[1000mp] Improving IM3 DR with Mark V and Inrad Roofing Filter

VE2FWW ve2fww at globetrotter.net
Sat Feb 2 19:57:02 EST 2008

Very Interesting...
Do you think the result will be the same with the MARK V Field...
I have two of them, and I would like tu make the mod also..on the inrad
----- Original Message -----
From: "Mike Schatzberg" <cherokeehillfarm at earthlink.net>
To: "'All about Yaesu 1000mp'" <1000mp at mailman.qth.net>
Sent: Sunday, February 03, 2008 00:06
Subject: [AVIS-NOTICE] Re: [1000mp] Improving IM3 DR with Mark V and Inrad
Roofing Filter

> Hello 1000MP Fans:
> I wanted to update this thread with some additional information from
> OK1VWK,  a member of OL7R multi contest team.  Milan has just recently
> emailed me regarding his experiences with the W2AJI modifications for the
> Mark V Inrad Roofing Filter Board.  He has given permission to post his
> comments here on our 1000MP Reflector.
> There have been several questions lately regarding the mod.  I hope that
> this will help a little towards answering them.  Perhaps W8JI will
> the modified Inrad board, and make before and after mod data available.
> Milan has also made a photo available of the mod, the way he performed it,
> using three parallel 470 ohm resistors for R6, as he did not have a 150
> resistor in his spare parts box.
> He goes on to say that his colleague, Mirek, OK1UFE,  tried to install the
> IC756PRO2 Inrad Roofing Filter in an IC718, as they both have the same 1st
> IF.  Mirek's data is presented in the correspondance below.
> 73 and Happy DXing,
> Mike
> Hi Mike,
> I would like to inform you about my experiments with Inrad roofing filter.
> I have aplied your roofing filter IMD mod in my FT1000MP with good
> It seems to be quite better than original solution from Inrad. I had big
> problem with RX IM overload mainly on 40m. After reduction LNA gain, which
> is installed on the roofing filter board is my RX more quiet than before.
> No problem with space on 40m band now. No problem listen weak signal on
> crowded band. I absolutely agree with your idea about this problem. I dont
> understand why is Inrad still standing on the RSGB and ARRL measurements.
> There is some picture form my modification:
> 73 de Milan, OK1VWK
> Hello Mike,
> > I see that you used about 157 ohms, the parallel sum, by replacing R6
> three
> > resistors.  Was this because you did not have a 150 ohm resistor?
> Absolutely right.
> > Did you test
> > the 150 ohm verses the 157 ohm resistor and find a better solution?
> No, it was only my problem with R6 value and my spare parts for use. I
> wanted to try your mod and I had 3x470 only, hi.
> > Several people have had big issues like you on 40 meters,
> > particularly during CW contests.
> It was terrible during last CQWWCW. I am member of OL7R contest team and
> had backup TRX TS850 also there. The TS850 seemed better than my FT1000MP
> with Inrad roofing filter without your mod. I was thinking "It isnt normal
> situation".
> > Maybe you know someone who could
> > make the measurements?
> Grrr, thats problem. I am sorry but I dont have any idea now. But see text
> below.
> My job coleague Mirek OK1UFE said to me, that he tried to install
> Inrad roofing filter into the IC718, because both TRXs have the same first
> IF and why doesnt try it. After instalation Mirek measured original filter
> loss and LNA gain . Filter loss was 2,5dB and LNA gain 6,5dB. He had to
> reduce LNA gain and his new value is 1,7dB. I asked him if he aplied your
> roofing filter IMD mod and he confirmed it. It seems that after your mod
> LNA 1,7dB gain. His roofing filter was purchased two or three months ago.
> Absolutely agree. LNA gain is designed for first VHF filter series with
> highier loss than current production line and thats difference between
> and RSGB test and real situation on the band. Inrad changed only filter
> without LNA gain re-design. Inrad says highier filter LNA gain is good for
> lower third IF gain. I think its total mistake. The major problem is total
> radio system gain distribution on each IF. Inrad solution causes first IF
> overload only and poor IMD results. Nothing else.
> > Would you mind if I share your results with our 1000MP Reflector
> Absolutely no problem. You may publish my info.
> Also thanks and nice to see you ...
> 73 de Milan,OK1VWK
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