An FM Antenna Case History

by Bruce Carter

Background

The idea for this article came to me while I was looking at the articles saved in my notebooks. They are almost 20 years old, and I wondered - is it still possible to even do a decent FM antenna installation? It has been almost 20 years since I bought an FM antenna or attempted an outdoor installation. These are the days of cheap stereo equipment, too many new stations being licensed by the FCC, and equipment companies going out of business or being bought out in consolidations.

My Reception Scenario

Every reception scenario is different, and mine is no exception. You can probably gain only a limited amount of information from this article, but my scenario combines many different problems - so it is a good example.

From my home in Palm Bay, FL, I want to receive WAYF, 88.1, West Palm Beach, which is about 100 miles away. One problem that is immediately obvious to anybody who tunes 88.1 with a car radio in Palm Bay is that WAYF is not the strongest 88.1 in the area. Most of the time, WJIS, 88.1, Sarasota is the station received in this area.

One resource that was NOT present 20 years ago is the Internet, specifically the Airwaves site on the World Wide Web. This site features a user friendly interface to the FCC database. Entering "FL" into the city/state search form gave a nice listing of Florida FM stations. All of the 88.1's in the state appeared at the top of the list. A new 88.1 has been licensed in Naples, FL, but it should not be a problem. Naples is at least 170 miles away. The reason why WJIS dominates is obvious, while both stations have relatively short towers, WJIS is 100,000 watts, while WAYF is only 37,000.

The following is the pertinant information from the search, although I have changed the color scheme to match this page:


Calls         Freq City                    State/  Power  Antenna
                                           Prov.          Height/DA

WJIS          88.1 Bradenton                 FL   100000    381
WANX(CP)      88.1 Holly Hill                FL     5100    118  D
WRGP(CP)      88.1 Homestead                 FL      165    399
WNCMFM        88.1 Jacksonville              FL     1000    475
NEW(CP)       88.1 Naples                    FL    16000    140  D
WHIJ          88.1 Ocala                     FL     1250    393
WUWF          88.1 Pensacola                 FL   100000    582
WAYF          88.1 West Palm Beach           FL    37000    469

Another useful thing that Airwaves provides is a map of the antenna site - you can get to it just by clicking the call letters. Sometimes, this offers some very useful information. In this case, WJIS is actually located way South of Sarasota (the farther away the better) and WAYF is actually a little North of the center of West Palm Beach. Even better! It also may affect how I aim the antenna, since I want to reject WJIS. Previously, you had to call the chief Engineer of the station to get this type of information. They were hard to get hold of and some were only marginally co-operative. Guess what? Now the station may not even HAVE a chief Engineer, he may only be a consultant that handles a lot of stations.

My reception problem, therefore, is to reject WJIS while providing gain on WAYF (not to take anything away from the good folks at The Joy FM, I simply prefer the programming on WAY-FM).

The Antenna

Many manufactuers have disappeared over the years, or simply gotten out of the business. Others have become quite expensive. A few years ago, I was told by one store that they could get me a Channel Master FM antenna for $160. Locally, I was able to locate an antenna from "Antennacraft" at Tedco electronics, and the price was $50 - more within my budget. Tedco is a typical electronics hobbyist store, offering the usual mix of audio, cable and satellite TV equipment, and parts. The model FM-10 is a ten element Yagi, and the elderly man behind the counter was well acquainted with the gain figure for a 10 element yagi: 13dB. When I unpacked the box (which was shorter than 120 inches), I found that the antenna was in two pieces (not counting a boom support). The days of gold anodized antennas are gone - although this one had a nice aluminum finish and the quality and durability looked good. All necessary hardware (except for one lockwasher) was included in two plastic bags, and easily assembled with wing nuts. There were no less than 3 "duh-warning" labels telling me not to install the antenna where it could fall on power lines (ah - insurance and courts, what a joy they are!). Actually, this is not as ridiculous as it might seem, as I will tell you later.

Hardware

The antenna was much easier (and cheaper) to get than I thought, but what about the rest of the antenna system? A visit to my local Home Depot was very encouraging, I found a nice line of TV antenna accesories from Magnavox. In Florida, the likelihood of tropical storms and hurricanes dictated that I be able to easily get the antenna down for storage (and easily put it back up after the danger passes). I opted for a "side of the house" installation. The antenna is free standing, requiring a bracket at roof line to support it. The brackets came two to a package, but I only needed one. I was able to find a prefabricated, molded 50 foot length of 75 ohm cable TV type coax, and a matching transformer to convert the 300 ohm impedance of the antenna to 75 ohms. My tuner only has a 75 ohm input, so I did not need a second matching transformer. The antenna mast was sold in 4 1/2 and 9 feet "slide together" sections. I bought 4 of the 4 1/2 foot sections instead of 9 foot sections, to make it easier to get the mast home. Antenna height was not going to be an overriding need for my installation (my station is not that far away, and my primary need is the use the yagi to reject the unwanted station). Therefore, I just needed to clear the roof line, and only ended up needing three sections of mast.

Here are the items that I bought to complete the installation:

Item Model # Cost
Antenna wall mount M61410 $3.95
Matching transformer M61009 $3.25
50 Ohm Coax M61208 $9.85
Mast   $6.69
Total cost with 4 mast sections and tax was $46.44, which brought the total project cost to just under a hundred dollars.

One problem that antenna installations have in Florida is frequent lightning. Unfortuately, I was unable to locate lightning suppressors for the antenna at Home Depot.

