[Lowfer] TS-890

[Douglas Williams]

Thanks for the tip, Mike. I would never have considered that.

On Thu, Oct 8, 2020 at 11:05 PM Mike via Lowfer <lowfer at mailman.qth.net>
wrote:

> Doug, Zack Jon & All:  Try terminating your unused RF and IF ports on your
> new radios into 50 or 75 ohm termination connectors. Doing so here in my
> station seems to be making a difference with my FT-817s and FT-847
> radios used as IF radios for my MF/LF converter reception for improving
> WSPR decoding performance at higher -SNRs.
> At the W3SO VHF contest station we had some radio-to-radio interference
> with the Elecraft K3s.  Most of that interferece was at the intermediate
> frequencies with the K3's only several feet apart on a long operating
> table. Putting terminations on the unused rear panel IF ports and
> transverter ports as well as making sure those ports were switched "off" in
> the  K3's software menu made a noticeable difference in low noise receive
> performance.
> Its simple stuff, but easy to forget.  I would think that an unterminated
> port on a PIN diode A/B switch inside a radio would not be anywhere near
> the 60~65 dB isolation that is often quoted or assumed.  The combination of
> high impedance and light capacative coupling in such an unterminated
> circuit could conceivably allow undesired LF and MF energy transfer....a
> look at those small value interstage coupling caps used in W1VD's 500 kHz
> Preselector should be a clue that small "C" values allow energy transfer in
> Hi-Z circuits....possibly resulting in undesired noise ingress....
>
> 73, Mike wa3tts