Bill,
I have a Paragon I here which oddly enough I hooked to
my spectrum analyzer the other day (I wanted to set the
power level to circa S9 so I could check out the key
clicks with my Drake R4C). Anyway much to my dismay,
I noticed some very nasty discrete spurs on the output
spectrum of my Paragon. I ran some more tests today
and took photos of the Analyzer display. The data is
posted on my website at the following URL:
http://www.dellroy.com/W4EF's-Ham-Radio-Page/Paragon/paragon_tx_spectrum.htm
Most of this stuff is very close to the carrier, but its very
strong (only -32dBc in the worst case). There are also
some weaker spurs at larger offsets which I couldn't
see with the spectrum analyzer (the HP141T has
limited dynamic range). For example, with the VFO
set to 7057.99 KHz (random setting) and the signal
level to my Drake R4C adjusted to -30dBm (~S9+40dB),
I could hear weak discrete spurs at +/-7.5 KHz and
+/- 50.7 KHz. These spurs were about 25dB above
the noise floor of the R4C (250 Hz bandwidth filter),
which would put them around -110dBm or -80dBc
below the carrier. Just to make sure these weren't an
artifact of the R4C, I also listened on my Yeasu FT-847
and heard the same thing. When listening on the R4C
with the input signal set to S9+40 (~-30dBm) the phase
noise pedastal from the Paragon is audible for ~+/- 25
KHz either side of the carrier.
Its also interesting to note that the level, number, and
position of the close-in spurs changes as a function
of frequency setting, suggesting that these are reference
spurs from the Paragon's multiple-loop PLL synthesizer.
There may be other spurs as I certainly didn't do an
exhaustive test today (I had a bad headache).
Anyway my apologies for using this piece of junk
on-the-air. I had absolutely no idea it was this dirty. I
don't have very good antennas right now, so perhaps
that is why nobody has complained. It will be interesting
to find out if something wrong with my particular radio,
or if all of the Paragon I's are like this. BTW, the rig has
pretty nasty key clicks in addition to the discrete
spurs.
73 de Mike, W4EF...............................................
----- Original Message -----
From: "Bill Tippett" <btippett@alum.mit.edu>
To: <tentec@contesting.com>
Sent: Sunday, December 14, 2003 9:00 AM
Subject: [TenTec] Paragon Spurs
> Is it normal for a Paragon to have spurs exactly
> 10 kHz away from the fundamental? I have a neighbor
> who seems to have this problem and wonder if it is
> normal or something is out of adjustment. This is
> on 160 where his fundamental is S9+40 and the spurs
> are probably S2-3, so they are well within the spec
> of 40 dB down from the fundamental.
>
> 73, Bill W4ZV
>
> _______________________________________________
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>
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