New subject: [Moon-net] Amp HV Switch or Transfer?

31 May 2011

More testing of phasing lines.

Previously I wrote:
...
 I have gone thru disconnecting and testing all the
phasing lines in 
the 2m-eme array:
1)  All eight antenna SWR were individually tested at the driven element.
2)  SWR from the TR relay to the Hpol antennas shows SWR = 1.2, Z = 52, j12
I did not disconnect the lines at the 4-way divider as this looks 
good (within tolerance of the MFJ analyzer).
3)  SWR from the TR relay to the Vpol antennas shows SWR = 1.4, Z = 79, j0
This required individually testing each phasing line, the 4-way 
divider, and ten-foot az-el coax jumper.
I found one phasing line with SWR = 3.9, Z = 116, j120. 
When I removed the connectors I found the aluminum foil and shield 
had oxidized indicating water penetration.  The new LMR-400 line 
tested Z = 51 + j0 (with a 51-ohm termination) and about 0.13 dB 
loss.  That is actually better than spec which would expect 0.27 dB 
loss and may reflect not being able to measure accurately enough 
using a 70w test signal.  BTW since one antenna essentially was not 
working this probably explains the 10-degree shift in azimuth 
calibration I saw last winter.

...
   The rest were SWR = 1.0, Z = 52-54, j0
The 4-way divider with 50-ohm terminations on all ports SWR = 1.1, Z = 59, j0 
With one termination on the divider and antennas connected at the 
ends of the other three phasing lines I see SWR = 1.2, Z = 60, j11.

Measuring cable loss with 70w test signal applied in the shack:
1)  Loss at the input to my relay matrix is 0.82 dB (58w)
2)  Loss thru the relay matrix is .97 dB (56w)
3)  Loss at the antenna end of one phasing line is 2.89 dB (9w x4 
=36w)!  At 1400w this would represent 720w reaching the antennas 
(ouch).  My goal is 1000w at antennas: expected total loss of 1.7 dB 
(0.68 x 1400 = 947w)

That is nearly 2-dB loss for 28-foot of LMR-400 plus the 4-way 
divider.  Should be 0.45 dB.  So I will repeat this measurement using 
the new phasing line I just made, once it is installed, for 
comparison (should see about 12w as 1/4 of total power).  I may have 
to test loss thru each phasing line and with result of replacing more 
lines?  Eight 18-foot LMR-400 and two 10-foot 
LMR-400UF.  Fortunately, I have a partial reel of LMR-400 and 
probably 25-feet of LMR-400UF, so it will not require ordering more cable.

I am hoping the 4-way dividers have not also gone bad.

But on the plus side I may have a much stronger signal (and better 
hearing) once all is fixed.  The last time I measured individual 
phasing line loss was when the new lines were installed in 1998-2000 
and I saw 0.23 to 0.27 dB.

73, Ed - KL7UW, WD2XSH/45
======================================
BP40IQ   500 KHz - 10-GHz   www.kl7uw.com
EME: 50-1.1kw?, 144-1.4kw, 432-100w, 1296-testing*, 3400-?
DUBUS Magazine USA Rep dubususa(a)hotmail.com
======================================

Progress Report - 3