Sailing boat antenna modeling & radiation patterns

[BocaIII]

Originally Posted by rdkinard

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

Sounds like a great installation!
What is the swr at the radio with at-140 tuned?
Have you tried in the evenings?

If you have you computer on the internet in port, the sailmail propagation
forecast by frequency is pretty good.

[rdkinard]

Do you have a suggestion for a good SWR meter?

That would be helpful.

[BocaIII]

Originally Posted by rdkinard

Do you have a suggestion for a good SWR meter?

That would be helpful.

Most available are only rated to 100 watts
you need 150 watts minimum, freq 1 to 30Mhz range


Found this one on ebay, looks good
https://www.ebay.com/itm/17535046548...gAAOSw3e5izv7P


You will also need short 2' coax jumper with male pl259 connectors to connect meter to radio.

[S/V Illusion]

Originally Posted by BocaIII

Most available are only rated to 100 watts
you need 150 watts minimum, freq 1 to 30Mhz range


Found this one on ebay, looks good
https://www.ebay.com/itm/17535046548...gAAOSw3e5izv7P


You will also need short 2' coax jumper with male pl259 connectors to connect meter to radio.

These CB type SWR meters are generally imprecise and therefore not a popular choice among ham radio ops. Stick with the reliable brands such as Daiwa and MFJ although with the latter, workmanship is haphazard and you might need to repair it out of the box.

[BocaIII]

Originally Posted by S/V Illusion

These CB type SWR meters are generally imprecise and therefore not a popular choice among ham radio ops. Stick with the reliable brands such as Daiwa and MFJ although with the latter, workmanship is haphazard and you might need to repair it out of the box.

O.k…maybe not as precise as a high end meter but they work fine for the purpose Rich has ….. i.e. if “Cb meter” reads 1.4:1 actual swr is 1.3:1 close enough to indicate any issues also, chance The “cb meter” could actually be perfectly accurate. I am speaking from lots of experience as I have 4 o 5 different meters….been doing this for 60 years.
Jack
w4grj

p.s. mfj meters work fine but not in the same class as Daiwa

[rdkinard]

Originally Posted by S/V Illusion

These CB type SWR meters are generally imprecise and therefore not a popular choice among ham radio ops. Stick with the reliable brands such as Daiwa and MFJ although with the latter, workmanship is haphazard and you might need to repair it out of the box.

Hey Guys,
At this point I’m looking to see what percent power is radiating from the antenna, in the middle of the marine SSB frequency range.
I’ll let you know, as soon as the Radio Shack SWR Meter arrives from EBay later this week.
Best Regards,
Captain Rich

[BocaIII]

Originally Posted by rdkinard

Hey Guys,
At this point I’m looking to see what percent power is radiating from the antenna, in the middle of the marine SSB frequency range.
I’ll let you know, as soon as the Radio Shack SWR Meter arrives from EBay later this week.
Best Regards,
Captain Rich

if the swr is approx 1.7:1 or better …< 1.5:1 is best
then the issue is propagation … hf freqs during the day these days are not real good. 20 meter ham band not to bad …. unless you have yaggi antenna, wire antennas are difficult to use during periods of poor propagation.

For example, refer to attached prop forecast…best frequencies to use is between 17 meters and 10 meters at this time of the day …. it changes during the day and every day is different.

[S/V Illusion]

The problem with these questionable SWR meters is not only one of precision but also reproducibility. Often, you will observe wide disparity between readings taken minutes apart. Among the reasons are the cheap parts and the effect of heating.

And, not that it matters, but I have been a ham since 1961 focusing primarily on antenna design and construction.

Cheap isn’t synonymous with good value.

[rdkinard]

Good Morning,
We’ll we reversed the position of S/V Seabee (ie bow South vs bow North) to see if there was a directional component to our transmitting issue.
After exhausting testing, NO difference.
We receive RadioFaxes and the Time Signal slightly better, but mo improvement on Sailmail.
Our SWR meter arrives Saturday for our next data collection morning.
Thanks for your ideas to try.
Captain Rich
Punta Gorda, FL

[rdkinard]

July 27th Update,
SUCCESS!
Just connected to Sailmail at Rock Hall, SC; Lunenberg, NS; Trinidad; Corpus Cristi, TX; and San Diego, CA, from Sloop SEABEE on the Bermuda Canal in Punta Gorda Isles, Southwest FL, after replacing the 18 year old RG-8(something) with 25-feet of brand new, extremely low loss LMR400 coaxial cable connecting the Radio and Auto-Tuner.
HAVE A GREAT DAY!
Captain Rich
PS: The RadioShack SWR Meter, after calibration, still gets pinned during transmit. Why, I don’t know.
PPS: Wish there was an ICOM 700-Pro tech in lower Florida who could see if it is working to max capabilities.

[S/V Illusion]

Originally Posted by rdkinard

July 27th Update,
SUCCESS!
Just connected to Sailmail at Rock Hall, SC; Lunenberg, NS; Trinidad; Corpus Cristi, TX; and San Diego, CA, from Sloop SEABEE on the Bermuda Canal in Punta Gorda Isles, Southwest FL, after replacing the 18 year old RG-8(something) with 25-feet of brand new, extremely low loss LMR400 coaxial cable connecting the Radio and Auto-Tuner.
HAVE A GREAT DAY!
Captain Rich
PS: The RadioShack SWR Meter, after calibration, still gets pinned during transmit. Why, I don’t know.
PPS: Wish there was an ICOM 700-Pro tech in lower Florida who could see if it is working to max capabilities.

I suspect as I originally did the choice of this brand SWR meter was infamously dubious.

[rdkinard]

Hello All,
Thanks to everyone’s help, I found the cause of the high SWR readings….. It was a bad connection to my Auto Tuner that prevented it from tuning!
The word TUNE was displayed, when I pressed the TUNE button, but there was no clicking back at the Auto Tuner!
As a result this morning, with the Auto Tuner working, and SWR’s no higher than 1.3, I connected to Sailmail Stations from Lunenberg, NS to San Diego to Panama to Trinidad! From SouthWest Florida.
WaHoo!!
The next step is to access RadioFax and GRIB weather data files via SailMail.
Captain Rich