Thread: 28.3MHz ???
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Old 01-26-2009, 09:52 AM
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Groucho Groucho is offline
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Join Date: Aug 2005
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Brian,

I will echo Bruce's comments about the sunspot cycle. The only 10M contact I have made in the last 5 years was just last summer when I managed to talk to California, and even then the QSB (Fading signals, either fading in our out or both) was intense.

The reason Bruce suggested the dipole point north and south is so you can get the best radiation to where you most likely will talk. The ends of the dipole antenna represent nulls, or points where the radiation will be extremely low if at all. So north-south direction will give you good radiation toward Cali and the east coast, whereas east-west setup would have you talking to Canada and South America. Just a matter of preference and possibly the most success right now.

One question, do you have a balun at the feedpoint of the antenna? Meaning, you say you have the pl-259 at the tuner, and the other end you have a BNC connector. I get the PL-259, that's easy. Is th BNC connector on the other end how the dipole from LGD came? I am just curious, because most times a simple dipole can be made by soldering the center conductor of the coax to one side of the dipole, and the shield to the other. I am not saying what you have done is wrong in any way, just wondering about the setup.

My next point would be the SWR without the tuner. I suggest anyone making a dipole trim it to the formula, and test it without the tuner, if possible. If your SWR w/o the tuner is greater than 5:1 or 6:1, or basically shoots off the scale, then something is wrong. I would first guess that maybe a math error was made, or the wrong frequency was used in the formula when compared to the actual frequency used to check SWR. The reason I suggest this method of testing is because if you try the antenna on your radio at the precise frequency you cut your dipole to length for and there is that much of a mis-match, then more calculating is in order.

I will regress a minute. Just because an antenna has a high SWR is not always bad. However, it is the most basic method to see how efficient the setup is performing. The radio you have (and most HAMs use) are set to see 50Ώ (ohms) at the output for the antenna. If the antenna is not at a 50Ώ (or within 10Ώ is good), then the mis-match causes output power to be lost in the form of heat. The tuner doesn't do anything but help eliminate that mis-match so that the radio thinks it sees 50Ώ. The tuner is basically a trick so that the radio doesn't fry its internal components when the mis-match occurs. My point? If you are trying to operate single side-band on 28.3 mHz, and your SWR is at infinity, the tuner may be able to "trick" the radio into thinking that there is a match of 50Ώ at the radio, therefore allowing the radio to put out maximum (100W in the case of the IC-7000) power. However, at a SWR reading of infinity, you may only be putting out 5W or less at the antenna. There is a formula for checking how different the power will be based on SWR that I will give if you want it.

Back from regression. If your antenna is not tuned (cut to length to achieve somewhat reasonable SWR first at a very specific frequency, then use the tuner to allow for moving up and down the band from the initial frequency) correctly, you may not be hearing anything for this reason as well. Any piece of metal will pick up radio waves, but remember that polarization as well as a list of other factors will determine the best antenna for receive.

My gut feeling guess? There is nothing on the 10M band, or no propagation (lack of sunspots) to help what might be on the air be heard well.

My suggestion? Lets get you a 20M dipole to test. Just hang it from a tree on a Saturday temporarily. Then listen to the 20M band on a weekend. My guess is that you will be hearing things all over the place. Then we have to get you up to speed with CW (or get you to upgrade your license) and you can set up dipoles for 20M, 40M and 80M and talk to a whole bunch of people.

Any of this help?
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