[TenTec] OCF antennas evolution

[Marshall Stewart]

Mike,

"Somewhere along the way, depending on the length of the coax between the
tuner and the balun, wouldn't I be just matching the say 14 foot run of coax
from the tuner to the balun? And not necessarily matching the antenna?" 


In no case will you be matching the antenna. The impedance matching network
("antenna tuner") is used to try to match the complex impedance at the
station end of the transmission line system, which includes the twin lead,
balun, and coax, to the impedance of your transceiver, which is probably
about 50 ohms resistive with little reactance.  

"Let's take it one more step. Place the 1:1 balun at the feed point 200 feet
away and feed it with coax? Doesn't sound like a good idea."

Generally coax has more loss that twin lead. Ideally try to keep the coax
from the balun to the station as short as practical. But the shortest length
of twin lead from the balun to the antenna may not work best. The impedance
of the antenna at the feedpoint, length of the twin lead, balun, and length
of the coax all together will determine the impedance the "antenna tuner"
needs to match at a particular frequency. Changing the length of the twin
lead can turn a frequency that can not be matched into one that is easily
matched.

73,
Marsh, KA5M
   

-----Original Message-----
From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of Mike Bryce
Sent: Thursday, July 11, 2013 5:18 PM
To: rmcgraw at blomand.net; Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] OCF antennas evolution

Interesting conversation! 

So what I am reading is this. 

Use a 1:1 current balun remote to the tuner to use my 600 ohm feedline. 

Now

Somewhere along the way, depending on the length of the coax between the
tuner and the balun, wouldn't I be just matching the say 14 foot run of coax
from the tuner to the balun? And not necessarily matching the antenna? 

Lets take it one more step

Place the 1:1 balun at the feed  point 200 feet away and feed it with coax? 

Dosen't sound like a good idea. 


Mike wb8vge 

Sent from my iPhone

On Jul 11, 2013, at 5:59 PM, "Robert Mcgraw" <rmcgraw at blomand.net> wrote:

> Because your antenna impedance is not 600 ohms but is more lilkely 25 to
> 75 ohms depending on height above ground.  Only the feedline is 600 ohms
> and that is really not an important issue.
> 
> 73
> Bob, K4TAX
> 
> 
> 
_______________________________________________
TenTec mailing list
TenTec at contesting.com
http://lists.contesting.com/mailman/listinfo/tentec