[SECC] Yeasu FT-1000MP

[Tom Rauch]

Hi Gordon (and other SECC),

The first mod you should consider is getting rid of the keyclicks all 
FT1000 series rigs have, unless you want to park next to a YCCC 
member in contests (just joking here, hi hi).

The ultimate "click" bandwidth of a MP on CW is almost the same 
as the SSB filter width, very poor engineering and inconsiderate to 
others to operate that way on crowded bands!

As to Rick's comments on the 70MHz IF. Anyone familiar with 
receiver design would really wonder about adding gain in the IF in 
front of narrow filters. While there may be cases where it improves 
S/N ratio, it has to do so at expense of both blocking and IM 
performance **INSIDE** the bandwidth of the roofing filter (that's the 
70MHz IF filter). The only exception to this is if the IF is so noisy 
you CAN'T hear a noticeable change in noise when switching from 
full RF gain (preamp on) to no RF gain (attenuator full) when the 
antenna is connected.

Measurements on FT1000MP's and D's confirm close-spaced IM 
DR and blocking DR are reduced (by about the amount of the 
amplifier gain) by adding 70 MHz IF gain, although the annoyance 
factor of the "hiss" on CW certainly is reduced with the mod.

My own experience with the FT1000(D) is that IF noise is an 
mostly an annoyance and most problematic when using the narrow 
CW filters on quiet bands.

There are very clear reasons WHY my FT1000 has the hissing, but 
I won't go into why. 
 
Overall, I'd pass on the 70 Mhz IF amp mod for contest use, 
although it would be useful if you operate where there are not 
multiple signals within 5 or 6 kHz of you. If the hissing bothers you, 
use an audio filter!

Watch the noise blanker control setting in the MP. Keep it OFF, 
even if you are NOT using the NB. If you turn the NB gain control 
up blocking and IM DR decreases about 10dB!!!

As for filters, the preference is up to the end-user. Everyone has 
opinions and favorites. I almost always use 250Hz filters for CW 
and 2kHz for SSB because S/N ratio improves in direct proportion 
to filter narrowness.

Switching from 500Hz bandwidth to 250Hz improves S/N 3dB when 
the signal is limited by smooth noise.

Filter ringing is often related to group delay errors in the filter 
passband. As a *general rule* more poles and sharper skirts come 
with more ringing, which can especially hurt copy of weak stations 
in the presence of clicks or rough noise. The exception is when the 
filter designer pays close attention to group delay performance 
(which I'm pretty sure no one ever does).

By the way most narrow crystal filters I have seen generally have a 
much better shape factor and ultimate attenuation than Collins 
mechanical filters, although the mechanical filters often have less 
ringing for the same bandwidth. When digging weak signals a 
mechanical filter tends to be better. When trying to separate a 20 
over nine signal a few hundred Hz away a crystal filter is generally 
better.  

The PIN diode mods going around are a bunch of bologna. Save 
your money or buy a pyramid and place it over the radio. It will do 
the same thing.

I don't believe "overload improvement mods" made by modifying 
AGC are very meaningful either.

73, Tom W8JI
W8JI@contesting.com 

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