What is so special about that magical length, for it does
not appear to be resonant anywhere!

Gareth's Downstairs Computer wrote:
What is so special about that magical length, for it does
not appear to be resonant anywhere!

Easily matched and has a decent pattern for most HF bands.

--
Jim Pennino

On Thu, 15 Mar 2018 15:36:21 +0000, Gareth's Downstairs Computer
wrote:

What is so special about that magical length, for it does
not appear to be resonant anywhere!

If you're building an all ham band antenna, you don't really want any
resonances, which are difficult to match, always end up on the wrong
frequency, and tend to move around.

http://www.hamradio.me/antennas/answer-to-everything-43-feet-antenna.html
http://www.ad5x.com/images/Presentations/Vertical43RevA.pdf

With an antenna tuna and ground radials, the 43ft vertical is easily
matched on all bands except 10m without any irritating resonances, and
has a decent pattern for an all band antenna. However, it's major
beneifit is the LACK of any resonances in the ham bands.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Jeff Liebermann wrote:

On Thu, 15 Mar 2018 15:36:21 +0000, Gareth's Downstairs Computer
wrote:

What is so special about that magical length, for it does
not appear to be resonant anywhere!

If you're building an all ham band antenna, you don't really want any
resonances, which are difficult to match, always end up on the wrong
frequency, and tend to move around.

http://www.hamradio.me/antennas/answer-to-everything-43-feet-antenna.html
http://www.ad5x.com/images/Presentations/Vertical43RevA.pdf

With an antenna tuna and ground radials, the 43ft vertical is easily

^^^^
Sorry, but that is such an impressive mental image, for /MM especially



matched on all bands except 10m without any irritating resonances, and
has a decent pattern for an all band antenna. However, it's major
beneifit is the LACK of any resonances in the ham bands.


--

Roger Hayter

A base-mounted tuner may have difficulty matching certain lengths.
According to my ICOM AT-150 manual, we should avoid multiples of half-waves.
The manual offers the formula 300/freq X 0.5 X integers 1, 2, 3, etc. (You
figure it separately for each integer but stop when the product is longer
than your antenna is.) For all your desired frequencies, you do the
calculations, then avoid that length. You will develop a list of lengths
that are "bad" and you avoid an antenna of that length.

I did the calculations and saved them with the manual. I observe from my
own results that 43 feet is in a sweet spot between 39.5 feet (which is bad
for 12m) and 45.8 feet (which is bad for 30m). Never mind who uses those
bands or doesn't. I simply ran the numbers for he frequencies we can bring
up and that's where the chips fell. By the way, ICOM says the antenna
should be more than 7 meters (23 feet).

Here are the "bad" lengths that I got, in meters.
5.05 - 5.30
6.00 - 6.03
6.99 - 7.14
8.25 - 8.30
10.10 - 10.71
12.00 - 12.05
13.99 - 14.85
15.15 - 15.81
16.51 - 16.60

So, obviously, some good lengths fall between those "bad" lengths. Here are
the midpoints of the "sweet spots" that remain in play:
7.75m (25.42 feet)
9 m (29.52 feet)
11.5m (37.72 feet)
13m (42.64 feet)
15m (49.21 feet) but this is a minimal sweet spot
16.25 (53.3 feet )

The 43' antenna is at one of those sweet spots. CAUTION: If you use a long
pigtail, that could mess things up.

I hope this helps.

================================================== ================================================== ========



"Gareth's Downstairs Computer" wrote in message
news
What is so special about that magical length, for it does
not appear to be resonant anywhere!

On 17/03/2018 01:01, Sal M. O'Nella wrote:
A base-mounted tuner may have difficulty matching certain lengths.
According to my ICOM AT-150 manual, we should avoid multiples of
half-waves. The manual offers the formulaÂ* 300/freq X 0.5 X integers 1,
2, 3, etc.Â* (You figure it separately for each integer but stop when the
product is longer than your antenna is.)Â* For all your desired
frequencies, you do the calculations, then avoid that length.Â* You will
develop a list of lengths that are "bad" and you avoid an antenna of
that length.

