Ummm ... not quite. A "perfect" half-wave transmission line will
reproduce the impedance of the load [which has been alleged to be 35
ohms but this is an all-band antenna so that may vary some] at the
source [TX] end. The real line will come close, its loss will have a
small effect. His ATU will see whatever the feedpoint complex impedance
is, not necessarily 50 ohms.
I'd suggest a good common-mode choke at the feedpoint too which might
mean a short pigtail of RG-8 ... not sure if there are ferrite toroids
that will fit the CATV hardline. Jim, K9YC, has probably the best
source of data on chokes, ferrites, et al at k9yc.com/Publish.htm
73,
Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County
On 3/31/2020 8:52 PM, John K9UWA wrote:
Cut the hardline to multiples of 1/2 wavelength and the swr will be 1 to 1 on
both
ends. 50 in 50 out. In this case the OP needs around 200 feet. Once your get the
velocity factor for the 1/2" hardline... that is ballpark 80 to 83%. for 3.540
mhz is
265 feet x .8 = 212 feet. If you don't have a piece of test gear to get it cut
correctly then put a 50 ohm dummy load at the far end keep cutting until your
wattmeter says 1 to 1 swr. 1/2 wave multiples will hit most of the ham bands. A
little high in the 30m band. Close enough.
73
John k9uwa
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