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LF: Re: Re: RE: CFA

To: [email protected]
Subject: LF: Re: Re: RE: CFA
From: "Steve Olney" <[email protected]>
Date: Mon, 15 Nov 1999 09:43:38 +1100
Reply-to: [email protected]
Sender: <[email protected]>
G'day All,

Am I wrong but doesn't the latest coverage map from the IoM site look a
lot
smaller than the old one?

Yes I am wrong, it is only a little smaller :-)

IMHO the IoM antenna will be deemed to be successful when commissioned. However, the question is, is that an endorsement of the theory. As has
been mentioned, already Amateurs are covering large distances on LF (at
lower frequencies than 279KHz to boot) without worrying about Div, Grad and
Curl.    However, they are all using (up until this point) antennae that
follow the conventional theories.

The question I would like to pose to those with more knowledge and
experience than I is;  when I can get a signal out to 60km which is
readable (using SSB) using a 7m high antenna, with one 2m earth stake and
6mH of lossing tuning coil (small gauge wire wound around PVC pipe) using a
power of less than 5-8W, is a coverage of a little over 600Km using
kilograms of copper plate, presumably low-loss tuning coils, twice the
frequency and half a MEGAWATT so remarkable?  I have seen standard loaded
short verticals with sizes of the order of a few percent quoted as being
almost as good as a full size vertical.  I fail to see what is so
revolutionary about the CFA (apart from the "theory" expounded for it). Even if the IoM CFA produces a far field signal strength which equals (as
expounded by the inventors) the expected field for a full size (270m high)
this still will not prove the direct synthesis theory.  You would have to
prove that it is not working as a conventional antenna by measuring the
currents flowing into the elements, thereby measuring the radiation
resistance.   Conventional short verticals exhibit a low radiation
resistance and are made to radiate efficiently by matching to that low Rr
while ensuring that losses are a small fraction of the dissipating load. If the CFA exhibits a high radiation resistance (the inventors vaguely
mention 377ohms - free space) then this indicates something special,
otherwise not.

BTW, I have constructed a CFA for 177.4KHz and provided with the correct
quadrature drive and swept the antenna through continuous phase and
amplitude variations and I can report that it didn't radiate any better
than a top-loaded vertical of the same size.  I must be stupid. I can say
that it is possible to get it to look like 50ohms, i.e. a low SWR.  This
has been taken by many amateur experimentators to indicate that it is
radiating efficiently.  I have a dummy load which exhibits the same low
SWR, unfortunately it doesn't radiate. Also, there is a narrowcast station
on 1665KHz here in Sydney,  Australia which uses a CFA commissioned by the
inventors.  Guess what ?  At 60km distance it is about 18dB down on a
similar standard stations in the area.  I'm sorry, but that makes me doubt
a little, whatever the excuses/explanations are.

I will be pleased if the IoM CFA works and wait with eagerness for the
outcome as long as we get the scientific answers, not the political.  All
my attempts to get answers from the local BC CFA station has been met with
a brick wall so far.

Finally, I disagree with the notion that the CFA will fade into the sunset.
It will be kept alive by its appeal to our imagination whatever the final
outcome is.

P.S. Maybe we would be wise to start up a separate CFA email group to avoid
raising blood pressures here.  Then those who want to subscribe and hear
about the latest CFA shenanigans can do so.  If there is sufficient
response I will setup a CFA group and invite subscribers.

73s Steve Olney (VK2ZTO/AXSO - QF56IK : Lat -33 34 07, Long +150 44 40)
=============================================
LowFer URL:
http://www.zeta.org.au/~ollaneg/lowfer.htm
AXSO LF Experimental Station URL:
http://www.zeta.org.au/~ollaneg/axsoextx.htm
LF Receiving - FRG-100, CHA antenna
LF Transmitting - 177.5/177.4kHz 8W - 7.6m vertical or CHA
Modes - AM, SSB, PSK31, SSTV, Hellschreiber, QRSS
and a new experimental mode - FDK.  See this URL for more:
http://www.zeta.org.au/~ollaneg/FDK.htm
=============================================




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