UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Building the 'Minimod' AM modulator-questions!

crackle · 28th Sep 2018, 5:01 pm

I have come to the conclusion that it is definitely an issue with L1.
I have fitted a very thin strand of knicker elastic and the core is very tight now, so tight that I had to re-profile the crappy plastic trim tool after screwing the core back in.
On first tests I have found that the frequency drift now only seems to be about 2kHz, (reduced from 4 to 5kHz) and that is normally upwards. So what I have done is set the frequency to 1069 and waiting to see if it creeps up to 1071.

Maybe I am being too fussy, I would be interested to hear others comments who have used a frequency counter to test the output stability when using the Spectrum coils.

I have just realised that my coils don't have a red ring around the core, as mentioned by Ian above.

Mike

28th Sep 2018, 5:01 pm	#40
crackle Rest in Peace Join Date: Mar 2011 Location: Basildon, Essex, UK. Posts: 4,100	Re: Building the 'Minimod' AM modulator-questions! I have come to the conclusion that it is definitely an issue with L1. I have fitted a very thin strand of knicker elastic and the core is very tight now, so tight that I had to re-profile the crappy plastic trim tool after screwing the core back in. On first tests I have found that the frequency drift now only seems to be about 2kHz, (reduced from 4 to 5kHz) and that is normally upwards. So what I have done is set the frequency to 1069 and waiting to see if it creeps up to 1071. Maybe I am being too fussy, I would be interested to hear others comments who have used a frequency counter to test the output stability when using the Spectrum coils. I have just realised that my coils don't have a red ring around the core, as mentioned by Ian above. Mike Last edited by crackle; 28th Sep 2018 at 5:29 pm.