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Radios

Postby subsurface53 » Fri Aug 23, 2013 9:46 pm

I have bought a sub with a Futaba fp-r127df dual conversion FM 7channel receiver. I am wanting to know is what Futaba radio I can use with this receiver?

Thanks Dave
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Re: Radios

Postby Giovanni » Sat Aug 24, 2013 7:37 pm

This is for 72MHz aircraft only.
You may still find new radios that are compatible.

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Re: Radios

Postby Sub culture » Sun Aug 25, 2013 2:39 am

Giovanni wrote:This is for 72MHz aircraft only.


Depends on the frequency it's tuned to. These receivers come in air and ground frequencies.
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Re: Radios

Postby Giovanni » Sun Aug 25, 2013 4:08 pm

In the USA, it is for air only.
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Re: Radios

Postby KevinMc » Sun Aug 25, 2013 5:31 pm

Giovanni wrote:This is for 72MHz aircraft only.

No, it's also entirely possible that it's 75MHz. They can be converted to 75MHz from 72MHz aftermarket or bought direct from Futaba that way. Need to check what it's set up for first.


subsurface53 wrote:I am wanting to know is what Futaba radio I can use with this receiver?

As above, have a look at the crystal and see if it's got a 72MHz or 75MHz. Usually the 72MHz Rx's come with a 72MHz sticker on their front face so you've probably got a 75MHz unit, but please check to be certain.

Assuming it is a 75MHz set, you've got many choices at hand. Any Futaba radio capable of transmitting FM-PPM on 75MHz will work. There are also a host of other transmitters that will work as well: Hitec, Polks Tracker, W-FLY to name a few.
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Re: Radios

Postby subsurface53 » Sun Aug 25, 2013 8:53 pm

Thanks to all for your input.
It is a FM 75.410/61Mhz receiver. It is out of an older OTW WTC I got with a X craft the X52 Shrimp . There was no radio and it says at the OTW site not to use a PCM radio so I will look for a FM radio. Or maybe a 2.4GHZ radio. My radios I have now are old Futaba Conquest and gold series.

Thanks again on all your help. Dave
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Re: Radios

Postby JWLaRue » Sun Aug 25, 2013 9:52 pm

Dave,

Unfortunately, the 2.4GHz radios will not work for r/c subs. For all practical purposes, the signal will not penetrate the water. You'll need to find a PPM 75MHz radio or get a 72MHz converted to 75MHz.

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Re: Radios

Postby Sub culture » Mon Aug 26, 2013 5:39 am

The reason OTW recommend not using PCM is because it has its own failsafes built in, which bypass the OTW failsafe built into the ballast controller.

PCM failsafes are designed for model aircraft, and react instantly on loss of transmission, which is precisely what you want on something fast moving and airborne, but underwater signal glitches tend to be far more common, so we don't want the ballast tank emptying everytime there is a split second hiccup. Therefore the OTW failsafe has a longer time period before it kicks in (I don't know the exact time, but I would expect two seconds or more).

PCM radios will always have PPM mode as standard anyway, so don't fret about it.
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Re: Radios

Postby subsurface53 » Tue Sep 17, 2013 2:53 pm

The last post says the PCM has a standard mode in PPM. Are all Futaba radios that are PCM have this standard mode of PPM?
Dave
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Re: Radios

Postby KevinMc » Tue Sep 17, 2013 9:42 pm

subsurface53 wrote:The last post says the PCM has a standard mode in PPM. Are all Futaba radios that are PCM have this standard mode of PPM?
Dave


I can't answer for every Futaba PCM radio, but every one I've come across does. Do you have a particular radio model in mind?
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Re: Radios

Postby Sub culture » Wed Sep 18, 2013 10:23 am

PCM is always proprietary, so it varies from company to company. Therefore manufacturers bolt it onto existing PPM, so its no sweat for the manufacturer to include the two modes.
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Re: Radios

Postby jonel » Fri Sep 20, 2013 4:01 pm

Re: Radios

Postby Sub culture » Mon Aug 26, 2013 5:39 am
The reason OTW recommend not using PCM is because it has its own failsafes built in, which bypass the OTW failsafe built into the ballast controller.

PCM failsafes are designed for model aircraft, and react instantly on loss of transmission, which is precisely what you want on something fast moving and airborne, but underwater signal glitches tend to be far more common, so we don't want the ballast tank emptying everytime there is a split second hiccup. Therefore the OTW failsafe has a longer time period before it kicks in (I don't know the exact time, but I would expect two seconds or more).

PCM radios will always have PPM mode as standard anyway, so don't fret about it.


I have an older Futaba Ft-5UAP 50 mhz radio that I intend to use with a new sub model using a FP-R129DP receiver that is labled as a PCM1024. I thought I read in the manual that its possible to either turn off the failsafe settings or choose settings that make the failsafe mode have no effect. Am I wrong?

Thanks
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Re: Radios

Postby Sub culture » Fri Sep 20, 2013 6:39 pm

Highly possible- PCM varies from manufacturer to manufacturer. I don't know the specifics of your set, but it doesn't sound like it will cost you much to try it and see.
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Re: Radios

Postby tsenecal » Fri Sep 20, 2013 10:44 pm

the 5uap is an older computerized (possibly first generation) radio. I owned its big brother, the 7uap, 20+ years ago. under the front panel, on the right side, you will see a switch labeled "PPM" at the top, and "PCM" at the bottom (see page 6 of the linked PDF). if you are using it with a FP-R129DP receiver, the switch on the transmitter will need to be in the "PCM" position, and right next to that switch are the two "fail safe" switches. setting both of those switches to "off" will effectively make your system act like a PPM system.

http://manuals.hobbico.com/fut/5ua-f-p-manual.pdf

by the way, for the OP, there is a 7uap on ebay right now for an incredibly cheap price... it and a module would work great for the OP's fp-r127df.
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Re: Radios

Postby KevinMc » Sat Sep 21, 2013 8:47 am

tsenecal wrote:if you are using it with a FP-R129DP receiver, the switch on the transmitter will need to be in the "PCM" position, and right next to that switch are the two "fail safe" switches. setting both of those switches to "off" will effectively make your system act like a PPM system.


Sorry be contradictory, but I'm afraid that's not quite right. When you "turn off" the failsafe with this Tx/Rx combination all you're doing is removing your ability to "preset" the throttle position when the signal is lost. Futaba PCM failsafe works in two stages. (Stage 0 is good signal, all operating normally.) Stage 1 is HOLD mode - the Rx detects one or more bad frames have been received and throws them out, all the while repeating the last known good servo information. Stage 2 is FAILSAFE and varies depending on the sophisication of your transmitter, but in general provides the user with the ability to pre-determine the position for some or all of the servos to be set to. The problem for us here is that when your "turn off" failsafe on a Futaba PCM system all you're doing is turning off Stage 2 of the above process, when the signal is lost the Rx will still generate signals for the servos based on the last good received data where a PPM system would generate no signal at all. That's why "missing pulse detector" failsafes don't work on Futaba PCM systems. (I believe one of the JR PCM systems operates similarly but I don't recall which one it is.)
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