Comments from our technical gurus?Last week, I attended an educational session at the Texas Association of Broadcasters Convention. The presenter was from Continental Electronics, a company that will be more than pleased to build you whatever kind of transmitter your heart desires. They make fine products. It's what they do for a living. He gave a very fair and balanced presentation. When I asked him if this power increase would cause increased interference, he said, "How could it not."
The real eye opener for many at the session was how much it is going to cost in order to implement a 10 dB power increase. There are several ways to go about it, but they all require changing out at least one transmitter and probably two. It seems with signal combining techniques, the analog transmitter needs about 66% headroom (additional power) over its normal TPO. Very few already installed transmitters can do that. Incidentally, that headroom requirement is after increasing its size to allow for dumping significant amounts of power into a dummy load. Yes, a dummy load.
To put it bluntly, the HD radios system is not efficient. A good installation is about 50% efficient, but some methods can yield a system that is only about 25% efficient, at least according to the gentleman from Continental. By contrast, most LPFM analog transmitters are it the range of 85% efficiency.
This revelation translates to greatly increased power bills just to run and cool the thing. It also means an increased cooling problem to keep it from burning up. Most air conditioning systems will have to be replaced with bigger units. Further, your electrical service may need to be significantly upgraded. If you have a standby generator, it may no longer be big enough, and could require replacing.
It gets worse. Depending on how you choose to do this, you may need to put a second (or a new larger interleaved design) antenna on your tower. Many existing antennas will not be up to the new power requirement and will need to be replaced. Since many stations lease their tower space, it is reasonable to assume that the landlord will want more rent. In fact, the tower may need to be beefed up to handle the increased weight load. If it is already maxed out, then you are faced with replacing the tower or moving to a different one. Of course, you have to pay tower climbers and riggers to put all this stuff up, install new feed line, etc. That is not exactly inexpensive.
Did I mention that these new improved transmitters and their associated diplexers, combiners and dummy loads take up a lot more space than most current analog rigs? That may require adding on to or remodeling the transmitter building. All this adds up to some very big numbers. The only person I saw in the room who said they were definitely going to do this was an engineer from Clear Channel. Just about everyone else left the room shaking their heads while
thinking about the projected costs. A few felt they had been sold a bill of goods by Ibiquity. I tend to agree. After spending somewhere between $100,000 and $250,000 to get this baby off the ground, someone is now telling you that you need to rip it out and pay even more. That goes over well.
The way political currents are running at the moment, I'd bet that the FCC rubber stamps this power increase request, even they now very well that it has
the potential to cause chaos on the FM band. Big business seems to have a way of getting what it wants. Of course, they wouldn't let an LPFM station have a 3 dB power increase, much less a 10 dB increase. NAB would run around claiming "unacceptable interference." Maybe one day they will realize how hypocritical they are.
Even if the Commission does pass it, I doubt that very many stations will run out and immediately raise their power. A few will, but not many. Just hope that one of them is not near you. In these poor economic times, the investment doesn't make very much sense to anyone but the really large broadcasters. The rest will probably wait to see if this actually works. Some folks say it really won't help save HD.
Those that do make the investment may find it is better to settle for a more modest power increase, say 3 dB. That is still substantial. I've discussed this a lot with engineers who are currently looking after existing HD installations. I really haven't found any who think this is a good idea. In fact, several have expressed the opinion that they don't think 10 dB will make much difference for radios inside buildings. It certainly will help car radio listening, but it turns out that the bulk of radio listening is not done in the car. You could have fooled me, but that is what the experts from companies like Arbitron say.
May you live in interesting times.
Chuck Conrad
KZQX Radio
Do you have similar observations, or is there a positive side to beefing up the HD installation?
Just curious.
