Not so much help - more an observation...

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Dodgy Geezer
Posts: 62
Joined: 17 Jun 2018, 09:54

Not so much help - more an observation...

Post by Dodgy Geezer »

I was repairing an old Macgregor 'all-transistor' Mk1 transmitter by replacing the only electrolytic on the board - which seems to be a standard fail item due to age. That electrolytic conveys the tone into the aerial circuit, so if it goes open circuit the Tx will radiate, but the tone button won't work. In this case, though, the tone seemed to be continually on - it could be heard very faintly on a SW radio.

I replaced it - and the tone burst into loud life - but we had an oddity. When the aerial was retracted down to less than 14" or so I got what sounded like a feedback whine through the radio. This was probably what was being interpreted by the Rx as a tone signal. I suspected that this was an aerial tuning issue, since I had also replaced the aerial, tried to turn the ferrite slug on the aerial coil, and found it was stuck fast. At the moment it's sitting with a drop of WD40 in it - has anyone got a better idea?
GliderRider
Posts: 3
Joined: 08 Nov 2021, 18:40

Re: Not so much help - more an observation...

Post by GliderRider »

Hi DG,
I can't aswer your question, but I can add some possibly useful info. On early transmitters prolonged operation with the aerial down could damage transmitter components. My first set was a secondhand Fleet three channel set dating from about 1971, bought from the Fleet Control Systems shop. I was told that mine failed for this reason. Anyway they replaced some internal component and told me to always have the aerial up except for a very quick range check.

The aerial on this set was really long. About 1 1/2 times the length of the Futaba L series with which I replaced it.
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