[NLRS] Harmonically related microwave frequencies

[Gerald]

On Sat, 2005-11-19 at 20:47 +0000, Scott wrote:
> 
> Question:
> 
> Where exactly did the normal calling frequencies on the microwave bands 
> (2304.1, 3456.1, 5760.1, 10368.1) come  from?  Seems to me it is 
> harmonically derived, ie 144 X 3 = 432, etc.

Way way back we all started with a 8.001 MHz crystal for all bands but
6m and 220. So we got 144.018, 432.054, 1296.162, 2304.288, 3456.432,
5760.720, 10361.296 using multipliers of 18, 54, 162, 288, 432, 720, and
1296, or 18 x 3 x 3 for 2 m, 432, and 1296. The rich used separate
crystals and multipliers. 2304 came from multiplications of 18 x 2 x 2 x
2 x 2. 3456 came from tapping that after the third doubler then tripling
18 x 2 x 2 x 2 x 3 that 1152 tap. 5760 came from the 5th harmonic of
that 1152 signal, and 10368 from the 9th harmonic of that 1152 signal.
All from that same 8 MHz crystal (that easily warped 20 KHz at 2m and
lots more up higher. Sometimes it drifted that far too!).
> 
> I'm looking at adding bands (have 10368 now).  DEMI transverter kits all 
> come with an external (not part of the transverter board) LO board.  It 
> seems wasteful to have to have 4 LO boards with 4 different crystals to 
> run 4 microwave bands.  If I set up one LO board to run at 1125 MHz (for 
> example), I could get signals (144 MHz IF) at 1269.1, 2394.1, 5769.1 and 
> 10269.1 ... not the traditional frequencies, but still within band 
> edges.  Seems I would get more bang for the buck.  In fact if I ordered 
> 3 transverter boards with parts only, I could get the fourth for free by 
> not having to pay for 3 LO boards.  I know these wouldn't fall into the 
> ARRL band plans, but being cheap, I could get on more bands without so 
> much approval from the local war department...
> 
> Comments?
> 
In theory you can use that same 144 signal and its harmonics for all LO
from 432 through 10368. The only troubles are that you get that 144 MHz
into the IF receiver, (so the calling frequencies are up 100 KHz from
the even harmonics to get away from that) and some of the
multiplications are prime numbers. Like 2 for 432, 8 for 1296 (not
prime), 15 for 2304 (not prime), 23 for 3456 (prime), 39 for 5760 (not
quite prime but 3 x 13), and 71 for 10368 (prime).

So 432 and 1296 could share the same multiplier string, maybe the first
tripler for 2304 and 5760, but there's nothing in the rest of the
multiplier strings that could be shared. And with crystals (in the old
days) costing 50 cents or less each, it wasn't that much of a big deal
to have completely independent transverters. That way when one breaks
others still work. And the LO chain can be as much trouble to keep
working as the mixers an amplifier stages. At least that's been my
experience over the past 40+ years of VHF and UHF operation.

-- 
73, Jerry, K0CQ
Dr. Gerald N. Johnson, electrical engineer
All content copyright, Dr. Gerald N. Johnson