Hi Chris Dick usually monitors the group but I am sure he would not mind me
passing his emal address to you. I am sure he will be keen to help you adapt
his instrument to 500kHz
E-mail Address(es):
[email protected]
Cheers de Alan G3NYK
----- Original Message -----
From: CHRISTOPHER OSBORN <[email protected]>
To: LF group <[email protected]>
Sent: 05 May 2007 18:29
Subject: LF: Field Strength Meter
> Has anyone built the field strength meter from the 'LF Experimenter's
Handbook' (p 83) ?
> I intend to make a similar one but for the 500 kHz band, however a couple
of things in the artical are confusing me:
> (1)
> The formula (3) for a Helmholtz coil pair gives H = I / (1.40 * r )
> where I is the coils' current in Amperes and r the coils' radii in
metres.
> Looking on the internet the Helmholtz formula also includes the
permeablility of free space - 4 * PI * 10 ^ -7 !! so is there a
misprint ?
> (2)
> The artical gives the required magnetic field to equate to an electric
field strength of 5 mV / m as being 13.3 uA / m
> I follow the working for this ok but if the Helmholtz coils are being fed
from a signal generator with a series 50 ohms resistor surely the output
voltage setting would be impracticably low - about 540 uV ( I think )
>
> I can make the Helmholtz coils as per the artical (i.e. with radii of
0.292 m) so what signal generator setting would I need to generate the
required field strength of 13.3 uA / m and how would I achieve this ?
> Any lessons learned by members of LF Group while making this meter would
be much appreciated.
>
> 73 Chris G3XIZ
>
>
>
>
> ---------------------------------
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