[TowerTalk] RCA Spider web antenna

[jeremy-ca]

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 at starpower.net>
To: <towertalk at 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 at gmail.com>
>>Subject: [TowerTalk] RCA Spider web antenna
>>To: towertalk at 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 at gmail.com
>>_______________________________________________
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>>
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