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G0HZU_JMR · 21st May 2019, 1:08 am

It's been on for about an hour since the 100Hz plot was taken and the oscillator has only drifted about another 25-30Hz in all that time. Impressive stuff!

I also noted that the earlier 100Hz plot had 8 averages on it but I don't think this matters much when the analyser is on a narrow span like this. The plot below has averaging turned off and it looks about the same and the carrier peak level is the same with averaging off.

The crazy 50Hz sidebands are also visible on these plots and this issue is affecting this oscillator and the Franklin when they are placed in the shielded box.

The only frequency determining parts are the resonator coil and the resonator caps. These caps are high quality porcelain parts from AT Ceramics. However, I suspect that this doesn't matter much on a test like this because the temperature inside the shielded enclosure must be quite stable.

21st May 2019, 1:08 am	#55
G0HZU_JMR Dekatron Join Date: Sep 2010 Location: Cheltenham, Gloucestershire, UK. Posts: 3,077	Re: Franklin VFO ? It's been on for about an hour since the 100Hz plot was taken and the oscillator has only drifted about another 25-30Hz in all that time. Impressive stuff! I also noted that the earlier 100Hz plot had 8 averages on it but I don't think this matters much when the analyser is on a narrow span like this. The plot below has averaging turned off and it looks about the same and the carrier peak level is the same with averaging off. The crazy 50Hz sidebands are also visible on these plots and this issue is affecting this oscillator and the Franklin when they are placed in the shielded box. The only frequency determining parts are the resonator coil and the resonator caps. These caps are high quality porcelain parts from AT Ceramics. However, I suspect that this doesn't matter much on a test like this because the temperature inside the shielded enclosure must be quite stable. Attached Thumbnails __________________ Regards, Jeremy G0HZU Last edited by G0HZU_JMR; 21st May 2019 at 1:14 am.