Thank you all for the very informative discussion. I love this site. Len |
http://www.antennaperformance.com/
It's an "interesting" discussion. BIGO, given where you live, APS can probably service you directly or recommend a technician who does. BTW, the installation was not difficult for either the technician or my $pocketbook. Lots of listening pleasure from live Tanglewood Concerts this summer, and BSO in Symphony Hall in the winter. BIGO should be able to get both Boston and NYC. |
Fyne: you do not want a plain old grounding block; you want a gas-discharge type surge supressor, similar to Tru-Spec model GRB-ARM. The grounding block will shunt any transients on the shield back to a good ground connection, but will not protect the center conductor, which is where most of the damage can occur if induced into your receiving equipment, be it a TV, a radio tuner, VCR tuner, whatever.
Yes signal losses do occur, but not so much from the protection device itself as from the two type-F connections (input & output). Expect around 0.5dB to 0.75dB typical loss through the whole arrangement, which is quite acceptable if the entire system is properly designed. |
Cdc: Does this grounding block create a signal loss? |
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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Sean, the 60 mile thing is based on typical flatland topography and a typical transmitter and receiver height. Obviously, if you have a 1000' antenna at each end, you're going to do better. But the point is that FM signals are line-of-sight only, that is, they do not bend around the curvature of the earth. AM signals do bend, because they are much lower in frequency, but FM does not. It will occasionally bounce off the ionosphere if conditions are right, but that is not a reliable method of receiving.
Therefore, if you are able to physically see the transmitter from your house (at least in a theoretical sense, ignoring smog, the tree across the street, etc.), then you will be able to receive very low-powered stations with very little difficulty. If you can't see the transmitter, then it's instantly a whole different ball game. And all those giant antenna arrays are needed to get the BOUNCE signal, that is, an extremely weak reflection of the original signal, whether it is off a geographical feature (usually) or even a man-made structure. That is why it is often best to aim a highly directional antenna at a big mountain, sometimes even if it's nowhere near or even in the same direction as the actual transmitter. The bounce signal off the mountain may be stronger and cleaner than any other bounce signal you can get, and even then you aren't going to pull it in unless you have a very good directional antenna. |
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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Get a grounding block from Radio Shack ($1.99 or so). The grounding block mounts to the house and is grounded to a ground wire. You cut the co-ax and mount a connector and screw the co-ax into each side of the grounding block.
Prevents lightening from going into your tuner - a good idea! |
I'm sure that there are scientific ways to get the most from FM, but I believe there is room for luck and magic (this is a departure from my usual way of thinking) in getting it all to work the way you want it to. |
Agree with most of the above, FM reception becomes extremely difficult past 60 miles. If there are ANY large mountains in the vicinity, it is worth a try to aim your Yagi at the mountain and see if you can get the bounce signal. This will often be stronger and more consistent than relying on atmospheric conditions and random luck to get you a strong enough signal. Good luck... |
A 120 mile range is going to require a LOT of tower height but it can be done; typically a professional is required for such an installation. Antenna requirement is a very high gain Yagi beam design for this distance. Rotor is only needed if you have more than a single location (city) that you wish to receive from, otherwise it's not needed. RG-6 is the preferred coaxial feedline. No previous mention of a head amplifier above, but you'll definitely need one. I use a high-gain Wineguard amp mounted at the antenna, with the FM trap switched OUT. You'll have provision to go directly into the amp with 300 ohm balanced flatline, then out to the drop with 75 ohm coax. Power for the amp comes from a power inserter box located in the house; the low voltage DC travels on the coax center conductor but is blocked from your tuner by the inserter box. Install a coaxial surge arrestor (properly grounded) at the coax just before it enters the house; maybe even a 2nd surge arrestor downline from that one. You should still disconnect the antenna from all inside equipment when away on vacation, &/or during any thunderstorm.
The tuner requirement is for high sensitivity; I suggest a Magnum Dynalab such as MD100 or MD90, or the more expensive MD102 is what I use, along with their Signal Sleuth, which is an indoor RF preamp that's tunable & has variable gain + a bypass switch. The Sleuth is very low profile & fits right on top of the tuner, if desired. Fanfare also has some good modern tuners available.
You are going to have to spend a considerable amount of $ to set this system up properly in order to receive from that great a distance, so be prepared. |
I recommend the Antenna Performance Specialties APS-9 (I use this) or the APS-13 with a Channel Master rotor. USe a straight run of coax to the tuner; no amps, boosters, or anything. No wall plates, either, if you can swing it. Make sure you contract with an antenna installation specialist. If you tell them what you are looking for the technician will give you a realistic picture of what you can expect. He will also have the right cable in his truck.
I live in Manchester, NH and listen to Boston stations 60 miles away in wonderful fidelity. I also listen to stations on Cape Cod that are over 100 miles away. I use a modified Accuphase and a MC 7083.
