The KISS SSB Counterpoise - Revealed ( with Pics )

[Paul Elliott]

Originally Posted by plebian99

The loss varies by as little as 1 to about 2 ohms across the 1 to 30mhz range. You also have to consider the dielectric constant of the ground medium VS frequency. The point is that you can calculate the overall radiation efficiency very accurately. [...]

Why don't you just show us how it's done then?

[Freedom45]

Uncertainty Principle - YouTube

[transmitterdan]

Originally Posted by plebian99

The loss varies by as little as 1 to about 2 ohms across the 1 to 30mhz range.

We may be discussing different things. I am talking about what is inside the boat and you seem to be talking about the properties of the water outside the boat. The complex impedance of sea water is well documented. What that has to so with antenna efficiency on a sail boat is virtually nothing. That mainly controls the propagation once the signal leaves the boat.

The variations in the ground circuit path (between the tuner case and the vertical radiator) is mostly in the boat. Because tuners are single ended there can be problems when the tuner case is not connected with low enough impedance to the water. The case ends up with RF voltage relative to boat "ground" and the the coax becomes a radiator and significant power can be wasted and even interfere with on board systems. The KISS is claimed to fix these problems without making a connection to anything else on the boat or in the water. The claim is you can throw it anywhere down below and it will always work. There is no reason to believe this is true in my experience.

Knowledge of SSB tuners tells us that to maximize the voltage fed at the base of the vertical we should make a low impedance connection from the tuner case to the sea. How low impedance this has to be exactly isn't well documented. Neither is there any instrument available that can measure it. The only way we can compare different installation scenarios on a given boat is to measure the far field strength for each case. Whichever grounding method gives the greater field (received signal) is "better". When independent testers have made controlled tests the "best" solution has been a short wide strap from the tuner case to a submerged thru hull. And not surprisingly this is the cheapest solution. Sometimes there is no convenient thru hull and owners do not wish to add one. But anything else has been shown to be "less efficient" in testing.

For a fixed length vertical radiator as frequency varies there is a wide variation in radiation resistance and a correspondingly wide variation in the magnitude of current returned to the case of the tuner. The lower the return current the less important the impedance of the "ground" connection becomes. But this current varies for every frequency and antenna/boat configuration. Sailors want a system that works well at as many frequencies as possible.

I think most people reading this thread would want to know what point you are trying to make other than that all the other posters are ignorant.

[klaus53123]

Hi folks,
I have read through the whole threat and I am not sure wheter or not I now know what to do. I am in the process of preparing for the General licence, so I am still trying to climb up the learning curve. So please forgive me for some ignorance on the knowledge level.

I want to ask a very practical question and I would be a happy man, if you could just try to guide me in a certain direction.

The situation on my boat:
Antenna: isolated backstay
Boat: Katamaran, 39'
Location of the tuner: port side sugar scube
possible area for a copper foil to be layed out 1,5 sqm (16sqft)
Dynaplat: installed, but do not know how well it is still working
Distance from ground connection of the tuner to Dynaplate through hull bolts: 1,5m (5 feet).
Tuner: CG 3000
TRX: Yaesu 857
Bronze through hull connections: none (all old existing once converted to plasic)

From all I learnt do far (or better what I believe I learnt so far) I understand I have the following options for ground or counterpoise
1. Kiss
2. Just a whire in some or similar lenght as KISS
3. Just any random combination of copper wires thrown into the bilge
4. Copper strap from tuner ground to Dynaplate bolts
5. Copper foil laid out and glued to the hull with maximum possible area of 1,5 sqm (10 sqft due to onbord restrictions), with or without a connection to the Dynaplate.
6. Any combination of the measures 1-5

What is your opinion which route I should go?

Another question with respect to the Dynaplate: I have no clue how much the thing is already rotton. I have cleaned the outside surface with sanding and stell brushing so it is shiny again. However what about the inside structures which I cannot reach? I bought the Dynaplate with the boat (or the other way round), so far I have not heard any good things about the Dynaplate (massive deteriation over short time). Why do you guys still think it is a good measure to connect the ground to the sea water?

Many thanks for your advice
Klaus

[Paul Elliott]

Since you've got a Dynaplate, I suggest that you run the copper strap to it from the tuner. Scrub the Dynaplate surface occasionally and it should work well for you. Any or all of your other options (except possibly #3) should work reasonably well. Generally the more stuff you connect to the tuner ground the better, but the Dynaplate alone is probably taking you close to the point of diminishing returns.

The Dynaplate has no "inside structure", it is merely a piece of sintered bronze. As long as the bolts are firmly attached it should be fine.

[transmitterdan]

Klaus,

I agree with Paul. Run a wide (10-20cm) copper foil from the tuner to the dynaplate bolts. If possible I would move the tuner closer to the dynaplate if that is feasible. Better to have 1.5m more antenna wire and 1.5m less ground foil.

If you have room around the dynaplate to install some additional copper foil against the hull below the waterline that will probably improve performance a bit.

Forget about just throwing wires into the bilge. That is nonsense in my opinion.

[SoonerSailor]

Klaus -

If your path and connection to the Dynaplate are good, additional ground plane strategies might help but only incrementally and you may not notice.

Throwing some ground lug connected wires into the bilge was touted as being equivalent to the KISS, not as an ideal. It wouldn't hurt your setup however and might help as an adjunct.

