I don't want to completely contradict TWL's post, but those figures do not sound right to me at all. I think that what i've read relates to reception distances being limited to appr 15 degrees beyond the horizon. This is strictly discussing "ground wave" and not a signal that is "skipping" across the Ionosphere. Obviously, atmospheric conditions and local terrain will affect reception regardless of how good of an antenna you have or how high it is mounted.
Regardless of all of that, you would want to run the largest directional array that you can and get it up as high and out in the open as you can. A specialty antenna dedicated to FM reception rather than a combo TV / FM design should work noticeably better. For the record, John Dunlavy is the designer / engineer that holds the patent on the "log periodic" design that is so commonly used on many FM & TV antennas. John started out as an RF engineer and switched over to audio much later in his career. This could be why he has a slightly different approach to doing things as compared to most audio engineers.
Obviously, line loss at that long of a run is another consideration. While there is some very excellent low loss cable available for very reasonable cost ( Quad Shield RG-6 ), the impedance transformers ( adapters ) that are required to mate it to most antennas and many tuners can DRASTICALLY knock down the amount of signal that the tuner actually receives. From what i recall, most "generic" impedance transformers that are commercially available knock down your signal by appr 3 dB's. This means a reduction of signal of 50% if you have to run one of these at the antenna. If your tuner does not have a 75 ohm coaxial jack on it and you have to run another transformer there, you are only going to end up with appr 25% of the original signal. If you are going to run a splitter, count on even less.
With all of that in mind, running low loss foam twin-lead may be a better alternative. While twin-lead may be more susceptible to other forms of interference and is harder to install correctly for those very reasons ( you have to use "stand offs" to minimize impedance problems ), try looking at it this way: The stronger the on-band signal you have making it down to your tuner, the less noticeable any other forms of interence will be. That is, unless you have a consistent problem with high level interference on a regular basis.
I'll try and figure out the difference in loss between QS RG-6 and low loss twin-lead at FM broadcast frequencies. In the meantime, you better sit down and prepare yourself for how much a good antenna and adequate rotor will cost you. Sean
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Regardless of all of that, you would want to run the largest directional array that you can and get it up as high and out in the open as you can. A specialty antenna dedicated to FM reception rather than a combo TV / FM design should work noticeably better. For the record, John Dunlavy is the designer / engineer that holds the patent on the "log periodic" design that is so commonly used on many FM & TV antennas. John started out as an RF engineer and switched over to audio much later in his career. This could be why he has a slightly different approach to doing things as compared to most audio engineers.
Obviously, line loss at that long of a run is another consideration. While there is some very excellent low loss cable available for very reasonable cost ( Quad Shield RG-6 ), the impedance transformers ( adapters ) that are required to mate it to most antennas and many tuners can DRASTICALLY knock down the amount of signal that the tuner actually receives. From what i recall, most "generic" impedance transformers that are commercially available knock down your signal by appr 3 dB's. This means a reduction of signal of 50% if you have to run one of these at the antenna. If your tuner does not have a 75 ohm coaxial jack on it and you have to run another transformer there, you are only going to end up with appr 25% of the original signal. If you are going to run a splitter, count on even less.
With all of that in mind, running low loss foam twin-lead may be a better alternative. While twin-lead may be more susceptible to other forms of interference and is harder to install correctly for those very reasons ( you have to use "stand offs" to minimize impedance problems ), try looking at it this way: The stronger the on-band signal you have making it down to your tuner, the less noticeable any other forms of interence will be. That is, unless you have a consistent problem with high level interference on a regular basis.
I'll try and figure out the difference in loss between QS RG-6 and low loss twin-lead at FM broadcast frequencies. In the meantime, you better sit down and prepare yourself for how much a good antenna and adequate rotor will cost you. Sean
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