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About Ramius-II

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    RC-Cam Visitor

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    Lomita, CA
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    R C Submarines
  1. Hi Guys: I did a little more research and the pitot approach is the best for high speeds as there is a fair amount of pressure to work with. There is an alternative method which is via a "flow meter". Basically, it's a tube where the inside is shaped like a wing. The advantage is by looking at the pressure comming into the tube there is a vacuum on the back side making the whole thing more sensitive. The ratio of the inside of the tube (largest part) to the hole is 3:1. This comes from an air flow engineer at the Honeywell Corporation. I have not tried this approach yet and plan to as a comparison to the pressure/static pressure method. Best, Ed
  2. Hi Terry: Brass is mostly copper so that is where is falls. What I was pointing out to you is that a dipole does not do as good a job as say a ground plane style of antenna. Dipoles are typically 300 ohms so again, I wonder if you have a true dipole? Most off the shelf systems I've seen use a single wire off the output of the transmitter so not seeing what you have or what you are working with does make it a bit difficult to come up with soild recommendations for improvements. Generally, in airborne applications there is no advantage of transmitting up above the aircraft unless you are at a lower frequency and plan to bounce off the ionisphere. Best (IMHO) would be a ground plane type if a colinear is not practical. Again, pictures of your system would be helpful. Best, Ed
  3. Hi Terry: If you go to www.cool-amp.com you can see the product. basically, if you have a clean surface of copper or brass, you take a damp cloth, add some of the powder and rub it onto the surface you wish to silver plate. In the order of conductivity, it's silver, copper, gold then aluminium. Silver is the best conductor and notice most high frequency components are silver. Moving on to antenna's, you might look at using a colinear antenna for the transmitter. The advantage is you can get some very good gain and still remain omni-directional. At 2.4 GHz the lenghts are short, therefore with a colinear, the first section is 1/2 wavelenght and the other sections are 1/4 wavelenght. As you add sections, you increase gain so the only limit is how much lenght you can accommodate. A basic colinear takes the second section and you attach the center conductor to the shield of the first section and the shield of the second section to the center conductor. You alternate this for as many sections as will fit. Most transmitter installations I've seen only use a whip antenna with no real ground reference as part of the antenna, thus the results are minimal. Best, Ed
  4. Hi Terry: I think what you might be missing is several key factors. Receive gain is best accomplished with the antenna. A simple co-linear antenna or PC board yagi can give as much gain as the amplifier. The coax you mention is terrible for 2.4 GHz. Rule of thumb is every 3 db is 1/2 the signal. The coax you mention has a loss of 3.2 db per foot! If you went to RG-6 it would be more like .8 db per foot. Part of the "getting the best reception" formula is to have the transmitted signal be as strong as possible. Again, incorporating a good transmitting antenna, especially with a decent ground reference can make a big difference. No amount of amplification can make up for what is not there to start! It's the old engineering question: Is it better to blow through a straw or suck from it?" One recommendation to solve your basic mismatch problem, is to write to the designer of the pre-amp and ask him/her how to change the output impedance to 75 ohms to match you receiver! You may find the modification very simple. Second is to make the antenna system as efficient as possible. This can be done by "tuning" the antenna, that is, cutting the antenna lenghts to be resonant for the exact frequency you are using or using larger elements to make the antenna more "broadband". Silver plating components with a product by Cool Amp, also helps. Best, Ed (WB6NSN)
  5. Wow! Thanks Jeff! I have not done the math, and with 0-1 psi being represented by 0-5 volts and a 12 bit A-D I think it will work Thank you so much! Best Ed
  6. Hi All: I've been searching for information on using a differential pressure sensor (Pitot vs Static pressure) to measure airspeed. I know the pressure is less than 1 psi, what I do not know is how much pressure represents what speed? The plan is to program the information into a PIC. Can anyone help or point me in the right direction? Thanks, Ed Ramius-ii-AT-earthlink.net
  7. Hi Dee: Just a few inputs for you. Adding wire can reduce the transmitters signal if the wire is not a "low loss" type. Typically, the smaller the cable, the more loss. Next is frequency. The resonant frequency of water is 2.4 GHz which means the water will absorb more signal than other frequencies. This is why microwave ovens are on this frequency. Even still there are some people who are using 2.4 and can receive a signal from a depth of 18 inches with 800 mw of power. Best, Ed
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