HG-10 VFO out issue's

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W3GMS:
Marty,
The 1 mh works great.  As Stu, AB2EZ noted above, the 28 uh choke just does not have enough inductance especially at 3.5 mhz.  Its clear that some users are getting away with 28 uh, but the engineering analysis shows that its not the correct value at the lower frequencies.  Both amplitude and waveform quality suffer.  Another interdependency  could be the differences in DX-60's.  The oscillator topology is different when used as a xtal oscillator compared to when the VFO is used.  Maybe the gain on my 6CL6 is somewhat low and that would explain maybe why I can't the grid drive when others Dx-60 users can.   At this point, I am going to make the HG-10 perform properly by putting the 1.1 mh choke in the plate circuit and using the smaller inductor in the cathode circuit. 
Thanks all for the comments on this subject.
Regards,
Joe

WA2ROC:
I had my late model (1975 vintage) HG-10B out of the case this morning and it has the 350uh RFC in the plate circuit and on the schematic and parts listing.  I relocated the physical position of the choke (the original builder put it in a straight line point to point) and I now get full drive at the top end of 75 meters.

I also developed, troubleshot and fixed a problem too.   After the choke was moved, I got no output at all.  After puttzing around, I found that the RFC was open!  I was able to re-solder the small wire to the lead and everything worked fine once again.

W3GMS:
Dick,
One thing for sure, you will get more out of the VFO with the 350 uh choke than the 28 uh.  In fact with the 350 uh choke I am sure the DX-60 would be able to develop enough grid drive.  I did not have the 350 uh choke in mine so the wimpy 28 uh was moved to the cathode and the 1.1 mh was placed in the plate circuit and the beast is operating fantastic. 
Thanks for your input on your late model HG-10B. 
Regards,
Joe, W3GMS   

Dave KA2J:
Here are two waveforms observed on the output my HG-10 VFO.  One with the existing choke on the plate of V1a (not sure if it is a 28uh, as it looks like it may be a replacement choke) and a 350uh I purchased from Mouser.  There is more grid drive on 3.7 MHz, as the gain pot went from a position of 3.6 to 1.3.

Notice how their is less energy in the harmonic content and more available for drive at 3.7 MHz.

Dave KA2J

w1vtp:
Dave

What's the scale on that scope reading?  What kind of load was it looking into?

Al

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