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Message: [QUOTE="EscapeVelocity, post: 21143, member: 3771"]EV's Best Top Rated FM &amp; HD Radio Antenna Guide &amp; Reviews.Welcome to EV's FM & HD Radio Antenna Guide!  Just getting started folks so please be patient.  I am not the world's authority on FM Technology/Broadcasting, Antennas or Antenna Theory & Design, nor HD Radio.  There are many others more knowledgable and experienced than I regarding these topics.  I am just an enthusiast that decided to write a helpful guide with the help of many others that have gone before me.   The guide is and always will be imperfect...and I am still working on it daily....however, I think the effort will prove useful.  If you have recommendations for additions to the list, they are most welcome, especially vintage or discontinued antennas.  Seeking photos of vintage, discontinued, and current antennas as well.GoalsExhaustive overview of commercially available antennasReporting hands on testing and comparisons of antennas on FM analog and HD Radio broadcastsHelping the Average Consumer make better antenna purchase decisionsDiscussing antenna and reception issues for better antenna/system performanceSpringboard of links and sources for further research for those so inclinedHistorical record of vintage and discontinued FM antennasLearn about FM Radio and HD RadioPlease join the forum and the discussion.  Look forward to seeing you here.  Please let me know if you liked the guide and found it helpful and how I can improve it.IntroWork in Progress....Topics for further discussion and expansion....Proper Lengths for telescoping or otherwise dipoles for FM ReceptionAM/FM Combo Antennas and their CompromisesPhilips SDV2750Winegard Mystery Antenna from the 70sFM Band - Where is it?  What's it all about?FM Stands for Frequency Modulation.  How does that work?  How do you get FM Stereo sound?HD Radio:  <a href="http://en.wikipedia.org/wiki/HD_Radio">HD Radio</a> the marketing name of <a href="http://en.wikipedia.org/wiki/IBiquity">iBiquity's</a> IBOC technology - In Band on Channel....an offset carrier standard used to broadcast digital audio and data.  HD Radio is a bit misleading because it isnt High Definition Audio, but rather its quality is variable between lower quality to mid quality MP3.  However the advantages of digital are nearly absent backround hiss and distortion.  I dont want to get into the technical aspects of HD Radio, nor the arguments over its advantages and disadvantages between it and analog FM as well as other digital broadcast standards here.  The main point I want to get across here, is that HD Radio does NOT require a different or special antenna....standard, regular FM analog antennas work for HD Radio.  Discussion HD Radio is encouraged in the thread.  One note about HD Radio, I would like to make is that because of its digital nature, it exhibits what is known as a digital cliff.  What does that mean?  It means that point of decoding or not decoding an HD Radio broadcast is a cliff, you either have enough to get clear audio or you dont.  Its not a slow fade like analog.  If you are familiar with OTA digital television, you may be familar with the digital cliff...its similar with HD Radio.  This (along with its current low 1% broadcast power which may be changing soon) may have people scrambling for better antenna solutions.  If you are on the digital cliff with HD Radio, what usually happens is that it reverts to the primary analog signal if its the HD1 signal.  It can switch back and forth between these like FM Mono and FM Stereo of yor, which is very annoying.  One solution is a Forced Analog switch, like the forced FM Mono switch of the past.Important Characteristics of AntennasThere are several characteristics that are important to know in order to choose the appropriate antenna for your situation.Gain:  This number reflects the antennas ability to capture and transform radio wave energy into electrical energy that can be used by your tuner which then decodes the signal that your amplifier can use to drive your speakers to make sound waves that travel to your ears which convert sound wave energy into electrical pulses that your brain then decodes.  Yeah!  The most common figures used are dBi and the much more historically common dBd.  Both represent a gain figure that relates the antennas ability to the ability of a reference antenna.  In the case of dBd, that reference antenna is a 1/2 wave dipole cut to the length of the frequency/channel....dBi relates to an <a href="http://en.wikipedia.org/wiki/Isotropic_antenna">isotropic radiator</a>, which is a theoretical point source of waves which exhibits the same magnitude or properties when measured in all directions. It has no preferred direction of radiation. It radiates uniformly in all directions over a sphere centred on the source. It is a reference radiator with which other sources are compared.  These 2 figures relate to each other as dBd + 2.2 = dBi.  0 (zero) dBd means that the antenna is equal to a 1/2 dipole....indeed many of these antennas are 0 dBd and many are indeed 1/2 wave dipoles!  It should be noted that a 1/2 wave dipole is a pretty good antenna, that is why it is used as a reference for judging other antennas....in other words 0 dBd aint too shabby!  One more note, 3 dBd equals a doubling of capture ability over 0 dBd, 6 dBd...a doubling again or 4 times the capture ability of 0 dBd, and 9 dBd yet another doubling for 8 times the capture ability. Front to Back Ratio, Directivity, Beamwidth, (and Multipath):   As antenna theory generally works out, to increase gain, you usually have to direct the ability of the antenna to capture radio wave energy more effeciently in one direction at the expense of others.  This is where the Front to Back Ratio number comes from...its the relationship of Forward Gain to Rear Gain.  (Not getting into lobe discussion here.)  This also can be thought of as Rear Signal Rejection.  The higher the number the greater the rear rejection (and usually this corresponds to greater forward gain).  As stated, dBd is the preferred historically used term, that is grounded in antenna theory....often dBi is used for psychological reasons to inflate the numbers for the unwary...but it is a valid modern standard often used in computer antenna modeling software.Why would this be of interest to us?  