"KU4YP" ) writes:
hello all,

i have a vfo from a heathkit hw-101. i also have a knight kit t-60.
question is what would it take and how much trouble would it be to build an
external vfo for my t-60 transmitter using this vfo? i have read some of the
old hanbooks but wanted to hear from the group.

I don't think it's a good choice.

The vfo from the SSB transceiver has a fixed range, I believe 5 to 5.5MHz,
and must have been linearized so the dial comes up properly.

The T60, or any AM/CW transmitter of that vintage uses a 3.5MHz or
7MHz (and that might change with the band) and multiplies up for the higher
bands.

In order to use the first with the second, you'll have to shift the
VFO down in frequency, likely by changing the coil. You'll kill
the linear tuning, and unless you do a good job, you may mess with
the stability. If the dial is still attached to the VFO, you will no
longer have the proper display of frequency.

The best way, though not the simplest, would be to feed the VFO into
a mixer, and then feed a crystal oscillator output into the other port
of the mixer. The output of the mixer will be the 3.5MHz or 7MHz that
the T60 needs, and the frequency readout of the VFO will remain true.
Tradeoffs are that if you don't put a good filter on the output of the mixer,
you will get spurious signals, and while the readout will remain accurate,
it will not show the actual frequency, since the T60 will be multiplying
it's output frequency. On the higher bands, as multiplication goes up,
the actual band will be covered by a smaller swing of the dial, though
that applies to any VFO used with a multiplying transmitter.

Michael VE2BVW