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On Tue, 29 Jul 2003 23:04:00 +0100, Paul Burridge
wrote: On Tue, 29 Jul 2003 04:12:43 GMT, (John Crighton) wrote: Or find, beg, borrow, "buy used," or build an ordinary AM R/C transmitter. Ten quid should get you an old style metal cased Futaba transmitter. Hi John, I've already got an AM tx and rx set-up, but am loathed to use it due to the much increased risk of interference from the speed controllers, motors, etc., which as you will know, is far more likely with an AM system. Keep thinking! -- Hello Paul, I would try out your old AM set for sure. You never know your luck. If the servo connections are compatible it will only take a short time. What brand/model? I agree with you that the AM set has an increased risk of interference from your own motors but you said some time ago that your robot works fine at your place but at the venue with other competitors and their transmitters around, the interference is bad for you with your present Sanwa FM set. Even if you do not fit the AM set to the robot, take the working AM set in a box to the venue and see if the servos misbehave in that electrical noisy environment. Regards, John Crighton. Sydney |
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On Wed, 30 Jul 2003 21:28:29 +0100, Paul Burridge
wrote: Even if you do not fit the AM set to the robot, take the working AM set in a box to the venue and see if the servos misbehave in that electrical noisy environment. See above. We won't be using that set-up ever again for this application! -- Hello Paul, I think you are missing my point when you said, "We won't be using that set-up ever again for this application!" My point is this. If the radio control set works OK, while just sitting in its own cardboard box , at the noisy Venue, meaning, the servos work nice and smooth. If you then install that same Rx and servo set into your metal box robot and the servos play up, that is now an " installation problem." You cannot blame the gear. Let's try and sort this out with some basic checks. Using a field strength meter (which is just a simple crystal set with a large moving coil meter as discussed months ago, I assume you have made one already), are both the Sanwa and Futaba transmitters producing similar output power when compared to a known good working transmitter? Yes or No? At your place, are range checks of both the Sanwa and Futaba R/C sets, on there own, not installed in anything, over 100 yards . Yes or No? At your place, are range checks of both the Sanwa and Futaba R/C sets installed in the robot or metal test box with "no" drive motors connected still over 100 yards. Yes or No? At your place, are range checks of both Sanwa and Futaba with drive motors being controlled and running nicely, still over 100 yards. Yes or No? At the noisy Venue, while doing a range check of less than 30 yards with all other competitors absent or their transmitters switched off in the Tx compound, do both your Sanwa and Futaba R/C sets play up? Yes or no? At The Venue, do other competitor's radio control sets play up like yours Yes or No? At the Venue have you scanned the band with a simple crystal set type radio or fancy scanner for some ******* with a transmitter who is determined to give you, personally, a hard time? One last thought, I take it that you have sorted your aerial out so that you do not have a long dangly piece of wire as an antenna lead-in, inside the metal robot body from the base of your whip antenna mounting bracket to the Rx input. If you do have a long wire lead-in, that is bad as it will pick up local motor noise very nicely. If your Rx is a long way away from your antenna base, use coax for the lead-in as explained here. http://homepages.which.net/~paul.hills/Radio/Radio.html If after all that basic stuff has been checked and still no joy then consider a dual conversion superhet Rx. like this one. http://www.norcim.fsnet.co.uk/Index.htm#U You could scratch build from the given circuit and the description of how it works on that web site. Or buy the kit from Micron for 32 quid. If you are still having problems after all that, sorry Paul, I give up. Regards, John Crighton Sydney |
On Wed, 30 Jul 2003 21:28:29 +0100, Paul Burridge
