Message-ID: <314E4EC5BF0B4EF0927346C1EABD1DBC@AGB>
From: "Graham" <g8fzk@g8fzk.fsnet.co.uk>
To: <rsgb_lf_group@blacksheep.org>
References: <4A0D91E3.9040602@btconnect.com>
In-Reply-To: <4A0D91E3.9040602@btconnect.com>
Date: Fri, 15 May 2009 19:30:30 +0100
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Subject: Re: LF: Aerial current
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Richard .

This bit may of been missed

//////   Any ideas?
//////   Incidentally, am I best to measure current in the link or in the 
aerail
//////   wire?

The ammeter 'has' to be at the point of feed to the Ae      and 'not' 
within the ATU  ie in a link .. the  circulating  currents  within the tuner 
may be  extremely large  and peak voltages also may be vast , due in part to 
the  Q of the  tuner

.. my  home brew  80 mtr tuner used to  un-solder the  tap's on the  coil 
and the ww2 cellulite coil separators used to  flash over ....

As for  measuring  power with the ammeter into the antenna this is 
virtually  impossible , unless you have a calibrated power  meter  and are 
able to  , measure the losses in the tuner and the power supplied to the 
tuner/Ae with a near perfect match , the current  value then may be 
extrapolated and used as a relative measurement .. for that frequency . with 
that Ae at that time due to the load being  'complex'

G ..


--------------------------------------------------
From: "Richard Newstead" <g3cwi@btconnect.com>
Sent: Friday, May 15, 2009 5:01 PM
To: <rsgb_lf_group@blacksheep.org>
Subject: LF: Aerial current

>
> After my success in getting more current into the aerial yesterday I
> decided to measure the RF current in the link (link coupled ATU) with a
> proper RF ammeter. I was somewhat surprised that the current pinned my 1
> Amp RF meter. How can that be? I can think of some possible reasons:
>
> 1) The meter is wrong (it must be nearly 70 years old)
> 2) The impedance is not 50 Ohms which is odd because I assume the TX is
> designed to have a 50 Ohm output and I carefully adjusted the link for
> maximum power transfer last night).
> 3) The transmitter is giving out far more power than expected (seems
> unlikely).
>
> Any ideas?
>
> Incidentally, am I best to measure current in the link or in the aerail
> wire?
>
> 73
>
> Richard
>
> PS - beacon on again 501.6kHz.
>
>



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