Excellent condition long boom 10 meter beam. Was only up a few years and
been stored inside for the past 6.
Pick-up only in WNY for $500.
Jeff
W2FU at frontiernet.net
-----Original Message-----
From: TowerTalk <towertalk-bounces@contesting.com> On Behalf Of
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Sent: Tuesday, October 3, 2023 12:00 PM
To: towertalk@contesting.com
Subject: TowerTalk Digest, Vol 250, Issue 3
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Today's Topics:
1. 40 meter dipole (jim.thom jim.thom@telus.net)
2. Re: 40 meter dipole (Jim Brown)
3. Re: 40 meter dipole (Jim Brown)
4. Re: 40 meter dipole (Steve Babcock)
5. Re: 40 meter dipole (Jim Brown)
6. Re: 40 meter dipole (gwj@me.com)
7. Re: 40 meter dipole (john@kk9a.com)
8. Re: 40 meter dipole (Leeson)
----------------------------------------------------------------------
Message: 1
Date: Mon, 2 Oct 2023 09:20:59 -0700
From: "jim.thom jim.thom@telus.net" <jim.thom@telus.net>
To: towertalk@contesting.com
Subject: [TowerTalk] 40 meter dipole
Message-ID:
<CAB4ZMgsu7qv+fjNRvSNe_LDy6aY3MnybWDN9XZ1910v3=vzWSA@mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"
Subject: Re: [TowerTalk] 40 meter dipole
<The performance of an antenna will depend on the overall element size
(length).?
<Shorter elements will have a narrower usable SWR bandwidth.?
<Thanks n 73,James
< On Sunday, October 1, 2023 at 11:00:47 PM CDT, john@kk9a.com <
john@kk9a.com> wrote:
<That depends on if you want a full size dipole or a shortened one. It also
<depends on your fabrication skills and available equipment and free time.
<It may also depend on how much aluminum tubing you have laying around.? In
<the past I designed and built a full size 40m beam. Full sized elements are
<massive, these days I am using commercially made 40m beams with shortened
<elements using High-Q loading coils.
<John KK9A
A simple DPST relay and 2 x coils in a nema box will provide for 2 x
segments. You can still buy the DPST kilovac vac relay from MFJ.
($20.00, 12 vdc @ 100 ohm coil). 2 relays will provide for 4 x
segments. Even 2 x segments will cover the entire 300 khz.
A 44' to 50' shortened 40m ele is pretty straightforward to design and
fabricate. Tubing coils, and / or capacity hats are simple to fabricate. I
used DXE's ' yagi mechanical' software to design, or modify existing
eles. Designing a shortened 40m ele to handle a 100 mph wind is a simple
task. The solid fiberglass insulators come in various diameters..and found
at Max gain systems. Mcmaster Carr has the rolls of aluminum tubing, used
for the coils. A single overhead truss made from 5/16" dacron rope is
ample.
Jim VE7RF
------------------------------
Message: 2
Date: Mon, 2 Oct 2023 09:57:28 -0700
From: Jim Brown <jim@audiosystemsgroup.com>
To: towertalk@contesting.com
Subject: Re: [TowerTalk] 40 meter dipole
Message-ID:
<aa84cc54-6a72-1516-398a-e8d3c75deb95@audiosystemsgroup.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
On 10/1/2023 5:17 PM, Gene Smar via TowerTalk wrote:
> You will need to wind a coax balun for the feedpoint - IIRC, it's 12 turns
about 6 inches in diameter.
That "balun" is really a lousy common mode choke. A far better thing to use
there is a really good common mode choke using these guidelines.
http://k9yc.com/2018Cookbook.pdf
The pattern of a dipole is quite broad, with deep nulls off the ends.
