[1000mp] Report on roofing filter install.

[W3JXP]

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