[Lowfer] down and out low down

Thu, 24 Apr 2003 00:49:36 -0400

Sounds like a winner! Any chance of a write-up?
Ralph
----- Original Message -----
From: "Bill Ashlock" <[email protected]>
To: <[email protected]>
Sent: Thursday, April 24, 2003 12:40 AM
Subject: Re: [Lowfer] down and out low down


> 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 <[email protected]>
> >Reply-To: [email protected]
> >To: [email protected]
> >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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