Those nulls are pretty narrow, and are really what matters. And what matters
far more is height -- study this piece, which I wrote for NCJ, but ARRL
rejected because the graphs were too much work for their graphics
department.
http://k9yc.com/AntennaPlanning.pdf
Dipoles are great antennas. As the link shows, higher is better! For 17
years, I've had dipoles for 80 and 40 at right angles to each other at
125 ft, and for about ten years, at 100 ft for 30M.
73, Jim K9YC
------------------------------
Message: 3
Date: Mon, 2 Oct 2023 10:06:09 -0700
From: Jim Brown <jim@audiosystemsgroup.com>
To: towertalk@contesting.com
Subject: Re: [TowerTalk] 40 meter dipole
Message-ID:
<6478c582-79c0-d0e8-1f0f-74a0df5f5847@audiosystemsgroup.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
On 10/2/2023 3:59 AM, J. Hunt via TowerTalk wrote:
> The performance of an antenna will depend on the overall element size
(length).
> Shorter elements will have a narrower usable SWR bandwidth.
Yes, but extensive modeling shows that SWR bandwidth is the only important
downside of loading that is not inductors at the feedpoint.
SWR is NOT a measure of antenna performance, and the added loss due to SWR
values below 3:1 at the feedpoint are too small to matter unless you're
using line smaller than RG8/11, and/or the lines are very long.
My 80M dipole at 125 ft fed with about 170 ft of a good RG11 presents a
5:1 SWR on 60M at the TX, but is quite effective running legal limit (100W
ERP).
73, Jim K9YC
------------------------------
Message: 4
Date: Mon, 2 Oct 2023 11:19:52 -0600
From: Steve Babcock <ve6wz@shaw.ca>
To: jim@audiosystemsgroup.com
Cc: towertalk@contesting.com
Subject: Re: [TowerTalk] 40 meter dipole
Message-ID: <11A41B51-A537-43B5-B7E8-7ED3B6104F27@shaw.ca>
Content-Type: text/plain; charset=us-ascii
Indeed SWR is not a measure of Yagi antenna performance.
However Yagi performance IS a function of the narrow bandwidth of a
shortened PARASITIC element. (not the driver) Explained here regarding a 2el
short 40m Yagi: https://youtu.be/VZ9esNGBP7Y?si=Xj8shPN9NnNALw8O
<https://youtu.be/VZ9esNGBP7Y?si=Xj8shPN9NnNALw8O>
Steve, ve6wz
> Yes, but extensive modeling shows that SWR bandwidth is the only important
downside of loading that is not inductors at the feedpoint.
>
> SWR is NOT a measure of antenna performance, and the added loss due to SWR
values below 3:1 at the feedpoint are too small to matter unless you're
using line smaller than RG8/11, and/or the lines are very long. My 80M
dipole at 125 ft fed with about 170 ft of a good RG11 presents a 5:1 SWR on
60M at the TX, but is quite effective running legal limit (100W ERP).
>
> 73, Jim K9YC
------------------------------
Message: 5
Date: Mon, 2 Oct 2023 11:02:07 -0700
From: Jim Brown <jim@audiosystemsgroup.com>
To: towertalk@contesting.com
Subject: Re: [TowerTalk] 40 meter dipole
Message-ID:
<78434594-0cda-c06e-fff7-b872806c62f7@audiosystemsgroup.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
On 10/2/2023 10:19 AM, Steve Babcock wrote:
> However Yagi performance IS a function of the narrow bandwidth of a
> shortened PARASITIC element. (not the driver)
No debate on that, but I'm specifically talking about dipoles.
Higher frequency bands in fan dipoles also exhibit reduced SWR bandwidth, as
low frequency bands in multi-band loaded dipoles (like the common 2-band
dipole with a loading coil near what would be the resonant point of the
second harmonic of the band for which the loading coils are used. For
example, 80/40 and 40/20. I was first introduced to the idea from commercial
versions of those designs for 80/40 and 160/80, and did my own designs of a
40/20 versions using both wire and aluminum elements for CQP expeditions.
Again, efficiency and pattern are not significantly affected by loading,
acting like ordinary half-wave dipoles on both bands.
