Topband: EIRP Measurement

Tod Olson tod at
Tue Feb 21 11:54:07 PST 2012

Joe, et. al 

I am quite certain that there will need to be different sense antennas for
160m and 630m. I would not be surprised if we did not also need bandpass
filters for each of the bands as well.

As I recall there were several circuits in QST using a single analog
Devices unit to measure RF input levels. I think that it have several
decades of measurement and the output was on a log scale. Since the input
of those circuits was broadband something would need to be altered to make
it usable on 160m and/or 630m for measuring rf at those specific

There is a device called a Helmholtz pair that might be used on low
frequencies to help with calibration.

See →

I have been advised by Dave Bowker, K1FK, that such a device might be
constructed for quite low cost.

Thanks for the suggestions Joe.

Tree, if this is going over the edge let me know. It was not my intention
to subvert the TopBand reflector.

Tod, K0TO

On 2/21/12 10:26 AM, "Joe Subich, W4TV" <lists at> wrote:

> > On Mon, 2012-02-20 at 19:04 -0700, Tod - ID wrote:
> >
> > The important thing is to have a way to assure that when someone
> > measured the same field at the same point with the same type of
> > measurement device they would get the same measurement result.
> > That would allow us to compare measurements between different
> > people even if we did not know the absolute field strength value.
>I think simple, repeatable and accurate are a difficult triad.  What
>you are talking about is an accurate Field Intensity Meter (FIM) and
>getting stable calibrations with home constructed equipment is not
>going to be easy - let along easy to duplicate.  The closest solution
>is to use standard antennas (not simple whips) and calibrate them
>against broadcast signals at known locations and known field strengths.
>This will still require separate antennas for 160 and 630 meters and
>separate calibration sources on the appropriate ends of the standard
>broadcast band (due to the antennas).
>    ... Joe, W4TV

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