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Re: LF: Re: Re: newbie help

To: <[email protected]>
Subject: Re: LF: Re: Re: newbie help
From: "Tom Boucher" <[email protected]>
Date: Thu, 2 Aug 2007 07:54:34 +0100
Delivered-to: [email protected]
References: <005001c7d3fe$e4786d80$6400a8c0@oem17oeylz9on8> <001901c7d42b$e6fbeaa0$86048351@w4o8m9> <00a001c7d43c$f4180690$0a7ee150@o> <[email protected]> <[email protected]>
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Good point Ha-Jo. When using my antenna impedance analyser, I always leave a 50 ohm load in parallel with the antenna, using a BNC T-piece. Only when the antenna is connected do I remove the 50 ohm terminator, that way hopefully any static on the antenna is discharged through it.

73
Tom G3OLB

----- Original Message ----- From: <[email protected]>
To: <[email protected]>
Sent: Wednesday, August 01, 2007 11:20 PM
Subject: Re: LF: Re: Re: newbie help


Dear all,

I have heard of a case that a german LF amateur had ruined his
capacitance meter because of a static loading on the aerial!

Therefore I have always preferred to measure aerial capacitance by
checking the detuning effect of the aerial to a tuned circuit. The coil
of this circuit will always ground the aerial for dc.

HW?

73 Ha-Jo, DJ1ZB


"John GM4SLV" <[email protected]> schrieb:

Rog,

That's an interesting idea - I've never thought of trying a digital Cap
meter. I must try it on the new antenna - and compare it to my homebrew
RF bridge, calculations and - more telling - to the valuse of L I
eventually need to resonate it.


John GM4SLV


On Wed, 1 Aug 2007, GW3UEP wrote:

> Re ant cap: you can use a DMM [Rapid 328] to gnd - I use 1000pF across
> its terminals to decouple RF for a stable reading. Simply subtract its
> value. 73, Rog.
>
> ----- Original Message ----- > From: James Moritz
> To: [email protected]
> Sent: Wednesday, August 01, 2007 12:05 PM
> Subject: LF: Re: newbie help
>
>
> Dear Paul,
>
> In a nutshell:
>
> - You can tune up more or less any bit of wire for reasonable results
> on 500kHz. For best results, make it as high up as possible, and
> secondarily as long as possible. An HF long wire, or dipole with
> feeders strapped would be fine.
>
> -Work out the capacitance of the wire (see formulas on ON7YD's
> antennas pages). and calculate the inductance for resonance around
> 502.5kHz. For most HF-sized wire antennas, this will be of the order
> of 100s of uH. The resulting coil is








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