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THE AM BULLETIN BOARD => Technical Forum => Topic started by: n5ama on August 23, 2023, 01:35:11 AM



Title: Globe King 500C
Post by: n5ama on August 23, 2023, 01:35:11 AM
Iím restoring a Globe King 500C and Iím having some difficulty wi the VFO. I get 300 watts out using a crystal but the rig doesnít like the VFO when I go from 40m to 20m on the doubler. Iím going to try an external VFO but was wondering if anyone has experienced this problem?

Thanks in advance for any help!

Tom N5AMA


Title: Re: Globe King 500C
Post by: n5ama on August 24, 2023, 09:37:21 AM
As it turns out, the frequency on the GK500 dial between 20m and 40m is different. GK doubles the 7100 kHz frequency for the 20m band as expected, but the 20m scale doesnít correspond to double the 40m scale on the vfo. The 20m scale on the vfo dial only occupies the left side of the dial versus the 40m scale that uses the full width of the scale.

The measured frequency is very near what is indicated on the 40m vfo dial. If I use the scale and double the 40m frequency, all is ok but canít understand why the frequency shift between the 40m and 20m scale on the vfo.

What am I missing here and is there some component in the vfo that isnít working that would make this frequency shift? Iím confused.

Thanks,
Tom N5AMA


Title: Re: Globe King 500C
Post by: KL7OF on August 24, 2023, 05:39:13 PM
those globe vfos have several silver mica caps that must  be within tolerance for the vfo to have any accuracy.  I speak from experience with a couple of globe VFOs.. I still use one of them.   I speak of the external type, altho I think they are the same as the ones in the King.  Good luck   Steve


Title: Re: Globe King 500C
Post by: n5ama on August 25, 2023, 08:53:46 AM
The one Iím using is built in and I plan to use a Collins PTO vfo I built awhile back for a BC-610. I havenít checked but I suspect the stability isnít all that great on the GK vfo.

Thanks,
Tom


Title: Re: Globe King 500C
Post by: n5ama on August 29, 2023, 09:17:18 AM
The vfo works fine, a balky switch and not realizing the doubled vfo frequency was different from what I was expecting. The vfo puts out exactly what it suppose to be doing, itís just not the doubled 40m signal as I was expecting. ;D

Have a great week,
Tom N5AMA
AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands