70 feet is about a quarter wave on 80, and a bit longer than half wave on 40M,
so might have either an impedance transformer function or an impedance
transfer as a half wave device on such bands, where it is half wave or
multiples of half waves.
Finally in RG 58 coax, the loss in 70 feet is minimal at HF, being per Belden
catalog: 1.4 dB at 50 M Hz, where this antenna does not cover, and being less
than a dB at 10 MHz in the range of the antenna, an amount of attenuation you
cannot distinguish by ear.
NO, this length will not cause loss of signal over the bands of the G5RV
antenna. It May make it easier to load on problamatical bands in which the
G5RV is not resonant inside the ham band. See Louis Varney's original write
up or the quotation of him in ARRL Antenna Compendium Vol. I. The G5RV is a
compromise antenna, providing some gain on 20M and up, and a reasonable match
on 40M, with possible use with a tuner on other bands except 15M and possibly
30M where SWR may go higher.
All that being said, it is a good approach to an "all band" HF antenna at low
cost, and ease of installation. I prefer to make my own version which follows
ZS6BKW's dimensions as related by Bill Orr, W6SAI in both CQ magazine awhile
back and in his latest antenna book.
Superior results will be gained by erecting the ladder line or twin lead
section horizontal, if one cannot get the required height for the dipole to
allow this matching section to drop vertically at right angles to the wire
dipole section. This does require a third support, but a chimney, or nearby
tree has proven helpful in my own case. Total height on one end was 15 feet
and 20 feet on the other end of the dipole. The ladder line was barely above
the single story house roof peak. However, with modest sunspots round tables
on SSB 90 watts or less were easily held with Chile, Stateside, and Australia,
at times other stateside stations reported loss of either the South American
or the Pacific stations. The G5RV and its matching line erected as a
horizontal Tee appears to have many lobes, covering both broadside and end on
directions.
IF you still don't like the idea of RG 58, then RG 8x is low loss at somewhat
more cost, but might require some added support to relieve its weight at the
junction with the parallel conductor line. I believe in the Ten Tec antenna
kit, you have to supply the coax, while they supply everything else.
73, Stuart K5KVH
rohre@arlut.utexas.edu
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