If you use coax for an 80 meter dipole and run it on 40 meters with
coax, the loss will be very high. That's because the additional loss
from a high SWR (around 100 to 1 in this case) is huge.
If you run open wire line on an 80 meter dipole and use it on 40 meters,
the additional loss is not that bad. That's why we use open wire line
on a single band dipole to use it on more than one band.
Carl Moreschi N4PY
58 Hogwood Rd
Louisburg, NC 27549
www.n4py.com
On 11/9/2013 6:49 PM, Ken Brown wrote:
That's a new one on me. How could loss be less with high SWR on a
short length of coax? It makes no sense.
The loss in coax at HF frequencies is not that high, and the additional
loss due to high SWR is also not that high. (At least compared to what
happens at VHF) For HF systems keeping SWR low on coax is still a good
idea, but it is more to reduce the possibility of HV arc over than to
minimize the loss. (A matter of opinion no doubt, but if you work out
the numbers you may have the same opinion) If the added line is short
and makes it easier for the tuner to match, the additional loss in the
coax is likely to be less than the reduced loss in the tuner when it
sees an easier to match impedance.
DE N6KB
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