Outdoor antenna setup

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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While i forgot to look up line losses for RG-6 quad shield vs low loss foam twin-lead at work today, i just happened to run across an "antique" GC Electronics catalogue that i had handy from 1976 !!! In it, i can find a multitude of antennas that list extreme distance FM reception. One of them lists 220 miles on FM ( this antenna has a 110" reflector and an absolutely huge boom ), one lists 190 miles on FM with 29 elements / 111" boom, another lists 120 miles on FM with 21 elements on an 85" boom, another dedicated FM antenna lists 150 miles on FM using 19 elements, another lists 190 miles on a 95" boom, etc... Obviously, these ratings are probably best case scenario and probably just a bit optimistic at that. None the less, they state that reception of signals within the FM broadcast band is possible for WAY, WAY over 100+ miles. Obviously, this would require a proper antenna installation and both good receiving AND a solid transmitter signal to do so.

While some of you may find those figures hard to believe, i can at this very moment pull in a local low powered FM station that is appr 30 - 40 miles away from me with no problems whatsoever. While you say that this is NOTHING in terms of distance, i am doing it using a 6' piece of coax as an antenna with NOTHING connected to it. The coax is simply connected to the 75 ohm antenna jack and lays horizontally across a shelf. There is the typical "copper stub" exposed that one would normally have hanging out of an "F" connector and that is it. As such, i'm getting 30+ miles of FM reception in stereo on what is basically a 100% shielded conductor. In effect, this has less capture area than if i literally had a coat-hanger stuck in the antenna jack.

While it is true that i have relatively flat terrain between my location and the transmitter, if you can't get 100+ miles out of a KICK ASS directional antenna installation mounted outdoors and up relatively high and in the open, you better think about buying some better gear or moving out of the caves down in the valley. There is NO reason other than having a poor installation and / or poor quality receiving gear that you should not be able to pick up a multi-kilowatt station 100+ miles away. That is, unless you have other nearby stations operating on the same frequency.

If local stations are not on the same exact frequency but are close enough to cause interference to the distant ones that you want to hear, you need to increase the selectivity and adjacent channel rejection of the tuner you are using. You can do this via the use of what is called a "pre-selector" in the radio communications field. Magnum Dynalabs markets one of these devices and markets it under the name of "Signal Sleuth". This device tightens up the front end of the receivers by fine tuning the "Q" or bandwidth of the received signals. As such, you can effectively "null out" unwanted signals simply by fine tuning the filter. Keep in mind that you would have to fine tune these filters for each individual station or frequency that you were trying to pull in.

Besides being able to "pre-select" the quality of the signal being fed into the tuner, it can also increase the quantity i.e. "amplify" it. This should increase the signal to noise ratio and improve stereo separation.

For the record, i'm pulling in that local "weak station in the distance" using a tuner that i paid $29 for from a pawn shop in Indiana. Sean
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Folks, i understand how all of this stuff works. I make my living working on, modifying and using radio communications gear. I also know that as frequency rises, ground wave transmission distance falls off. I also know that various modes of operation offer greater communications range i.e. AM transmits further than FM for the same average power levels when used on the same frequency, SSB ( single sideband ) transmits further than AM, morse code transmits further than SSB, etc... While some of you might not know it, this is the reason that morse code is used rather than voice communications in times of distress or poor conditions i.e. it has the most chance of getting through.

My business partner is going to bring in an article for me to check out written by Gordon West. He is a reknown amateur ( ham ) radio operator that does a lot of work with antennas. In this article, he is working with SSTV ( slow scan tv ) signals in the 400+ MHz range. SSTV is exactly what it sounds like i.e. a television broadcast that uses slow scan or "reduced resolution picture frames per minute". The distance that he was able to transmit a visible / audible signal at this frequency range is quite incredible according to my business partner. Given the fact that he was appr 4X higher in frequency than the commercial FM broadcast band AND transmitting video makes this even more interesting given this thread and the theories discussed in it.

For the record, we've been able to talk 100+ miles base to mobile using what is called "simplex" ( no tower mounted repeaters ) on the two meter amateur band. The two meter band primarily uses FM as a mode of communications and is 40 MHz higher in frequency than the FM radio. Obviously, this means we were using similar mode of transmission at a higher frequency making this even more difficult. The fact that we were in a "hybrid" ( big base antenna mounted up high to a little car mounted mobile antenna on the ground ) situation stresses that this type of range is quite easily obtained. Keep in mind that we were using 100 watts of power for each transmitter. Given the fact that FM radio stations use THOUSANDS of watts and both the receiving station ( your outdoor directional FM antenna ) and the transmitting tower would in effect be using "base" i.e. BIG outdoor antenna systems mounted up relatively high off the ground, i have to once again stress that this type of range should NOT be a problem. Sean
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