[600MRG] Antenna Food and alternate antenna thoughts...
michael polia
ab1aw at yahoo.com
Thu Dec 7 15:51:23 CST 2017
DaveDo you have any experience or opinions about top-fed grounded Marconi antennas (e.g. the "steeple" and "double-bass" antennas described in John Heys' (G3BDQ) book)? I've got one built and have been testing. My challenge is getting enough ground radials installed.
73MikeAB1AW
From: Dave Riley <dave.riley3 at verizon.net>
To: 600mrg at w7ekb.com
Sent: Thursday, December 7, 2017 4:36 PM
Subject: [600MRG] Antenna Food and alternate antenna thoughts...
> When I oversaw the rework of the WBZ transmitter site in 1979 I
> perceived a LOT of Westinghouse history and spent a year with hands on
> experience as well as overseeing the building trades for a complete
> makeover which had been exaserbatedby a recent violent storm that
> rendered the entire site almost useless, however we stayed on that
> air... The project included an immediate emergency overhaul of the on
> site diesel generator, a complete building overhaul, rework and repair
> of the two 190 degree high towers, new 3" transmission lines, new line
> terminating units and a clean up of the salt marsh radial field...
> This was an up close and personal look at watching a lemon becoming
> lemonade...
> After we ran a full proof of performance on the new array along with a
> brand new building electrical feed we returned to 'remote control'
> operation and it has remained that way for 38 years now...
>
> Lesson learned: Taller than one half wave towers work about the best
> and then on a salt water platform....
>
> This means that a short vertical antenna becomes less that normal
> efficiency if we try to make say a 1' vertical and then learn the
> reasons for looses which render the short vertical almost useless...
>
> Here is what I see as an improvement to short vertical antennas as
> well as for loop antennas at these frequencies:
>
> If we really want to run a 'Tesla' coil as an antenna then we must
> counterpoise it against a real ground like salt water, a large steel
> ship, or take the looses that are sure... Then make our 'wet noodle'
> in the same fashion as Tesla himself did with his coil, take it from
> there...
>
> If I want to make my vertical loop radiator more efficient then I have
> to use something like 4" copper strap all around for the entire loop
> instead of #16 wire then I can expect to run something like 8 watts in
> for a 5 watt eirp... Right now I'm only getting about 10% efficiency
> and certainly do notice the poor power factor... It's that simple but
> I do not have 4 inch copper strap to go around and feel that the pay
> back would straight line to about 30 years and I'm on my last legs now
> so why don't I just enjoy a very lossy antenna...
>
> Anyway, its food for thought... TNX for sharing all this old time ham
> radio fun... DaveR AA1A
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