Topband: Nested Loops with one feedline results

[Charlie Cunningham]

Hi, Herb 

Something you might consider is feeding the paralleled loops via a 4:1
current balun. I used this very successfully on a 2 el 5-band quad (my own
design) fed with RG-213 through a 4:1 current balun. Net result was that,
while the VSWR wasn't 1:1 anywhere, it was below 1.6:1 across all 5-bands
20-10m.  Worked great for me, and the antenna was a wonderful stellar
performer!  I did spend some months of modeling and working with
interactions in EZNEC, but it was well worth it, and the antenna tuned up
and performed just as the model predicted! A big part of the success was the
use of the 4:1 current balun to feed the paralleled drivers.

73,
Charlie, K4OTV

-----Original Message-----
From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of Herb
Schoenbohm
Sent: Monday, September 02, 2013 6:09 PM
To: TopBand List
Subject: Topband: Nested Loops with one feedline results

Several replies to my inquiry on having a closed 80 meter inverted delta
loop inside a 160 meter delta loop brought me some nice replies.  So I
decided to build one for 18Mhz and 24Mhz with the feed going to the outside
Delta loop hoping this would properly allow dual band operation with a
single feed.  The inside 24 Mhz delta was closed and hung inside the fed 18
Mhz antenna.  The results showed that it had no impact on the
18 Mhz antenna but the VSWR on 24.9 was unusable.  Then I decided to open
the 24 Mhz Delta and connect the two wires to the 18 Mhz feed and now have
both bands working with a VSRW below 1:2 to 1 on either band.  
The feed-line for the antenna is RG-213 with a 1/4 wave piece of RG-11 cut
for 18 Mhz.  I am surprised that the 1/4 wave matching piece did not seem to
impact the antenna on 24.9 at all.

I will now proceed to build an 80 meter full wave delta inside my 160 meter
one and rely on the simulation on 18/24 Mhz to get a good match.  
I trust it will work although the ground proximity might have some impact on
everything.


Thanks for the replies on this.


Herb Schoenbohm, KV4FZ
_________________
Topband Reflector