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      Abbreviated rules   07/28/2017

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allene222

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About allene222

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    SF Bay
  1. Masthead VHF antenna and cable

    I was not talking about CB antennas but rather using a 2m HAM antenna for the top of a mast. That was basically all that people had and a lot use them. My impression is that the "racing" antennas are little better. But I am not seeing antennas that are clearly a problem like the last time I looked. Maybe they were driven off the market by legal concerns. If I were to put my antenna under water, the water would be part of the antenna but it is not underwater. My antenna has no connection to the water. The water is part of the transmission path, but not part of the antenna. It will reflect any energy that hits it but the water directly under my boat is getting very little energy because the pattern in horizontal with very little going either up or down.
  2. Masthead VHF antenna and cable

    Any quality antenna on a tower will not use the tower as its counterpose. Some marine antennas are that way but what I am warning about is using 17 inch antennas that use the mast as the counterpose. There was a link to an antenna that specifically said it did not need a ground plane. That was likely just fine for using on top of a mast. I am curious why that was a Europe only antenna. I am kind of old and some of my information might be almost as old so perhaps the vast majority of 17inch antennas are well made and will work fine on top of a mast but I am also old enough to know that a lot of what you buy is crap. I have noticed that since I started discussing this topic a few years ago, many of the shorter antennas are no longer on the market. Maybe vendors have wised up and are isolating their antennas from the mast. It would take a coil and some probably some ferrite. I honestly have no idea because I make my own antennas. My particular antenna is a dipole with both and active and ground element. The lifelines are also part of the ground element and my SWR meter said the match was excellent. I can't see where the water has anything to do with it. it is just the water, not part of the transmission antenna. Now the water is there but I don't think it will have the effect you said. There might be multipath issues but that is a different story. Again, the OP asked what I was doing. My only "advice" would be don't use an antenna designed to go on the roof of a car on the top of a mast. That was, at one point, common practice. Perhaps it is no longer the case. I guess I should also add, if you are putting an antenna on the top of a mast, consider the loss in the coax. it can be significant. I am an Electrical Engineer and a HAM. Perhaps that gives me a false sense of security in what I am doing. I have the test equipment to make sure my antenna is working and matched but that doesn't mean it has good range. I just know it works for me. As some of you know, I was hit by a large schooner and dismasted. Wouldn't you know that they hit me right in the pulpit about a foot from where the antenna was. The antenna ended up on deck and people could hear me transmit but I could not hear them. If it had been on the top of the mast, it would have been in the water. I am completely happy it was not on the top of the mast.
  3. Masthead VHF antenna and cable

    1 meter is good. Make sure it is RF isolated from the mast and the coax.
  4. Masthead VHF antenna and cable

    1) That model is for over land. If you are interested in over land, use it. You don't need scattering if you have ducting and that is what you have over water because the dielectric constant of moist air (near the surface of the water) is different that that higher above the water. This causes the radio waves to follow the curvature of the earth as they are bent by the ducting. Use AREPS for radio propagation over water. It was developed by the navy. They seem interested in the subject :-) 2) A good vertical dipole antenna and the 3 meter antenna have patterns that are more or less horizontal so most of the energy goes out toward the boat you want to talk to. As you make the ground element longer, the pattern is shifted away from the long ground. If you get along enough ground element, the pattern is almost straight up. The mast is pretty long. This is helped somewhat by the rigging and the thickness of the mast. Model it with 4NEC2. The pattern is decisively up. On the other hand, a rail mounted antenna pattern is disturbed by the lifelines if they are metal. When I built my antenna, I modeled my stern pulpit and lifelines. They actually helped the match of the antenna. I explained it as the dipole would have been 70 ohms and if the rigging were solid it would have been 35 ohms. It ended up at 50 ohms, just like you want. I can't run AREPS but a HAM friend can and did it for me when I was designing my antenna and again for the conversation with Stan for his parameters. My particular goal was to be able to talk to the Coast Guard and they have very high antennas. I must say that I had very little interest in using the heavy coax that is required of the offshore racing specification or in putting a large antenna at the top of my mast. Stan's concern was that we had not modeled boat to boat communications and he thought that was important. He was also concerned that specifying an antenna down on deck level would be difficult. I guess I would agree with that as well as I spent a fair amount of time doing the modeling of my boat. In addition, people are constantly bending my antenna when we raft up so there is that as well. My challenge of the 3 meter vs a poor masthead antenna was not based on an antenna like the shakespeare one in the link. That antenna does not need a ground plane and is really a 1 meter antenna coiled up. It should not have the problem I mentioned in 2 above. A 1 meter antenna would be even better. But many people use antennas that have the problem outlined in 2 above. They also use cheap lightweight coax. If that is what you are going to do, I say you are better with an antenna on the stern pulpit. If you are going to use a good antenna like the link and low loss coax, the masthead will be better than a 1 meter antenna on deck. Might still not be better than a 3 meter one but I can't really say that for sure. Bottom line, I am not trying to convince anyone. I am just offering my view and you can take it or not. I just think that a lot of people would be better off with antennas on the stern because they don't use the right coax or the right antenna.
  5. Masthead VHF antenna and cable

    I really have no idea. I do recall talking from Catalina to the mainland on a 1 watt HT as a kid. They were CB HTs so perhaps that is different as well. The only way to tell is to do a test. That said, I would bet that an 8 foot antenna on the stern would outperform a 17 inch one on the masthead. If I really wanted range, that is what I would use. I gave one to a friend thinking that might answer the question. He said it worked great. Oh well.
  6. SCIENCE!

