[HBR] That General Coverage HBR Project -- 2

[Bill Cromwell]

Walt KJ4KV said:

But Bill, if you do something that turns out too silly to mention and 
you keep quiet, that means I have to do it too!  I have my very own 
silly ideas!

One of the most interesting things about this list is hearing what other 
people are doing, building, restoring, and what all. Learning what 
doesn't work well is probably the most useful part of that.  I've been 
writing some further adventures with the VXO thing that I'll probably 
post today, but the short story is, doing it again from scratch this 
isn't where I'd start for a BFO that must tune a frequency range as 
large as ~0.1%.

Walt
KJ4KV

OK Walt,

Maybe somebody else has been down the street I'm looking at and bumped
into a dead end. VXOs are recommended for stability (among other things)
in portable equipment. The drawback with a VXO is the limited tuning
range. A VXO might be built in the mid to high HF range with a few small
kHz of tuning range and the output multiplied into the vhf or uhf area.
The tuning range gets multiplied, too, along with any instabilities.
Another crystal controlled oscillator can be multiplied to a nearby
frequency and mixed with the multiplied output from the VXO. If we are
really lucky, or maybe if we plan it that way, the difference frequency
can be the range needed for operation as our local oscillator in the HF
band. Maybe we can increase the tuning range 3 kHz to 50 or 100 kHz.
Maybe this approach will work for your BFO. Of course the complexity
increases.

We might also start with an overtone crystal oscillator or two. I have
observed a fairly large "tweaking" range on those at the output
frequency and the initial oscillator frequency is already higher than
our HF bands. That will help reduce the number of mines in the
'minefield'. Again with the birdies and other spurious pitfalls. 

73,

Bill  KU8H