Welll........
As as an isotrope is a point source, it must have one dimensional
polarisation mustn't it :-}
In reality, polarisation cannot be defined - a true omnidirectional radiator
is (probably) not possible. If it were, its polarisation would have to be
uniform in all directions at the same time.
Having said that, I remember being told by someone who worked on the UK
space programme in the 1950's that they put up an ionospheric drag
monitoring satellite that consisted of a completely spherical spacecraft
that they wanted to freely tumble. The diameter would have been in the
region of 0.5 to 1 metre I imagine. Consequently it had to have a good
isotropic radiating pattern at VHF. They ended up with a surface made up of
three equal sections each fed 120 degrees out of phase that exhibited a
pattern within 1.5dB of isotropic. With a radiatiator made up of three 1m
type sections, there must have been some polarisation sensitivity, and that
probably comes into the 1.5dB error budget.
Working in a government scientific establishment in those days must have
been quite interresting.
Andy G4JNT
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of captbrian
Sent: 10 October 2006 11:06
To: [email protected]
Subject: LF: Re: RE: Re: Re: erp eirp - bluff
Aha I wasn't so stupid then.....
Now , you asked for this.......what is the polarity of an 'isotropic '
radiator .?
Bryan
----- Original Message -----
From: "Talbot Andrew" <[email protected]>
To: <[email protected]>
Sent: 10 October 2006 08:04
Subject: LF: RE: Re: Re: erp eirp - bluff
> It should be, but the 'rule makers' way-back-when in their infinite
> wisdom decided that dipoles were easier for the humdrum public to
> visualise so defined ERP as being relative to a perfect dipole.
>
> As it is difficult to make dipoles at high frequencies (actually it is
> a
lot
> wasier easier, but... Never mind) ERP there was defined as being
> relative
to
> isotropic. So...
>
> Below 1000MHz ERP is defined as being realitive to a dipole, above
> 1GHz
ERP
> is defines as being the same as EIRP.
>
> Its just a matter of semantics. I fell into this trap and queried the
> ERP limits when 50MHz was first introduced several decades ago. 50MHz
requires
> EDRP, so the actual maximum RF power could be more than would be
> needed
for
> an isotrope.
>
> Andy G4JNT/G8IMR (still lurking)
>
>
>
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]] On Behalf Of captbrian
> Sent: 10 October 2006 03:13
> To: [email protected]
> Subject: LF: Re: Re: erp eirp - bluff
>
> Then why isn't ERP called EDRP ?
>
> eg EIRP, EMRP, EDRP ......s'obvious innit.?
>
>
> ----- Original Message -----
> From: "James Moritz" <[email protected]>
> To: <[email protected]>
> Sent: 09 October 2006 21:56
> Subject: LF: Re: erp ierp - bluff
>
>
> > Dear Bryan, LF Group,
> >
> > >< snip >>
>
> > Cheers, Jim Moritz
> > 73 de M0BMU
> >
> > (BTW, it is EIRP, not ierp)
> >
> >
> >
> >
> > > G3GVB/ Bryan
> > >
>
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