Hi Bill & Amps reflectees
I've remeasured the intermodulation characteristics of my 4CX1000A
amplifier, more thoroughly, using two transmitters and a Wilkinson
combiner. These results, and also measurements of the harmonics from the
amplifier, are on
http://granta.digital-crocus.com/Linear_design_notes.php3 (half way down
the page).
73, Mark, G4AXX
-----Original Message-----
From: Bill Fuqua [mailto:wlfuqu00@uky.edu]
Sent: 24 March 2005 17:30
To: Mark Marsden; amps@contesting.com
Subject: Re: [Amps] 4CX1000A for SSB??
Ok, I just took a look at this and see where the problem is.
With a resolution bandwidth of 3kHz the 3 order IMD products are masked
by the real signal. For example if you should have a 14.2815 MHz signal
and a
14.282 Signal producing 14.2825, you will not see the 14.2825 MHz signal
because it will be a tiny bit added to the 14.282 signal in the spectrum
analyzer's detector. What you need to do is to reduce the RBW to say
500 Hz or a bit less and sample longer (a lot of talking)until you get
the full spectrum filled in as you did before. And you should see a
difference. In fact since the bandwidth of the SSB signal is only 2.5kHz
or so wide to start with you will most likely not see any IMD products
using a 3kHz resolution bandwidth. A 2 tone test is good because it is
easier to compare results but there is nothing wrong with what you are
doing. You in fact could do a infinite tone test (random noise source)
and perhaps get results that would be easier to compare to others if
they should try it.
73
Bill wa4lav
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