[bars] Cobra Ultralite Balun

[apizer at comcast.net]

Hi Jason,

 

I see your antenna every time I drive though our neighborhood so I know the situation.  If the wood is dry and there are no metal fasteners nearby it should not affect the VSWR.  You can check for hidden nails nearby with an electronic stud finder; your dad probably has one.  That being said, if the line is subject to high VSWR  at some combination of frequency and power, at could be subject to heating, melting and arcing (I have seen all of the above) then it would be good to isolate it from the wood to prevent fire hazard.  If you want to switch over to a balun and coax before entering the house here are some suggestions:

 

*	Keep the coax run as short as possible; the longer the coax then more loss you will have vs. frequency as the wavelength get shorter and electrical length of the coax gets longer, and dielectric loss increases. You will be “heating” the coax, probably not noticeable to the touch but you will waste some power.  That being said, I have used this method with some success on Field Days through the years.  The low bands. i.e., 40 and 80 should not be too much of a problem.

 

*	Make sure what ever balun your are using is over-rated for power handling as it will be subject to mis-match and reflected power.  For example, if you are running a 100 W use a 1 KW balun so it won’t burn up.

 

Good luck,

Art

NF1A

 

 

From: bars <bars-bounces at w1hh.org> On Behalf Of Jason M. Sanroma - K1NAD
Sent: Sunday, July 3, 2022 1:04 AM
To: bars at w1hh.org
Subject: [bars] Cobra Ultralite Balun

 

Hello,

I have a Cobra Ultralite Senior. It is approximately 105 feet up in my pine trees. When the ladder line comes down, it goes through a porcelain insulator and then through a slit of wood in the eave of the house. My grandfather believes the VSWR is affected by its contact with the wood.

I was wondering if I should add a balun and run coax into the house instead of the feedline? Does anyone have recommendations for the Cobralite antenna balun?

I have attached a few pictures to explain what I am writing about.

Thanks.

73,
Jason
K1NAD

-

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.w1hh.org/pipermail/bars_w1hh.org/attachments/20220703/1f8391dd/attachment.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image007.jpg
Type: image/jpeg
Size: 67207 bytes
Desc: not available
URL: <http://mail.w1hh.org/pipermail/bars_w1hh.org/attachments/20220703/1f8391dd/attachment.jpg>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image008.jpg
Type: image/jpeg
Size: 23181 bytes
Desc: not available
URL: <http://mail.w1hh.org/pipermail/bars_w1hh.org/attachments/20220703/1f8391dd/attachment-0001.jpg>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image009.jpg
Type: image/jpeg
Size: 44980 bytes
Desc: not available
URL: <http://mail.w1hh.org/pipermail/bars_w1hh.org/attachments/20220703/1f8391dd/attachment-0002.jpg>