wrote: Even if you do not fit the AM set to the robot, take the working AM set in a box to the venue and see if the servos misbehave in that electrical noisy environment. See above. We won't be using that set-up ever again for this application! -- Hello Paul, I think you are missing my point when you said, "We won't be using that set-up ever again for this application!" My point is this. If the radio control set works OK, while just sitting in its own cardboard box , at the noisy Venue, meaning, the servos work nice and smooth. If you then install that same Rx and servo set into your metal box robot and the servos play up, that is now an " installation problem." You cannot blame the gear. Let's try and sort this out with some basic checks. Using a field strength meter (which is just a simple crystal set with a large moving coil meter as discussed months ago, I assume you have made one already), are both the Sanwa and Futaba transmitters producing similar output power when compared to a known good working transmitter? Yes or No? At your place, are range checks of both the Sanwa and Futaba R/C sets, on there own, not installed in anything, over 100 yards . Yes or No? At your place, are range checks of both the Sanwa and Futaba R/C sets installed in the robot or metal test box with "no" drive motors connected still over 100 yards. Yes or No? At your place, are range checks of both Sanwa and Futaba with drive motors being controlled and running nicely, still over 100 yards. Yes or No? At the noisy Venue, while doing a range check of less than 30 yards with all other competitors absent or their transmitters switched off in the Tx compound, do both your Sanwa and Futaba R/C sets play up? Yes or no? At The Venue, do other competitor's radio control sets play up like yours Yes or No? At the Venue have you scanned the band with a simple crystal set type radio or fancy scanner for some ******* with a transmitter who is determined to give you, personally, a hard time? One last thought, I take it that you have sorted your aerial out so that you do not have a long dangly piece of wire as an antenna lead-in, inside the metal robot body from the base of your whip antenna mounting bracket to the Rx input. If you do have a long wire lead-in, that is bad as it will pick up local motor noise very nicely. If your Rx is a long way away from your antenna base, use coax for the lead-in as explained here. http://homepages.which.net/~paul.hills/Radio/Radio.html If after all that basic stuff has been checked and still no joy then consider a dual conversion superhet Rx. like this one. http://www.norcim.fsnet.co.uk/Index.htm#U You could scratch build from the given circuit and the description of how it works on that web site. Or buy the kit from Micron for 32 quid. If you are still having problems after all that, sorry Paul, I give up. Regards, John Crighton Sydney |
In article ,
says... Hi chaps, I've decided to bite the bullet and try to build an RF filter for 40Mhz. This filter will ideally have a very, very sharp characteristic at one single spot frequency +-20Khz and attenuate the crap out of anything either side of this. It'll need to be tunable over a range of say 200Khz. Can anyone give me a steer on what type of arrangement would be best suited to fit this purpose? Thanks, p. -- "I believe history will be kind to me, since I intend to write it." - Winston Churchill i just read this thread and had a few thoughts. i don't know what kind of interference you're dealing with, nor do i know what restrictions are placed on your competitions. i was thinking about front end overload, also. the types of interference vary in different countries, but those paging towers and, taxis, etc. all play hell on a front end. you really need a spectrum analyser to figure out what you're deaaling with. as for those ceramic resonators, they're ok, but in the better receivers, they're followed by if xfmrs to get rid of the spurious response of the ceramic filter. since you are thinking of just starting from scratch, here's what i'd do if you're not bound by rules. http://www.aerocomm.com http://www.radiometrix.com cost? i dunno. i figure if you can afford one, good. then you can spend more time on the robotics and weaponry. if you can use these, the question becomes a matter of whether you can retrofit one of these in time. i'm not ready to look into using them yet and therefore haven't gotten into the details. so i don't know what you'd have to do to get a PWM signal in and out, but since they handle a higher data rate (1 Mbps) than std R/C PWM, you could bust the PWM signal up into little "chips" and reconstruct it on the receiving end. maybe an integrator/LPF would be all you need. on the other hand, maybe you can just send" the PWM directly. I'm sure the applications engineers could help. hope this helps. mike |
sorry, i did mean PPM, not PWM a link was provided earlier. might be this, or it may link to this. there're links to radios for robot wars. according to this page there are 2 bands allowed, so maybe those 2.4GHz radios are verbotten. that sucks! it's a robot competition, not a ham competition. http://homepages.which.net/~paul.hills/Radio/Radio.html mike |
sorry, i did mean PPM, not PWM a link was provided earlier. might be this, or it may link to this. there're links to radios for robot wars. according to this page there are 2 bands allowed, so maybe those 2.4GHz radios are verbotten. that sucks! it's a robot competition, not a ham competition. http://homepages.which.net/~paul.hills/Radio/Radio.html mike |
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