FM – Page 13 – Engineering Radio

The NASH: WNSH, Newark, NJ

Lately, I have been working at a site in West Orange, NJ connecting various parts and pieces, and thought that this was interesting:

WNSH 94.7 MHz, Newark, NJ main antenna (top)

That is the main antenna for WNSH, 94.7 MHz Newark, NJ, aka “Nash-FM.” Below that is the backup antenna for WEPN-FM (98.7 MHz), WQHT (97.1 MHz) and WFAN-FM (101.9 MHz). More on those stations later.

This is the WFME studios, located off of NJ Route 10. It is kind of hard to see the call letters behind all those trees and whatnot. There is an older picture from 1999 floating around, which shows the studio building in better condition. This is a better angle:

I believe WFME is still originating its programming here, now being broadcast on WFME 106.3 MHz, Mount Kisco. I had to use the facilities there, the interior is like a way back 80’s time machine, which is kind of cool. If I owned a radio station, I would go for the 70’s office decor; dark wood paneling, shag carpets, bright blue bathroom tile and avocado green appliances, but hey, that’s just me.

This is the WNSH backup antenna, mounted on top of a UHF slot antenna for WFME-TV. There is an LP TV antenna mounted there also, but I don’ t know who it belongs to. Overall, it is an interesting transmitter site on “First Mountain” in West Orange, NJ. Also located here, WFMU-FM, an old ATT microwave site, now owned by American Tower and several cell carriers. In other words, it is just like most other mountain top transmitter sites, except there is a shopping plaza across the street.

I gave a listen to the NASH while driving there. For where it is, it seems to have a pretty good coverage area. As for the music, well, I am not sure how a Manhattenite will relate to Tracy Byrd’s “I’m from the Country” wherein:

Everybody knows everybody, everybody calls you friend
You don’t need an invitation, kick off your shoes come on in
Yeah, we know how to work and we know how to play
We’re from the country and we like it that way

Being from upstate NY, I get it. Perhaps the Manhattan salary man will too. There are no DJ’s on air quite yet, just music, some commercials and a few “Nash-FM” liners that sound slightly distorted.

Goodbye you piece of junk

We are scrapping several old transmitters these last few weeks as part of a site upgrade A couple of Harris FM20 and 10H transmitters are out the door.

Some people like these transmitters. I am not one of those. I found that they were of dubious reliability, tended to drift out of tune and have AM noise problems, and had multiple catastrophic failure modes. If it was not tuned just right, it also had a tendency to have HF oscillations and internal arcing in the PA cabinet.

This transmitter had a non-factory authorized modification installed as a tuning aid. Tune for best efficiency, and minimum AM noise then check and see if it is arcing. It is also advisable to wear hearing protection during the tuning process.

This particular transmitter was my nemesis for a couple of years. It is actually possible to hate an inanimate object, I can tell you. Goodbye, you piece of shit.

We tend to scrap these instead of dumpster them. It saves the client a little bit of money on dumpster charges. If all the metal is sorted out by category, e.g. all the copper windings are cut from the HV transformer and PS filter inductors, and all the brass, aluminum, and wiring harness are separated, then it is almost worth the time and effort. Personally, I’d rather see all that material reused than landfilled.

Nautel Radio Coverage Tool

This is a Webinar video from Nautel about their Radio Coverage Tool:

Highlights of the Nautel RF tool kit:

Analyze the proposed transmitter location’s coverage
Tower heights can be adjusted
Antenna gains can be changed
Transmitter power levels
Includes Terrain data
Includes population within coverage areas
Frequency Range 30 Mhz to 3GHz
Useful for general broadcast or point-to-point systems

This can be a useful tool for those looking to gauge the realistic coverage of a station in terrain-challenged areas. It can also be useful for studying STL paths, RPU coverage, etc.

One problem is the power levels and antennas are preset, with the minimum setting of 200 watts into a two-bay antenna. These settings are too high for use when investigating a potential LPFM. For that, Radio Mobile Online (which is the engine behind the Nautel RF tool kit) can be accessed directly via www.ve2dbe.com/rmonline.html. Requires an account, which is very easy to set up. For most users, FM broadcast band frequencies will not be available, however, 2 meter amateur frequencies (146 MHz) are the default, and for all practical purposes, will model coverage in the FM band (88 to 108 MHz) just fine.

