[AMRadio] Junior Collins on AM


John E. Coleman (ARS WA5BXO) wa5bxo2006 at pctechref.com
Mon Jan 22 16:29:21 EST 2007


Hi Paul:
	I think there is some linearity problems in the mixers or IF amps of
the 75A4 that detract from the audio as well as the distortion of the audio
amp stages.  I was not impressed with the audio on the 75A4 but I understand
that there are some modification on the mixers, IF and AGC that will help it
a lot.  Then use an external audio amp.

I'm here once in awhile.
John, WA%BXO



-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net] On Behalf Of VJB
Sent: Monday, January 22, 2007 11:36 AM
To: amradio at mailman.qth.net
Subject: [AMRadio] Junior Collins on AM

Bob, I should think any linear amplifier, when given
enough headroom, should be able to cleanly boost the
signal of a good sounding lower-power transmitter.
There's no real fidelity question to consider. It's
parameters of RF in/out.

As such, Joe's point that the 30S cannot produce "full
legal limit" AM remains valid, on a power basis, not
audio quality.

But it's an audio problem with the KWS-1, and its
companion 75A4. Both reflect a very deliberate attempt
by Collins to transition to the pinched and narrow
SSB, in which higher distortion was also considered an
acceptable design factor.

Distortion and limited frequency response in the stock
audio circuitry of the 75A4 ruins good quality
reception of AM, regardless of the choice of filter.

The poor audio quality designed into the speech amp
stages of the KWS-1 also need to be addressed to bring
that transmitter toward what's available stock from
the senior Collins models KW-1, 30K and 32V.

And yes, I admit that I like messing with the amen
chorus of those who collect the S-Line products and
think they're "better" than anything prior. That's why
I refer to those radios as the "junior" models, since
they lack the capability of running wholesome AM.  

(feed your ears, it's good for ya)

Paul/VJB




 
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