[INRAD] FT1000MP Roofing filter

[Giancarlo Moda]

Hi Bill,

please see my comments below.

73

Giancarlo "Gian" Moda
I7SWX

Date: Thu, 5 May 2005 12:32:49 -0500
From: "William E. Sabin" <w.sabin at mchsi.com>
Subject: [INRAD] roofing filters
To: <list at inrad.net>
Message-ID: <000801c55198$76a2b260$6402a8c0 at DBYKXS51>
Content-Type: text/plain; charset="iso-8859-1"

Regarding the amplifiers that are associated with the
Yaesu etc. front 
end roofing filters: Are the amplifiers ahead of the
filter or after 
the filter? 

> The INRAD Roofing filter for the FT1000MP has the
amplifier after the filter. It is a two bjt amplifier.
I guess all the other INRAD roofing filters may have a
similar solution.

Inrad roofing flt have been designed to be inserted
without the use of a soldering iron. Every RTX owner
can easily add these to their equipment.
The problem is that if the front-end and mixer plus
first IF do generate IMD, the filtering will be on
signals within the Band Pass window plus IMD products
generated before the Inrad r.f.
I am studying some hard mods on an FT1000MP to see
what kind of improuvement we may have.
1) Replacement of second mixer (with an I7SWX H-Mode
Mixer) and 2nd IF gain redistribution.
2)Possible 1st mixer replacement with an H-Mode Mixer.
Here we may not see much benefit due to possible 1st
oscillator PLL phase noise.
3) New 1st If chain using the INRAD roofing filter and
redistributed IF gain.

I do not know when I will complete the "trial". If you
like I can keep you posted (pse e-mail direct).
I am at stage 1) working on the 2nd IF gain
redistribution. Mixer replaced.

For those interested, I have posted on www.mods.dk a
switch over diagram to remove the Inrad roof flt when
selecting AM+FM or 6KHz BW.

What is their effect on the strong signal performance.

> Peter Hart, G3SJX, has published recently, in
RadCom, a report on FT1000MP Inrad filter addition.
Please let me know it I will send you the copy.

73

Gian
I7SWX
W1-I7SWX




		
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