The APS-14 is a very high quality "high end" FM Broadcast Band reception antenna. It has built a solid reputation as being one of the finest FM antennas available. As you should expect, it is somewhat more expensive than a typical FM antenna.

This is a large antenna. It is 17 feet long and its long boom needs to be trussed at both the front and rear by a thin Dacron support rope ("non-conductive guy wire"), suspended from a clamp a couple of feet above the antenna. The mounting mast must extend above the antenna a couple of feet for attachment of the truss clamp (the higher above the antenna it is attached, the better the support). This is because of the substantial weight of the antenna's 14 elements, especially its multi-boom quasi-LPDA/multi-driven element section. There is even a second lower support boom to help reduce boom sag and also the potential for boom failure. The antenna is well made of high quality aluminum alloys for a product of this type. Trussed as per the manufacturer's recommendation this is a sturdy FM antenna. I understand that it is actually manufactured by a big name antenna house, Antennacraft, to APS specifications. I also understand that Antennacraft recently combined forces with TDP Electronics, who made the RCA line of antennas. The antenna uses substantial Polypropylene boom separation insulators for the quasi-LPDA/multi-driven element section and other high quality parts. In front of the heavy multi-boom 8 element quasi-LPDA/multi-driven element section, there are 6 parasitic directors to focus the pattern and increase the gain of the antenna. There is no colored finish on the elements or boom and once naturally oxidized the antenna should be non-reflective and relatively unobtrusive looking, since there will be no weird colors or shininess to draw your eye to the antenna installation. Its bulk is similar to a large TV antenna.

What about the electrical performance you say? Well, it clearly deserves its reputation as one of the best FM antennas available. The large bandwidth requirement of an FM antenna is taxing on any antenna design. This bandwidth is after all 20 percent of the FM Broadcast Band's center frequency, a full 20 MHz in bandwidth. This antenna performs well over the entire 88 to 108 MHz band, with good gain and pattern across the whole band. Its pattern is predictable over the full band, allowing the intuitive aiming of the antenna towards desired distant stations. The gain peak of the antenna pattern is always towards the front of the antenna, with substantial rejection to the rear and sides of the antenna, regardless of frequency. This is important for both DXing as well as general use as a Hi Fi antenna. One does not want to think about antenna pattern anomolies while trying to tune in a desired station.

When you want to listen to a station in a particular direction, you just rotate this antenna to that direction. It is as simple as that. With many antennas the pattern varies substantially by frequency, with gain peaks often in other directions than the front of the antenna, and major lobes in various directions, resulting in aiming difficulties and interference from undesired co-channel stations, but that is never a problem with the APS-14. This antenna is very well designed from an electrical standpoint. It is obvious from the taper and spacing of the directors that modern electromagnetic analysis software has been used in its design. Today, this is the best way to optimize an antenna design over such a wide bandwidth. The one thing that struck me as odd is that this antenna design does not employ a parasitic reflector. I have always found that using a reflector helps to improve the pattern, and sometimes the forward gain as well.

I spoke with Ed Hanlon who is the designer of the antenna and principal of APS, Antenna Performance Specialties. He is a competent antenna designer dedicated to improving the art of wide bandwidth antenna design. His attention to detail is also evident in the good impedance match of this antenna to coaxial cable feedline over the full bandwidth of the FM Broadcast Band. Direct connection of coaxial cable eliminates the need for lossy impedance transformers. APS also supplies a ferrite bead choke for use on the coaxial cable feedline near the antenna's feedpoint, to eliminate any negative effect that the dress of the coaxial cable feedline may have on the antenna pattern. This is a great idea, and one that has been proven in the ham community for many years. In fact, in the other antenna articles on this home page you will note that I am a big believer in this technique. Another big believer in direct coaxial feeds, and ferrite bead feedline chokes is Joe Reisert, W1JR. I had the opportunity to speak with Joe on the topic of FM antennas and it turns out that Joe has known Ed for some time and has actually tested a number of Ed's antennas. Joe confirmed Ed's steadfast quest to make the best FM antennas available. Ed feels that he would rather use an extra driven element in the quasi-LPDA/multi-driven element section, than use a parasitic reflector.

I would have to assume that the inherently good front-to-back of the basic quasi-LPDA/multi-driven element section and the bandwidth challenge of full FM Broadcast Band coverage are why Ed came to this conclusion. I have not analyzed whether the inclusion of a parasitic reflector would further improve the performance of this antenna. Before obtaining and installing the APS-14, I had a Channel Master CM 3025 FM Stereo Probe 9 Element antenna installed in the very same location here at WB2VVV. I was disappointed with the antenna pattern of the Channel Master antenna at frequencies other than the middle of the band, and in my quest to improve that antenna's pattern I had tried modeling the Channel Master with the inclusion of a parasitic reflector, since it also lacked one. The inclusion of the parasitic reflector substantially improved the antenna pattern of the Channel Master antenna according to the computer. I never did have the opportunity to try and physically mount one on the antenna and range test it, to see how much it actually helped in practice. Possibly the inclusion of a parasitic reflector is a further refinement which might also benefit the APS-14 as well.

I really enjoyed listening to FM stations on the APS-14, through both my HK Citation FM stereo tuner and also my trusty Icom R-7000 mono receiver. Accordingly, I have given my rotator quite a workout. I was actually able to log some 50 different FM stations in just the bottom half of the FM band, in the first week of listening. Of course being located here in Park Ridge, NJ on a small ridge top, overlooking the NYC skyline ensures an abundance of stations to listen to. This is a fine antenna that allows you to listen to distant stations clearly, despite potential interference from closer co-channel stations. I was able to enjoy listening to a New Haven, CT station that I used to listen to back when I was in college in Rhode Island, even though I am now physically much closer to this station's NJ co-channel neighbor that runs over three times more transmitter power. I was simply not able to do this with the Channel Master CM 3025 that I just replaced. In addition, this antenna cleaned up some multipath problems I was experiencing since it has a better, more focused antenna pattern. Those lucky folks with really high end FM stereo tuners should throw away any lesser antennas they are using and install an APS-14 with a good rotator immediately. The antenna is the most important element in any receiver chain, and for FM reception it should be high, outside, and horizontally polarized. A horizontal turnstile omni is a good starter antenna, but a whole new world of FM stations becomes available to you when you use a high gain directional antenna like the APS-14.

