Phase noise can have a number of effects. For SSB transmitters the main
effect is that a small amount of splatter appears either side of the main
signal. This results from the phase noise either side of the that signal
will rise and fall in line with the amplitude variations of the main signal.
For digital transmissions using frequency or phase modulation, the noise can
introduce errors causing the bit error rate to rise.
For receivers the main problem is an effect known as reciprocal mixing. To
look at how this occurs, take the case of a superhet receiver tuned to a
strong signal. The signal will pass through the RF stages and then it will
be mixed with the local oscillator to produce a new signal at the correct
frequency to pass through the IF filters. However it will still be possible
for the phase noise on the local oscillator to mix with the strong signal
incoming but outside of the passband to produce a signal that will fall
inside the pass-band. This could be sufficiently strong to mask a weak
station. Emphasis on the word "could". I've also heard this incorrectly
described as "filter blow by".
As to the Paragon, it uses several sufficiently designed VHF PLL circuits,
which are divided down to the required mixing frequency. This division
process also divides the phase jitter by the same amount so as to minimize
the amount of actual phase noise introduced at the mixer.
73
Bob, K4TAX
----- Original Message -----
From: "JT Croteau" <jt.w6fo@gmail.com>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Wednesday, January 18, 2006 5:53 PM
Subject: [TenTec] Paragon Phase Noise problem
Some of my 'friends' who are very active lowbanders are giving me a
hard time for going with a Paragon because of a phase nose problem
common with both the Paragon I & II.
I always though the Paragon had a pretty nice receiver for lowband
work with decent noise floor but hadn't heard of the phase noise
problem.
Could someone educate me on this?
- JT
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