[ICOM] ICOM 718 SWR meter
Patrick Schwarz - KB8RTZ
kb8rtz at oh.rr.com
Sat Feb 26 19:32:30 EST 2011
Curious if anyone else has checked the SWR meter built into the IC-718
with the SWR meter of an antenna analyzer such as the MFJ-269?
Here is the setup:
Antenna - Hustler 6BTV
Analyzer - MFJ-269
Process of tuning the antenna prior to purchasing the antenna analyzer:
Connected a 25 foot feedline (RG8U) between the antenna and transmitter.
Per the antenna manual, tuned the antenna on 10m, 15m, and 20m. 30m on
down did not tune well or at all. Ground radials helped, but not enough
below 30m. Came to the conclusion that my tuning skills left a lot to be
desired so invested in an analyzer.
Process of tuning the antenna with the antenna analyzer:
First, reset the trap lengths to factory lengths, then overall tube
lengths to suggested starting lengths using ground radials. Connected a
9 foot feedline (LMR-240) between the antenna and analyzer, manually
tuned the antenna per the manual. Disconnected the analyzer and tuning
feedline from the antenna. Reconnected the transmitter feedline (this
time a 75 foot feedline (RG8U)).
Checked the SWR at the transmitter feedpoint with the analyzer. The
results at the antenna with the tuning feedline and at the transmitter
feedpoint were comparable. Disconnected the analyzer and reconnected the
transmitter. The SWR meter built into the IC-718 measured relatively
close results on 10m and 15m. The SWR on 20m was a little higher than
measured by the analyzer, higher yet on 30m and 40m, and worse yet on
75/80m (granted, 75m is not fully tuned yet).
Seems as though one or the other is incorrect. The SWR at the antenna on
say 7178KHz on the MFJ reads 1.6. The SWR at the transmitter feedpoint
using the MFJ reads 1.6. The Icom SWR meter reads 2.1 or so requiring a
little tuning.
Has anyone else noticed these types of results?
Thanks,
Patrick...KB8RTZ...
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