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RE: Kenwood TH-F6A all mode HT

My biggest unknown observation on 70 cm was that with out the whip antenna
the radio sounded like a normal SSB receiver(light noise).  But attaching
the whip antenna gave an instantaneouse full FM noise from the SSB
receiver.  This made me think it was oscilating and the full noise power
of the oscillating was totally wiping out any sigs from FO20.

Then I heard that the 1st stage had NO AGC, so it could have just been too
much gain.  But why the 20 dB noise level difference with a matched
antenna (noise) and no antenna (quiet) unless the unloaded RF amp then
went deaf?

It was this unusual behavior that caused me pause...

On Sun, 2 Dec  2001, Howard Long wrote about the TH-F6A:
> I bought one a couple of months ago. It's now the radio I take with me
> everywhere. My 'go everywhere rig' was an IC-T81, but I hardly ever used 6m
> or 23cm with it, although I often used the FM broadcast band receiving
> capabilities. Having the TH-F6A's wideband all mode RX is more useful to me
> than 6m or 23cm TX on an HT.
> I find the RX very sensitive. My test on VHF is to try to hear a 2m CW
> beacon 30 miles away in various parts of my basement apartment. It's the
> most sensitive radio I have used yet.
> The next test is to use it for a few weeks in the car driving in and out of
> work and see what it's like in the usual strong signal areas of Central
> London. No better or worse than any other radio IMHO. (FWIW, in case you
> ever needed to know, 'places to avoid in London' due to strong sigs are, in
> decreasing order: Hyde Park Corner, Birdcage Walk at the Buckingham Palace
> end, Piccadilly Circus, Knightsbridge Barracks, Gresham Street in the City,
> Victoria Embankment and Lancaster Gate).
> On the sats, as long as you don't mind half duplex operation, it will
> resolve FM sats down to 5kHz [less if you can work out the intermediate
> steps using 6.25 and 12.5kHz steps]. Lower step sizes are not available in
> FM.
> However, less impressive is the SSB resolution for Ham purposes. Not only is
> the SSB filter bandwidth wide [to be fair, Kenwood acknowledge this], it's
> also rather unstable particularly on 70cm, making readability on FO-20 &
> FO-29 rather difficult. It's possible, I've done it, but it's rather raspy,
> I would guess due to the inaccuracy and noise on the LO. Certainly it's hard
> work. Now you know why it won't resolve SSB beyond 70cm...
> A nice feature is the built in ferrite bar antenna for AM operation.
> 73 Howard G6LVB

de WB4APR@amsat.org, Bob

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