Another good point Gus. "Switchable baluns."
I wanted to mention that too but you pulled the trigger faster!
You can easily build two 1:1 choke baluns on two different cores.
Use larger cores for more power.
Use bifilar 100 Ohm windings.
The TX side of each is always wired in parallel.
The ANT side of the two can be easily switched in parallel for 50 Ohms or in
series for 200 Ohms.
This gives you the best of both worlds. But there is a catch.
Also, the matching range of all Elecraft automatic tuners is outstanding
compared to most other tuners.
What works just as well is to always use a 1:1 choke balun (Guanella) and
the have the option to insert a 4:1 voltage balun between the choke balun
and the antenna. THIS WORKS EVEN BETTER than the switchable balun under
high SWR condx. This only becomes apparent when running high power.
73 - Rick, DJ0IP
(Nr. Frankfurt am Main)
-----Original Message-----
From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of Augie "Gus"
Hansen
Sent: Sunday, September 14, 2014 4:29 AM
To: tentec@contesting.com
Subject: Re: [TenTec] Zepp?
On 9/13/2014 7:55 PM, Bob McGraw - K4TAX wrote:
> I been puzzled by the most frequent and most common uses of the 4:1
> balun. It seems that hams believe necessary to use a balanced feed
> system, open wire line and such that they must employee a 4:1 balun.
> Most oversight is that we are not matching the line but matching the
> load.
Hi Bob,
For the record, I have a doublet that is in the inverted vee configuration,
cut to 100 feet per side. It is feed via open wire (~600
Ohm) parallel line (nominally balanced) down the tower and to the eaves,
with a shorter run of window line (~400 Ohms) under the eves to a DXE
1:1 current balun (I prefer to call it a choke) at the back of the house.
There is then an eight foot run of RG213 coax into the basement-located
shack to an Elecraft KAT500 auto tuner. I use this on all bands from 80m to
20m. It can tune up through 6m, but I have other antennas for those bands.
And I shunt feed my tower for 160m ops.
I don't normally use a 4:1 or 1:4 balun, and was only responding to your
question about semantics in my previous post. Elecraft sells a nice
low-power balun that is switchable as 1:1 or 4:1. I have used it for
field/portable ops, but it's usually set to 1:1 for the antennas I use (44'
or 88' doublet).
73,
Gus
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