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| To: | <[email protected]> |
|---|---|
| Subject: | LF: RE: Field Strength Meter |
| From: | "John W Gould" <[email protected]> |
| Date: | Wed, 30 May 2007 09:01:41 +0100 |
| Delivered-to: | [email protected] |
| Importance: | Normal |
| In-reply-to: | <[email protected]> |
| Reply-to: | [email protected] |
| Sender: | [email protected] |
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Chris, your experiments of measuring ERP are interesting. How
close is the result that you obtained with that derived from aerial modelling
and aerial current measurement? To what extent do you think that local
environmental factors can explain any differences?
I
wouldn't be too concerned about leaving a 6dB margin. My off-the-cuff
feeling is that so long as we make reasonable efforts in terms of accuracy and
can demonstrate an intent to operate within the -10dBW limit that this should be
acceptable to Ofcom.
73
John, G3WKL
-----Original Message----- This bank holiday I finished PA0SE's field strength
meter (LF Experimenter's Handbook) duly modified for 500 kc/s.From: [email protected] [mailto:[email protected]] On Behalf Of CHRISTOPHER OSBORN Sent: 29 May 2007 21:05 To: LF group Subject: LF: Field Strength Meter I knocked up Helmholtz coils of almost identical proportions to those in Dick's published design and with these calibrated the F/S meter. Initial results look very promising and the meter seems quite linear up to my calibrated maximum of 6 mV/m. This evening I trudged around the fields in Biggleswade making sundry readings, while my PC/TX put out a test signal every 3 minutes. If (?) my calculations are correct then I have an ERP of 40 mW averaged over 3 (1 km distant) readings. I know this is not much of a sample but initial results are satisfactory and fairly consistent. Apparently I am told that field strength measurement uncertainties are notoriously high - one RadCom informed letter suggests by as much as 6 dB. If I wanted to be pedantic then presumably we should ensure that we measure no more than 25 mW ERP to allow for the worst case uncertainty (tongue in cheek!) 73 Chris G3XIZ
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