[1000mp] Roofing Filters

[Mike Schatzberg]

Hello Pete:

Exactly!  I have posted here my findings several times, but I have never
received any comments.  I have lowered my IF gain setting by two numbers
following the installation of the filter, and would estimate that the noise
floor is lower by approximately 10 DB!  This is not a small improvement, it
totally changes the ability to work weak signals.  S0 signals are Q5 now,
with no difficulty to read at all.  According to my signal generator, the
overall gain in sensitivity of the receiver is around 2 DB, and the noise
floor is still way down.

The same findings were reported in the RSGB publication, where they reported
lowering the IF gain setting in menu 9-1 by three numbers, which is what I
found brought the S meter back to parity with the reading before the
modification.  My S meter showed a 15 DB increase in reading after the mod,
prior to my lowering the 9-1 setting for best signal to noise ratio.

You do not need both mods, as the net gain is apparently greater that Inrad
states with the two stage low noise amplifier on the mod board.  The net
gain stated by Inrad was around a couple of DB.  It appears to be much more,
and according to the RSGB article, is around 8 DB!

The difference with the preamp in and out in the Mark V becomes tremendous.
Weak signals pop out clearly now.  It does not merely bring up the noise
floor as well as the signal, and not improving the readability of the weak
signal.  Many people have recommended leaving the IPO button lit all the
time.  I would recommend using the preamp all the time with the RF gain set
between typically 1 and 2 o'clock if you have the mod.

With the overall bandwidth using no filter in the 2nd IF and the 6 Khz
filter in the 3rd IF (with the mod installed) being around 4.8 Khz, this
setting, using the digital product detector, is very powerful for low signal
strength reception. You can superimpose the digital 2nd IF filter for added
selectivity without increasing the noise floor.

As far as I am concerned, this modification is like receiving a new
receiver.  Don't forget to do the noise blanker mod also, for best overall
performance.

Happy New Year and Happy DXing,

Mike Schatzberg
WB2AJI
----- Original Message ----- 
From: "Pete Smith" <n4zr at contesting.com>
To: "All about Yaesu 1000mp" <1000mp at mailman.qth.net>;
<1000mp at mailman.qth.net>
Sent: Sunday, December 26, 2004 5:23 AM
Subject: Re: [1000mp] Roofing Filters


> QST's review of the roofing filter cites a 7 dB improvement in MDS with a
> Mark V, and 3 db with a regular MP, compared to the stock figure.  Doesn't
> this imply that the amplifier in the roofing filter mod accomplishes some
> or all of the same effect as the amplifier in the original IF mod?
>
> 73, Pete N4ZR
>
> At 10:57 PM 12/25/2004, Thomas Beltran wrote:
>
> >Winston, I haven't sold my IF mod kit yet, its been sitting here since
> >August or so, when I got the roofing filter kit.  But I agree, and I
think
> >you'd agree, it would be nice to have both, and not have to choose
between
> >them.  Just knowing that Rob Sherwood has some involvement in this thing,
> >I'm hoping that there might be a switching kit for the MP, like Rob's
mods
> >for the Drake R4C.
> >
> >(For those not familiar, Rob has had switched First IF roofing filters
for
> >about 20 years, 600 hz for CW, and 2.4 khz. USB and LSB, switched from a
> >small relay control board that fits inside the radio - there is a
> >replacement double-duty knob that replaces the AGC knob (which came out
more
> >recently), so that the larger rear knob switches the AGC positions, and
the
> >smaller front knob switches the filters - very elegant.  It was nice to
see
> >some of this 20 yr. old technology applied to the Yaesu.)  Rob has the
> >results of his testing, and those old R-4Cs of bygone years make a good
> >account of themselves.
> >
> >Since the connections for the Inrad filter and IF mod kit are exactly the
> >same, it doesn't seem like such a thing would be sooo difficult [easy for
me
> >to say].  There is certainly a lot more room in the Yaesu, than in the
> >Drake.  When I wrote to George over a year before coming out with the
kit,
> >raving about how well Sherwood's stuff worked, he said that he had been
> >working on it, but a roofing filter of any real selectivity seemed to be
> >impractical in the Yaesu, because of the high IF frequency.  But he did
it,
> >and maybe not a "must have" as some might say, but it works quite well.
So,
> >I'm saving my IF kit, hopefully, I'll be reinstalling it with a switch
kit.
> >Certainly there is a business motivation also, instead of an either-or,
> >every MP owner could conceiveable own (and use) both.  Sign me, "holding
out
> >for the switching kit."  Tom W6EIJ
> >
> >
> >
> >_______________________________________________
> >1000mp mailing list
> >1000mp at mailman.qth.net
> >http://mailman.qth.net/mailman/listinfo/1000mp
>
> _______________________________________________
> 1000mp mailing list
> 1000mp at mailman.qth.net
> http://mailman.qth.net/mailman/listinfo/1000mp