Have fun. |
In Los Angeles, most of the broadcast transmitters are located on Mount Wilson at a height of 5400+ ft. This helps with the line-of-sight problem, adding another degree of arc earth radius and extending the range to 100+ mi through the Southland basin. Nevertheless, at a distance of 20 mi. from the KUSC (the premiere classical station in the area, 91.5 MHz) tower, I had to install an APS-14, a highly-directional, 12 dB gain antenna, on a 20 ft. roof mast with rotator, to receive it cleanly and avoid interference from a station from Mexico broadcasting at 91.7 MHz. This was with an Onkyo T-9090. |
Lightning is one reason I like mine under the roof in the attic. There it also does not alter the appearance of the house. |
Lightning can be a problem. I always unplug my stereo - including FM lead-in - whenever a storm is overhead. |
Does having an outdoor antenna subject your whole stereo system to the possibility of being fried by lightning? A salesman at rat shack told me lightning hit his tv antenna and not only took out his TV but even the two inch bolts screwed into his chimney were blown out of the brick. |
While I cannot comment on how the phases of the moon and the mating habits of insects affect the FM signal, I can pass on some real world results. I am running a very large Winegard TV/FM Antenna in my attic crawl space. The entire FM band is between TV channels 6 and 7, so a good VHF TV antenna will work as good as any FM only antenna, despite what the sellers of over-priced FM antennas will tell you. Just make sure the FM trap is OFF if the antenna has one. I do use Star-Quad RG6 coax cable. You could also consider a powered preamp to boost the signal. I find 60 miles is the best I can do for a quality FM stereo signal. I can get stations further out with the mute off and in mono for better sound. I would do slightly better if my antenna was outside. A bonus is that I also use it for television in some rooms that don't have cable/satellite hookups. A great web site for information on classic tuners is:
http://www.geocities.com/tunerinfo/ |
Sean, the earth's circumference is approximately 24,900 miles at the equator. This is where you will get the longest arc. If you divide 24,900 miles by 360 degrees, you get 69.16666 miles per degree. This is at the equator(longest arc) and is less at other latitudes and angles(the earth not being truly spherical, and all) and excluding terrain obstacles. So, our best case is 69 miles for one degree of arc. This is the horizon. Depending on the height of the transmitting and receiving antennae, the direct distance may be somwhat increased. However, any way you slice it, the 120 mile distance(almost 2 degrees of arc) is at the very outer reaches of possiblity for reception. This is compounded by the fact that it is just far enough to also be right in the typical "skip zone" for ionosphere reflection, so it is neither close enough nor far away enough for direct or rebounded signals. |
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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Hello Len. The classic outdoor antenna for FM is Channel Master's Stereo Probe 9, a 9-element directional antenna which has unfortunately been discontinued. The Winegard HD6065 is very similar and is still available for about $75. It should be mounted on a rotor for optimum results. Although 300 ohm twinlead has slightly less resistance, my advice is to stick with a good grade of 75 ohm coax such as RG-6. The coax has much better durability and interference rejection. Twinlead actually acts like an antenna itself and screws up the directional aspects of your antenna, reducing selectivity and promoting multipath interference. Check out starkelectronic.com for great information on antennas and as a source for the Winegard. (I bought my Channel Master from Stark but have no affiliation with them.) You might also check out a company called Antenna Performance Specialties (APS) for higher gain, more directional antennas than the Winegard/Channel Master variety. While the APS antennas offer ultimate performance, they are very large (making installation difficult) and expensive.
Regarding tuners, your desire to receive stations 120 miles away means that you'll need a great one, especially if the stations are crowded together, as I imagine they are in the CT/NYC area. Unfortunately, the golden age of tuners is history, but some great ones are readily available on the used market. A few you might consider are the McIntosh MR-78 or MR-80, Onkyo T-9090Mk.II, Tandberg TPT-3001, Accuphase T-100 or T-101, Pioneer TX-9800, TX-9500Mk.II, F-91, or F-93, Denon TU-800 or TU-850, Yamaha CT-7000, T-2, or T-85, Rotel RHT-10, Kenwood L-07TMk.II, HK Citation 23, Luxman 117, and JVC 1100. (Sorry, I can't remember exact model #'s of the last two.) Magnam Dynalab makes the best modern tuners, and many of their models are also readily available on the used market. I hope this information is helpful. |
Several things come into play when installing an outdoor antenna. First, you want it high. Second, you want it where is is not going to get reflected signals, causing multi-path distortion. The peak of your roof is a good place on the roof, because the roof surfaces are angled away from the antenna. If the antenna is on one side, the roof will reflect a second signal to the antenna very shortly after the original signal enters, causing smearing(multi-path). The same is true of large buildings, or other hard surfaces in the nearby area. For pickup of stations 120 miles away, you have a tough problem. First the power levels of many radio stations are not sufficient for distances like that. Second, you are out of the direct signal path, as the signal is directional, and you have 2 degrees of arc(earth's curvature) between you and the station. 1 degree of arc(60 miles) takes you out of Line-of-sight transmission. Therefore you must rely on reflected signals which is dubious at best. A high mast would be the best solution. Anything over 60 miles is considered "fringe area". 120 miles is out-of-range. AM broadcasts, particularly at night, may reach you, if there is no required power reduction of broadcast, as there is in many areas. There is little hope for FM to make it that far. If you are on a hill, and you are getting some FM from those distant stations, there may be some hope. I'll leave the wiring questions for somebody else. |
