TopBand: Slinky Beverage

[km1h @ juno.com]

On Thu, 31 Jul 1997 14:50:36 +0000 w8jitom@postoffice.worldnet.att.net
writes:
>> From:          W2pm@aol.com
>> Date:          Thu, 31 Jul 97 13:07:07 +0000
>
> Hi Pete,
>
>> Does anyone have any experience with a slinky beverage?
>
>I played around with slow wave structures (which is what that would 
>be) in the 70's.
>
>> This antenna should behave like a 1 wavelength long end-fed wire and 
>when
>> terminated should provide the expected directivity. Any opposing 
>views to
>> this?
>
>Coiling the wire does several things. One thing is it increases the 
>phase delay along the wire, another is it increases the 
>surge impedance of the wire. There are other effects also, but those 
>are the main issues.
>
>500 feet of wire in a ten foot area does NOT work like 500 feet of 
>wire stretched out. The Beverages directivity is determined by 
>the spatial area it occupies as well as the phase delay along the 
>wire.

I doubt if anyone has ever tried to do it in 10' Tom.... As you VERY WELL
know this subject was discussed at length last year.  Fortunately many
tried it and were very pleased, despite your negative comments. 

>
>The ideal phase delay depends on the spatial (or physical) length of 
>the antenna, as well as the rate of propagation along the wire. For 
>a half wave long physical area, optimum Vp is about .5 freespace.
>
>Kraus covers this in his book Antennas, as does "Kuecken" on page 72 
>in Antennas and Transmission Lines (published in paperback by MFJ as 
>book number 3305). The Kuecken book has an entire section on 
>travelling wave antenna theory, and Kuecken is rated in the top 1% 
>of inventors based on patents held.
>
>I'm sure, from my experiments in the 70's and theory, the 
>impedance of a "slinky Beverage" is much higher than the same six 
>non-coiled conductor. I'm also sure the optimum Vp varies with the 
>overall length of the structure. 

Since you are always so sure of everything why dont you put one up and
actually measure it?  Up to now your comments are pure guess work. Yet
you are the one who always goes off into the theory when trying to debunk
anything that you do not agree with.  How about some real numbers this
time Tom???


>
>You'll probably just have to build one and see if it makes you happy 
>or not, with the understanding that it probably will never be as good 
>as a conventional Beverage unless you stumble on a good combo.

Wont, maybe, unless, probably, stumble, ad nauseum. ...all great terms
from a "expert" .


>
>You could model it on a NEC based program, buy using a large number 
>of inductive loads along a thick wire. You can watch the pattern and 
>impedance change as you change the inductance. 


If you have the software why not tell us all the real facts.....

To those new here, this is almost a repeat of last year. I still cant get
a straight answer. 

73....Carl   KM1H



>73, Tom W8JI 
>
>--
>FAQ on WWW:               http://www.contesting.com/topband.html
>Submissions:              topband@contesting.com
>Administrative requests:  topband-REQUEST@contesting.com
>Problems:                 owner-topband@contesting.com
>


--
FAQ on WWW:               http://www.contesting.com/topband.html
Submissions:              topband@contesting.com
Administrative requests:  topband-REQUEST@contesting.com
Problems:                 owner-topband@contesting.com