It might be good to add alternative to the Dynaplate since as it becomes fouled it could lose efficiency.

Chip

[transmitterdan]

Originally Posted by SoonerSailor

It might be good to add alternative to the Dynaplate since as it becomes fouled it could lose efficiency. Chip

Fouling should not much affect the efficiency of a dynaplate as an SSB return. Some of the dynaplate marketing is needless hokum in my opinion. They claim that lots of little imperfections in the surface improves the efficiency. I don't think this theory stands up to scientific scrutiny. But a dynaplate works ok even without the imperfections and it is made from high quality rugged material. They have a good and useful product. But I would challenge anyone to actually make a controlled test that shows significant degradation of efficiency because the submerged plate is fouled.

[klaus53123]

Originally Posted by transmitterdan

Klaus,

I agree with Paul. Run a wide (10-20cm) copper foil from the tuner to the dynaplate bolts. If possible I would move the tuner closer to the dynaplate if that is feasible. Better to have 1.5m more antenna wire and 1.5m less ground foil.

If you have room around the dynaplate to install some additional copper foil against the hull below the waterline that will probably improve performance a bit.

The antenna tuner is not yet placed, so I can really optimize the location. I find the above statement interesting as in the past I have always been under the impression that the advice is rather to keep the feed line to the real antenna as short as possible. Some people advice on "not more than 0,3 m (1foot). I am probaly able to reduce the feed to the ground to approx 0,5m (1,5 feet) by mountig the tuner to the rudder axes. In that case the copper strap would just "hang in the air" with no contact to the hull. Is that a problem? Antenna feed line in this set up would than increase to around 2 meters, maybe 1,5 meter (5-7 feet). What are your opinions?

[SoonerSailor]

I think a shorter feed line to the antenna would be more important than a shorter distance to the dynaplate. The RF ground benefits from more area, while the radiating vertical antenna benefits from being free and clear, i.e. away from grounded elements - and the feed from tuner to backstay is actually part of the radiating antenna.

[Paul Elliott]

Originally Posted by transmitterdan

Fouling should not much affect the efficiency of a dynaplate as an SSB return. Some of the dynaplate marketing is needless hokum in my opinion. They claim that lots of little imperfections in the surface improves the efficiency. I don't think this theory stands up to scientific scrutiny. But a dynaplate works ok even without the imperfections and it is made from high quality rugged material. They have a good and useful product. But I would challenge anyone to actually make a controlled test that shows significant degradation of efficiency because the submerged plate is fouled.

I've been meaning to suggest that the sintering and surface roughness of the Dynaplate do nothing to improve its performance as an RF ground -- the irregularities are too small to have any effect at the SSB wavelengths. It probably improves the DC grounding (not that we care about that), and does no harm at radio frequencies, but I suspect that a solid block of bronze of the same dimensions would have identical characteristics as a radio ground.

[transmitterdan]

Originally Posted by klaus53123

The antenna tuner is not yet placed, so I can really optimize the location. I find the above statement interesting as in the past I have always been under the impression that the advice is rather to keep the feed line to the real antenna as short as possible. Some people advice on "not more than 0,3 m (1foot). I am probaly able to reduce the feed to the ground to approx 0,5m (1,5 feet) by mountig the tuner to the rudder axes. In that case the copper strap would just "hang in the air" with no contact to the hull. Is that a problem? Antenna feed line in this set up would than increase to around 2 meters, maybe 1,5 meter (5-7 feet). What are your opinions?

Klaus,

The "real antenna" begins right at the antenna bolt on the tuner. Everything from there onward is the antenna.

It's ok for the ground foil to run straight to the dynaplate even through the air. You may wish to insert a parallel bank of capacitors in this foil as explained here: http://www.westmarine.com/webapp/wcs...s#.UmYP9Yx5mSM

If you want to add foil against the hull around the dynaplate that's ok and not a bad idea. Increasing the area of the foil may help a bit but what does the most good is connecting the foil to submerged metal. The small extra length of the antenna feed cable will not hurt anything. Try to keep the antenna wire spaced 50cm or so away from any other metal that is connected to the water. Don't wire tie it to grounded metal.

[transmitterdan]

Originally Posted by SoonerSailor

I think a shorter feed line to the antenna would be more important than a shorter distance to the dynaplate. The RF ground benefits from more area, while the radiating vertical antenna benefits from being free and clear, i.e. away from grounded elements - and the feed from tuner to backstay is actually part of the radiating antenna.

The antenna begins right at the tuner output bolt. By keeping the grounding copper foil short it allows the maximum current in the antenna and reduces inboard interference.

[s/v Jedi]

Originally Posted by transmitterdan

The antenna begins right at the tuner output bolt. By keeping the grounding copper foil short it allows the maximum current in the antenna and reduces inboard interference.

Sorry Dan, your advice is not right. The tuner must be placed so that the antenna wire (most use GTO wire) is as short as possible. Every inch that is not in an optimal radiating position is extra loss, while the length of copper foil is much, much less critical.

The simplified way to envision this is to take total length of antenna wire from tuner to mast head. Every percent of that length that is inside the boat, is a percent loss.

[transmitterdan]

For a metal boats this may be so but for plastic (and most wood composites) the boat does not much affect radiation. The inductance between the tuner and the water makes a much bigger effect.