[UK-CONTEST] More on Feeders

[Ken Eastty]

I've seen the results of comprehensive tests carried out between open-wire &
co-ax when used for reception on frequencies up to 30 MHz. The conclusion
drawn from these tests was that co-ax was far superior to open-wire even
though the cost & loss is greater. If anyone's unsure about the performance
of open-wire feeder I suggest that they try terminating the distant end of a
line with a (non-inductive) matched resistor and see how much can be still
be heard, even if the line is well balance there will almost certainly still
be some pick-up.
With multiple feeder runs (lucky the amateur who has this problem!) there's
coupling between the runs to be considered if they run on the same set of
posts. Even if there's no local interference any pick-up on the line reduces
the directional properties of the antenna that it's connected to.
GPO (later BT) Rugby Radio was a transmitting station, when connected to a
transmitter a broken line soon shows up as high SWR but is much harder to
detect on receive.
The main reason for using open-wire feeders on receive stations would have
been cost, loss was a factor on long lines before the advent of high
performance solid state amplifiers.
If I were looking for some hard line I would start by paying the local scrap
yards a visit, failing that try to find out what the cellular companies do
with the scrap end of reels after they've completed an installation.

73...

Ken

G3LVP



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