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.
Harris FM20H transmitter, circa 1970
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.
Harris FM20H3 PA cabinet modification
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.
Harris FM20H3, circa 1972
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.
One of the stations that we do contract work for installed a Broadcast Electronics FM20T transmitter on June 6, 2001. It is still running on the original tube, a 4CX15,000A. By my calculations, that is 11 years, 7 months, and 9 days, or 101,712 hours.
Broadcast Electronics FM20T transmitterBE FM20T filament meter
The hour meter shows 101,168 hours, which accounts for some maintenance, and other anomalies. Overall, the transmitter has a 99.5% up time. I do not think the transmitter suffered any failures, rather, things like the generator and the STL failed instead.
EIMAC 4CX12000A tetrode
Almost twelve years on one tube is pretty impressive. I know that other Broadcast Electronics T model FM transmitters have similar tube life expectancies. I wonder what Broadcast Electronics’ secret is.
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.
Zone Broadcasting Conceptual Diagram
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.
We are currently installing this sweet little transmitter:
Nautel NV-5 FM transmitter
Like its big brother, the NV-40 at WVPS, the NV-5 is a very cool transmitter. I am a born skeptic, things like touchscreen displays tend to make me a little nervous, especially on a transmitter connected to a 350 feet tall steel tower right next to the transmitter building. That is the one major difference between WVPS and this site; at Mount Mansfield there are many things between the transmitter and antenna, but in this place, not so much. Even so, Nautel makes a good product, so troubles are not expected.
The ground strap, AC power, remote control, and composite audio connections were all made without difficulty. The result, new transmitter on the air:
Nautel NV-5 FM transmitter GUI
This unit is analog only, but the information on the spectral display is still useful. The GUI uses Linux with a touch screen, which is a neat feature.
Nautel NV-5 FM transmitter controller board
In case the front panel GUI goes out, all transmitter controls can be accessed via push buttons on the remote control interface, which is the small board to the right. The main controller board is on the left.
