Pierre-Francois, F5BQP:
Substituting the xtal LO with a PLL will solve the frequency drift
issue. One caveat is making sure the PLL has low phase-noise as that
affects ability to handle strong adjacent frequency signals when
trying to copy weak signals (which is why you are using JT65). One
of the shining parameters of the K3 design.
I had DEMI transverters long before I acquired my K3/10 (and KX3) so
have continued to use them. I have heated xtal osc on 144 and 222
but use a PLL on 432, 1296, and 3400 MHz. Recent re-design by DEMI
has improved xtal LO frequency stability while the xtal oscillator
has excellent phase-noise performance. I see about 7 to 10 Hz drift
on the 101 to 194 MHz xtal oscillators in the new L-series of DEMI
transverters. But LO's for higher bands multiply the xtal oscillator
frequency which also multiplies drift.
For 432 and higher I found using the N5AC ApolLO PLL's worked well in
DEMI transverters. The N5AC Apol series is not the lowest in
phase-noise so that could be a real concern for those doing VHF-plus
in high density RF environments. So one should consider phase-noise
when deciding on a PLL. W1GHZ has a new VCXO design that exhibits
lower noise than a PLL. Of course this is for the experimenter ham who DIY.
I do think there will be a increasing use of PLL in VHF and higher
equipment due to demands of digital modes and need for better
frequency stability on the higher bands.
One issue is the need for an external 10-MHz reference. That is not
hard to embed into current equipment. I did that for a 432-MHz
transverter customer.
73, Ed - KL7UW
http://www.kl7uw.com
"Kits made by KL7UW"
Dubus Mag business:
[email protected]
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