Well, if you have FM transmissions in mulitiple directions...then you may want to go with an Omni-Directional antenna with extremely low F/B ratios.  It may be desireable to have a lot of rear rejection to help with multipath interference problems.  Beamwidth is also related to F/B Ratio, in that high F/B ratios (which generally indicate high Forward Gain) also indicate tight Beamwidths.  Beamwidth as a numerical value is generally described as the off axis point where gain is down 3 dBd compared to maximum forward gain.  As you off angle from the direction the antenna is pointing, gain drops off as well, when you reach 3 dBd down, that angle is the measured Beamwidth.  This is also important for multipath rejection and reducing or eliminating possible co-channel or adjacent channel interference.  What is this multipath and why should I be concerned about it?  Multipath happens when objects in the environment reflect radio waves in different directions.  Large geographical objects like hills and mountains and also smaller objects like buildings and trees can be sources of deflected/reflected signals.  These reflected signals can be picked up with your antenna along with the direct transmitted signal and be passed along to your tuner which may be confused by these out of phase signals and thus reduce its ability to decode them cleanly...resulting in poor quality music reproduction.  The tuner can jump back and forth from the primary and reflected signals.  Tuners are designed to deal with this to varying degrees of success, but you can help the tuner by understanding mulitpath...identifying it as a source of trouble...and selecting a proper antenna to reduce it.  Co channel and Adjacent Channel interference is similar except that the source of the objectionable or interfering signal is another FM broadcast, either right next to the frequency that you are attempting to listen to, or on the same frequency/channel at another distant location/direction. Bi-Directional, Figure 8...........Directional...........Omnidirectional<img src="http://i302.photobucket.com/albums/nn88/EscapeVelo/polarpatterns.gif" class="bbImage" alt="" data-url="http://i302.photobucket.com/albums/nn88/EscapeVelo/polarpatterns.gif" />Horizontal Dipole, Helical.......Yagi, Rhombic.......Whip, Vertical Dipole, TurnstileHere you can visualize the directional nature of differing antenna designs.  Lets look at a 3D visualization of a Vertical Dipole...this may help you visualze what is going on, better.  <img src="http://i302.photobucket.com/albums/nn88/EscapeVelo/dipolepattern3.jpg" class="bbImage" alt="" data-url="http://i302.photobucket.com/albums/nn88/EscapeVelo/dipolepattern3.jpg" />The antenna is in the center standing up or in a vertical orientation.  As you can see the round donut shape if cut in a horizontal cross section corresponds to the circular pattern of the Omni-Directional above.  Now if you take your Vertical Dipole and turn it sideways to a horizontal position, then the donut rotates with it, now half of the donut is below ground with the rest arcing over the top fo the dipole.  If you look at the Horizontal Dipole plot above, you will see that the Figure 8 pattern is a horizontal crossection of this 3D donut rotated on its side.  In the horizontal position the dipoles nulls point off of the antenna ends, instead of up and down now side to side, thus it doesnt have a circular pattern.Polarization: Circular, Vertical, and Horizontal:  What you need to know!Without getting to deeply into the physics aspect of polarization, what you really need to know is that FM is broadcast in both vertical and horizontal orientation, simultaneously most often.  Some stations only broadcast on horizontal only, so you may need to look into a specific station you want or are having trouble with.  In the past when vertical whips were the most common vehicle antennas, some broadcasters boost the power to their vertical broadcast antenna, at the expense of the horizontal broadcast antenna during rush hours....then later brought them back into equal or favoring the horizontal component of the broadcast antenna.  Im not sure most FM users should concern themselves with all of that.  What the average consumer may concern themselves with is atmospheric propagation issues.  Horizontally oriented antennas may perform better than verticals at longer distances depending on the atmospheric propagation conditions.  A good discussion of this can be found on Wikipedia, <a href="http://en.wikipedia.org/wiki/E-skip">TV and FM DX</a>.  For this reason, you may favor a horizontally oriented antenna, depending on your needs and wants.Amplification:  Is it useful?   Generally speaking the answer is a qualified NO.  Amplification is useful for overcoming signal loses in long cable runs of over 100 ft or so at FM frequencies....or splitter loses.  It can be useful in systems that use an undersized antenna, which starts off with a much lower signal and then boosts it to useable levels.  However amplifying the signal introduces its own noise into the system and can degrade analog reproduction quality.  Generally speaking amplification is much more useful (while still not being a panacea) for television reception....one reason being the noise of television tuners themselves is higher than a low noise amplifier....thus increasing the Signal to Noise ratio.  FM tuners are generally less noisey and thus do not give this benefit.  You will see that many antennas that offer amplification also offer selectable power gain or the ability to turn it off completely, which is a good feature for reasons stated....these selectable gain amplifiers do offer some flexibility in the system....but are not as good a solution as going with a larger higher gain properly placed antenna.Types of Antennas and How They Compare to One Another Performance WiseHere we will discuss the various types of antennas what characteristics they exhibit and how they relate to one another. Location & Building Materials:  Where to place the antenna?<a href="http://www.dtvusaforum.com/dtv-hdtv-reception-antenna-discussion/5677-whats-most-optimal-place-put-your-indoor-antenna.html">What's the most optimal place to put your indoor antenna?</a>FM Interference Sources:The <a href="http://www.arrl.org/fcc/tvibook.html">FCC Interference Handbook</a> (courtesy of AARL) gives advice on how to isolate the sources of electrical interference..[/QUOTE]

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