[1000mp] Roofing filter and weak sigs

[Mike Schatzberg]

Hello Vidi:

There has been quite a bit written here about the roofing filter.  The
archives will be worth a review on this subject.

To summarize my experience, the noise floor is reduced by perhaps as much as
8 to 10 db from my stock Mark V, making it far easier to copy weak signals.
In fact, after reducing the IF gain in menu 9-1 by two numbers, I am able to
read S0 signals Q5.  Following the installation of the mod, my S meter
readings were 15 db higher.  A reduction of 3 number reduced the readings to
parity with before the mod readings.  I settled with a reduction of 2
numbers, which I felt gave the best signal to noise results for reading very
weak signals.

The improvement comes about for two reasons.  The first you have already
stated, the 6 pole 4 khz crystal 1st IF filter in series with the stock 12
khz filter, lets in less noise.  Secondly, the latest production Inrad
filters have lower insertion loss, and the two stage low noise amplifier has
a net gain of several db.

You will find that the roofing filter mod will accomplish the same noise
reduction that your IF amplifier mod does, but has all the advantages of the
narrower 1st IF filter as well.

It is well worth the investment, you will discover a new receiver when it is
installed.  Don't forget to do the Noise Blanker Mod as well.

Regards and Happy DXing,

Mike Schatzberg
WB2AJI
----- Original Message ----- 
From: "Vidi & Hester" <zs6al at cis.co.za>
To: <1000mp at mailman.qth.net>
Sent: Monday, March 14, 2005 8:02 AM
Subject: [1000mp] Roofing filter and weak sigs


> Hello everyone
>
> I took part in the BERU contest using a FT-1000MP with the Inrad original
> front end mod installed.  I had to deal with a lot of VERY weak signals
more
> so than with  overpowering nearby  stations.  I have read a lot about the
> advantages of the roofing filter in strong near signal situations.
However
> I was wondering if the restricted front end bandwidth brought about by the
> roofing filter will limit the band of total background noise entering the
> rig and thereby making it easier to pick out signals from in the normal
low
> level of background  noise.
>
> Bottom line:  Will a roofing filter improve weak signal reception?
>
> Comments based on experience will be appreciated
>
> Regards,
>
> Vidi, ZS1EL
>
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