[DSP-10] Mixers under the board

[Courtney Duncan]

Ron,

Mounting the mixers under the board is a good thing and is recommended 
for "new kit construction" at the diagnostic page

http://www.proaxis.com/%7Eboblark/u15_mod.htm

When I got to this step in my post-assembly testing (see

http://home.earthlink.net/%7Ejccool3/dsp10.html

at 2005 March 10)

I did not want to take the board out of the box and risk the mixer by 
removing and reinstalling it, so I just did the ground-braid mod.  In 
the process I got the part so hot that I could smell it, but it still works.

By the way, I don't really understand the explanation for the problem 
that I fixed with this test.  It says that phase noise from the 19.68 
MHz oscillator gets into the mixer washing out everything upstream.  How 
come phase noise from the mixer doesn't just go through the amplifier 
chain and cause the problem anyway then?  I can see how other hash 
inside the box could get onto the mixer, however, and the extra 
grounding did yield the expected improvement in my case, so it is in 
fact a lot quieter now.

Good luck as you continue,

Courtney, n5bf/6



From: Ron Meiring <rmeiring at iinet.net.au>
Date: Mon, 21 Mar 2005 05:38:59 +0800
To: Yamamoto Jiro <jyamamoto at katch.ne.jp>
Subject: Re: DSP10 question
X-Mailer: PocoMail 2.63 (1077) - Licensed Version

To all replying to this topic.

Thank you for the ideas and tips on how to remove the IC.
I decided to sacrifice the IC, because I don't rely on them after
removal. (and the value of the board is more than the component ...)

<snip>

I mounted the Mixers under the board, had the feeling that this would
give better isolation and grounding to the mixer ... Any feedback
here ?