[NLRS] Checking out performance of a satellite ground station

[Chris Elmquist]

Thinking about just checking the feedlines ...

The MFJ Antenna analyzers, such as the MFJ-259D have a TDR or "Distance
To Fault" mode.

https://cdn.shopify.com/s/files/1/0289/7782/3843/files/MFJ-259D_User_Manual.pdf

page 13.

Ideally, you could get the "dumb guy" to put 50 ohm terminators on in place
of your antennas and then use the TDR mode to check out everything else from
the ground up to those dummy loads.

To check for loss, you could replace the dummy loads with opens and then
put a little bit of power in at the bottom and watch reflected power and
you should see close to what you put in coming back (ie, not too much lost
all the way up and back).  You can calculate the expected loss based on
the specs for the feedline (at frequency) and twice your length (since
it's going up and back).

Unfortunately, I think it does require someone to go up and disconnect
the antennas temporarily while you make these measurements on the ground.

Chris NØJCF


On Tuesday (05/03/2022 at 03:30PM +0000), Jon Platt via NLRS wrote:
> That some of the coax connectors were not weather sealed may not be good.  I have seen cases where there has been water in the feedline but that the SWR was still low, so SWR alone may not be an indicator.   My only thought would be to borrow a Time Domain Reflectometer (TDR) that can see any bump in impedance along the feedline.  I do not own a TDR but perhaps someone on the list here may.  Otherwise a visual inspection by moving the connector and seeing if moisture is present can work too.   Good luck.
> 73, JonW0ZQ

-- 
Chris Elmquist