New Internet Subscriber Introduction

[Anonymous]

Hi,

Bill Russell, KD8WMJ, here.

I attended the Ham Radio Bootcamp at Boxboro in September and became aquainted with your club. I joined as an “Internet subscriber” because Nashua is quite far from my home.

As an introduction, I got my ham license about February of 2012, but had no Elmer available for help.  I have been looking for one, off and on, since then.  Hopefully this will be THE place.  I operate from two very different locations:

The first is my home QTH in Rhode Island.  Here I have a Kenwood TS480 SAT, along with a MFJ 939 tuner through some hommade RF choke/filters and into a W5GI dipole antenna, center at 43ft, ends at 26ft.  The setup seems to work fine.
The second is a boat.  It is a trawler (motorboat).  Here I use the same radio but have a SGC SG230 tuner, fed into a 23ft vertical antenna.  The counterpoise is a KISS, which is a commercial counterpoise made especially for situations where the traditional “100 square feet of copper foil in the bilge” is not possible.  Again, this setup seems to be fine.

Like most hams, I am looking to improve the performance of my station.  The most concern is for the /MM station.  Operating with such a short vertical is challenging.  I am hoping that this Elmering forum can help me with some of my questions.

Hope to hear from some of you soon.

73,

Bill

[Fred Kemmerer]

Hi Bill,

Welcome! We’re glad to have you join us as an Internet Subscriber. We hope that you enjoyed Bootcamp.

The best thing that you can do to improve the performance of your vertical antennas is to improve the associated ground plan.

Scott, NE1RD just wrote a good article about radials and that may give you some good ideas about how to improve the first of your antennas. Here’s a link to Scott’s article.

It sounds like the setup in your boat will be more challenging. Water (especially salt water) can be an excellent ground plan if you can figure out how to couple the ground side of your antenna to it.

I hope that this helps you and again, welcome! Please continue to post here and we’ll try to help you.

Best and 73,

 

[Hamilton]

Hello Bill,

Welcome to NARS.

There are many in the club that can and will help, just post your questions or contact us directly. This is new territory for many and no question is too simple.

For /MM salt water is your friend. You may already have enough metal  below the water line. Often the ground side of the antenna feed is capacitively coupled to prevent electrolysis.

“Net Logger” is a good resource to find open nets including the Maritime net out of ME. These nets like traffic so do not hesitate to check into the XYL, Navy, ME Potato, or other net.

[Anonymous]

Hi Fred,

I use an inverted dipole at my home QTH, so that is not a problem.

I am really concerned about the ground plane (counterpoise) on the boat.

I often read about the vertical antenna on land, and the general advice is to add radials.  The same articles imply that radials are added until the point of “diminishing returns”. So, just how does one measure when you are getting “diminishing return”?

On the boat, it is difficult to just add things, so I am interested in how to “measure” the antenna.  I know my tuner /”coupler” makes the radio happy but that doesn’t mean that the antenna itself is any good.  I assume that the closer the vertical/counterpoise measures to 50 ohms, the better.

But, what about the capacitance/inductance part of what an antenna analyzer tells me?  What value should that be?  I do have a nanoVNA to do measurements with.

Thanks,

73

Bill

[Fred Kemmerer]

Hi Bill,

You are on the right track with the idea that you can “measure” the effectiveness of your vertical antenna by using an antenna analyzer to measure its impedance. For this approach to be accurate, you’ll want to make the measurement as close to the feedpoint of the antenna as you practically can. As the length of the coax cable between the antenna and your analyzer grows to more than a few feet, it will begin to distort the measurements somewhat.

An “ideal” 1/4 wavelength vertical with a good ground system will have an impedance of about 25 ohms. As the efficiency of the ground field decreases, the impedance will increase towards 50 ohms. You will see a capacitive impedance if the vertical radio is “short” compared to a 1/4 wavelength on the frequency that you are measuring and an inductive impedance if the vertical radiator is “long”.

Radials are difficult on a boat as the associated wires will tend to end up in the boat’s propeller or drive. I don’t have any experience with putting antennas on a boat but the idea that you mentioned in a previous post of using copper sheeting on the inside of the hull to couple the ground side of the antenna to the antenna seems “right” to me. The idea is to create a capacitor using the boat’s hull as the insulator and the “saltwater” on the outside of the full as the opposite plate and ground. I would expect this approach to work quite well. It might be possible to do this with strips of copper sheeting laid as radials inside the hull as well.

I hope that this helps you,

 

[Anonymous]

Hi Fred & Hamilton,
Thanks for the replies.
Well, to start with, my boat is located in freshwater for the near future. That means that the ‘water’ is about as good as rocky New England soil.
You are correct that I need to use a capacitive connection to the water. The method that I am currently using is a KISS (check it out at http://www.kiss-ssb.com/). It really does work. I am just trying to “make it better”
So, I was happy to read your response Fred, that using an analyzer to measure the impedance is the way to go.
My antenna coupler was designed for a wire antenna in that it has one connection for the vertical antenna and a separate connection for the counterpoise. It is not designed to use a PL-259 connector. The coupler also has a built is coax cable to connect to the radio itself. So I will have to measure the impedance after the antenna “system” after it passes all the above. I am hoping that since all measurements will be made using the same combination, it will be acceptable.
I will be trying these in addition to the KISS
1) Connect the counterpoise connection to the bow railing
2) Connect directly to the engine block, and through that, to the entire DC wiring system.
3) This vessel is NOT bonded in that all the underwater metal parts are MOT wired together, so that is not a possible addition to the counterpoise.
I will not be back to the boat until May, so I will let you all know the results of my testing.
73,
Bill

[Fred Kemmerer]

Hi Bill,

Thanks for the update. We’ll look forward to hearing how your testing went when you can get back to your boat. Good luck with the project!

 

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