LPB AM-30 Carrier Current

Before you commit to purchasing this you should check the rules for carrier current operation. Carrier current is for an educational institution campus and you may not be able to legally use this as a private citizen at your residence.

You asked about CC experience and I have this so if there is something in particular I can help you with please ask.

Neil

"Carrier current is for an educational institution campus"

Well, carrier current was most frequently used on campus but I'm not aware of any statutory reason for that, I think it's more a matter of practicality.

I think the limiting question is "what carries your current?"

Colleges usually own, or have more privileges to, the wires used for radiating a carrier current station. We private citizens at our residences don't have any such access to the utility that goes past our homes.

It's likely today's investor-owned utilities would take a dim view of a customer doing anything but drawing KWh's and paying the bill on time.

Another challenge is that most homes are now served by service drops that go through a transformer, also known as a dead stop to a CC signal.

Now the good news.

If you were to partner with some entity that did own some wires and was interested in supporting a CC service, it could be really cool.

Farmer's markets, community facilities, shopping malls, assisted living communities, there could be all kinds of opportunities out there where Carl's interest and Neil's experience could join up with an interested facility and really provide an exciting CC opportunity.

A final bit of bad news, I was involved in a project in 2001 that used LPB as a vendor and the experience was not positive. In fact, the project failed because of equipment and vendor issues - and there was only one vendor...

Radio8Z I think 15.221 (a) gives radiation limits for carrier current and leaky cable systems on the AM band, and applies to transmitters operating as intentional radiators. It is not confined to educational use.

However, as SCWIS suggests, I would wonder if the power utility has its own rules regarding use of their lines for communications purposes.

At the same time, there are devices at Radio Shack and other outlets which utilize carrier current. There are loudspeakers, for example, that operate "wirelessly" by sending audio on the house power wiring in an RF envelope; intercoms which communicate within the house through power lines; computer network devices that use house wiring as a connection to printers and other devices.

In 1990 I purchased a carrier-current radio station that used an LPB transmitter, although it was an older model.

This station ran legally from early 1991 through 1995. I sold the LPB as I was re-entering the world of commercial radio.

In those days I was not familiar with neutral injection, and ran into the aforementioned signal stop at a transformer.

In the small community of Carrabelle, Fla., an older gentleman has been operating a CC station on 1610 with 5 watts. It drops out sharply once you leave the town but covers most of the area decently. I believe he may have signed off now due to health problems, but has not had any legal issues. And shouldn't as Carrabelle does not have any stations licensed to it.

CC is governed by signal strength primarily. Many campuses seem to have abandoned CC as students aren't that interested anymore.

I recently acquired a Radio Systems TR-20. I have not yet done anything with it, but perhaps later on this year I'll try a CC system with neutral injection and see how it works.

I'm on 17 acres that is family owned, so no neighbors or associations to deal with:)

Enjoyed your description, radioboy, of those several CC situations.

The TR-20 doesn't seem to be mentioned any more on the Radio Systems site. They only name 2 transmitters that I could find: AT-162 which is 10-watts for Carrier Current and IAM Talking House, a Part 15 unit for a low 99.95.

What is the power of TR-20?

By the way, Radio Systems has some very attractive slim 10-foot vertical fiberglass antennas with center-fed coils tuned to a selection of frequency ranges. The antenna for 1620 to 1700 kHz is the AT-162.

Oh, and another matter bending back to where SCWIS suggested teaming up with, among other organizations, a retirement center to provide carrier current radio. Well my late wife and I worked up an entire proposal along that line.

First, we were going to propose FM transmission tied into the center's in-house cable system, with studio operation manned by the residents themselves.

At that time we ruled out Part 15 AM because large concrete buildings are not conducive to AM radio, and we did not consider carrier current because we thought the cable system would be easier to connect.

The TR-20 appears to be a 20 watt CC transmitter.

I've been kicking around the idea of applying for an LPFM when/if another window opens up. The idea being to provide programming for the older residents of the area, plus I'm close to hiking and nature trails, and would also provide information for folks using the trails.
I founded a nonprofit (that's not a 501c3) in 2001 and keep it active
"just in case" an opportunity comes along.

