[Elecraft] Random wires

[David Gilbert]

I suggest reading W8JI ... and others.

http://www.w8ji.com/radiation_resistance.htm

Dave   AB7E



On 10/1/2013 2:53 PM, k3ndm at comcast.net wrote:
> Sorry roger, Roger, your analysis is not totally correct. You do raise the feed impedence from 36 Ohms as compared to using a single 1/4 wave wire over perfect ground. As most of us do not have perfect ground, there is an imperfect representation of the virtual 1/4. Because it is imperfect, you can look at this part as absorbing energy and just returning heat. By raising the radiation impedance, less energy is absorbed by ground and more is radiated. How much additional efficiency do you obtain is a matter of the ground system you put in and the ground constants under it. In my experience, it is worth the effort to build the antenna as it will outperform a similar single wire inverted L. I suggest reading Bill Orr, and others, on this antenna.
>
> 73,
> Barry
> K3NDM
>
> ----- Original Message -----
>
> From: "Roger D Johnson" <n1rj at roadrunner.com>
> To: elecraft at mailman.qth.net
> Sent: Tuesday, October 1, 2013 3:40:49 PM
> Subject: Re: [Elecraft] Random wires
>
> This is NOT true! It merely raises the feedpoint impedance...just the same as
> adding a
> 4-1 transformer.
>
> 73, Roger
>
>
> On 10/1/2013 3:10 PM, Barry LaZar wrote:
>>
>> As I read your post, I infer that at the moment you are wanting to add 160
>> meters to your capability. An antenna that I have used and liked is the Twin
>> Lead Marconi. It's a simple, cheap, and effective antenna. I first saw it
>> written up by Bill Orr years ago. The premise of the design is that a quarter
>> wave antenna driven against ground may not be the most efficient antenna due
>> to low radiation resistance. Therefore, raise the radiation resistance by
>> using the theory of a folded dipole. The folded element raises the radiation
>> resistance by a factor of 4 for 2 elements as the impedance changes as the
>> square of the number of elements. You will still need radials, but your ground
>> losses will decrease.
>>
>>
>> 73,
>> Barry
>> K3NDM
>>
>>