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repair aerial lead


J.N.
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I have a Futaba R136F receiver with a snapped aerial lead 20mm from the printed circuit board. I am reluctant to re-solder the lead onto the board because of heat transfer even though I am familiar with heat sinks, I thought to bind and solder the lead together. Can someone please advise.

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I've seen spliced 35 and 27 MHz aerials, just make sure the length isn't altered too much - an inch here or there is nothing - and that the splice is well supported with heat shrink tube. Personally I'd replace the aerial at the board using a 15W pencil tip iron.

The other option is Martyn's hammer, after all 35MHz receivers are two a penny second hand, or new after market units can be had from GS, BRC, Micron and the like for a fraction of Futabas prices.

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I'm with Bob - solder in a new aerial wire, So long as you have a clean iron and it and the wire are well tinned, the iron will only be on the board for a second. I've done a fair few over the last 40 years and never had a problem.

The key thing is getting the aerial the correct length so it resonates in the right frequency band. Doesn't have to be spot on but once you have fixed it then do a range check. The further away you get from the ideal length then the range will deteriorate.

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  • 8 years later...

It’s getting a bit nostalgic to read about 35 Meg radio nowadays, it’s tending to bring back long distant memories… Aerials are another of those little aeromodelling items that have had their share of comments and discussions here on the forum over the years and I can remember that on one occasion I collected together half a dozen receivers and compared the aerial lengths by lying them side by side. This was just to see how important it was to have exactly the right length, there was a school of thought at the time that suggested it could be very critical, almost to the millimetre. Needless to say, they were all different lengths and there was about 6 inches* difference between the longest and shortest.

On a later occasion I was flying a 100 inch powered glider and this had the rx right at the back with the full length aerial hanging out under the rudder. At one stage I noticed that this was considerably shorter than it was supposed to be, by perhaps a bit more than half I should think, and I never did quite understand how that came to be so… also I didn’t have a clue as to how long? it had been like that either, it might well have been a while. After a full distance ground range check I tentatively tried soaring it again and quickly found it made not an iota of difference wherever the model went. Then I though I’d try the inverse state so taking some odd wire from the field box plus the 12 volt iron and in a twinkle an aerial about 6ft long was in perfect working order. Again, neither a single tiny glitch nor a lone tiddly wibble wobble was there ever to be seen in many a jolly jaunt toward yonder cirrocumulus, and I often tended to fly right on the limit of visibility, just to see how far I could get. The set up was a Graupner 600 brushed motor back then, a speed control from one of the very early small electric helicopters, a ‘Whisper’, and 7 and 8 cell nickel packs. The receiver was the Fleet 4 channel miniature one with a MPX crystal and MPX transmitter with a very ducky rubbery MPX aerial.

If I’m remembering correctly, Micron advised approximately 39 inches aerial length for their homebuilt rx.

I’ve always owned an estate car and always with a second 12 volt battery right at the back permanently connected to the car battery charging system and therefore always charged. I flew in a very convenient private field where I was invariably on my own anyway so I could just sit on the back ledge of the motor and fly. I charged the flight packs by simply connecting them directly to the car battery under the bonnet via the long lead, there was enough resistance to limit the current by an amp or two; the 7 cell packs I disconnected when they got really nice and warm (hot) and an 8 cell could just stay there very slowly simmering anyway, 12 volts are not enough poke to take a 9.6V NiMH pack right up to it’s Delta Peak point; probably at least 13.5V plus required. Still enough charge for a goodly flight, though.

NB * Please note the now inevitable revert back to the use of ‘real and proper’ units of measurement in a few days time, will this now be mandatory from 1st Jan or still require a further 4.5 years of debate, d’ya think….. But just as long as a pint is still a pint, looks like a pint and always stays as a pint…….milk, naturally….

All this is just relating my own random experiences of course, merely an observation and definitely not intended to be seen as any form of instruction or recommendation, others may well find that their equipment might respond in a much different manner.

PB

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I remember one of the receiver circuits published in RCM&E or RM used an FET buffered front end that detuned the aerial so that any length could be used depending on the range required, presumably without affecting S/N ratio. Other receivers used tuning coils to base load for the required aerial length but this still left quite a broad response band. I suppose you wouldn't want it too tight or it would favour particular crystal sets.

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