[1000mp] Roofing Filter

[Mike Schatzberg]

Hello Yaesu Fans:

Before I installed the roofing filter into my Mark V, I injected a 50
microvolt signal on 10 meters into the radio, with the tuned preamp engaged.
The S meter read S9.  Following the installation, it read about S9 plus 15
DB or so.

It took 3 numbers of reduction in menu 9-1, to bring the S meter back to S9,
or parity with the initial readings.

Based upon signal to noise, while listening to an S1 signal, I finally
changed the menu to 2 numbers lower than the original settings.  This left
the meter reading about 5 DB higher on 10 meters than before the mod for 50
microvolts.

I notice something interesting however.  The S meter does not seem to be so
linear below S9 anymore.  Although the second receiver calibrates with 50
microvolts at S9 within a few DB of the main receivers S meter, the main
receiver will often read S0, when the second receiver sees signals in the S1
to S3 range.

In any event, I usually have the second receiver on the main receivers
frequency, and I use its S meter for reporting signal strength. The higher
first IF gain from the Inrad two stage amp allows me to keep the RF gain
control cut back considerably for best signal to noise ratio from the main
receiver.  It is easier and I believe more accurate to just use the second
receiver S meter for reporting signal strength, no matter what the RF gain
control may be set to.  I use a Collins 2.0 mechanical filter in the second
receiver IF to narrow the passband down, and improve the accuracy of the
readings.  The Collins filter, available from Inrad,  may be merely plugged
into the second receiver open filter slot, and manually selected from the
front panel.

73 and Happy Dxing,

Mike Schatzberg
W2AJI
Tryon, NC
----- Original Message ----- 
From: <Cqtestk4xs at aol.com>
To: <1000mp at mailman.qth.net>
Sent: Tuesday, February 14, 2006 10:30 AM
Subject: Re: [1000mp] Roofing Filter


> I will always listen to Bill's experience and sage advice.  Besides,
what's
> an S meter anyhow?
>
> 73,
> Mike, W4UM
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Thanks for the vote of confidence.  Besides, who has time to look at an
> S-meter during a contest..and I keep the AF up and the RF gain down, so
the S-meter
> never really indicates what it should.
>
> Bill K4XS
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