Bob,
I have had a "play" with a TS 850SAT, as a try before buy offer. I can
confirm it works better than I would have thought on receiving LF. The
circuit diagram shows it has a separate pre-amp for tuning below 500
kHz. While it tunes down to 30 kHz, the sensitivity is fairly dreadful
down there, so there must be a lot of roll-off below 100 kHz. We do not
have access to a 76 kHz band down this way. I have asked our regulatory
authority to be able to use the CEPT band at 136 kHz. Our current
access is to 165 - 190 kHz. But whatever, the TS 850 can technically
tune all.
I find it very good on LF, especially with two CW filters fitted!
I was also impressed by the TS 850 NB1 noise blanker, as we have a hash
problem in Wellington. NB2 is specifically for the now defunct
woodpecker, and did not do much good for spike suppression (but may be
able to be redesigned for general use?)
Noise blanker doesn't seem to work much with the narrow filters in, but it
depends on the character of your noise!
Unfortunately I found the sensitivity of the receiver on HF to be around
20 dB below spec. Also the 12 dB attenuator appears to be "open
circuit" when selected. I can hear the relay clicking, so the series
resistor in the L pad seems to be open? So I suspect it has had an
inadvertent squirt of RF in the front end, while the HF rather than LF
pre-amp was selected. As it meets spec on LF, it shows that there is
not too much to be fearful of? It goes back to the vendor for a "covers
off inspection" on Wednesday evening.
Yes indeed, probably a diode in the switching on the RF filter board. I
fixed a similar fault on a friend's rig.
I am still at a bit of a loss to see why Mr Kenwood would provide such a
good spec for below 500 kHz, as it has resulted in extra circuitry and
obviously meant a higher cost of design and manufacture. I'm not
complaining!
The 450 is just as sensitive. Same front end.
Should the HF receiving problem be resolved, I am likely to purchase the
TS 850 SAT, and I would then look for a way to transmit on LF. I
currently do this with my Icom IC-735, by making it all band transmit
(snipping the appropriate diodes) and adding a suitable low pass filter
(inductor input T, to be hi Z to all HF) to the Tx mixer to tap off the
LF Tx signal.
The particular TS 850 also has transmit windowing in the 3 lowest bands
(160, 80 and 40 metres) and gives less coverage than my licence allows.
It also seems to clamp the output power to 50 watts on 160 metres. If I
buy it, I will need to also find out about "band plan" diodes or
whatever they use, but all that may be overtaken by events if I opt for
"all band transmit".
If you get it, I have all the info on the thing.
73, Dave G3YXM.
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