Sailing boat antenna modeling & radiation patterns

[Goudurix]

Hi folks,
haven't been here on this forum for quite a while.
With all discussions on choice of HF antenna (isolated backstay - whip vertical - sloping wire alternative backstay antenna etc) - and using a 9.2m end-fed sloping wire myself - I was interested to find out what the radiation patterns are (horizontal & vertical) and the influence of the rigging.
Have made a model of a 37ft sloop including spreaders, lower shrouds, boom, guardrails, and modeled in 4NEC2 for several type of antenna's:
41 ft isolated backstay
41 ft sloper parallel to backstay
9.2m isolated backstay
9.2 m sloper
9.2m vertical whip (just for fun...)
7.2m vertical placed midstern - placed 0.3m from center - on side 1.5m from center.
Quite interesting to see the patterns from 2.2 Mhz up till 28 Mhz and directivity effects of the rigging on some frequencies.

Anyone interested in the file? PM me jan dot de dot smet8 at telenet dot be
I am also interested to share conclusions with people who have done the same.
Jan
ON3ZTT, Belgium

[BocaIII]

Jan, tried sending you a email but it bounced back. Appreciate if you could send file to me W4GRJ at Arrl.net
73's
Jack
W4GRJ

[wguinon]

Jan, I would be very interested in seeing your modeling result. Please send the files to wguinon@gmail.com Regards Walter Guinon

[Goudurix]

Hi Walter have sent you the file. Enjoy

Jan

[SoonerSailor]

Originally Posted by Goudurix

Hi Walter have sent you the file. Enjoy



Jan

Jan -

Good job. I would like the file too.
summitradioman@gmail.com

Thanks
Chip

[Wireless1]

Originally Posted by Goudurix

Hi folks,
haven't been here on this forum for quite a while.
With all discussions on choice of HF antenna (isolated backstay - whip vertical - sloping wire alternative backstay antenna etc) - and using a 9.2m end-fed sloping wire myself - I was interested to find out what the radiation patterns are (horizontal & vertical) and the influence of the rigging.
Have made a model of a 37ft sloop including spreaders, lower shrouds, boom, guardrails, and modeled in 4NEC2 for several type of antenna's:
41 ft isolated backstay
41 ft sloper parallel to backstay
9.2m isolated backstay
9.2 m sloper
9.2m vertical whip (just for fun...)
7.2m vertical placed midstern - placed 0.3m from center - on side 1.5m from center.
Quite interesting to see the patterns from 2.2 Mhz up till 28 Mhz and directivity effects of the rigging on some frequencies.

Anyone interested in the file? PM me jan dot de dot smet8 at telenet dot be
I am also interested to share conclusions with people who have done the same.
Jan
ON3ZTT, Belgium

This sounds awesome Jan. I would love to see your modeling file. Please use info@tryonmastering.com.

In the past I have used slopers on two different sailboats; one a Rawson 30 and the other a Morgan 41 Classic CC sloop; both with the backstay insulators right at the masthead for sort of an unbalanced sloper with the braid of the coax connected to all the rigging. Funny quick story; I sold the Rawson 30 to a couple that took it all the way around the world in a seven year voyage and I was living aboard my Morgan Classic with its sloper installed. We had incredibly good communications "sloper to sloper" all the way down through the South Pacific.

Now my situation has changed and I've just purchased a Beneteau 473 with TWO backstays! Talk about complicating things! Ha! I plan to run a sloper on each backstay; one short and one long in an effort to pick two lengths that are sort of electrically invisible to each other. Then the plan is to be able to switch between them with two SPDT latching relays at the masthead which can choose my 4:1 and 9:1 Unun for either backstay. My goal being to have the Kenwood TS-480SAT be able to tune all the bands I need without an external tuner.
BalunDesigns.com has some incredible baluns and ununs. Here's a link to the multi-ratio Unun I plan to get >> https://www.balundesigns.com/model-4...-1-54-mhz-5kw/

Thanks much!
Martin
s/v Lucky Spin
Ventura, CA

[rdkinard]

