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Old 28-11-2019, 08:55   #16
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Re: Amplifier for 100 watt 12volt shortwave

FYI (shameless plug for my boating site)

http://briandphoto.net/WA6CCA.htm - This is Bill's vertical dipole discussion

http://briandphoto.net/KISS-SSB.html - John's analysis of the KISS-SSB and how to build your own

https://briandphoto.net/WA6CCA/Sea.pdf - Why use miles of copper, Gordon West says do this instead
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Old 28-11-2019, 12:42   #17
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Re: Amplifier for 100 watt 12volt shortwave

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Originally Posted by cburger View Post
Thanks all for replies here. Vessels HF equipment is 100 watts, antenna tuner to end fed back stay, Kiss for ground. I am new to all this and am enjoying the learning curve. My vessel is currently on hard for extensive repairs and I mess around with trying to raise hams on different bands. The last attempt was trying to reach Cruisers Net control in Houston, Tx. with the operator indicating he couldn't pull me out of the "Slop", considering he was over 1600 miles away from me in NY I thought that was pretty good and maybe a little more wattage would of made a difference. When I can find the time would like to install dedicated vertical antennas optimized for 20 and 40. Very often on 20 meters can here incoming signal crystal, and cant raise sender.
AhHa, now we know a bit more. I'm sorry to raise a big controversy which always happens when we talk about RF grounds on a boat. As far as I know, the KISS ground is literally no more than a few wires strung along the inside of the hull. If I am wrong, someone please correct me.

A few wires strung inside the hull is not a good ground. You can't get enough straight length in all directions to make a 1/4 wave ground, which is required if you just use wires. On land we can use a number (usually at least 8) wires preferably buried in the ground in a 360 deg. radial pattern from the base of a vertical antenna, loaded to look like 1/4 wavelength. The ground wires should be at least 1/4 wavelength at the lowest frequency in use.

For boats, we don't have the room for this, so methods other than just wires, are required. I think you'll get much better results if you connect a significant amount of copper sheathing epoxied to the hull inside the boat, immediately below the antenna tuner. This creates a capacitive coupling to the seawater. Also connect the engine, connect an outside grounding plate if you will, all with the shortest possible big wide copper straps to the tuner, and the tuner located just below the antenna feed.

You'll probably reduce RF interference in the boat and get a bigger signal without stressing your pocketbook or the batteries.
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Old 28-11-2019, 18:14   #18
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Re: Amplifier for 100 watt 12volt shortwave

Well then, tell that to the station I connect to 1100 miles away from my home with my DIY KISS which are four wires bundled into a 10ft tube.
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Old 28-11-2019, 18:53   #19
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Re: Amplifier for 100 watt 12volt shortwave

Short radials work differently on a boat compared with land based antennas simply because boat radials capacitively couple to an infinite counterpoise. On land, the coupling essentially ends at the radial.

Parenthetically, it’s a common myth that the best counterpoise is copper sheathing. As in the case above, the efficacy of the counterpoise is directly related to coupling with the water which has been shown to work effectively by interconnecting one or more thruhulls to the ground side of the antenna system.

And while I’m writing, the dynaplate so-called ‘ground plates’ are just that - for grounding and not for serving as a counterpoise. While they may serve that purpose, they are not ideal and can exacerbate electrolysis but creating multiple ground paths of varying potentials when connected to single use electronics.
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Old 29-11-2019, 15:01   #20
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Re: Amplifier for 100 watt 12volt shortwave

What power level you at now. MOst HF and SSB radio are already at 100-150 watts. so adding 100watts isnt going to help, Its not +100watts, its just 100 watts. As noted a 500watt amps would be the next level both those draw a lot of power. YOu would be better off improving the antenna system.
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Old 29-11-2019, 22:41   #21
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Re: Amplifier for 100 watt 12volt shortwave

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Short radials work differently on a boat compared with land based antennas simply because boat radials capacitively couple to an infinite counterpoise. On land, the coupling essentially ends at the radial.

Parenthetically, itís a common myth that the best counterpoise is copper sheathing. As in the case above, the efficacy of the counterpoise is directly related to coupling with the water which has been shown to work effectively by interconnecting one or more thruhulls to the ground side of the antenna system.

And while Iím writing, the dynaplate so-called Ďground platesí are just that - for grounding and not for serving as a counterpoise. While they may serve that purpose, they are not ideal and can exacerbate electrolysis but creating multiple ground paths of varying potentials when connected to single use electronics.
If you connect thru-hulls to the ground system how is that any different for RF grounding, from connecting an external ground plate? Seems to me you will have about the same result either way, though the dynaplate will give more area to couple and you won't worry about electrolysis there.

I agree that short radials on a boat work a bit differently than the land based case in fact they should not be referred to as radials in the normal sense, as you say they just provide some capacitive coupling to the water. That coupling can be very much enhanced with a square meter of copper bonded to the inside of the hull below the waterline, and using wide copper straps instead of wires for the "radials".

I forgot to mention any steel tanks could also be part of a good ground.

Each of these methods works a bit differently and there is no one "best" method. But I believe the best ground system will use a combination of all of them.
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Old 30-11-2019, 19:15   #22
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Re: Amplifier for 100 watt 12volt shortwave

We have to be careful about where we ground things. We are dealing with to monsters here; DC and AC. With DC being a voltage component and AC being a radio frequency component. The two should never meet without some kind of decoupling device. I know that modern antenna tuners are suppose to have decoupling capacitors built in, but damn if I can find them. Anyway, it is better to have multiple points of decoupling than to assume the device has sufficient decoupling.

JMHO
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Old 30-11-2019, 19:41   #23
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Re: Amplifier for 100 watt 12volt shortwave

All manner of things have some sort of "common ground" between DC and some form of AC. For example, NMEA 0183 typically has one side connected to -12v. The shield on the coax output of a VHF radio is typically connected to -12v. The base of a lot of VHF antennas is connected to the mast, thus grounding it to -12v. Some HF antenna tuners have the RF ground point connected internally to the -12v power connection. To isolate all of these requires a lot of care.

But the problem is less a matter of DC "grounds" versus "AC grounds" than it is a matter of single-point grounding and avoiding ground loops, i.e. multiple different ground connections between the same devices.

The above discussion does NOT reference the question of the connection of AC neutral wires to safety grounds.
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