Glider Electronics TM62 - UK Vintage Radio Repair and Restoration Discussion Forum

sortedradio · 29th Nov 2008, 6:57 pm

Hi there,
I have been asked by a friend to alter the channel 1 frequency on this mobile radio from 129.9MHz to 129.975MHz. He has also given me a TM61 as a "donor" set if needed, which has a 129.975MHz channel.
I can see two crystal and two adjustable trimmer coils per channel, Tx and Rx I assume. I have aligned domestic sets before and have a strong electronics background and a fair amount of test equipment.
Any information/advice on how to tackle this would be appreciated.

Thank you
Martin

Station X · 29th Nov 2008, 7:51 pm

The transmit crystal will be on some sub multiple of the actual transmit frequency. Possibly one twelfth thereof. With any luck it will have the actual frequency engraved on it, so a quick calculation will show you what the multiplication factor is.

The receive crystal will be a sub multiple of the local oscillator frequency. Generally you take the actual receive frequency, subtract the first IF frequency and divide by say 3. Once again the crystal may have the actual frequency engraved on it.

If the TM61 and TM62 use similar crystals on similar frequencies it will just be a matter of swapping the crystals. The frequency change is so small that no realignment of the radio will be necessary beyond adjusting the trimmers you describe to get the frequency exactly right.

sortedradio · 29th Nov 2008, 8:15 pm

Thank you Graham.
Martin

29th Nov 2008, 6:57 pm	#1
sortedradio Heptode Join Date: Jan 2008 Location: Sheffield, South Yorkshire, UK. Posts: 656	Glider Electronics TM62 Hi there, I have been asked by a friend to alter the channel 1 frequency on this mobile radio from 129.9MHz to 129.975MHz. He has also given me a TM61 as a "donor" set if needed, which has a 129.975MHz channel. I can see two crystal and two adjustable trimmer coils per channel, Tx and Rx I assume. I have aligned domestic sets before and have a strong electronics background and a fair amount of test equipment. Any information/advice on how to tackle this would be appreciated. Thank you Martin

29th Nov 2008, 7:51 pm	#2
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,288	Re: Glider Electronics TM62 The transmit crystal will be on some sub multiple of the actual transmit frequency. Possibly one twelfth thereof. With any luck it will have the actual frequency engraved on it, so a quick calculation will show you what the multiplication factor is. The receive crystal will be a sub multiple of the local oscillator frequency. Generally you take the actual receive frequency, subtract the first IF frequency and divide by say 3. Once again the crystal may have the actual frequency engraved on it. If the TM61 and TM62 use similar crystals on similar frequencies it will just be a matter of swapping the crystals. The frequency change is so small that no realignment of the radio will be necessary beyond adjusting the trimmers you describe to get the frequency exactly right. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

29th Nov 2008, 8:15 pm	#3
sortedradio Heptode Join Date: Jan 2008 Location: Sheffield, South Yorkshire, UK. Posts: 656	Re: Glider Electronics TM62 Thank you Graham. Martin