From: DK7FC <73dk7fc@googlemail.com>
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Date: Mon, 15 Dec 2014 14:18:49 +0100
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Subject: Re: Fw: LF: Antenna Current meters
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For antenna current measurements i'm using a simple full wave rectifier 
out of 1N4148 diodes (UF5404 alternatively, for example), a ferrite core 
with a high mu and about 40 turns secondary (1 turn primary) , as well 
as 100nF, a R network to drive an analog meter (100uA or 1mA) for the 
desired range. I find this extremely simple, cheap, nearly lossless and 
quite accurate. I do not at all understand why antenna current 
measurements (in the kHz range) appears to be problematic for some.
Does it matter if the device costs  1E-24 or 0.001 or 0.1 or 1 or 5 
amounts of your preferred currency? :-)

73, Stefan


Am 15.12.2014 12:54, schrieb M0FMT:
> Hi all
>
> A 60p festoon auto bulb from Halfords in series with the ant up lead serves equally well. There is generally no need for antenna current precision measurement its really tune for max smoke i.e. max brightness. A reasonably accurate self calibrating indication of current in the up lead subjectively judging the brightness relative to the DC current rating of the bulb. A more sophisticated set up can be achieved at extra expense.
>
> 73 es GL Pete M0FMT IO91UX
>
>
>
>
>
>
> Sent via my own personal Too-Way (two way) Earth Station to and from the Eutelsat Ka-band satellite  http://www.tooway.co.uk/  at approximately 172 degrees Azimuth in the Clarke belt owing to BTs 19th century cable technology inability to provide a good enough 21st century broadband service. I agree for this message to be passed on to BT Plc at 81 Newgate Street, London EC1A 7AJ  via the snoops at GCHQ Cheltenham, thanks for your cooperation it is appreciated.
>
>
> --- On Sun, 14/12/14, Alan Melia<alan.melia@btinternet.com>  wrote:
>
>    
>> From: Alan Melia<alan.melia@btinternet.com>
>> Subject: LF: Antenna Current meters
>> To: rsgb_lf_group@yahoogroups.co.uk, rsgb_lf_group@blacksheep.org
>> Date: Sunday, 14 December, 2014, 16:31
>> Hi all there has been discussion
>> about Aerial Current measurement on many
>> occassions in the past, and many have built versions of the
>> "Clothes Peg"
>> clip on ammeter.
>>
>> Dave Powis G4HUP announced a kit for an HF clip-on current
>> meter in the
>> December Radcom. After some prodding by me he has had a
>> sample tested at 136
>> and 475kHz and as expected the instuments works well and
>> sensitivity is flat
>> from here up to 30MHz or more. The instructions include a
>> simple calibration
>> proceedure. Sensitivity down to 100mA FSD allows it to be
>> used with low
>> power systems where the use of a thermocouple RF meter is
>> not posssible.
>>
>> Dave also produces a board intended to break out the IF
>> signal from many
>> standard tranceivers for input to an SDR dongle. These were
>> intended to work
>> in the IF frequency range and use SMD parts to give an
>> add-in pcb little
>> larger than a postage stamp. A look at the circuit shows
>> that this is very
>> similar to the circuit used by Roelof (mini-whip) and others
>> for use in
>> E-field antennas. I believe the coupling capacitors will
>> need to be
>> increased in size, but I believe Dave can produce these for
>> LF to order,
>> either as a kit or completed board. He has not yet had a
>> chance to try this
>> out at LF but it's a chance to experiment at little cost.
>> Getting the
>> receive antenna away from habitation and power wiring 
>> is a good move at VLF
>> !.
>>
>> I have no pecunary interest but I admit that Dave is a good
>> friend and ex
>> work collegue, and an excellent engineer.  Look at his
>> web pages
>> http://g4hup.com
>>      email  g4hup@outlook.com
>>
>> Alan
>> G3NYK
>>
>>
>>
>>
>>      
>