>This has been a issue since the first synthesized TX hit the band.
>
>>From all indicators "it aint getting better".
>
>Take a serious look at the TX waveform picture in QST....most all of our
>rigs have been pictured over the past 12 years or so....at least back to
>the TS930 era.
>
>Now, look at that picture of the transmitted composite phase noise.
>Next, look at those spikes on either side of the carrier. Yep, most
>Riceboxes have them and they are typicallly 1.5 to 5 KHz from the
>carrier. Some worse than others, some have multiple peaks. What you see
>is what you hear.
>
>
[stuff deleted...]
>73......Carl KM1H
>
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>
>
Carl makes a good point about the phase noise problems in the synthesized
radios. I would like to add that the rigs which transmit high phase noise
sidebands will also have a reciprocal problem on receive because the same
noisy synthesized local oscillators are used on transmit and receive.
When I bought my TS940S over ten years ago, I was shocked at the high level
of garbage generated in the receiver by loud signals. At first I was
convinced my '940 was defective but I soon discovered that others had
observed the same problems. Fortunately, in the case of the TS940S,
a fix--the so-called "Lowe modification"--was soon published by G3???
(I forget the call) and it helped considerably in lowering, although
not entirely eliminating, the phase noise. I did a series of lab
measurements on the stock and modified radios, using a spectrum analyzer
to look at the transmitter and receiver outputs. The data was published
in the YCCC Scuttlebutt newsletter and later reprinted in The DX Bulletin,
and it showed that the stock TS940S was indeed a rather "dirty" radio.
(I can furnish reprints of that material to anyone interested for an SASE).
I would like to think that the awareness of these problems is much greater
now than it was when the first synthesized rigs appeared and that today's
radios are much improved in this area. On the other hand, I agree with
Carl that the old Collins and Drake stuff are the still the standards for
comparison.
73, John W1FV
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