Re: LF: More on Admittance

[Peter Dodd <g3ldo@ukonline.co.uk>]

Hi Alan,
Thanks for the information. Most noise bridges use serial variable 
resistance and reactance bridges but there is a circuit of a bridge 
using a parallel arrangement in the W6SAI radio Handbook although it 
doesn't say what the advantage of such an arrangement is.
Regards

Peter, G3LDO
> Hi Peter I think it more due to the fact that commercial bridges and meters 
> really want to cover the widest range. There is obviously a problem with serial 
> connected reactances when one is very much larger than the other. Then the 
> nulls on bridges become shallow and ill defined. If you use a parallel 
> arrangement this is not a problem. For most Amateur aerial cases you can get 
> away with serial connection because there is not the need for the wide range 
> needed for laboratory equipment.....10^3 compared with maybe 10^6.
>
> Alan G3NYK
>
>
>
>
> --- On Wed, 19/11/08, Peter Dodd <g3ldo@ukonline.co.uk> wrote:
>
>   
> > From: Peter Dodd <g3ldo@ukonline.co.uk>
> > Subject: LF: More on Admittance
> > To: rsgb_lf_group@blacksheep.org
> > Date: Wednesday, 19 November, 2008, 6:55 PM
> > Many thanks to those who responded to my question regarding
> > an 
> > Admittance to Impedance converter.
> > I have a further question. Since most of the measurements
> > we make on 
> > antennas and transmission line require the answer in term
> > of impedance 
> > why are there so many commercial instruments calibrated in
> > units of 
> > Admittance, particularly at VHF and UHF. I suspect that it
> > is because it 
> > is easier to make accurate variable bridge standards if
> > they use a 
> > parallel arrangement; is this true
> > Regards
> >
> > Peter, G3LDO
> >
> >
> >     
> > > The best program (as far as I am concerned) is called
> > >       
> > Z-Y Converter, 
> >     
> > > which was sent to me by Rik Strobbe.
> > > It came direct because it gave the reflector
> > >       
> > indigestion although it 
> >     
> > > is only 160KB.
> > > I was given a General Radio 1602-B Admittance Meter as
> > >       
> > a pre Christmas 
> >     
> > > present, which is calibrated in millimhos, which I
> > >       
> > guess is the same 
> >     
> > > as millisiemens.
> > >       
>
>
>