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[linrad] Hardware Help Needed!

Hello, All!

I need some hardware help.  As you know, I have been having fun playing
with Linrad and the Time Machine on LF and HF lately.

I would like to use the Time Machine to explore the spectrum (with
Linrad of course) above 14 MHz.  But I have slightly modified the Time
Machine so that the LO is a PTS synthesizer rather than a crystal and
the ICS501.  I did this primarily so I would have better frequency
agility than if the Time Machine were crystal controlled, as is
standard.  Things seem to work better if I avoid feeding the PTS into
the ICS501, and instead feed it directly into the 16V8B.

To use the PTS in this way I have needed a circuit that squares the PTS
sine wave into a square wave that the Time Machine can use.  The circuit
I am using is from DJ8ES and uses a BC849C to a 74ls00 to a 74ls90 (the
circuit was in VHF Communications 4/00, and was meant for use with a 10
MHz oscillator).  Its performance drops off above 14 * 4 = 56 MHz, so I
cannot use it to listen to the bands above 20 meters.
I am thinking of using a simple wave squarer circuit from page 7 of the
July/Aug 2002 QEX that just uses a BFR92 and 2 gates from a 7400, but
with substituting ASL or F logic for the HC logic specified to improve
the high frequency performance.  But I suspect someone on the list may
have a better suggestion.

I would like to get at least to 10 meters.  That would require 30 * 4 =
120 MHz performance of the pulse squarer.

EVEN BETTER would be if someone had a multiplier and squarer circuit
idea, so that I could then with a PTS 500 run a direct conversion
receiver on 144 MHz with the Time Machine.  This would require an output
at 144 * 4 MHz = 576 MHz.  Input could be 144 MHz sine wave if the
circuit is quadrupler, or  288 MHz sine wave if the circuit is doubler.
Output must again be square wave.

Any help or advice or criticism of this approach would be appreciated!

Time Machine has indicated they are 'working' on an approach for 144 mHz
themselves, but although this was discussed with them in mid July, and
they have good plans in this area I have not heard anything lately, so I
want to proceed on my own.  What Bill Coleman N4ES said in July was:

As an interim solution for those desiring improved LO phase noise or
more frequency agility, we are considering LO daughter boards that plug
into the 16V8B socket. The board would comprise a comparator to square
up an external LO, plus the 16V8B. For VHF or UHF, the 16V8B would be
replaced by a lumped element or stripline quadrature hybrid power
splitter. We are also checking with the crystal supplier in China on
purchasing oscillators operating at 4x the popular crystal frequencies,
and incorporating a socket on the daugher board for the oscillator as a
way to eliminate the need for the ICS-501.

End of Bill Coleman's email of 7/16/02

Thanks to all in advance, and


Roger Rehr
W3SZ   FN20ah
2 Merrymount Road
Reading, PA  19609-1718