Topband: 2 Parallel Beverages

[GeorgeWallner]

Mike,

You are willing to run 2 coax cables and have 2 
transformers, but don't want to bother with remote relays, 
etc. You could simply have a single wire, terminated at 
each end by a transformer. Run from each transformer a 
coax to the shack. Use a DPDT relay or manual switch in 
the shack to swap the RX and the loading resistor. (75 or 
50 ohm loading resistor.) I.e. when the RX is connected to 
Coax 1 the resistor is connected to Coax 2, and vica 
versa. You could even use a variable resistor to optimize 
the F/B.

I have been using this method to switch directions on my 
DHDL and it has been working well for some time now (with 
some limitations).

73,

George

On Wed, 23 May 2012 15:46:56 +0100
  <g3pqa at onetel.com> wrote:
> Jeff,  EZNEC confirms what you and Neil have found.
> Modelling Neil G0JHC's antenna with 1000ft beverages at 
>12ft and 10ft, 
> offset by 30ft length-wise, shows almost identical 
>patterns to a single 
> beverage.
> Terminating both ends of the unused bev improves the f/b 
>as one might 
> expect, but does not appear to change the basic pattern.
> If you terminate both ends though, isn't it easier just 
>to use one wire and 
> relay switch between the feeder and termination R?
> 73
> John
> 
> -----Original Message----- 
>From: Jeff Woods
> Sent: Wednesday, May 23, 2012 3:19 PM
> To: topband at contesting.com
> Subject: Re: Topband: 2 Parallel Beverages
> 
> I missed the original post, but if the question pertains 
>to running two 
> independent beverages in opposite directions on the same 
>supports - Yes.  It 
> works well.
> 
> 
> I began doing this last winter, adding shorter, opposite 
>direction beverages 
> to my NE and NNW (EU and JA) antennas.  Performance in 
>the primary 
> directions is not compromised by any discernible amount. 
> The antennas are 
> completely independent, sharing only the PVC support 
>mast.  The two 
> "secondary" antennas share a feed point (DC relay 
>switched) where the two 
> primary antennas cross.  The two primary antennas were 
>up and running before 
> the secondary directions were added. No changes in 
>performanceof the primary 
> antennas was noted after the addition of the shared 
>secondary wires.
> 
> 
>>From a theoretical point of view, this is no different 
>>than the operation 
>>of a typical 2-wire bi-directional array that relies on 
>>either wire working 
>>independently as a single-wire beverage in generating the 
>>common-mode 
>>signal.
> 
> 
> Jeff W0ODS
> Somewhere in Iowa
> 
> 
> 
>>
>>>   For various reasons I am considering two single, 
>>>parallel but 180deg 
>>> opposing direction beverages on the same supports rather 
>>>than a single 
>>> switchable bidirectional beverage.  The bevs would be 
>>>separated by 12 to 
>>> 18 inches or so. I've read that parallel bevs present 
>>>performance 
>>> degradation issues but has anyone had any experience 
>>>with this type of 
>>> setup versus the traditional bidirectional beverage? 
>>>Thanks for reading 
>>> this and for any thoughts you could offer. 
>>> Mike  W2LO
>>
>>
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