Stay tuned to this home page for the development of my prototype FM Band active canceller, which is progressing along nicely. It takes advantage of stealth technology, developed in the EW trade, to eliminate the reception of FM interference from a strong station while you are trying to listen to a distant weak FM signal from a different direction. This technology takes over where antenna pattern spatial selectivity reaches its practical limits, to further expand ELINT capabilities.

The fine impedance match of this antenna being fed with coaxial cable is evident in the following antenna sweeps:

The subject of the importance of an antenna's impedance match is always an interesting discussion. For a receiving antenna such as this, a VSWR of lower than 5:1 across the band of interest is generally considered sufficiently good. This relatively high VSWR is tolerable because impedance matching and VSWR analysis are all steps to improve the Power Transfer Function. Efficient power transfer occurs when there is a close match in the impedance of one device, to the impedance of the other device coupled to it. In the case of a receive-only application we are speaking of the power transfer between the antenna and the coaxial cable, and between the coaxial cable and the receiver. The antenna input section of a receiver uses very low power and relatively broadband devices, therefore it has efficient power transfer to a relatively wide range in impedances.

On the other hand, a transmitter is a relatively high powered device which has a much narrower frequency response, and thus much more careful attention must be paid to matching its impedance to the impedance of the antenna system (antenna and feedline) for efficient power transfer to occur. For example, most transmitters will substantially roll back their power output as the antenna system VSWR rises above 2:1, to avoid overheating, etc.. This is really not all that much reflection in relative terms. A VSWR of 2:1 exhibits a Return Loss of 9.6 dB. This means that the power reflected back to the input connector is 9.6 dB less than the power put into the input connector. Return Loss refers to the delta between forward and reflected power, and more Return Loss is better. Since 10 dB is ten times in linear units, this represents only 1/10th of the power being reflected back to the input connector. The other 9/10ths, or 90 percent, is the forward power. Therefore, a 2:1 VSWR represents a power transfer efficiency of about 90 percent.

If you are interested in a more detailed analysis of the above antenna sweeps you need to bear in mind the conditions I that employed in making these measurements. I used a short run of double shielded 50 ohm coaxial cable to the antenna, because it was available for me to connect to, and it represents only a very small mismatch to the specified 75 ohm input impedance of the APS-14. Also, the vector network analyzer I used references all measurements to 50 ohms with no reactance, so connection to the 50 ohm feedline presented no mismatch right at the input connector. The mismatch at the antenna between the 50 ohm feedline and the 75 ohm input impedance antenna (assuming the antenna's input impedance is 75 ohms with no reactance) represents a VSWR of 1.5:1, or a Return Loss of 14 dB. In linear terms 14 dB is equal to a factor of 25 times, so this means that reflection is only a factor of 1/25^th. Therefore, 24/25ths, or 96 percent, is sufficiently high matching efficiency for this application.

In actual fact, your situation will probably involve the use of the recommended 75 ohm coaxial cable, which will reduce the whopping 1/25^th , or 4 percent, measurement inaccuracy which I introduced. All of this matching business should be treated with respect to its relative importance. The fact of the matter is whether the antenna has good gain and a clean predictable pattern, and represents a reasonable match for power transfer to take place. A 75 ohm resistive dummy load would be an absolutely perfect match, but of little value as a reception antenna.

The following Polar Plots were measured via range testing the APS-14:

The mechanical engineering of the APS-14 delivers the best possible mechanical performance for a large complex antenna built around standard boom and element stock. This delivers the maximum antenna performance for the money you spend on this antenna. The fact that it is actually built by a major antenna house and is made of standard materials improves the quality control consistency from antenna to antenna, and further drives down the cost you pay for this high performance antenna. Having said this, I did have to struggle quite a bit to install the APS-14 on my "heavy duty" 1.5 inch rotating mast, since the APS-14 U-Bolts and brackets were geared only for mounting on standard TV antenna 1.125 or 1.25 inch masts. I am still surprised at this since it is such a substantial antenna, and will obviously put substantial stresses on the mast and rotator used with it. The smaller 12 foot long Channel Master FM antenna had a boom-to-mast clamp which easily accomodated my slightly larger than normal diameter mast, and for that matter this antenna also included a pair of substantial aluminum pipe boom trusses rather than a dacron rope truss. In this regard the Channel Master is a more elegant mechanical design. Unfortunately, from an electrical performance perspective it doesn't even come close to the APS-14. In my personal opinion, I would rather see a more massive main boom on the APS-14, than a second lower support boom plus a Dacron rope truss, although these changes would clearly manifest themselves in increased cost. When I assembled the antenna I applied Noalox to its joints to maintain good electrical connections at these points. The APS-14 was fairly easy to assemble and even to install by myself, notwithstanding my point about having to field modify the U-Bolt arrangement to accept my admittedly slightly larger than normal mast. The Yaesu ham rotator that I am using turns this mast through a thrust sleeve arrangement, and will not actually accept a mast any smaller than the one I am using. Depending upon your installation type, location and weather concerns, however, a standard diameter TV mast and rotator may be just fine. I am often accused of over-designing antenna supports. I have found that this practice generally keeps them from blowing over very often, and at least when they finally do fail, they make a bigger thud.