General – Page 56 – Engineering Radio

Pandora and me

I finally broke down and purchased a smartphone. Instead of the ubiquitous iPhone however, I opted for a HTC Incredible Android phone. Not that I have any distaste for Apple, Inc. Rather, it is more because of the lack of ATT coverage in areas where I travel and the new data plans from ATT.

The phone is great, I enjoy the functions, the GPS navigation tool, Gmail, news, and all the other apps. It fills many roles while I am out gallivanting around earning a living.

HTC incredible Android phone with Pandora App

I have tried Pandora in the past on my computer. I found it to be okay, not great. I guess my main issue was it seemed a little boring just listening to music. It was good music, and when I interacted with the programming, voting a song up or down, the music selections got better. But it was distracting to interact while I was trying to work on the computer and in the end, I turned the volume down and it became background noise.

In the car, I figured, things would be different. I could listen to Pandora the same way I listened to my car radio. Lots of music would be great and not distracting at all.

Except… I found it to be… boring. The music was great but the whole thing lacks personality. I suppose we are blessed around here with several radio stations that play new music. With Pandora, there was almost no new music, even if I created a new music radio station. Further, it seemed like something was missing: human interaction. I enjoy hearing the deeeejay talking about some band factoid or some such. Just listening to music endlessly left me wanting something more. Perhaps that is just me.

Whilst on the road to various places, I like to listen to WEQX in Manchester, VT; WDST, Woodstock, NY; WKZE, Salisbury, CT; WXPK, White Plains, NY. All of those stations have personalities and play great music. They also stream audio, which means I can listen to them on my phone.

So Pandora gets a meh, and the phone gets a thumbs up.

NAB Engineering Handbook

I just found my old copy of the NAB Engineering Handbook, sixth edition. I have enjoyed thoroughly looking at the AM antenna sections. It reminds me, that while we tend to think we have come up with new answers to old problems, really most of this was figured out a long time ago, this particular edition was copyrighted in 1975.

It is a thick book and covers AM, FM, and TV broadcasting technology as it was understood in 1975. There are several chapters about “current” things that no longer apply, there are also many very useful items, such as studio construction, AM and FM broadcast antennas, tower maintenance, and so on.

I will keep this on my shelf because it is an interesting primer on AM broadcast antennas with all attendant formulas and charts. It is quite interesting and fun if one is looking for the theoretical efficiency of a 185-degree radiator at 1 mile. I remember WPTR (now WDCD) in Albany had a three-tower with 206-degree radiators, 50 KW carrier power on 1540 KHz. It seemed to be quite effective, when I was chief engineer there, we used to get reception reports from South Africa.

Perhaps one day, I’ll put some of that information to good use with an AM station of my own.

Blanketing Interference and RFI

Blanketing interference refers to the phenomenon of receiving radio signals on devices not designed to do so. In broadcast radio, this is defined for AM stations in part 73.88 as:

The licensee of each broadcast station is required to satisfy all reasonable complaints of blanketing interference within the 1 V/m contour.

And for FM stations, it is part 73.318:

Areas adjacent to the transmitting antenna that receive a signal with a strength of 115 dBu (562 mV/m) or greater will be assumed to be blanketed.

Any interference to any device with that signal contour is blanketing interference. 73.318 further states that:

permittees or licensees who either (1) commence program tests, or (2) replace their antennas, or (3) request facilities modifications and are issued a new construction permit must satisfy all complaints of blanketing interference which are received by the station during a one year period.

I have always taken a more pragmatic approach to interference complaints. Rather than pass the buck and tell the homeowner or business owner that it is not our (the radio station’s) problem, I’d go and try to help them out. Generally speaking, the interference problems are close to the transmitter site, so on the next trip to that site, I would bring RFI filters and my 25 years of RF experience and solve the problem. I would like to think this helps the station’s and the company’s image in the community.

Most of the problems are pretty easily solved, although once in a while, I have come on some head-scratchers. An AM station playing on the outlets in a guy’s garage, the mic cords on a church PA system, and an off switch on a blender, off all things. The Bare Naked Ladies had a line in the song Light up my Yard: “we can dance to the radio station that plays in our teeth.”

What I have found is to start with the simple stuff first, check the ground on the electrical service entrance panel. One might be surprised to find it disconnected, corroded, or missing completely. On more than one occasion, I fixed all of the RFI problems with a simple turn of the screw holding the ground wire to the grounding electrode. In my experience, this is the most common single failure point. A disconnected ground will cause the entire neutral wiring system to act like a giant AM antenna, with all sorts of bad outcomes.

Most often, telephone answering machines, cordless phones, and other devices powered by wall warts are suspect. Those devices do not have a path to ground. A few turns of all the wires coming and going from said device around a ferrite core such as a snap on TDK RFI EMI filter available from Mouser will take care of it. Mouser has several different versions available.

Occasionally, one needs to put on a detective hat and do some footwork. Mast mount TV antenna preamps can cause untold heartache and problems. One such incident involved the second harmonic of an FM station falling exactly on channel 11’s audio frequency. This was affecting several houses in a one-block area. I finally found the problem at one of the complainant’s houses when I pulled the TV out and found the preamp power supply. Unplugging it made all the problems go away (I hate Radio Shack).

Usually, the process of elimination will discover the problem and thereby reveal a solution. The aforementioned church incident was discovered after I began unplugging microphone cords from the back of the Mackie mixer in the choir loft. It turns out several mic lines were plugged into the back of the mixer, unused and unterminated, creating a large long receiving antenna on the cable shield, which happened to be aligned perfectly to pick up RF from an AM station.

Move AM stations to channel 5 and 6

It might happen, at least according to Commissioner Clyburn, they aren’t saying no right away. According to her prepared statement:

I believe it is time that we consider the fate of Channels 5 and 6 as they relate to current radio service. These channels have proven difficult for television broadcasting, and I have a hard time imagining that they would fare much better as additional spectrum for mobile broadband use. This spectrum is not well suited for digital transmissions. It certainly is possible that this spectrum could be used for LPFM, expanded NCE use, and AM broadcasters.

That would, indeed, be an interesting development, if it were allowed to happen. Of course, there are quite a few hurdles to get over, even if it gets the FCC’s nod, which is a long shot, to say the least. There would likely be some type of congressional “input” into the matter, which could stall things for years if not forever, depending on which way the money flows and which one of our wonderful congressional representatives can be bought and sold.

Getting new radios on the market with the expanded FM band (77 through 87 MHz) will take some time. Thankfully, unlike HD radio, no licensing fees will be required. Manufacturers simply need to increase the frequency range down. It might take several years, but it would happen eventually, as is the case with expanded AM band radios, which are universal now.
Existing AM stations should be given the option to move, those that stay on the AM band will get the option to improve their facilities or go non-directional as the interference contours allow.
Those that choose to abandon AM need to surrender their AM license before commencing broadcasting on FM, none of this expanded band crap where they were supposed to surrender licenses after five years and never did.
Those that choose to abandon the AM band also will not be assured the same theoretical coverage areas they had on the AM band.
AM migrants should not have to compete in an auction.

Indeed, if LPFMs get a boost in the process, all the better. It might actually give radio the shot in the arm it needs, add a good deal of local competition, and satisfy several needs.