Towertalk
[Top] [All Lists]

Re: [TowerTalk] 43' Vertical - Feed Point Tuner or Shack Tuner?

To: towertalk@contesting.com
Subject: Re: [TowerTalk] 43' Vertical - Feed Point Tuner or Shack Tuner?
From: K4SAV <RadioIR@charter.net>
Date: Fri, 06 Feb 2009 17:54:48 -0600
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Feedline radiation is the same way that the TAC antenna gets an SWR of 
1.0 on 40 meters from an antenna that has a feedpoint impedance close to 
5 ohms.

It appears your Zero Five conclusions are correct.  The SWR data on the 
website appears to be taken using either the 200-T-1220 balun ot the 
"AS-200-tuner" balun.  They are now recommending the ZF-MB-5K UN-UN.  
Assuming it is really an UN-UN it wouldn't produce the curves shown.  I 
guess they conveniently forgot about that.  Maybe they don't know. 

It seems that in the beginning Zero Five recommended the ZF-MB-5K for 
use with this antenna.  Sometime after that, someone somewhere screwed 
up and started recommending the "AS-200-tuner" balun, also they must 
have recommended the 200-T-1220 too since some of these antennas have 
that one too.  Array Solutions now seems to have now done a flip-flop 
and fixed the web page, except for the data.

I have visions of someone running SWR curves with various baluns and 
picking the "best one".

Jerry, K4SAV

Terry Conboy wrote:
> It would appear that the SWR curve that is still on the Array Solutions 
> web site was measured with a misapplied 4:1 voltage balun (which puts 
> half of the antenna RF voltage on the outside of the coax shield).  
> http://www.arraysolutions.com/Products/zero_five.htm
>
> This could probably explain how an SWR of under 2:1 is obtained in the 
> 160m band, where a 43 foot antenna alone has a modeled impedance of 
> about 7.5 - j 570 ohms over a good ground system with a 5 ohm equivalent 
> loss resistance.  This should give an SWR over 100:1 in either a 50 ohm 
> or a 200 ohm system.
>
> 73, Terry N6RY
>
> On 2009-02-01 8:09 AM, K4SAV wrote:
>   
>> Here is an article that should answer your question:
>> http://www.vk1od.net/multibandunloadedvertical/index.htm
>> Also notice the paragraphs about the balun used in some of these antennas.
>>
>> Here is a link to a long discussion on this balun, which eventually 
>> determined that the manufacturer was including the wrong type balun for 
>> use in this system.
>> http://www.eham.net/forums/Elmers/201882
>>
>> Jerry, K4SAV
>>
>> Richard Thorne wrote:
>>   
>>     
>>> I have a vertical in my backyard that I currently feed at the base with 
>>> an SG-239 200 watt tuner.  I want to increase my power from 100 watts to 
>>> 400 watts.  In order to accomplish this I either need a tuner at the 
>>> base like an SG-235 or CG-5000 both expensive.
>>>
>>> The other less expensive solution is a tuner in the shack.
>>>
>>> So how much loss will I have if I tune a 125' length of coax?  I know it 
>>> works as I bypassed the base tuner and used my rigs tuner.  No problem 
>>> tuning, I'm just curious how much loss I'll have compared to the tuner 
>>> located at the base of the antenna.
>>>
>>> Rich - N5ZC
>>> _______________________________________________
>>>     
>>>       
>
>   

_______________________________________________



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

<Prev in Thread] Current Thread [Next in Thread>