My 458VFO runs from 160 through 10 with low output on 10 meters. Actually the doubling schemes seems to be questionable! I intend to build the 10 add-on from the bama site and try that for 10 meter am.
I have 2 of the 458VFO units both are working in the same manner, (low 10 meter output). My second one came in none functional, as the tube was plugged into the wrong socket, not much of a problem, but once that was corrected I only had output on 160 meters. So I did the logical thing, I opened the first one and looked at the layout of the coils. Yep the 2nd vfo had the coils pretty much in line with each other (mutual coupling) I changed the positions and 80 -15 came to life, it helps if you have a frequency counter or even a receiver (general coverage) to listen for the injection output frequency. If anyone wants to see the coil layout I can take a picture of it and send it to you. Remember the 458 provides the 5 mhz signal and also harmonics that is what you do with the cap and coils, the bandswitch puts the correct coil to tune to the harmonic frequency. You will still see the 5 mhz signal if you have a spectrum analyzer and look at the output. Oh yeah, I have 20A and 10B and 10A exciters the 10B has coils for 160 through 40 meters. as I have not found any documentation that tells what the other coils consist of. It shouldn't be hard to come up with coils that work however. One other thing about the 20A and harmonics and oscillation when driving the Johnson Thunderbolt, it is recommended that the swamping resistor be in place. It really works better when there then when it isn't, the mike isn't hot no RF back to the 20A, make sure the chassis is grounded from the 20A to the Thunderbolt. Jim WB2FCN http://eshop1.chem.buffalo.edu MIke Wells wrote: > > I'm enjoying the 20A discussion. I have a 20A that I want to get on the air > so keep the messages posted here for the benefit of others. > > Tell me more about the VFO, are you having good luck with it on all bands? > I've only got mine working on the low bands, no oscillation on 40 meters. > Suggestions? > > 73, > > Mike W0FD > > Subject: [AMRadio] "Reply" button got me... > > Regarding the previous posting to the list: it was unintended. The old > "reply" button got me again! > > If you're interested, read it. It's part of a discussion Jim Candela and > I are having about a vintage SSB exciter, the venerable Central > Electronics 20A. If not, the "Delete" button is much more predictable in > its effects than "Reply." :>) > > 73, and back to AM... > > -Larry/NE1S > > _______________________________________________ > AMRadio mailing list > [email protected] > http://mailman.qth.net/mailman/listinfo/amradio
