[evlatests] Bandpass Ripple in ea28, RCP, L-band

[Dan Mertely]

Hi Rick.  Tyler Mobraten & I checked out the W8mon tap cables
yesterday, cleaned connectors & swapped out a damaged connector.
It would be useful to know if it is any better now.  The forever
ripples we see on the W8mon data didn't seem to change after our
work however, but I don't know if what we see at the end of our tap
in any way relates to what you see in the scientific data stream.

The new commercial amp we swapped-in a couple of years ago still
seems to be functioning properly.  I doubt if the I/O isolation
spec on the amp would change with time.  All the connectors we
worked on were at the FE output, in front of, and immediately
after the medium power amp.  I sorta doubt that work at that end
of the cable would fix a 4.6 MHz ripple.  Anything after the amp
"should" be isolated from the directional coupler tap at the FE.
(The Mini-Circuits ZX60-2534M-S+ amp has an I/O isolation figure
of better than 20 dB, which I think is fairly decent.)  -Mert

On 9/3/2019 11:01 AM, Rick Perley via evlatests wrote:
>      Bandpass solutions from my Cygnus A observations, taken in April 
> and August this year show a strong bandpass ripple in RCP only, for 
> antenna 28 and L-band.  The period of the ripple is about 4.6 MHz, 
> corresponding to 30 meters if the cause is a reflection.  The problem 
> was not visible in data taken in December last year.
> 
>      The ripple pattern is strongly time dependent (both in its 
> amplitude and phase), so is very difficult to calibrate out.
> 
> 
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