For those of you who like me are using older gear on LF here's a hint worth
following up.
The Yaesu FT757 like many other rigs provides a 'band data' output for use
with the matching linear amp etc. This data is in the form of binary data on
a 4 bit wide buss that appears on the back of the rig on an 8 pin connector
along with ptt etc.
In the 757 case the published info lists 8 valid states corresponding to
'below 2.5 MHz', 2.5 to 4 MHz, 4 to 7.5 MHz, and so on up to 30 MHz etc.
The 'below 2.5 MHz' output is binary 1. But with the rig 'broadbanded'
(probably applies regardless) tuning below 2.5 MHz shows there is in fact
another valid data output, binary zero. This corresponds to 'below 1.5 MHz'
and the binary 1 state actually corresponds to the range 1.5 to 2.5 MHz.
Something Mr. Yaesu didn't bother to document that is potentially very
useful.
What this means is that there is a valid band data output (i.e. 'below 1.5
MHz' and binary zero) that can be used for the LF range, and you don't have
to put up with it being combined with the 160 metre output ( 'below 2.5 MHz'
or binary 1) as would be the case if you believed the published info.
It would be worth checking this output, or similar ones on other
manufacturers gear, to see if the same logic has been used. Later Yaesu
rigs may be identical?
So what's it useful for?
Well it's very handy for automatic antenna switching etc, when rapidly
swapping between LF and the HF bands. Just switch VFOs etc, and the antenna
switching follows along. I personally find manually switching antennas to
be a major nuisance when using the same rig for LF and HF, even if only for
receiving.
Incidentally, the 757 can give a good account of itself on LF reception
anyway as it can (with the preamp on - yes it does work on LF!) readily hear
a -125 dBm CW signal. Transmit-wise the low level RF out is down a bit on
the spec (for HF) output of -6dBm, but no great trouble to amplify it up a
few dB more than usual to drive an LF linear.
73
Dave
ZL3FJ
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