[Antennas] SWR Isn't Enough - Working in a high SWR setting
Jim Shaw
[email protected]
2002年4月29日 07:31:59 -0700
Thanks for the tips on using ladder line, especially about keeping it away
from objects by two to five times the line spacing.
Yes, I am leaning toward use of a tuner (because commercial ones are so
readily available) although I haven't totally ruled out use of switchable
matching stubs. The indecision is due to considerations for getting the
ladder line into the shack to a manual tuner versus using a remote auto
tuner under the eve of the house. My indecision must have come through in
the last note. Sorry for the confusion.
73 de Jim WA6PXU
[email protected]
-----Original Message-----
From: Harvey&Bessie [mailto:[email protected]]
Sent: Monday, April 29, 2002 6:56 AM
To: [email protected]
Cc: Dave Shrader; antennas
Subject: Re: [Antennas] SWR Isn't Enough - Working in a high SWR setting
Ladder line is definitely not suited for use in conduit, buried or
otherwise. There is an RF field surrounding such a line that needs
protection from:
Metal objects (running parallel to it for any appreciable length),
because such will alter the impedance and (probably) lower the
efficiency by introducing loss near current loops.
Poor dielectrics (running parallel) because they will introduce
losses near voltage loops.
Different authorities recommend different amounts of separation of the
line from these influences, ranging from twice the line spacing to 5
times the line spacing. I tend to go along with the higher separation
limit.
I don't understand what you would be using matching stubs for. It is
obvious that you envision using a "tuner" (transmatch) because you wish
to use the ladder line to avoid the losses associated with high SWR.
Under that condition, no matching stubs are necessary.
Harvey/W4TG