Originally Posted by Goudurix

Hi folks,
haven't been here on this forum for quite a while.
With all discussions on choice of HF antenna (isolated backstay - whip vertical - sloping wire alternative backstay antenna etc) - and using a 9.2m end-fed sloping wire myself - I was interested to find out what the radiation patterns are (horizontal & vertical) and the influence of the rigging.
Have made a model of a 37ft sloop including spreaders, lower shrouds, boom, guardrails, and modeled in 4NEC2 for several type of antenna's:
41 ft isolated backstay
41 ft sloper parallel to backstay
9.2m isolated backstay
9.2 m sloper
9.2m vertical whip (just for fun...)
7.2m vertical placed midstern - placed 0.3m from center - on side 1.5m from center.
Quite interesting to see the patterns from 2.2 Mhz up till 28 Mhz and directivity effects of the rigging on some frequencies.

Anyone interested in the file? PM me jan dot de dot smet8 at telenet dot be
I am also interested to share conclusions with people who have done the same.
Jan
ON3ZTT, Belgium

Would you please send the radiation patterns to RichKinard@usa.net?
Now that our 37 O’Day is canal side, east of Charlotte Harbor, FL, we’re having problems transmitting to SailMail servers, despite major maintenance on our backstay antenna, AT-130, ICOM 700-Pro, Pactor IIpro modem, counterpoise, etc.
The 700-Pro is showing 5-8 bars on transmit, and we can clearly receive Radiofax Transmissions from Boston and pt Reyes, CA.

Could the signal be blocked by the surrounding canal-side homes?

Any help or ideas what to try next is appreciated.
Rich Kinard
Punta Gorda, FL

[BocaIII]

Originally Posted by rdkinard

Would you please send the radiation patterns to RichKinard@usa.net?
Now that our 37 O’Day is canal side, east of Charlotte Harbor, FL, we’re having problems transmitting to SailMail servers, despite major maintenance on our backstay antenna, AT-130, ICOM 700-Pro, Pactor IIpro modem, counterpoise, etc.
The 700-Pro is showing 5-8 bars on transmit, and we can clearly receive Radiofax Transmissions from Boston and pt Reyes, CA.

Could the signal be blocked by the surrounding canal-side homes?

Any help or ideas what to try next is appreciated.
Rich Kinard
Punta Gorda, FL

My experience has been in a marina with lots of surrounding vessels I can hear fine but transmit is severely degraded. Also, make sure your swr is acceptable...suggest you try in open water for comparison.
Good Luck
Capt Jack
W4GRJ

[rdkinard]

Captain Jack,
Thanks for your quick and succinct response!
You make a lot of sense, since in our case, only the top 1/3 of our backstay antenna sticks above the surrounding canal-side homes, potentially cutting our signal strength by 2/3,
We’ll sail off-shore and test the transmit at night, when sunspot interference is negligible.
Thanks,
Captain Rich
Punta Gorda, FL

[S/V Illusion]

Originally Posted by rdkinard

Captain Jack,
Thanks for your quick and succinct response!
You make a lot of sense, since in our case, only the top 1/3 of our backstay antenna sticks above the surrounding canal-side homes, potentially cutting our signal strength by 2/3,
We’ll sail off-shore and test the transmit at night, when sunspot interference is negligible.
Thanks,
Captain Rich
Punta Gorda, FL

There is no such thing as “sunspot interference” but rather solar flux effects on the various layers of the ionosphere which affect signal propagation.

Testing at night vs. during the day can and do result in very different conditions with the same antenna.