73, Jim K9YC
------------------------------
Message: 6
Date: Mon, 2 Oct 2023 11:27:07 -0700
From: gwj@me.com
To: towertalk@contesting.com, sflory@mindspring.com
Subject: Re: [TowerTalk] 40 meter dipole
Message-ID: <1E284584-DB6F-4CD2-A4A8-DB54C82E214A@me.com>
Content-Type: text/plain; charset=utf-8
JK401, definitely. It?s a proper 100 MPH design with no stays needed, USA
materials, USA support and a very nice manual. I have to be pretty
desperate to buy an antenna from anyone else these days.
I have an Optibeam OB1-4030 and it?s built like a wet noodle. An estimate
using YagiStress showed that it was, at best a 60 MPH design. I completely
replaced all the parts in the center 6 ft to beef it up to almost the JK
standard for my hilltop location. Only bought it because we also needed 30m.
Gary NA6O
>
> is it better to build our buy a 40 meter rotatable dipole? any good
> kits? what is the best facotory made Steve Flory W9KOP
> sflory@mindspring.com <mailto:sflory@mindspring.com>
------------------------------
Message: 7
Date: Mon, 2 Oct 2023 17:42:24 -0400
From: <john@kk9a.com>
To: <towertalk@contesting.com>
Subject: Re: [TowerTalk] 40 meter dipole
Message-ID: <000001d9f579$54f5e7b0$fee1b710$@kk9a.com>
Content-Type: text/plain; charset="us-ascii"
I agree that loaded center fed 40m rotatable dipole is an effective antenna
, even on portions of the band where the SWR is higher.
On 80m many people use a 1 WL section of 50 ohm coax following by a 1/4 WL
section of 75 ohm coax to make their dipole cover both the CW and SSB
segments of the band. Obviously this does not change the actual antenna
feed point SWR but it may make the radio, amp and operator happier. I
wonder if anyone has used this type of broad band transmission line match on
40m?
John KK9A
Jim Brown K9YC
SWR is NOT a measure of antenna performance, and the added loss due to SWR
values below 3:1 at the feedpoint are too small to matter unless you're
using line smaller than RG8/11, and/or the lines are very long.
My 80M dipole at 125 ft fed with about 170 ft of a good RG11 presents a
5:1 SWR on 60M at the TX, but is quite effective running legal limit (100W
ERP).
73, Jim K9YC
------------------------------
Message: 8
Date: Mon, 2 Oct 2023 15:27:05 -0700
From: Leeson <leeson@earthlink.net>
To: towertalk@contesting.com
Cc: john@kk9a.com
Subject: Re: [TowerTalk] 40 meter dipole
Message-ID: <7c9f7a14-eb5e-7141-4618-bb2f064ea8ea@earthlink.net>
Content-Type: text/plain; charset=utf-8; format=flowed
Yep, it works as you suggest, have used it here and in HC8. Because the 40m
band is a narrower percentage width, it takes only a half-wavelength 50-ohm
line, plus the quarter-wave transformer, to cover the band.
For history, see
http://lists.contesting.com/archives/html/Towertalk/1997-11/msg00695.html
For references, see
http://www.arrl.org/files/file/QEX_Next_Issue/Nov-Dec2018/Leeson.pdf
"Give it a try."
Dave, W6NL/HC8L
On 10/2/23 2:42 PM, john@kk9a.com wrote:
> I agree that loaded center fed 40m rotatable dipole is an effective
> antenna , even on portions of the band where the SWR is higher.
>
> On 80m many people use a 1 WL section of 50 ohm coax following by a
> 1/4 WL section of 75 ohm coax to make their dipole cover both the CW
> and SSB segments of the band. Obviously this does not change the
> actual antenna feed point SWR but it may make the radio, amp and
> operator happier. I wonder if anyone has used this type of broad band
> transmission line match on 40m?
>
> John KK9A
------------------------------
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