[TowerTalk] Fwd: Open wire choke?

[hanslg at aol.com]

 How said the ladder line can't be equipped with a bal/un choke. I made one by winding two wires next to each other on a 4" PVC pipe. I had some 25 feet of wires and basically made a 1/1 transformer. Right connected you will have introduces a nice decoupling inductor in line with the ladder line. Needless to say I build my own ladder line out of #14 wire and 4" spacers (spaced 9" apart). Gives you ~400 ohms line. In my case I am feeding a windom antenna, cut for 80 meter and up. (Works OK on 160 meter too).

Losses? Probably, but most stations hear me when I am calling bare-footed, the conditions are OK and no pile-ups.

73 de N2JFS - Hans


 


 

-----Original Message-----
From: Steve Hunt <steve at karinya.net>
To: Tower Talk List <towertalk at contesting.com>
Sent: Tue, Sep 29, 2009 7:48 am
Subject: Re: [TowerTalk] Open wire










I'm not sure I would use the same language as Jim, but I *do* think 
there is widespread misunderstanding amongst Hams about the performance 
of "ladderline". There seems to be an ill-informed presumption that any 
form of "ladderline" will have negligible losses, whatever the 
application. This is a view which has been reinforced in magazine 
articles and books.

Take, for example, the October 2009 QST article describing a "half-wave 
loop". It shows a quarter-wave section of commercial ladderline being 
used to "tame" the feedpoint impedance. Nowhere is there any mention of 
the potential 7dB loss in the ladderline !!

73,
Steve G3TXQ


Jim Brown wrote:
> On Mon, 28 Sep 2009 18:42:34 -0400, Tommy wrote:
>
>   
>> I believe the objection was to your comment: " Open wire line is 
>>     
> highly
>   
>> over-rated.." to which hardly anyone agrees. 
>>     
>
> Because its virtues have been preached for so many years in the ARRL 
> Handbook and Antenna Book. Science is not a matter of opinion, but of 
> fact. Open wire line (and window line) are wildly over-rated, because 
> they are preached as a one-size fits all solution. They are NOT! 
>
> Because it cannot be choked, any imbalance in the antenna system makes 
> ANY feedline radiate (and receive). This happens whether it's coax or 
> a so-called balanced line, BECAUSE of antenna imbalance. The virtue of 
> coax is that you can choke it to kill the radiation. The shortcoming 
> of balanced lines is that you CANNOT choke them effectively. 
>
> It doesn't take much to make an antenna unbalanced -- ground slope, or 
> the antenna slopes, or one end is close to a building or tower or tree 
> and the other is not, or the two sides of the antenna are of unequal 
> length. 
>
> This is a big deal if you live in an urban neighborhood, with noise 
> sources all around you. We have few weapons in this fight, and two of 
> the most important are 1) antenna directivity and 2) moving the 
> antenna further from the noise source. A feedline that radiates (and 
> receives) defeats both of those weapons. 
>
> 73,
>
> Jim K9YC
>
>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
>
>   

_______________________________________________



_______________________________________________
TowerTalk mailing list
TowerTalk at contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk