Hi Mike,
Icom R-75:
'Consumer Reports' and 'Which?' magazine four-star best buy.
As has been mentioned, the R-75 works very well out of the box at LF, and has
become a fave amongst 'Lowfers' over here. I have a couple and they're
mainstays for the 'Grabulators'.
Further to other remarks, under software control the AGC can be made 'Very
Fast', intended for use during scanning as a poor man's spectrum analyser. But
it is quite useful as an alternative to turning the AGC off and letting the receiver
clip/saturate on static crashes - 'Argo' seems to make nicer plots under 'Very
Fast'.
The receiver uses a single lowpass filter for 1.6MHz and below - no transition at
500kHz-ish. There is a fixed attenuator in this path of nominally 3dB, presumably
just to secure a sane source impedance for the filter. However, its removal
makes considerably more difference than that with highly reactive and hi-Z LF-ey
antennas - the input impedance of the first mixer is probably quite a bit higher
than 50R. No obvious nasty side-effects from the attenuator's removal and is so
considered a plus.
Inrad's 125Hz filter makes for a well worthwhile 'microscope'; for most
circumstances if the radio is in a house the TCXO is not worth it; the DSP option
is useless for LF; the noise blanker is amazing - allowing plots to be made under
lighting-dimmer noise if need be.
Kenwood TS-440:
Has a discrete front-end filter-set for 500kHz and below, with no fixed attenuator
and is very sensitive even down to 100kHz. Optional filter (500Hz or 270Hz
Kenwood, 400Hz or 250Hz Inrad) a must. Ho-hum noise blanker.
Recommended - circuitry and performance almost identical to the highly-
regarded TS-850.
Kenwood TS-140:
A real surprise for an 'entry-level' radio. Very lively down to 200kHz, sensitivity
dropping off towards 100kHz but still adequately sensitive at 136kHz - in fact
this one here has been sitting collecting dust plotting DCF-39 for however long
now.
Same front-end filter as 1.6MHz and below, but below 500kHz the fixed
attenuator is switched out - thank you Kenwood! There is tons of room to
kluge in a <500kHz filter in that position.
IC-781:
Very good at LF. Just a bit too much radio for the job!
IC-751a:
Very sensitive at LF, but d r i f t s way too much for QRSS, and so can't be
recommended except for a band-cruiser.
Hope this is helpful.
Cheers,
Steve
07/12/04 16:49:57, "Mike Dennison" <[email protected]> wrote:
I am compiling a list of receivers and transceivers suitable
for 136kHz.
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