I did commercial radio from 1979-2004. including managing an AM for several years.. Can't hardly get past the receptionists now, unless a colleague is on the air. THAT got me into both the Clear Channel and Cumulus clusters:) No real jobs in the market, though. Looks like ownership is the only real way to stay in the biz anymore.

Carl,

You wrote Radio8Z I think 15.221 (a) gives radiation limits for carrier current and leaky cable systems on the AM band, and applies to transmitters operating as intentional radiators. It is not confined to educational use.

I had 15.221 (b) in mind and had forgotten exactly what (a) said so you could be good to go. Glad you checked into it.

Neil

I had an LPB 5 watt tube transmitter and an LPB
coupler on loan to me from a friend.
It only went to the house next door. It was
on 860 kHz during the day.

So for me it was not successful.

I miss LPB, though. I always thought it
was a cool company, and they had a long
interesting history.

Best Wishes,
Bruce,MICRO1690/1700

CC would be cool if i could utilize it here. Even leaky coax buried around the park would be really effective even with a moderately weak signal.
(am or even fm)

Though i am certain Carrier Current would not be as effective as one would hope for here. Just from my point of view, there seems to be a ground mounted transformer for a small handful of mobile homes.
The power lines come into the park on poles then is routed into the ground by a thick conduit.

My guess is based on the number of homes surrounding each transformer, perhaps they serve 5 homes at a time??
Anyway, the fact that there are these green boxes peppered all over the park would suggest the signal (no matter the mode) would possibly stop at the 5 homes to which i share the same transformer.

So there is potential to serve 5 or more homes before the signal hits an iron wall.

The concept of Carrier Current is really cool in my humble opinion.

Up the scroll a way radioboy mentioned "neutral injection" as something that, I think he inferred, got the signal past transformers and on down the line.

I hope someone is conversant with neutral injection.

When I soon talk to LPB I'll find out what they say.

Carl, I don't think LPB (as we all knew it)
exists anymore. I
believe they fell apart around 2001.

There is still an LPB website, though, which
is real weird. I think most of the links on it
are dead.

Somebody else here will know, and I'm sure
somebody else will also know more about
neutral loading.

I think I tried neutral loading years ago in
my carrier current experiments. But I don't
remember what I did when I wired the coupler
into the power line. It was just too long ago.

And, as I mentioned, my 860 KHz signal only
got to the house next door.

Best Wishes
Bruce, MICRO1690/1700

Found here:

• Carrier Current Broadcasting Theory
• Carrier Current System Design
• Neutral Loading Option

The TCU-30 unit referred to in the Neutral Loading Option diagram is a variable inductance loading coil

• Carrier Current System Maintenance

One problem with using carrier current is that compliance with the field strength limit cannot be determined. LPB Technote #1 (Carrier Current Broadcast Theory), linked by scwis, suggest finding the distance at which an ordinary radio receiver becomes noisy. This will result in the field strength being too high, because the 15 uV/m limit of 15.221 is so low that it can't be heard at all on a radio receiver. LPB Technote #2 (Carrier Current System Design) suggests bringing a standard FSM to half of the radianlength specified in 15.221 to make the measurement. At half of the radianlength, the FSM will be in the near field, and the electric field will be at eight times the level at one radianlength. The trouble is that FSMs made for use below 30 MHz measure the magnetic field, and not the electric field. The readout is in electric field units, but the electric field is not measured. In the far field, the electric field is directly proportional to the magnetic field, making calibration in electric field units possible; but this is not true in the near field. So the field strength measurement method of LPB Technote #2 will not work.

Just what does that mean to an experimenter?

I'm glad we know that the method proposed by LPB is not the best approach but really, I think most of us would be pretty happy if we could get a CC op to work at all - half a radianlength notwithstanding

🙂

While I imagine it's likely there might be an NOUO in the FCC database for a carrier current effort out there somewhere, I don't recall seeing any.

In light of the fact that there are only a handful of NOUOs for any kind of AM operation, I hope those interested will forge ahead, remembering not to use LPB's advice on measuring field strength.