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Old Radio

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Old 01-06-2005, 10:10 AM
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Edge 540
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Default Old Radio

I am helping someone get back into the hobby. Ten years ago they built a PT 20 and flew it once or twice. The plane has set intact for 10 years in a basement with absolutely no use. They gave me the plane to go over. The radio is a Futaba FP-T4L with a 4 channel FP-R4F receiver and 4 FP-s48 servos. I cleaned the engine,( OS MaX .25 ) and it started as soon as I hit it with the electric starter! I charged the batteries and to my surprise the radio did quite well in a range test. Everything works fine.
Here are my questions:
1. All plugs are the old G? plugs. The switch harness, where it plugs into the receiver has 3 wires, just like a servo. It has red black and gray. I was thinking that the third wire was just not used, and Futaba didn't want to bother with modifying the leads, but the battery has three wires coming from it too. Anybody know what is up with that? Don't all modern radios have two wires on the battery and switch harness?
2. The radio is AM. I am only partially familiar with the current regulations on that spectrum. I do not see any "gold stickers." We were planning on flying the plane a few times just to see if he was still interested in the hobby, or if it wasn't something that he wanted to do.[&o] If he does decide to go for it, I would definitely suggest a new radio, or a thorough checking and gold sticker approval of the current equipment from a qualified source. That way, he can join our club.
Also, I will be replacing all of the batteries in the system. I only used the originals because I did not have any compatible ones on hand. I do not think the old ones have a satisfactory capacity anymore, but they worked well for testing.
Thanks
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Old 01-06-2005, 10:57 AM
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Default RE: Old Radio

Based on the information I saw on the Futaba narrow banding FAQ http://www.futabarc.com/faq/service-faq.html#q41 it sounds like the transmitter and receiver are not narrow band. You may be able to find someone to convert the transmitter, but the receiver will always be wide band. I went through this same decision process last May. I decided that by the time I bought new batteries and sent the transmitter and receiver off to have the transmitter narrow banded and the receiver tuned, that it wasn't worth the money. I bought a Futaba 6EXA instead. I then bought a 4YF to give me a second flight pack, spare transmitter (which could be used as a buddy box), and transmitter battery. I'm really glad I went with the 6EXA, the computer features are far superior to a basic 4 channel.

When I ran out of S3004 servos I started changing the plugs on some old S38 and S48 servos. Buy some leads with the new style connector, cut off the old ones and solder the new leads on. So far, I'm only using these in a slow plane, Piper Cub. Works fine.
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Old 01-06-2005, 10:59 AM
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Default RE: Old Radio

The old Futaba systems with the 'G' connectors only used two leads on the battery pack, but had the 3-pin connector.

As far as the transmitter is concerned, it would not be legal to use in the current RC environment. Very likely, it's not even on a legal channel. Unfortunately it is not possible to get the transmitter converted to the narrow-band specifications. Even if it were, by the time you paid (anyone!) to convert it and purchased a new narrow-band receiver (you cannot convert a wide-band receiver to narrow-band), the costs would equal or exceed the purchase price of a new 4 or 6-channel basic system that would comply with the narrow-band specifications.

All wide-band R/C equipment became illegal to use in 1998. The Futaba 4L transmitter went out of production in 1986.
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Old 01-06-2005, 11:36 AM
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Default RE: Old Radio

The crystal says (type 72-5 72.080 AM RX)
Do you know what channel that is. Is it indeed illegal?[] If it is, I will suggest a new radio, and let him get some stick time on one of my planes.
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Old 01-06-2005, 05:24 PM
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72.080 is not a legal RC frequency. It became illegal in the mid-1980's, when the "old" RC channels were phased-out and the "new" (our current ones) were phased-in.
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Old 01-06-2005, 09:14 PM
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Thanks, I guess I will just change all the plugs on the servos to modern J plugs and use them with a new radio. At least I can salvage those. []
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