Barett wrote:

I have been reading loads.

Good for you!


I have managed to borrow a Rigexpert AA-200. Is it possible to measure
the impedance with a AA-200 analyser and how would I do that?

I don't have one of those particular analysers, but be VERY careful when
measuring the high impedances that you'll typically see in RF chokes.

Most antenna analysers are primarily designed to measure impedances
around 50 ohms, and they may be quite inaccurate for impedances of
several k-ohms. Check with a 4.7k or 10k chip resistor... you may have a
nasty surprise.

Also read Jim Brown's notes about the effects of the analyser's own
shunt capacitance. Choke resonances in the HF region are the product of
several uH of inductance but only a few pF of inter-winding capacitance,
so a few pF of additional shunt capacitance from the analyser can make a
big difference. The more advanced Vector Network Analysers have the
facility to "calibrate out" such errors before making measurements, but
the AA-200 doesn't seem to have that.



--

73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

"Ian White GM3SEK" wrote in message
...
Barett wrote:

I have been reading loads.

Good for you!


I have managed to borrow a Rigexpert AA-200. Is it possible to measure the
impedance with a AA-200 analyser and how would I do that?

I don't have one of those particular analysers, but be VERY careful when
measuring the high impedances that you'll typically see in RF chokes.

Most antenna analysers are primarily designed to measure impedances around
50 ohms, and they may be quite inaccurate for impedances of several
k-ohms. Check with a 4.7k or 10k chip resistor... you may have a nasty
surprise.

Also read Jim Brown's notes about the effects of the analyser's own shunt
capacitance. Choke resonances in the HF region are the product of several
uH of inductance but only a few pF of inter-winding capacitance, so a few
pF of additional shunt capacitance from the analyser can make a big
difference. The more advanced Vector Network Analysers have the facility
to "calibrate out" such errors before making measurements, but the AA-200
doesn't seem to have that.



--

73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

Ok Ian all noted.

Thanks