    This made me think of another sailing analogy. I worked with a guy who sold his house and bought a boat to sail the South Pacific. He had GPS and the best charts. He was headed toward a reef but he knew the charts were not accurate so he stayed 5 miles off. What he didn't know was that the charts were not even that accurate and he hit the reef. Hard aground on the reef. They could walk off the boat and were knee deep in water standing on the reef. He took an anchor and all the line he had on the boat and hung it off the stern and it didn't hit ground. So here we are with inaccurate charts (models) but 97% consensus that we are headed to a reef. What I hear is one side saying that going 20 miles out of our way to avoid the reef would take too much time so let's just continue on our present course. The other side says, we better change course so we don't hit the reef and die. My co-worker used a HAM radio to call for help and was rescued but left his boat and life's savings on the reef. I am too old to see how accurate the climate models are so I don't really care.
  7. SCIENCE!

    Think of it like the current on SF bay. The prediction may be an ebb current but you are in a whirlpool and the water near you is coming in. Even though you can't tell exactly where the tide line will be, you know that when the sun and moon are where they are, that the tide will be going out. Same with the temperature. Climate change is predicting a very small change in the average temperature compared to the variations across a season or across a day. But the average over a year is much easier to predict. Many things are like that. Use a GPS to read your speed. It will have noise of a knot but average over 15 seconds and you can get it down to .02 knots. The bigger the sample (global) and the longer the time (decades) the less noise in the result and the easier to predict with precision.
  8. SCIENCE!

    1) Depending on exactly how you measure the expert consensus, it’s somewhere between 90% and 100% that agree humans are responsible for climate change, with most of our studies finding 97% consensus among publishing climate scientists. 2) The greater the climate expertise among those surveyed, the higher the consensus on human-caused global warming. ref Basically it is the big picture that is settled. The model itself is being refined. F = M * A is very well accepted but Einstein said there was more to it and people have shown he was right. But F = M * A is still a very good approximation. And I think you would get 100% agreement that applying a force to a mass will cause it to accelerate.
  9. Masthead VHF antenna and cable

    I don't recall saying that and we never simulated that. The handheld example had a 1 meter antenna at the other end. Two handhelds would cut that range way down. I have not run it but likely half as far and only over water.
  10. I use NOAA data to provide free weather information for sailors. Sounds like that will continue so at least that is good. I had 2500 hits for weather data yesterday. Nothing compared to the big guys but the US Coast was one of the users yesterday (and most days) so I must be doing something right. Go on the site and click on the Weather tab. Enter your location and the entire page is set up. Customize if you wish. The Coast Guard made lots of input to the site for example the ability to list the airports that report conditions so they could encompass a large area without listing airports they could not land at. Normally, you just set a radius and get reports from all airports in that area. I think the default is 30 miles but you everything like that can be customized. Here is an example for my home port and home city. https://goo.gl/oTrRj2 Allen http://L-36.com/
  11. SCIENCE!

    All of you anti-american Trump haters should leave America ASAP. This man is YOUR president whether you LIKE IT OR NOT. So get behind him and support him! This is the problem with this country, you whine and whine about him, when he's out there representing our Country. God bless America and Trump. He is a SHINING example of what someone with severe Alzheimer's can do.
  12. SCIENCE!

    Link? All I can find is an opinion piece by Peter.
  13. SCIENCE!

    You talking about Peter Ward?
  14. Masthead VHF antenna and cable

    I probably should say something about the conclusion Stan and I came to. There are really three cases. 1) Boat to Coast Guard. The simulation says very small advantage to masthead but assuming 3 foot antenna. Probably an advantage to the lower antenna if a 1/4 wave is at the masthead 2) Boat to mob with a beacon. Again, slight advantage to masthead in the simulation using his specs. 3) Boat to boat. This was not simulated so I don't know. Stan thought that a masthead antenna would out perform the simulations due to some technical factors about mast capacitance. He also felt that boat to boat would be better with masthead antennas, something I could not comment on. There was the added complication of writing a spec for rail mounted antennas so that you would get the performance anticipated. Finally, Stan felt that while sailors don't like the weight aloft, since everyone had to have it and this is afterall a race, it was fair. He felt racers would not like having an antenna down near deck level as it would get in the way of things. So that is where it was left. No compelling reason to change the spec, something I agree with. But my boat has the antenna on the transom as I am not subject to the offshore rules. And the question I was asked was what do I use.
  15. Time to Un-Zip! Wheeeeeeeeeeeeeee...............

    I had that and put the jacket in a washing machine. The zipper came out fine but the pull tab was so corroded that it to was washed away. Good luck.