[Boatanchors] antenna question

[hwhall at compuserve.com]

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

 

-----Original Message-----
From: Al Parker <anchor at ec.rr.com>
To: RAY FRIESS <rayfrijr at msn.com>; boatanchors <boatanchors at mailman.qth.net>
Sent: Sun, Aug 24, 2014 5:07 pm
Subject: Re: [Boatanchors] antenna question


Hi,
	Just something to look for, some beam traps have a problem with spiders 
getting in and building nests which cause tuning problems. (It's 
happened to me.)
73,

Al, W8UT
www.boatanchors.org
www.hammarlund.info

"There is nothing -- absolutely nothing -- half so much
worth doing as simply messing about in boats"
Ratty, to Mole

On 8/24/2014 6:33 PM, RAY FRIESS wrote:
> I'm a bit puzzled about something even after about 40  years as a ham.  Would 
be interested in comments or
> thoughts from the group.
>
> I have a triband beam for 10, 15 and 20.  It's one of the old Hy-Gain Explorer 
beams.  It has two traps in the reflector
> and two in the driven elevent and four traps in the director.    It worked 
perfectly on all three bands for a long long time,
> and now on 15 it is unusable, but remains perfect on 20 and 10.
>
> As I understand the operation of the driven element, everything (element wise) 
between the boom and the trap is for 10 and 15 meters.  Everything from the 
outside of the trap to the end of the element is for 20 meters.
>
> My problem is this...  I have a fantastic SWR on 20 and 10 ...  practically a 
1.2 to 1 on each band across the entire band.
> I am able to work just about anything I can hear with 100 watts barefoot, and 
seldom have to turn on the 30L-1 except
> in big pileups.   However, on 15, the beam is unusable.  It pegs the SWR meter 
at infinity and in my TS 50, the protection
> circuit drops the power output from 100 watts to barely visible.
>
> My question is this ...   what could be causing the high SWR on 15 meters, 
while not affecting 20 and 10 at all?
> If everything from the outer edge of the trap to the end of the element is for 
20 and the trap is for 15/10 discrimination,
> shouldn't 20 SWR also be through the roof if the trap was bad on 15?  The RF 
for 20 has to go through the trap and
> if it has gone bad on 15, wouldn't it also mess up 20?
>
> what should I be looking for or at?
>   		 	   		
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