----- Original Message -----
From: "Raoul Coetzee" <raoulc@smmcape.co.za>
It is also important to note that not everybody lives in a high density
Amateur Radio area/country. Those lucky Amateurs would be very happy with
the radio, I suppose.
If you look at Tom's list after clicking on the 'sorted by IM3 'and
looking
at no 5 on the list, this a "stock" FT1000MP MKV
WITHOUT an Inrad roofing filter but with the very simple NB mod done.I
have
done this easy to perform mod but I would still like to ask why is the
radio
better without the Inrad roofing filter installed? Is it because of the
amplifier that is included? This report is the one reason I have not
considered the roofing filter, also,I live in a relatively low HAM
area.(About 5 in a mile radius and not very activey at all.)
Tom, have I lost the plot?
73
Raoul ZS1REC
Raoul,
If it really is the 2N5179 amplifier on the roofing filter board and not
some other subtle thing like an upstream mixer or amplifier termination
impedance problem then it should be a simple matter to reduce the
gain of that 70 MHz amplifier to unity (with a pad) or just eliminate the
amplifier altogether.
Assuming the above adjustment brought the 2MHz IMDR back into
parity with the FT1K MK V with W8JI noise blanker mod, I wonder
if any of the other numbers would be any better? If the roofing filter
was simply a band-aid for the noise blanker problem, then the answer
might be "no". After the noise blanker is fixed, if the 1st mixer is the
limiting factor, I suppose then the roofing filter might not offer any
improvement in dynamic range.
BTW, Tom's data for the MK V doesn't seem to indicate whether the
pre-amp is on or off (IPO).
73, Mike W4EF................
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