The installation

I started by assembling the antenna and attaching the matching transformer and coax. This is where I encountered my first problem - the weatherproof boot on the matching transformer was only designed to accomodate unterminated cable. I had to take a pair of dikes and hack off some of the rubber to make the hole bigger for my pre-terminated cable. It was not a pretty hole, but it hangs upside down and there should be no moisture intrusion problem.

TIP 1: I had my antenna up and aimed before I realized that my coax was neatly coiled with three tie wraps - out of my reach! I had to take the antenna down to unspool the coax.

I started the installation to the side of the house by selecting a location for my mounting clamp. This is where I encountered some more problems:

The roof line of house is more than a foot from the wall. I could therefore only use one clamp. The only thing left to do with the other end of the mast is push it into the ground. This is a poor ground, but in moist soil like Florida's, it is probably acceptable. I realized and accepted that the bottom of my mast will corrode and have to be replaced occasionally. I will have frequent opportunities to inspect when I take it down for approaching storms. I pushed the bottom mast section from 8 to 12 inches into the ground, allowing the antenna to temporarily self support until I was able to bolt it to the supporting bracket.

TIP 2: A second person would really be helpful to provide temporary support to the antenna. I used the ladder ---

Another problem that I found was that the roofline of the house was narrow, and I could only place a bracket on horizontal sections. It is also aluminum, and I worried about what was under the aluminum. I tugged pretty hard on the antenna once it was up - the aluminum structure on the roof line seems strong enough. Still, I had to discard the screws that came with the bracket in favor of some screws with threads all the way to the head - salvaged from a black and white TV smashed during the 1970 Lubbock, TX tornado. These screws are really nice because they have a captive washer about an inch in diameter that holds the bracker securely.

This is where you get my speech about safety. As I said above, I had to install the antenna mounting bracket on a horizontal section of roofline. Before I took time to think, I found myself eyeing a section at the side of the house where there was a plywood panel with other wires and boxes attached. I had lots of coax - I bought 50 feet when 25 would have been plenty, so I though of just moving the antenna down to the corner of the house. What I did not immediately consider was that the power feed to the house also came into that corner!!! If I had installed the antenna there, and it fell it would have 200 amp, 220V service shorted to it! It might not be fatal IF I happened to be dry when I touched it, but it would certainly deliver a very memorable jolt. If I could have a mental lapse - YOU CAN TOO! Do NOT install the antenna where it can touch power lines! You have been warned.

Enough of that --- before I tightened the antenna for the last time, I needed to aim it. I went on the Internet one more time - this time to do a listing of AM stations in Florida. My idea was to use an AM portable radio to find a station in Sarasota, and then null the station out with the AM radio's internal ferrite bar antenna to get a precise direction to Sarasota. Unfortunately, even though I have a GE Superadio III, (with the speaker connection CORRECT, by the way) - there is no Sarasota station receivable in Palm Bay, FL. This is just as well, considering that WJIS is considerably South of Sarasota anyway, so the direction would have been WRONG. I was able to find a Tampa station. Tampa is North of Sarasota, and it just so happened that it lined up perfectely with the side of my house! I was then able to make a guess as to the correct angle, using a map to get the angle.

I then routed the wire down the mast using some tie wraps - one of the advantages of coax is that you can attache it directly to the mast, something you cannot do with twinlead! I then routed it to the window by my stereo --- where I encountered an aluminum window that absolutely did not have enough "give" to pass a coax into the room!

TIP 3: I took a pair of pliers and was able to bend the aluminum frame at one end on the bottom to pass the coax. The aluminum is flexible enough to bend (and bend back when I move out).

From start to finish, the installation was under an hour!

Reception Results

Wouldn't you know it - when I attached the wire and turned on the tuner - WAYF played two "clunkers" in a row. I thought I was receiving WJIS and all my work was in VAIN! I waited anxiously for the station ID that would tell the story ---. But it was WAYF after all - I guess they have a few listeners who still like slow songs. Reception on WAY-FM is good, characterized by typical "deep fringe" momentary fades - but very listenable and enjoyable. Much better than I expected, and much better than the aging antenna in the attic that I was retiring. There is no trace of WJIS, unless an airplane flying nearby reflects its signal at an angle my antenna CANNOT reject.

Of course, I could not resist the temptation to try other stations. I had some very spectacular results, virtually every station from the Miami / Ft. Lauderdale area (that was on a clear frequency) was receivable and listenable, even ones up to 180 miles away with low transmitter power and short towers. If anything, I have too much gain in my antenna system. Even with enhanced selectivity, stations in towns 30 to 45 miles south interfered if they were on adjacent freqencies.

One of the more spectacular results was that I could receive the WSCF translator station in St. Lucie, about 65 to 70 miles away, even though it is only ten watts!

I had one other purchase to make - I was able to locate "screw coax to quick disconnect" adapters at Astro Too electronics - another surplus / hobbyist store. This will make it easier to quickly unhook my antenna from the back of the tuner and hook up another antenna - since my next project will be an antenna for WJIS! They have stepped up their musical format considerably in response to the unjust and hostile takeover of WCIE by Moody broadcasting. They still are not WAY-FM, but are better than they used to be. I will re-condition my old antenna, and describe the restoration process in another article.

The answer to the question ---

The bottom line is that YES - it is still possible to construct a quality antenna system for FM - and get good results even with modern stereo equipment.