Regarding the 775's spur: Icom America recently gave me a full refund on a
3.5 year old 775 after admitting that they could not (or would not) correct
this problem without disabling QSK above 20 wpm. I'd have rather they fixed
the problem, but a refund is far better than nothing.
73,
Dave, AA6YQ
> -----Original Message-----
> From: owner-amps@contesting.com [mailto:owner-amps@contesting.com]On
> Behalf Of Tom Rauch
> Sent: Wednesday, June 02, 1999 3:44 PM
> To: 'Jon Ogden'; 'amps'; Peter Chadwick
> Subject: Re: [AMPS] IMD & Phase noise
>
>
>
> Hi Jon,
>
> > limitation on how much IMD performance a receiver needs is how
> much phase
> > noise exists from other transmissions on the band. I've heard a
> number of
> > FT1000s on the band that weren't too good - this on CW. So that
> could be a
> > limit. Fortunately, tube PAs aren't generally too bad for
> wideband noise,
> > but the wideband noise from
> >
> > some solid state drivers leaves a lot to be desired.
>
>
> It's the 1000MP that has the bad TX phase noise, I can tell you that
> after listening to many rigs on 160 meters while trying to work
> weak DX signals close by.
>
> Other rigs have other problems.
>
> The 775DSP transmits on both VCO frequencies at once, and also
> receives on both VCO's at once even with the second VFO turned
> off according to the front panel. The closer the VCO's to the same
> frequency, the stronger the spur.
>
> Other rigs click on split because the VCO's are still settling in
> while the rig goes into transmit.
>
> I measured an old Collins KWM-2 and IMD was 50 dB below one
> tone in a two tone test almost independent of drive. The same test
> on a 751A produced IMD 29 dB below one tone at optimum drive,
> and worse IMD performance as power was raised or lowered!
>
> Does anyone know why the ARRL started using dB below PEP
> instead of dB below one tone, like the commercial folks use? Did it
> have anything to do with the poor TX IMD performance of the KWM-
> 380 and other solid state rigs, to make them look acceptable?
>
>
> 73, Tom W8JI
> w8ji@contesting.com
>
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