Topband: Twin Lead Marconi Antenna

[Herb Schoenbohm]

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?
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> 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. 
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> 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.
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> 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.
73

Herb, KV4FZ
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