LF: Re: Loading Coil Q

["PA0WFO" <pa0wfo@chello.nl>]

To All ,

Lacking a "Q"meter I use the following procedure :

Connect the coil in series with a variable capacitor to a noise bridge with the RX output of the bridge to a receiver ( small bandwith of a few hundred cycles )  on 137 Khz . Bring the the bridge to resonance with the variable capacitor and the internal potmeter of the bridge and read the  loss resistance of the coil .

The Q factor is the Xl of the coil divided by the loss resistance . With this procedure the "Q"is measured on the working frequency . With a good shielded Rx and bridge very precise measurements are possible . By replacing the capacitor with the real life antenna ,  measurements of the total resistance to be matched is possible .

73, William PA0WFO

 

 

----- Original Message -----

From: "Gary - G4WGT" <g4wgt@tiscali.co.uk>

To: "LF (Rsgb LF Group)" <rsgb_lf_group@blacksheep.org>

Cc: "LW Wave" <lowfer@lwca.org>

Sent: Thursday, July 06, 2006 11:38 AM

Subject: LF: Loading Coil Q

> Hi All,
> 
> Thanks to all for additional comments on 
the previous thread 'LF Loading
> Coils'.
> 
> Continuing on 
the theme of loading coils, is there a simple method of
> calculating the 
'Q' of an LF loading coil without using a 'Q' meter (a
> device I have not 
got access to). I would like to carry out my own
> tests/experiments on my 
antenna system, it can only add to my knowledge
> base.
> 
> 
73
> 
> Gary - G4WGT.
> 
> 
>