In a similar vein many of the old boatanchor ham and SW receivers were
designed for high impedence inputs to be used with long wires or open wire
line. A low impedence antenna/feed will load down the front end and
dramatically reduce performance.
I use a multiband RX antenna consisting of traps, loading coils and parallel
dipoles to cover from .5-30MHz. It works well on just about any frequency
with acceptable VSWR. The feed is RG-6 to a distribution box that can feed
up to16 radios. In the box is a low noise 2N5109 broadband preamp feeding
the splitter network. From there RG-6 goes to each receiver and is fed
direct to the receivers that are designed for low impedence or thru 12:1
baluns to the others. My BA's range in age from the 20's to the early 60's.
When I built this place in 1989 I installed 2 or 3 CATV outlets in all BR's
plus LR and FR. Every cable goes to the walk up attic and I can configure
outlets for TV or BA's at will.
Carl
KM1H
----- Original Message -----
From: <donovanf@starpower.net>
To: <towertalk@contesting.com>
Sent: Wednesday, August 15, 2007 8:51 AM
Subject: Re: [TowerTalk] RCA Spider web antenna
> Barry,
>
> Its described on page 83 of the the 1937 Frank C Jones Radio Handbook.
>
> The "RCA Spiderweb Antenna System" was one of the antennas that RCA
> marketed for their pre-war shortwave radios. The other shortwave radio
> manufacturers marketed their own receiving antennas. The RCA Spiderweb
> used five dipoles cut for 49, 25, 16, 9 and 5 meters and fed with a
> twisted wire transmission line, 75 feet long (they emphasize the
> importance of not cutting the transmission line!). The 49 meter dipole is
> loaded to reduce the total length of the antenna to 37 feet,
>
> Its not much different than today's more common parallel antennas. In the
> RCA Spiderweb, the feedpoints of the dipoles are separated vertically over
> a ten foot span and the ends of the dipoles are relatively near each
> other. It definitely has the appearance of a spiderweb! Its primary
> advantange was probably that that it could be supported by only two ropes.
>
> Its kind of the opposite configuration of our typical parallel dipoles,
> where the feedpoints are immediately adjacent to each other and the ends
> of the dipoles are fanned outward. In the RCA Spiderweb, the ends of the
> dipoles are near each other and the wires are fanned out to feedpoints
> that are separated by 10 feet.
>
> I'd expect big problems trying to get this antenna to be an acceptable
> transmitting antenna. Feeding the spaced dipoles with acceptable
> performance will probably be a big headache. Receiving antennas are much
> more forgiving of compromises than transmitting antennas!
>
> 73!
> Frank
> W3LPL
>
> ---- Original message ----
>>Date: Wed, 15 Aug 2007 10:59:50 +0800
>>From: "Barry Kirkwood" <barry.kirkwood@gmail.com>
>>Subject: [TowerTalk] RCA Spider web antenna
>>To: towertalk@contesting.com
>>
>>Hi all:
>>I mentioned this ingenious form of a mulit band parallel dipole in an
>>earlier post.
>>Have since had feedback that no info can be found via Google etc.
>>Am currently travelling in SE Asia, no access to my library, hi.
>>I know this antenna was described in the 'Radio Handbooks' and Antenna
>>books
>>published by Editors and Engineers before WW II.
>>Also it may have been subject to patent.
>>Would be grateful if anybody could find a reference to it, better, post it
>>somewhere on the web.
>>The actual antenna used dipoles cut for the SW AM broadcast bands eg 49m
>>and
>>the like.
>>The ingenious feature was the way the dipoles were configured such that
>>there was good spacing between them, and the whole array could be
>>suspended
>>from just two masts.
>>Imagine it would be easy to reconfigure for amateur bands.
>>tnx es 73
>>Barry ZL1Dd
>>
>>--
>>Barry Kirkwood PhD ZL1DD
>>barry.kirkwood@gmail.com
>>_______________________________________________
>>
>>
>>
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> _______________________________________________
>
>
>
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