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am vs fm vs spectra radios - 9/9/2007 11:38 PM   
hansvonpensch


 

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From: VERO BEACH, FL, USA
Status: offline 		I went to the lake this morning with my Crockett and a $50 AM 2 channel radio. With about 8 boats running 2 radios were interfering with my boat, because the were no other boats on the same channels me, at first we could not figure it out, until some one pointed out because I was on an AM radio, the band was very wide, I guess this is true, but the questian I ask is, to what degree, thanks Randy.

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RE: am vs fm vs spectra radios - 9/10/2007 1:32 AM   
Ghost in the shell



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From: Stoke on TrentStaffordshire, UNITED KINGDOM
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quote:

ORIGINAL: hansvonpensch

I went to the lake this morning with my Crockett and a $50 AM 2 channel radio. With about 8 boats running 2 radios were interfering with my boat, because the were no other boats on the same channels me, at first we could not figure it out, until some one pointed out because I was on an AM radio, the band was very wide, I guess this is true, but the questian I ask is, to what degree, thanks Randy.


the 27mhz wave band used to have a handful of coloured bands, red, blue, orange, yellow, brown etc, however recently they have increased the channels here in the EU, if your radio is of an older type, it may not be narrow enough.

best idea: if you are in the eu, go for a 40mhz unit, am or fm, if you are stateside, get a cheap 75mhz set am or fm as you are a 2ch set. 2.4ghz is good though if you are runnnig a 2ch boat, do you need the expence? probably not.

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RE: am vs fm vs spectra radios - 9/10/2007 2:09 AM   
hansvonpensch


 

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From: VERO BEACH, FL, USA
Status: offline 		It is a 75 MH Band 2 channel.

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RE: am vs fm vs spectra radios - 9/10/2007 2:21 AM   
Ghost in the shell



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From: Stoke on TrentStaffordshire, UNITED KINGDOM
Status: offline 		does it react the same when you swap crystals over with someone else using an identical radio on a different frequency? does it jutter when solo? also where is your antenna running, are your rx batteries charged?

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RE: am vs fm vs spectra radios - 9/10/2007 3:00 AM   
mfr02


 

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From: BlackpoolLancs, UNITED KINGDOM
Status: offline 		FM transmissions will be picked up by AM receivers, but the AM RX will not do anything sensible with the signal, just produce a gibberish signal. Check the frequency numbers on your TX crystal. If you can check out the TX frequencies of the TXs that you think are interfering and find that they are very close, that is a clue to get some spare crystals as far away in the band as possible.
One test is to switch off the suspect TXs and see if the interference stops.

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RE: am vs fm vs spectra radios - 9/10/2007 4:20 AM   
hansvonpensch


 

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From: VERO BEACH, FL, USA
Status: offline 		I was planning on buying a spectra radio.
the shop owner told me it came with servos for planes and I might have to buy larger servos or use the ones on my cheap radio.

Questian. is what I was told today true, " AM raidos have a wider band. so they are subject to more interference.

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RE: am vs fm vs spectra radios - 9/10/2007 12:56 PM   
mfr02


 

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From: BlackpoolLancs, UNITED KINGDOM
Status: offline 		The transmitted band of AM as used for model control is actually narrower than FM, but the working methods are different. AM sets work by switching the signal on and off to provide the control pulses. FM works by altering the transmitted frequency. A minute change, but there. The FM receiver responds to the changes, an AM set being presented with an FM signal will do the best it can, which results in random operation. An FM set presented with an AM signal will tend to ignore it.
The above is not totally accurate, but close enough for understanding where the problems come in.

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RE: am vs fm vs spectra radios - 9/10/2007 1:01 PM   
LtDoc


 

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Status: offline 		No, AM signals are not 'wider' than FM signal, just the exact opposite is true. An AM signal is typically about 6 Khz wide. An FM signal can be between about 12 Khz and 25 Khz (depends on how/where it's used, 'wide FM' or 'narrow FM'). The problem is mainly associated with the spacing between channels, and that AM will sort of pick up FM stuff (isn't really usable, but still possible). It's a matter of how selective (not sensitive) the AM receiver is, which is never all that selective with R/C systems. Just one of 'those' things when mixing AM and FM.

There are no 'air' servos, as such. The biggest difference between 'air' servos and 'surface' servos is in physical size and strength. Since stuff in planes needs to be as light weight as possible, using 'smaller' servos is sort of nice, kind of. That's a terrible way of explaining it, but you get the idea. Most servos are interchangeable, can be used with almost any radio system (the plug being the biggy, may not fit?). They may not fit in the model, but the radio system doesn't much care about that part of it.
- 'Doc

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RE: am vs fm vs spectra radios - 9/10/2007 1:32 PM   
Ghost in the shell



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From: Stoke on TrentStaffordshire, UNITED KINGDOM
Status: offline 		even if you go down the spektrum route,

there is JR's own spektrum radio
though Futaba have brought out FASST

which ever one you choose, chances are you will only need the rx and tx set up, as your servos that are already in the model, along with your speed controller (presuming you are running electric) will fit the reciever, you may however need to file off the direction protection tabs on the servo-wires if you are using futaba. however if you want a good radio on 2.4, go for Futaba's 6EX

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RE: am vs fm vs spectra radios - 10/7/2007 9:47 PM   
texas_hippie


 

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From: Somewhere in, TX, USA
Status: offline 		I have the Spektrum DX6 2.4ghz radio in my American Enterprise by Dumas. I LOVE this radio! You'll have no problems with interference from any other radio.The radio is built for "park flyer" aircraft. (I.E. small electric powered planes built for use with limited range). With a boat, I've never sailed at over 150 yards, so never had any problems with range. As for the servos, yes, they are very small, however by no means would I consider them weak. I wouldn't use them in a very large boat, but for something like the Crockett's rudder, there would be no problem. If you're using an ESC for speed control, no servo is required anyway. If you're using a mechanical (variable resistor style), no problem there either, plenty of torque to move the actuator. Glitches from the motors, and switches in your boat are eliminated also with the 2.4 ghz system! The servo set up is all done in the transmitters computer. You can mix channels, set servo throw lenghts, reverse throw on the servos, ect. It's a six channel radio, and I use the flap channel, and the gear channel to actuate switches for the navigation, deck, search, and work lights. I highly recommend this radio, and see it as the "wave of the future" as far RC boating is concerned. At less than $200 bucks, you can't go wrong! By the way, when you fire it up, it automatically searches for, and locks on to an unused frequency! You NEVER again will have to worry about buying, and switching chrystals again. I got mine through Hobby Lobby via their web site, (Just thought I would throw in a plug for them since they have been a very pleasureable company to work with).

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