Topband: EIRP Measurement
w2xj at nyc.rr.com
Tue Feb 21 12:12:19 PST 2012
As I posted earlier field measurement is not an accurate method of
determining power. I seriously doubt an administration permit such a
technique unless it was very dumbed down and produced very 'safe'
results or in other words less power than could otherwise be achieved.
On 2/21/12 2:54 PM, Tod Olson wrote:
> 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 → www.ets-lindgren.com/page/?i=6402M
> 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 subich.com> 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
> UR RST IS ... ... ..9 QSB QSB - hw? BK
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