I did the calculations and saved them with the manual.Â* I observe from
my own results that 43 feet is in a sweet spot between 39.5 feet (which
is bad for 12m) and 45.8 feet (which is bad for 30m).Â* Never mind who
uses those bands or doesn't.Â* I simply ran the numbers for he
frequencies we can bring up and that's where the chips fell.Â* By the
way, ICOM says the antenna should be more than 7 meters (23 feet).

Here are the "bad" lengths that I got, in meters.
5.05 - 5.30
6.00 - 6.03
6.99 - 7.14
8.25 - 8.30
10.10 - 10.71
12.00 - 12.05
13.99 - 14.85
15.15 - 15.81
16.51 - 16.60

So, obviously, some good lengths fall between those "bad" lengths.Â* Here
are the midpoints of the "sweet spots" that remain in play:
7.75mÂ*Â*Â*Â*Â*Â*Â* (25.42 feet)
9 mÂ*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â* (29.52 feet)
11.5mÂ*Â*Â*Â*Â*Â*Â* (37.72 feet)
13mÂ*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â* (42.64 feet)
15mÂ*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â* (49.21 feet)Â* but this is a minimal sweet spot
16.25Â*Â*Â*Â*Â*Â*Â*Â*Â*Â* (53.3 feet )

The 43' antenna is at one of those sweet spots.Â* CAUTION:Â* If you use a
long pigtail, that could mess things up.

I hope this helps.

That's useful info, thanks -
FWIW my Butternut vertical comes in at around 26ft +/-
--

---
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On 17/03/2018 01:01, Sal M. O'Nella wrote:
A base-mounted tuner may have difficulty matching certain lengths.
According to my ICOM AT-150 manual, we should avoid multiples of
half-waves. The manual offers the formulaÂ* 300/freq X 0.5 X integers 1,
2, 3, etc.Â* (You figure it separately for each integer but stop when the
product is longer than your antenna is.)Â* For all your desired
frequencies, you do the calculations, then avoid that length.Â* You will
develop a list of lengths that are "bad" and you avoid an antenna of
that length.

I did the calculations and saved them with the manual.Â* I observe from
my own results that 43 feet is in a sweet spot between 39.5 feet (which
is bad for 12m) and 45.8 feet (which is bad for 30m).Â* Never mind who
uses those bands or doesn't.Â* I simply ran the numbers for he
frequencies we can bring up and that's where the chips fell.Â* By the
way, ICOM says the antenna should be more than 7 meters (23 feet).

Here are the "bad" lengths that I got, in meters.
5.05 - 5.30
6.00 - 6.03
6.99 - 7.14
8.25 - 8.30
10.10 - 10.71
12.00 - 12.05
13.99 - 14.85
15.15 - 15.81
16.51 - 16.60

So, obviously, some good lengths fall between those "bad" lengths.Â* Here
are the midpoints of the "sweet spots" that remain in play:
7.75mÂ*Â*Â*Â*Â*Â*Â* (25.42 feet)
9 mÂ*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â* (29.52 feet)
11.5mÂ*Â*Â*Â*Â*Â*Â* (37.72 feet)
13mÂ*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â* (42.64 feet)
15mÂ*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â* (49.21 feet)Â* but this is a minimal sweet spot
16.25Â*Â*Â*Â*Â*Â*Â*Â*Â*Â* (53.3 feet )

The 43' antenna is at one of those sweet spots.Â* CAUTION:Â* If you use a
long pigtail, that could mess things up.

I hope this helps.

================================================== ================================================== ========




"Gareth's Downstairs Computer"Â* wrote in message
news
What is so special about that magical length, for it does
not appear to be resonant anywhere!

An interesting analsis, thank-you