And I second Jim K9YC, The current that radiated is on the outside of the
shield and that current has to come from somewhere. In most cases it comes from
the junction point at the antenna. If you have a transmitter without proper
shield, like the "old days" you may get it from there.
High SWR can be an indication of an unbalance at the feeding point with
current returning along the outside of the coax. A simple test is to add (or
subtract) some of the coax between the SWR meter and the antenna. If you have a
change in the SWR you have current on the outside of the coax.
Hans, N2JFS
____________________________________
From: jim@audiosystemsgroup.com
To: towertalk@contesting.com
Sent: 8/12/2008 3:38:48 A.M. Eastern Daylight Time
Subj: Re: [TowerTalk] OT: Exterior Ethernet Cable
I said:
>>SHIELDED EQUIPMENT
>> DOESN'T RADIATE OR RECEIVE. ANTENNAS DO!
Roger said:
>So does feed line with high SWR.
I reply
NO! SWR does NOT cause feedline radiation. IMBALANCE IN THE ANTENNA
causes common mode current on the feedline, and that common mode
current causes radiation.
73,
Jim K9YC
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