In 2010, Joel, W1ZR (Alias "the Dr. is in") published an article in QST
comparing various kinds of openwire.
We have always suspected that homebrew openwire would have less loss than
the brown window-line (whatever you care to call it) which is typically sold
by THE WIREMAN or The RADIO WORKS.
Well the results of Joel's test more or less disproved that.
He found that the efficiency of all of these were more or less equal for
typical runs used in ham applications.
Joel did find a difference:
He found when the window-line gets wet from rain or snow, its impedance
changes a little and you have to re-tune your matchbox - but the efficiency
is still the same.
And when homebrew openwire gets wet, it's impedance remains pretty much
unchanged, so you don't have to re-tune.
This changed my opinion of window-line so much that I bought several hundred
feet of it before I moved back to Germany.
I've built openwire many times over the years, and it's a lot of work.
Of course the finished product is very rewarding.
QUESTION:
And while our focus in on this topic, does anyone know of a 100w to 200w
"real" symmetrical matchbox available on the commercial market today other
than the MFJ-974? PLEASE don't list all of the T-Matchboxes or L-Matchboxes
with current baluns. I'm talking about real symmetrical matchboxes.
I am aware of the high power symmetrical matchboxes but I am curious why
there are no low power versions on the market.
DEAD AND GONE:
- E.F. Johnson Viking Matchbox (275w)
- Annecke Symmetrical Koppler (200w)
- DECCA KW EZ-Match (100w)
Where have all the flowers gone?
73
Rick, DJ0IP
-----Original Message-----
From: tentec-bounces@contesting.com [mailto:tentec-bounces@contesting.com]
On Behalf Of Carl Moreschi
Sent: Thursday, January 26, 2012 3:00 AM
To: k9yc@arrl.net; Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] Re. [Ten Tec] Grounds and balanced fed verticals
The reason open wire line has less loss is that the dielectrics for true
open wire line is air. And this reduces feedline losses for high SWR's
substantially.
Carl Moreschi N4PY
121 Little Bell Dr.
Hays, NC 28635
www.n4py.com
On 1/25/2012 7:28 PM, Jim Brown wrote:
> On 1/25/2012 3:09 PM, Stuart Rohre wrote:
>> Les Moxon. in his RSGB England book, "HF Antennas for all Locations"
>> shows ladder line fed quarter wave verticals as you describe.
>
> BALANCE is defined by equal impedances from each side of the circuit to
> the reference plane (in this case, the earth). The feedline is only one
> part of that circuit, and using twin lead does NOT provide balance if
> the ANTENNA is not balanced and the antenna tuner is not balanced. A
> vertical antenna is NOT balanced.
>
> The primary virtue of using higher impedance feedlines has NOTHING to do
> with balance, but rather that their higher impedance reduces losses if
> the system is matched. But twinleads are just as likely to carry common
> mode currents and couple them to the antenna if they are not very
> effectively choked.
>
> 73, Jim K9YC
> _______________________________________________
> TenTec mailing list
> TenTec@contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec
>
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
|