You ask many questions in a short space.
I am a big fan of the straight, long/random wire antenna as a starting point. You can add loops, dipoles, active antennas, and other fancy antennas, but you should start with a simple long wire (really known as a "random wire") antenna, and enjoy listening to the radio right away.
Foremost, your long/random wire antenna will enable you to listen to the many interesting stations which are broadcasting from around the world without delay, while you construct other antennas, and test them against your initial random wire antenna, which will be your test or "control group."
Start with a simple wire antenna that has no coax cable feed line, but which uses a simple wire feed line - and locate the antenna outside your mobile home. Perhaps you could string one from one end of the home to the other, on poles attached to each end of the home, projecting higher than the roofline. Bring the feed line in through a window or some other crevasse, and start listening right away. Connect this to the high impedance terminal on your radio. You may or may not benefit from an RF ground wire connected to a copper/steel ground stake. (I do not get any benefit from one at my location, but things may be different at your lication.)
Next, construct that 40 foot long wire you mention, using coax cable feed line, and employ, perhaps, a 9:1 balun/transformer to match the high impedance of the random wire antenna element to the 50 ohm input on your receiver. Compare the performance of that second antenna to the initial random wire antenna you set up.
Then, perhaps, purchase one of the Kaito/Degen SWL loop antennas from one of our Chinese friends selling them on eBay for something like $16-$20 plus shipping, or, perhaps, from one of the American vendors for slightly more, depending on your socio-economic and political predilections, and threshold for economic pain. I have had good luck purchasing such items from Radios4you.com which charges a little more for these items, but has quick, reliable service. I have had good luck with from the Chinese guys on eBay, as well. There are other sellers, as well, many of whom are reliable, also. I am not picking favorites here.
I am not sure what you intend by "wrapping the coax cable around a homemade dog bone" -- Are you trying to make some sort of RF choke? If so, I would start out without it, and only add one if it becomes necessary to solve some kind of interference or noise problem you encounter. Usually, the most parsimonious solution is the best solution, and certainly the least expensive in terms of time and effort. However, post back if I am missing your point, and perhaps you could explain why your want to "wrap the coax" as you describe.
The purpose of a balun/transformer is to match the high impedance of the long/random wire to the lower 50 ohm input on your radio. You can use the high input connection and not use any impedance transformer, and see how it goes. You may get good reception with that simple arrangement.
Conversely, many suggest coax cable can reduce the pickup of environmental electronic and magnetic interference (noise) from household appliances, the home's electrical system, a television set, a light dimmer, florescent lights, and other sources of EMI/RFI in and around the home. The balun is a transformer to that converts the high impedance of the random wire down to the 50 ohm impedance of the radio input and matches the long wire impedance to the rated impedance of the coax cable (typically 50 or 75 ohms). Many times, however, you can feed the radio directly with a simple straight wire connected to the high impedance connector on the radio, and get listening with good results. You will have to determine whether or not you need to use coax cable in your case, depending on the noise and interference you receive at your listing location.
Keep it simple to start with, and compare other antenna designs to your original high impedance random wire antenna. If you do not like the notion of stringing your initial antenna from one end of your home to the other, you might just lay the initial antenna right on the roof (temporarily) as you compare it against other antennas that you install. As you get better antennas, take down the weaker ones, and continue building other ones, continually comparing them to what you know is a good performer.
You may find however, that one antenna works better one day than another, but on another day, it rates the other way around - depending on many often unquantifiable factors, including weather, propagation, directionality vis-a-vis the broadcast station you are listening to, various different frequencies, various different times of the day, and various unknown factors including good and bad luck.
Do not consider one antenna a weaker performer until you have compared it against another antenna(s) for several days under differing conditions at differing frequencies and differing times of the day and night. Only move to a different antenna design after much testing and consideration. I had up to seven antennas installed at my old home, and it amazed me that the different antennas were comparatively better and worse vis-a-vis the others under various differing conditions. Only after much testing and experimentation good one or two of them proved to be best, overall.
One final note concerning your intended long wire, which you say can only be 10 feet high. Make sure that it does not sag in the middle, and become a danger to yourself and others.
Just MY take. Best Regards. //// Richards ////
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bongo432002 wrote:
soon put up a longwire about 40'long and 10'high(best I can do)but I
would like to have them both just to have 2 antennas.
re..I'm going to wrap the coax around a
homemade 'dogbone'and
