After seeing much discussion on SWR indications regarding TenTec
equipment I couldn't sit by and not put in my thoughts.
SWR is a relative value which is determined by comparing 2 values.
Hence, Standing Wave RATIO. The TenTec radios do not have provision for
setting the forward meter calibration. Hence they are calibrated at
typically 100 watts output. At that point the reflected (SWR) value is
close to correct. At lower forward power, the SWR value indicated is
less than actual. Situation normal.
Regarding SWR meters reading different values at different points in a
transmission line, i.e. radio and tuner. This is most commonly caused
by current flowing on the outside of the coax between the tuner and
radio. In most cases it is small enought not to cause operational
concerns but will make meters read slightly different. Adding a ferrite
choke with 5 to 7 turns of coax in line between the tuner and radio will
most often correct the concern.
The most accurate method of determining SWR is to measure forward power
and reflected power and then calculate the SWR ratio. The cross needle
meters do a good job of doing this for you.
Happy New Year and happy SWR computing.
73
Bob K4TAX
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