Re: 7912AD Repair


 

On Sun, 9 Apr 2017 17:45:31 +0200, you wrote:

On 8 Apr 2017 9:17 p.m., "very_fuzzy_logic@yahoo.com [TekScopes]" <
TekScopes@yahoogroups.com> wrote:

Link to your new pictures is missing - what rise time do you measure with
the 7A29? I was estimating maybe 550-600psec when thinking of looking for
one.

I sent a second mail with the link in, but here it is again in case that
didn't make it:

https://goo.gl/photos/oRsrhCVqU5cGnhNt8

I haven't checked the risetime yet. Doing that requires getting the 7912AD
and my CSA803A within a couple of feet of each other, which is no small
feat considering their size and weight. I worry about creating a black hole
due to the concentration of mass. And one's at home and the other's in the
office. I'll do it and report back though.

Chris
The distance restriction can be relaxed a little by using larger
diameter coaxial cable (1) so it might pay to make a custom mimimum
length RG-8 sized patch cable for this sort of thing. LMR-400 cable
might be the best commonly available cable for this but maybe someone
else has some experiece with it. I get by with some 1ns and 2ns
length but practially indestructable RG-400 (RG-58 size) cables.

My personal experience is that the performance limitations of
RG-174/RG-316 is very apparent at any useful length and RG-58/RG-400
slightly so. There are some examples here at the bottom of using
different types and length of transmission lines:

<http://www.amplifier.cd/Test_Equipment/Tektronix/Tektronix_other/284.html>;

(1) Up to the TEM cutoff frequency anyway which is 16 GHz for LMR-400
and 13.5 GHz for RG-8 so that is not a problem.

https://www.microwaves101.com/encyclopedias/coax#cutoff

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