[Lowfer] down and out low down

[Bill Ashlock]

>Sounds like a winner! Any chance of a write-up?
>Ralph

Yah, ....but I've got to warn you - I tend to be tardy on these promises.

Bill



> > Eric,
> >
> > Relative to building Lowfer transmitters, the Lowfer receiver is 100 
>times
> > more critical. Some of the important characteristics are:
> >
> > 1) Very narrow selectivity, but at the same time, very good impulse
> > response, IE: very low ringing in response to noise.
> > 2) Good frequency stability. And if used for QRSS - Very, very good
> > frequency stability.
> > 3) High gain.
> > 4) Good rejection and low IM in response to strong out-of-band signals.
> >
> > These tight requirements are the reasons why no LF receiver kit is
>available
> > at the present time - with the possible exception of a direct conversion
> > receiver (which only partially meets the above criteria).
> >
> > I've mentioned from time to time about measurements with my portable 
>SVM.
>I
> > spent almost a solid year of spare time designing this receiver  with 
>the
> > aim of making it solid, RF-wise, so that it can be built and tuned up in
>kit
> > form, without the normal oscillations from misplaced wires, and slightly
> > mismatched components. This receiver comes close to beating my R75 on 
>low
> > level signal grabbing but has totally inadequate frequency stability for
> > QRSS use. I had a PCB layout about 99% complete a year ago and lost the
> > inspiration when all the TX loop activity began. By coincidence, last
>night
> > I located a source for a LO xtal that would allow QRSS reception of the
> > 185.3 group plus a little extra ground and am anxious to purchase a
>sample.
> > There have been a number of other guys interested in a PCB blank so I'll
>try
> > to get this project re-started as soon as I pass the code exam.
> >
> > Bill
> >
> > >From: Eric Smith <eric@willow.nutstreet.net>
> > >Reply-To: lowfer@mailman.qth.net
> > >To: lowfer@mailman.qth.net
> > >Subject: [Lowfer] down and out low down
> > >Date: Wed, 23 Apr 2003 20:08:37 -0500 (CDT)
> > >
> > >While the audio final has been out in my GT-550, I've been able to use 
>a
> > >crystal earphone :)
> > >
> > >Now, RF is out.  I don't know if it is the front-end or the finals, but
> > >the S-meter doesn't even move when I tune around.  Dead as a doornail.
> > >
> > >There are about two $500 expenditures I need to make before I'd feel 
>very
> > >good about spending $500 on a radio.
> > >
> > >In about 15 minutes I can build a radio that will pick up the AM
>broadcast
> > >band with an oatbox, a length of wire, a resistor, a 1N34, and my 
>trusty
> > >crystal earphone.  Of course, those stations are 50,000 watts :)
> > >
> > >But it looks like I could build a more complex circuit (with some RF
> > >amplification and better selectivity) that would work BELOW 500 kc,
> > >without going to the complexity of a synthesized tuner.
> > >
> > >I have plenty of 365pf air variables :) and thousands of feet of
>telephone
> > >wire.
> > >
> > >Do any of you know where I might find such a circuit?  Point me to a
> > >schematic, and I'll build it!
> > >
> > >Thank you,
> > >Eric, KD5UWL, hurting BAD in EM25
> >


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