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Re: Topband: Twin Lead Marconi Antenna

To: Garry <>
Subject: Re: Topband: Twin Lead Marconi Antenna
From: Herb Schoenbohm <>
Date: Sat, 13 Jun 2009 21:55:34 -0400
List-post: <">>
Garry wrote:
> Years ago, Bill Orr wrote a book titled Wire Antennas. On page 104 in this 
> book, he described an inverted-L type of antenna called a Twin Lead Marconi 
> built using TV win lead in the L section with a length of single conductor 
> wire making up the last 17 feet of the L with a few radials. It was suppose 
> to give a reasonable match to 50 ohm coax. Has anyone on this forum ever 
> built this antenna and what were the results?
> Gary,  For portable use this is a fine antenna IMHO. This is precisely the 
> antenna I used for numerous DX-Peditions from South America and rare 
> Caribbean Islands in the 60's.  I was compact to pack along with the gear and 
> was easy to get to work with a nearby palm tree on the beach.  The twin lead 
> Marconi (mine was 1/4 wave of 300 ohm twin lead over the entire length) was 
> an easy match for my Drake's T-4XC Pi network which fed the antenna directly 
> sloping out of the cottage window to the highest palm tree on the beach.  For 
> portable or vacation use antenna worked well and I was able to give many new 
> countries to those chasing DXCC on 160. 
> I do recall however that the theory that the ground losses were reduced by a 
> 4 to 1 base impedance multiplication factor has been disputed.  I always 
> carried along some small 1/4 wave bell wire radials which terminated at the 
> rig ground.  The twin lead Marconi may improve on the rigs ability to match 
> the antenna with a built in tuner but you can raise the impedance by making a 
> single wire the antenna longer like 180 feet.  This antenna can be generally 
> brought to resonence by a series variable capacitor to remove the inductive 
> reactance it imposes.
> The twin lead is two close spaced for much bandwidth improvement and the 
> ground loses are a factor of the radial system. But for certain applications 
> it is a good antenna to consider.

Herb, KV4FZ

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