[BocaIII]

Originally Posted by rdkinard

Captain Jack,
Thanks for your quick and succinct response!
You make a lot of sense, since in our case, only the top 1/3 of our backstay antenna sticks above the surrounding canal-side homes, potentially cutting our signal strength by 2/3,
We’ll sail off-shore and test the transmit at night, when sunspot interference is negligible.
Thanks,
Captain Rich
Punta Gorda, FL

Agree with S/V Illusion


Now for your case, unfortunately your math is logical but it doesn't work that way.The only way to know how your antenna installation patterns
is to model it with software like https://www.eznec.com/


Best thing to do is take it out on a day or night(usual best) with decent propagation for the frequency to use. You can get a good idea of propagation with
https://qrznow.com/real-time-band-conditions/


good luck,
Capt Jack
W4GRJ

[Pizzazz]

I have seen a number of radiation pattern monitoring on sail and power boats and while an interesting exercise, the answer is always the same. Nothing is better than a (near) vertical end fed antenna and ground with good bonding to seawater. Also, you need an antenna tuner of course. There is a slight chance that you may hit a resonant frequency at a specific backstay length (which will give the tuner a headache) but that is easily corrected if it happens on a frequency that is important to you.

Testing in a marina is useless but a correctly mounted antenna and ground will give you solid performance in a marina, although quite noisy. My advice would be to spend time and effort on the ground and mounting the tuner as close to the backstay as possible. If you have a split backstay, feed one of the legs, isolate the other. If you have running backstays, disconnect the idle one before using or switch to a non conductive wire.

I have had numerous transpacific contracts from the marina and it was always the quality of the ground connection that made the difference.

On a powerboat, it is more complicated but the best solution seems to be a vertical antenna mounted at the stern, so that the tuner is closer to the ground (seawater).

Pizzazz

[S/V Illusion]

Originally Posted by Pizzazz

I have seen a number of radiation pattern monitoring on sail and power boats and while an interesting exercise, the answer is always the same. Nothing is better than a (near) vertical end fed antenna and ground with good bonding to seawater. Also, you need an antenna tuner of course. There is a slight chance that you may hit a resonant frequency at a specific backstay length (which will give the tuner a headache) but that is easily corrected if it happens on a frequency that is important to you.

Testing in a marina is useless but a correctly mounted antenna and ground will give you solid performance in a marina, although quite noisy. My advice would be to spend time and effort on the ground and mounting the tuner as close to the backstay as possible. If you have a split backstay, feed one of the legs, isolate the other. If you have running backstays, disconnect the idle one before using or switch to a non conductive wire.

I have had numerous transpacific contracts from the marina and it was always the quality of the ground connection that made the difference.

On a powerboat, it is more complicated but the best solution seems to be a vertical antenna mounted at the stern, so that the tuner is closer to the ground (seawater).

Pizzazz

I think your description is correct but in the interest of clarity rather than semantics, the efficacy of a vertical is dependent on a good counterpoise, not a good ground although they can sometimes be synonymous. It’s important only in the sense that some might think having a good ‘ground’ is all that is required.

[BocaIII]

Originally Posted by S/V Illusion

I think your description is correct but in the interest of clarity rather than semantics, the efficacy of a vertical is dependent on a good counterpoise, not a good ground although they can sometimes be synonymous. It’s important only in the sense that some might think having a good ‘ground’ is all that is required.

There are two types of grounds
1. DC ground
2. RF ground. ie., antenna counterpoise

You need both for proper operation.

Jack
W4GRJ

[rdkinard]

Originally Posted by BocaIII

There are two types of grounds
1. DC ground
2. RF ground. ie., antenna counterpoise

You need both for proper operation.

Jack
W4GRJ

Hi Capt Jack,

We have :
1) a good DC ground (<2 ohms between sea water, dynaplate & common boat ground),
2) a good RF ground (2” wide x 36” long strip of copper foil between the AT-140 and sole grounded thru hull and
3) an excellent counterpoise (20 sqft of copper mesh bonded to the inside of the hull and tied to the at-130 with 12” of 2” wide x 0.020” copper foil).

NOTE: I don’t have an RF ohm-meter to measure what the RF resistance/impedance actually is.

Since we’re in a narrow canal between buildings, facing North-South, with the bow pointing North, do you think the back-stay antenna facing South, would primarily radiate into the atmosphere South of us, the opposite direction from most SailMail stations?

I’m rotating the boat to point South, so the antenna radiates primarily North, to see if there is directionality.

Your thoughts?
Captain Rich