By creating a hypothetical LP100 transmitter site, the coverages between the FCC 60 dBu contour and the actual coverage based on terrain can be compared. This is the FCC 60 dBu coverage contour:

Example contour, LP-100 station — Example 60 dBu contour, LP-100 station

According to the US Census data, this station has a population coverage of; 30,721 in the 70 dBu or 3.162 mV/m contour, 92,574 in the 60 dBu or 1 mV/m contour, and 165,183 in the 50 dBu or 0.316 mV/m contour. Courtesy of REC Network. The 60 dBu contour is considered the protected area licensed for use by the FCC.

Looking at a coverage terrain map, the picture changes somewhat:

This is based on predicted receiver location using terrain data; receiver antenna height 1 meter, 90% reliability, minimum signal level 10 µV (20 dBu, yellow, very good car radios) and 31.62 µV (30 dBu, green, good radios and indoor reception). Areas to the south and east of the transmitter are shaded by a large hill, thus they show low or no signal on the terrain based coverage map. UN Population data indicates the yellow has 178,573 and the green area has 72,014 persons. This map does not take into account co-channel and adjacent channel interference, which there is sure to be.

When comparing the two maps, one can see the coverage holes in the terrain map that are within the 60 dBu contour. There may also be a slight difference in populations covered because the FCC map uses 2010 US Census data and the Radio Mobile Map uses UN population data. For general planning purposes, the area shaded in green would be a safe bet on good reception, all other things being equal.

Since the LPFM stations are very limited in their ERP, finding a good transmitter site that will cover the desired area will be key to a successful operation.

Zonecasting; the Technical Details

I saw this item many weeks ago, but, had not had time to look at it until now. Geo Broadcasting Solutions has filed Petition for Rule Making (RM-11659) based on a system that divides the coverage area of major stations into smaller zones allowing for ad targeting of specific audiences. They have coined the term “Zone Casting” to describe the scheme. It is covered by two US-issued patents filed by Lazer Spots, LLC: 20120014370 and 20110065377. After a look at these two patents, it seems there are three possible ways to accomplish this Zone Casting Scheme:

In the first described method, the main transmitter is broadcasting area wide and all the zone transmitters are muted. An inaudible signal is transmitted to all units, the main transmitter is then muted and the zone transmitters turn on and transmit localized content. After the local information is transmitted, the zone transmitters mute and the main transmitter resumes broadcasting.
In the second described method, the main transmitter and the zone transmitters are broadcasting area-wide information. The main transmitter ceases broadcasting area-wide information and the zone transmitters begin broadcasting localized information. At the end of the localized information, the main transmitter and zone transmitters transmit area-wide information.
In the third describe method, the main transmitter and zone transmitters are broadcasting wide area information with “capture ratio pattern.” The main transmitter initiates an alteration, temporarily becoming a zone transmitter. The zone transmitters then transmit localized content. After the localized content, the main transmitter becomes a main transmitter again.

All of the transmitters are linked to the studio via digital STL systems, and content for the zone transmitters is distributed via IP network. The transmitter frequencies are synced with GPS, similar to FM on channel booster stations. Method number three includes possibly switching the transmitter output to a lower gain and or lower height antenna.

Of the three methods, the first system will result in the fewest interference issues. No matter which method is used, there will be interference issues between the zone transmitters and or the main transmitter where the signal strengths are equal and the audio is 180 degrees out of phase. These can be moved around slightly by adding delay to the audio signal, but they will always be present. More about Same Frequency Networks (SFN) and Synchronized FM signals can be found here. While the zone transmitters are transmitting dissimilar localized information, standard capture effect rules apply.

The system has had limited testing in Salt Lake City, Utah (KDUT) and Avon Park, Florida (WWOJ), which according to the filing and comments, went well.

Geo-Broadcasting is applying to conduct a full test with WRMF in Palm Beach, FL. The expected installation will include up to 22 zone transmitters.

Conceptually, tightly targeted advertising is not a bad idea. Advertisers like it because they perceive a better return for their dollar. The cost of such a system is not insignificant. Transmitter site leases run $1-2K per month, leased data lines, equipment, installation work, equipment shelters, etc will likely run several hundred thousand dollars or more.

If it gets approved by the FCC, it will be interesting to see how it works and whether or not the system is financially justifiable.