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Derived Noise Figure(s) for FT-736



Hello once again,

I thought I might answer my own question!  ...and while I'm at it, share the
results with the list, in case someone else might be interested.

I measured the 12dB SINAD point of my personal FT-736 on 435MHz, as being
-120 dBm.  (This is with a 20kHz ceramic filter in the 2nd IF).

Working backwards, assuming that a C/N ratio of 8dB is required at the input
to the demodulator to produce a 12dB SINAD on the output, I calculate that
this radio has a Noise Figure of 4.7dB, which is an equivalent noise
temperature (Te) of 574K.

Using the Yaesu specification of -116dBm for 12dB SINAD gives a Noise Figure
of 7.76dB, or Te = 1442K.

I rang Mike at muTek to confirm these figures...  he recalls measurements of
20 736's as giving a range of NF between 6dB and 8dB, however this was on an
early batch...  perhaps mine is slightly improved, or I just happened to
have a particularly fortuitous combination of component tolerances :-)

For my own calculations, I'm going to use a NF of 5dB.   Receive performace
can obviously be improved significantly by the addition of a decent
mast-head pre-amp!

If anyone is interested, I'll post some further calcs quantifying the
benefit of using a typical mast-head preamp (NF = 0.9dB, Gain = 10dB).

73 Chris VK6KCH
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 |  Chris Hill            email : vk6kch@amsat.org |
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