[Boatanchors] antenna question

[hwhall at compuserve.com]

Well, we do know a beam's feedpoint impedence is affected by the number and spacing of parasitic elements, among other things. So I wouldn't be surprised that if it's designed for three active elements and one goes bad, the impedence would change and thus show an altered SWR. But how badly the SWR would change, I am unsure.

My thinking assumed that when he stated the number of traps that was really the number of traps. But if the description is really just a visual count of the number of enclosures on the elements, perhaps some of those enclosures contain something more clever than simple single parallel LC traps. If that may be the case, diagnosis attempts before opening it up may be useless since we wouldn't be understanding the way it really was to work.

I guess since we don't have the model number, the manual, etc., the problem will have to be revealed by actual inspection.

 

 Wayne

 

-----Original Message-----
From: D C _Mac_ Macdonald <k2gkk at hotmail.com>
To: hwhall <hwhall at compuserve.com>; Al Parker <anchor at ec.rr.com>; rayfrijr <rayfrijr at msn.com>; boatanchors <boatanchors at mailman.qth.net>
Sent: Mon, Aug 25, 2014 1:21 pm
Subject: RE: [Boatanchors] antenna question



I believe that problems in the parasitic elements (director and reflector) won't show up much in VSWR anomalies. I believe that points to driven element problems.  That is the only element directly connected to the feedline! 
 
As I wrote earlier, I really suspect the trouble lies in the outer half of one or both driven element traps. 
 
* * * * * * * * * * * 
* 73 - Mac, K2GKK/5 * 
* (Since 30 Nov 53) * 
* k2gkk hotmail com * 
* Oklahoma City, OK * 
* USAF & FAA (Ret.) * 
* * * * * * * * * * * 
 

 

> To: anchor at ec.rr.com; rayfrijr at msn.com; boatanchors at mailman.qth.net
> From: hwhall at compuserve.com
> Date: Sun, 24 Aug 2014 23:07:55 -0400
> Subject: Re: [Boatanchors] antenna question
> 
> If it's working well on 10m & 20m, but not 15m, I'd suspect the parts unique to 15m, and those sound likely to be two traps in the director. The other two elements are using the same traps for 10 & 15 so they SEEM to be doing their jobs right. 
> 
> Since it works well on 20, I'd guess one of the director's 15m traps is detuned. If they are lumped L and C traps, perhaps a capacitor is faulty since it SEEMS the trap's inductance is working correctly to make 20m work right.
> 
>  
> 
>  Of course, there could be something more complicated going on besides what the symptoms immediately suggest. Of course, if the antenna has to come down for repair, check everything before sending it back up.
> 
> Wayne
> WB4OGM