"W5DXP" wrote in message
...
Dr. Slick wrote:
I didn't think you could tell us. I've never seen an SWR meter
that you could "calibrate" to 50 or 75 ohms, or less.

The calibration of the SWR meter is controlled by the internal sampling
load resistor, the 'R' in Peter's V + IR equation. I have a home-brewed
SWR meter that measures SWR on both balanced 450 ohm feedlines and on
300 ohm feedlines simply by changing the internal load resistors.
--
73, Cecil http://www.qsl.net/w5dxp
Cecil,

When you do this, does the scale still display the correct SWR for
conditions other than 1:1 ?

Tam/WB2TT

Tarmo Tammaru wrote:

"W5DXP" wrote:
The calibration of the SWR meter is controlled by the internal sampling
load resistor, the 'R' in Peter's V + IR equation. I have a home-brewed
SWR meter that measures SWR on both balanced 450 ohm feedlines and on
300 ohm feedlines simply by changing the internal load resistors.

When you do this, does the scale still display the correct SWR for
conditions other than 1:1 ?

The scale is calibrated using known loads so yes, it displays the
correct SWR up to 5.83:1. Above 5.83:1 the resolution of the scale
is poor because the full scale SWR is infinity. I have marks at
5.83:1 and 10:1. 5.83:1 is where the reflected power equals half
the forward power. Incidentally, the Z0 of my '450' ohm ladder-
line is closer to 388 ohms.
--
73, Cecil http://www.qsl.net/w5dxp



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