[TowerTalk] Testing Antennas

[n4kg@juno.com]

It could be that at LOW power, the detector DIODES are
not conducting (0.7 VDC threshold for silicon) and therefore
giving a false LOW SWR reading.

For measuring cable loss, connect a dummy load at the end,
measure power into the coax, move the SAME meter to the
dummy load, and measure output power.  
Loss = 10 LOG (Pout / Pin)

Tom  N4KG

On Tue, 28 Nov 2000 13:20:41 -1000 Mike Sato <chucky@aloha.net> writes:
> I recently bought the latest MFJ model (the one with UHF too)...I 
> like it...initial battery check and sleep mode is handy...
> 
> I found an interesting thing about a few measurements.  SWR with MFJ 
> versus SWR with high power changes...I think it is due to 
> die-electric breakdown???  (e.g. old cable or water in cable, 
> etc...)  Seems the higher power will see the problem and not the SWR 
> test sets...
> 
> As a rule of thumb, I would add about .3 to SWR readings to get a 
> better picture on what higher power would discover...
> 
> I would appreciate comments on this subject...
> 
> Also, what would be best method to test integrity of cable itself? 
> (assuming already strung to an antenna)...I was thinking of cable 
> loss measurements.  But not sure if I need higher power (again) to 
> see dielectric breakdown....
> 
> Mike KH6TO
> 
> 
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