[HBQRP] requesting information on feeding balanced antenna with a L match atu

[Rick Bennett]

Shubham,

Not sure if anyone else has responded.  Unfortunately feeding a loop antenna for multi-band operation and high efficiency is somewhat complicated. If you were just going to operate at the resonant frequency, then matching for high efficiency is not difficult.  The problem comes when you go to a different band.  So if you are optimized for 7 MHz, then when you feed say 14 MHz to it, the feed point impedance is going to be very different.  Even if you can match your transmitter to the coax, you are going to have a lot of coax loss.  

Many years ago I put together a full wave loop antenna and used an SG230 automatic feed point tuner (they were pretty expensive) directly connected to the loop.  It worked OK but not great.  I could tune it to any frequency I wanted to, but the performance was another issue.  On the resonant frequency it performed OK and maybe some other frequencies (not necessarily the ones I was interested in) it was OK but for the most part I would not have called it a multi-band antenna.  After that experience I have switched to using fan dipoles, off center fed dipoles or various forms of simple wire antennas for multi-band operation.

All that to say, have you considered a different type of antenna?  There are many, many designs for multi-band antennas out there.  Just food for some thought and research.

Rick, KC0PET






----- Original Message -----
From: "VU3SXN / KC3CWD" <vu3sxn at gmail.com>
To: vu3sxn at gmail.com
Sent: Sunday, July 9, 2017 6:48:47 AM
Subject: [HBQRP] requesting information on feeding balanced antenna with a L	match atu


Hi,

I am trying to feed a resonant length 7 mhz full wave delta loop 41 
meters of total length with an L-match ATU,

Since the l match is a non balance tuner and a full wave loop is a 
balanced antenna , so can please provide few of your expert tips that 
how can I feed this balanced loop antenna to a unbalanced l match 
antenna tuner, I am planning to use this loop antenna on all the freq 
from 7 to 30mhz will also try it on 6m,

I have few options in my mind but I am confused what arrangement to use..

Option1. Use a 1to1 current balun between loop antenna to l match tuner,

Option 2 use a 1to4 balun between loop antenna and l match tuner

Will these baluns feeding the loop antenna will be efficient as I use 
homebrew rigs with 15watts output and I am trying to make it very 
efficient ….

Vu3sxn / kc3cwd

Shubham tiwari
reply at -- vu3sxn at gmail.com

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