we did se it happen. The<BR>2048 didn't do it but the 1024 JR and Futaba stuff could easily. In fact we<BR>had two 9303's and copied the program between them. We just swapped off the<BR>TX that was off, then the pilot that was flying would shut his TX off and<BR>the next guy turned his on. Man it really was a cool experiment and proved<BR>the reliability and consistency of the systems.Pilot saying ready off, #2 Ok<BR>I'm on, got it.<BR><BR>Our club was very impressed with the PCM rejection of the signal. In fact I<BR>felt the model was in many cases better in control with the PCM holds going<BR>in and out than the FM responses. The model never flipped upside-down, never<BR>snapped or went wild. It just held its path and input. If that happened to<BR>be a roll or loop it would continue to roll or loop at the given rate but<BR>that was all. The other note was many club members felt PCM hold
was a<BR>forever lockout thing meaning the hold meant the model was going to crash<BR>period and they wanted to have some control. Well we never had that. Once<BR>the interference (shoot down TX) was off every single time the primary got<BR>immediate control. And I mean right now as if it never had the issue coming<BR>back.<BR><BR>The FM systems in the same test didn't care about brand of TX, and didn't<BR>care about distance or antenna extension on the shoot down TX. In fact most<BR>cases the models became uncontrolled and while it would still respond to the<BR>primary TX in the middle of some of the glitching the models were just<BR>basically all over the place. It seemed like the RX was passing just any<BR>signal through. Of big note if the shoot down TX was FM mode also the models<BR>were glitchy but the primary could still have an effect not really to fly<BR>the model in a save situation but it had an effect. . If the Shoot down TX<BR>was PCM there was no hope. The
models were literally all over the place and<BR>yes some primary control was getting through but you could not rely on the<BR>input to fly the model.<BR><BR>We conducted this testing on several weekends and with lots of club members<BR>present. Yes we took some risks but we really wanted to see if there was a<BR>difference. The result of this test made my local club hit the hobbyshop<BR>with a huge order of PCM RX's. I think he sold like (25) JR R770's over the<BR>course of the next week. The old guys in the club found out their model was<BR>better protected using the PCM over their FM and it was a black and white<BR>comparison. Besides most sport models they guys are flying are in the<BR>$400-800 range and what is the extra $40 from the R700fm to the R770pcm. Now<BR>both of these are Synth so that is cool too.<BR><BR>Our club now has requirements for a F/S device or PCM on all models over<BR>7lbs. Why 7lbs? well we felt that we didn't want to discourage trainers
and<BR>new folks starting out, but we did want basically anything 60 sized and<BR>bigger to have some F/S capability and the club rule is a safety officer can<BR>ask you to show it before you fly. I know most of the GS fly-ins in our area<BR>and the Joe Nall now require this. Before you take off the flightline<BR>official asks you to turn off your TX to prove a low throttle setting. The<BR>groans came from the old guys for sure, but in the end they were the ones<BR>that really felt the clubs responsibility to our neighbors and to our selves<BR>was more important. The next thing was a phase in period of 1 yr. We are now<BR>coming up on that 1yr and the rate of crashes has dramatically reduced at<BR>our field. The concern was older FM TX's that could not use do PCM well H9<BR>answered the call with a $20 F/S module for use on FM systems. Now I think<BR>there are 3-4 different brands out there. So for the cost of a gallon of<BR>fuel and a few props you can have PCM or a FS
device for FM. We have a log<BR>book that you are suppose to log any crashes or mishaps. We use it to razz<BR>the guys and also to keep track if we have an issue on certain channels or<BR>with a specific brand or RX or the like. Well the 2005 log book was always<BR>an issue of radio quit, glitched or what ever. Since the testing and mass<BR>exodus to PCM the crashes are greatly reduced and top it off the crashes we<BR>are having with radio issues are the type of stuff than you would see like<BR>dead battery or bad switch not the mystery glitch or I got hit. Guys now<BR>know what radio problems look like and they are diagnosing crashes better<BR>and preventing them. Now with everybody flying PCM its really rare to see<BR>radio problems at the field. Our field is mostly JR thanks to our semi-local<BR>Team guy. The most common radio now is the 6102, 8103 and the 9303.<BR><BR>Seems that pattern guys tend to spare no expense in the TX department lots<BR>of 9Z's and 10X's as
well as the 9303 and 9C systems yet I'm seeing many use<BR>a PPM RX. My curiosity was peaked as I would have expected nobody to use FM<BR>in this group. Before the NATs the young man was having issues with his<BR>system and when he told us what he was using for servos, leads and radio<BR>gear I was shocked. A competition level pilot using aftermarket extension<BR>leads and FM Rx'. I was always taught to stay within the brand. Servos are<BR>OK to mix brands with but for switches, extensions, and RX's stay in your<BR>own yard the OEM stuff is just a dollar more you have less trouble with it.<BR>The models are expensive and we spend hours and hours building and trimming<BR>them up. The real cost in loss of a model is the time trimming and setting<BR>up a new plane to be just perfect. The Money is one side but to me its all<BR>the time and passion working toward the perfect flying model. It sucks when<BR>you are 1/2 way there or even 99.99999% and the model is gone hit the
CLR<BR>key in the TX and start over with a new one.<BR><BR>Just passing on some experience we had with it. We proved to ourselves that<BR>PCM not only protected our people and neighbors better but it saved more<BR>airplanes too. I understand we really only tested a single condition shoot<BR>down situation and real interference is more random and rare in the real<BR>world. We felt that the shoot down was the worst case situation for our<BR>field as we are our away from industrial areas and other noisy environment<BR>stuff. We do have some homes about 1/2 mile back behind our pit area to the<BR>south but models are never flown back there. We have a rule to keep<BR>everything North of our runway.<BR><BR>By the way lots of guys locally are using the Spectrum DSM as it has a<BR>failsafe like PCM and it works great in those small parkflyer models. One<BR>guy is even flying it in his 40 sized trainer converted to
electric.<BR><BR>thoughts?<BR><BR>Wayne<BR><BR>_______________________________________________<BR>NSRCA-discussion mailing list<BR>NSRCA-discussion@lists.nsrca.org<BR>http://lists.nsrca.org/mailman/listinfo/nsrca-discussion<BR></BLOCKQUOTE><BR>