[1000mp] Report on roofing filter install.

[Bob Main]

You had busy weekend.  I have the roofing filter on order and I was also on 
160 this weekend and wondering what differences it would have made. 
Happiness is turning the radio back on and no smoke or sparks AND it still 
works.

73s
Bob
KB4CL

----- Original Message ----- 
From: "W3JXP" <w3jxp at adelphia.net>
To: "ft1000mp mail list" <1000mp at mailman.qth.net>
Sent: Sunday, February 27, 2005 9:41 PM
Subject: [1000mp] Report on roofing filter install.


> Hi All:
> I thought I'd report on installing the roofing filter in my FT1000md 
> Mark-V Field this weekend.
> It was an easy install. I used the oscillator from Elecraft to reference 
> the S-9 point. Before installing the filter with the IPO on (pre-amp out) 
> the 50 uV output in the CW mode read exactly S-9 The pre-amp would put it 
> up one block over S-9. After installing the roofing filter the IPO on 
> reading had jumped to one block over S-9. I set my IF gain setting on the 
> hidden menus from 12 to 11 and the reading was back at S-9.  Friday night 
> I had spent some time on 160M during the SSB contest. The band was packed 
> with signals that were 30+ over S-9. I had a few instances of mixing, IMD 
> and the like but the radio was in no way bad and I made many contacts even 
> though I have a poor antenna and no high power.
> Saturday night I was back on 160M after the putting in the filter. I heard 
> no instances of mixing IMD or what ever. So it made an improvement. It may 
> be my imagination but the noise blanker works better too. I could use it 
> with strong signals nearby and not have too much distortion. So I'm very 
> happy with the results. I think it made the receiver better.
> I was wondering just how much gain that one block increase was.As it was 
> the same as what the preamp gave,  I used the Elecraft oscillator and a 
> calibrated step attenuator to measure it. The gain turned out to be 6db. 
> That lead me to measure the db steps over the rest of the S meter range. 
> Here is what I found:
> Meter reading     Attenuator setting
> S-9                             0db
> S-8                             9db 9db/S unit
> S-7                             15db 6db/S unit
> S-6                             18db 3db/S unit
> S-5                              21db 3db/S unit
> S-4                              23db  2db/S unit
> S-3                              24db 1db/S unit
> S-2                              25db 1db/S unit
> S-1                              26db 1db/S unit
>
> Its not 6db per S unit.  I switched the output to 1uV and the signal was 
> gone after 30db of attenuation was switched in. I just put this numbers 
> out for the interest of the group.
> At the time I did the roofing filter, I also installed the key click mod 
> and did the modification to open the transmitter up for the 60M 
> frequencies. I hope the CW guys appreciate the work I did as I'm not a CW 
> guy. The 60M mod worked well too. As we are limited to 50 watts ERP on 
> that band I modeled my antenna (80/40M fan dipole with a loaded 160/30M 
> dipole at right angle to the fan) and found the gain to be identical to a 
> 60M standard dipole at the same height. But the feed point Z was 
> 388-j1227ohms. I used the TL software to model the feedline, 130' of 
> LMR-400 and it showed a lost of 7.33db  due to line loss and  high SWR 
> excess loss, with loss a of 0.09db in the tuner for a total loss of 7.43db 
> That means my 100w into the coax equals 18w at the antenna  which means 
> I'm legal.
> Its been a good weekend.
>
>
> John Passaneau W3JXP
> State College Pa.
> W3JXP at adelphia.net
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