[Elecraft] KPA1500 in the IARU Contest Last weekend

[donovanf at starpower.net]

Hi Skip, 


Conceptionally you're correct about rhombics and V-beams but your time frame is way off. 


Edmond Bruce's rhombic antenna patent was filed in 1931. 


www.aktuellum.com/mobile/circuits/antenna-patent 


ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=1685103 


The heyday for the rhombic ran from the 1930s through the 1970s with 
the advent of satellite communications. The 200 foot tower for my 
40 meter stacked 3 element Yagis came from a decommissioned 
Laport Rhombic installed at the NSS receive site in Cheltenham MD. 
We removed it in 1985, but it hadn't been used for years. 


73 
Frank 
W3 






----- Original Message -----

From: "Fred Jensen" <k6dgw at foothill.net> 
To: elecraft at mailman.qth.net 
Sent: Thursday, July 16, 2020 9:41:21 PM 
Subject: Re: [Elecraft] KPA1500 in the IARU Contest Last weekend 

Indeed! Probably the least unbalanced of "balanced" antenna systems 
that ever existed were the HF point-to-point rhombics and V-beams at the 
RCA, Mackay, and Marconi shore stations in the first 60 or so years of 
the 20th century. Despite very precise engineering to make them 
balanced, the RF currents in each side of the open feeders were never 
exactly the same. 

As a teenage ham, I tended to think in absolutes and exactitudes. If my 
Heath MM-1 multimeter said the screen voltage was 176.5 V, I believed it 
was, exactly, and if the spec said 177.5 V, I needed to do something to 
"fix" it. If the ARRL Handbook said the two halves of my 40 meter 
dipole needed to be exactly 32.9114 feet, I believed that the antenna 
would not work if I didn't assure my dipole was exactly 32.9114 on each 
side. As I grew older, both in age and ham longevity, I realized my 
Elmer was right when reminded me on multiple occasions, "We're 
amateurs. Most often, 'close' is good enough." 

Seems like many today are convinced that 32.9114 ft will work but 
32.9000 ft won't. 

73, 
Fred ["Skip"] K6DGW 
Sparks NV DM09dn 
Washoe County 

On 7/16/2020 1:00 PM, Jim Brown wrote: 
> On 7/16/2020 1:14 AM, Victor Rosenthal 4X6GP wrote: 
>> If the antenna is well-balanced and fed via a true balanced antenna 
>> tuner (preferably link-coupled) then there shouldn't be a problem 
>> with common mode currents. 
> 
> Few ham antennas are perfectly balanced -- they are often unbalanced 
> by their surroundings. For example, ground slope, unequal heights of 
> the two halves, other conductors around the antenna, even vegetation. 
> And yes, all elements of the antenna system, including the feedline, 
> the antenna, and matching at both ends, contribute to the balance of 
> the SYSTEM. 
> 
> THAT'S why it's wrong to talk about "balanced line," using "parallel 
> wire" or 2-wire" line instead. 
> 
> 73, Jim K9YC 

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