[AMPS] 2 tone intermod test

[Dave D'Epagnier]

Rich, why should the receiver only be tuned to a 3.7khz offset? What about
the rest of the band? Also, what is generally accepted as an adequate signal
to splatter ratio? 

The reason I'm asking this is because I recently have gained access to a
160' tall tower that sits on a mesa top with a steep drop off. This combined
with QRO results in a very high profile signal at this installation. I
received a complaint of splatter and think I've got it isolated to the
transceiver, not the 89A. I suppose that having an exceptionally strong
signal really accentuates any nonlinear behavior in the exciter or amp.
Nonlinearities that are normally not noticed seem to become a problem in
this situation. That's why I'm trying to perform the test. I want to know if
my exciter is out of spec. or not.

If John Fielding's comment about the 2 tone levels not changing fast enough
to adequately exercise the amp are correct then John how about if I
amplitude modulate the 2 tones (on and off rapidly)? I guess I can run a
test with voice but it just seems so subjective and would be hard to show
the results to anyone at the Icom factory in case I decide to send the
exciter in for a tune up.

Thanks,

Dave

	----------
	From:  measures [SMTP:measures@vcnet.com]
	Sent:  Tuesday, November 23, 1999 11:39 AM
	To:  Dave D'Epagnier; 'amps@contesting.com'
	Subject:  Re: [AMPS] 2 tone intermod test


	>
	>Hello, I want to run a 2 tone intermodulation distortion test on my
hf
	>transceiver to check for splatter vs. compression level, microphone
gain
	>settings etc. I know this is not an amplifier question, but this
list is
	>probably where I can get the best answer. I'm running an Icom-756
(and Alpha
	>89A). Running this test on an amp would be pretty straight forward,
but how
	>about on a transceiver? Does anyone know how the test is done on
	>transceivers?
	>
	The 2-tone test does not simulate genuine rotten splatter.  For this
you 
	need a complex waveshape.  A human or an African gray parrot is such
a 
	source.  The splatter test is done by tuning a double-filter Rx
(such as 
	a TS-830) about 3.7KHz above and below the test signal to isolate
imd 
	products from the fundamental) and then comparing the signal
strength to 
	the fundamental.  Since S-meters tend to be inaccurate, a 1db step 
	attenuator.should be used to measure relative signal strength.  
	>
	cheers, Dave

	- BTW --   the only splatter that matters to the FCC is what goes
beyond 
	the Amateur Radio Service band.  
	..

	-  Rich..., 805.386.3734, www.vcnet.com/measures.  


	--
	FAQ on WWW:               http://www.contesting.com/ampsfaq.html
	Submissions:              amps@contesting.com
	Administrative requests:  amps-REQUEST@contesting.com
	Problems:                 owner-amps@contesting.com
	Search:                   http://www.contesting.com/km9p/search.htm

--
FAQ on WWW:               http://www.contesting.com/ampsfaq.html
Submissions:              amps@contesting.com
Administrative requests:  amps-REQUEST@contesting.com
Problems:                 owner-amps@contesting.com
Search:                   http://www.contesting.com/km9p/search.htm