[TowerTalk] Measuring the resistance of ferrite

[Steve Hunt]

Bob,

Even the technical literature wont give you a complete picture because 
it wont take account of the stray capacitance introduced by the choke 
winding.

The most effective technique I've found is outlined at the bottom of 
this page;
http://www.karinya.net/g3txq/chokes/

Basically you place the choke in series between an RF source and load, 
and measure the attenuation that it introduces. You must be able to 
measure both the magnitude of the attenuation and the phase change that 
the choke introduces, if you wish to measure the choke's resistance and 
reactance; that's why I use a 2-port VNA as the source and load rather 
than a simple signal-generator/RF-voltmeter arrangement.

Steve G3TXQ



On 28/04/2015 14:56, Bob Good wrote:
> Other than using the sales / technical literature,  how can I measure the resistance of ferritecore or beads to ensure that I have the recommended 5000 ohms resistance?  I gather that the resistance is frequency dependent and rises as frequency increases.  Also I gather that the best overall mix for HF is #73.  I assume this designation is universally recognized regardless of the supplier?  Can you help shed some light for this Old old timer?  Thanks,  Regards,  Bob K4BG (QRZ Info current)
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