Re: NEC-LIST: Loopstick data?

Doug

Thanks for that reference and I suspected you were familiar
with at least some of what I wrote.

I had not seen the DeVore paper but I have now got a copy and
on a quick look the basics seems to be well stated. I was
interested that they said the measured Q can be as low as one
sixth of the predicted Q, because I have also found that is
true, and it means we are not good at predicting the losses
in and around the loop. Also, I did not at all follow their
reasoning in deriving a value for Qideal (page 499) because
this must equal the reactance divided by the radiation
resistance, and if you do not know the Rrad by calculation or
field measurement it seems to me to be impossible to determine
Qideal. Anyway, tables III-VI appear to show they found
extremely low values of radiation efficiency. In figure 3
they show the reduction in gain due to the presence of the
ferrite, but the main issue would be the absolute value of
radiation efficiency on the IEEE definition, which I suspect
is low. If the paper actually says otherwise, blame my poor
speed-reading.

73

Alan

-----Original Message-----
From: nec-list-bounces+alan.boswell=baesystems.com_at_robomod.net
[mailto:nec-list-bounces+alan.boswell=baesystems.com_at_robomod.net]On
Behalf Of D. B. Miron
Sent: 06 July 2005 14:03
To: nec-list_at_robomod.net
Subject: Re: NEC-LIST: Loopstick data?

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Good day Alan and Arie,

Thanks for the more modern references, I might have two of
them. We are all aware of the problems of using ferrite
rods on transmit, but, as Arie suspects, if you use a big
enough core it can work. See Devore and Bohley, IEEE Trans.
A&P, July, 1977. They experimented with small cores working
up from one to, I think, five in a bundle. In any case, I'm
only interested in the receive application.

Regards,
Doug Miron

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