and why not?
I am playing around with carrier current as well but here is where i have to do things differently. Aside from Rock 105.3 FM station radiating on a home made folded dipole i also have a Sstran broadcasting on 800 AM using the shield side of 50 feet of 75 ohm coax. The AM signal is limited range i guess about 30 feet from the house before the signal dies out. That AM signal is intentionally limited as it was only meant to be an experiment to limit the signal to my house only.
Now here comes the part where i am doing things differently.
I have resurrected the old frequency of 95.7 fm by wrapping a length of wire measured for said frequency and wrapping that around the extension cord and grounding the transmitter to a separate ground outside. I tried this without the ground and was hearing a hum in the audio but it was not AC hum, i suspect it was a ground loop of sorts since it sounded much like the hum or buzzing you hear when you have a bad audio cable.
After connecting the ground the hum was gone. The transmitter I started to use was the Ramsey FM 25b but 25 mW did not seem to go much further than the mobile home park over a car radio and a Grundig portable shortwave/Am/Fm Radio. Reception was better on the car radio than it was on the portable but if you put the Grundig close to one of the many lamp posts' in the park the signal was there so i have every reason to believe this is working. At this moment I am using a Mobile Blackbox V6000 which is adjustable to 200 mW and mono. I see a bit more improvement at 100 mW. If i keep the CC FM going it will just re-broadcast what is going out on Rock 105.3 FM.
It does seem to me that anyone could listen in their mobile home if their radio was plugged into or was close to an outlet or wall. I have been pretty busy with some family business that is more important than radio at this point but my plan is to take my Grundig G3 to a friends house on the other end of the mobile home park, plug the radio in and see if any signal is making it into his home.
Whatever the CC FM won't cover the transmitter on the folded dipole should fill in those dead spots if anyone is listening to it on a car radio.
More later.
It's always nice to hear from you!
Well, I don't understand the theory
side of what your doing, but I guess
as long as your RF radiation is within the
rules you're good to go.
My mind is a little foggy. Are you the
person that's starting the network, or
have I got the wrong guy? I guess my
mind is really foggy.
Best Wishes To You, Barry
Bruce, DOGGRADIO STUDIO 2
Well, it seems I've been operating a 160 kHz carrier current station for some time now and wasn't aware until this evening.
My Realistic Plug'n Talk FM Wireless Intercom operates at 160 kHz with 75mW RF output. I always figured it to be a little further up the band.
So, I have the distinction of operating an LF FM CC station.
Programming has been dead air except for occasional ambient sounds and noise I make when working in the garage.
I keep the transmitter on to monitor happenings in the garage like the occasional racoon that wanders in.
I have not received any RECEPTION REPORTS yet but I have QSL cards ready - just in case.
I am wondering, MRAM, since the serious CC rule only covers 530-1700kHz, why is the intercom device legal? Maybe like the raccoon, you are a bandit wearing a mask.
Obviously I am being silly with that, you and the raccoon are simply in the proximity of a LW operation.
I just skimmed through the rules looking for the power limits that apply in general, prior to the sections granting special "intentional radiator" limitations, but it made me dizzy.
Why wouldn't it be legal?
Does CC only mean CC applies to the MW band?
Why would CC be considered non-compliant on another band besides MW?
For decades there have been such devices like baby monitors and intercoms using CC. As long as those devices in the 160-190Khz band operate with the 1 watt power input limit, it don't matter if your coupling to a 50 foot pole or the power grid.
There is nothing within the rules anywhere saying that CC shalt not be used on any band other than MW.
RFB
Agreeing with RFB, I suppose Radio Shack submitted the device to the FCC and they said OK.
The power companies use CC on the high voltage power transmission lines to monitor and control the grid. There are lots of consumer products that use CC; things like remote control switches and outlets, telephone extensions over AC lines, etc.
Hey, maybe I could convert these intercoms from CC to FREE RADIATE. Let's see, 75mW into a 50 foot antenna...
Everything being said regarding the baby monitor type of CC has been digested in my brain's sausage packer, and I wonder the following:
How can the AC power line be tapped by the antenna input of a LW radio to scan for neighborhood baby monitors?
I would guess the same way RFB has told us to just get the radio near the AC line. The signal may be strong enough to radiate to your LW radio.
Perhaps simply wrapping a few turns of the antenna wire around an AC cord would do.
Years ago when i was in high school an old friend of the family installed those great light switches, outlets and other modules for indoor & outdoor lights. From his armchair he could use a remote control just like a t.v. remote and turn on and off lights,a radio or control outdoor appliances like the light above the barn. The remote receiver could also be programmed to turn things on and off at set times during the day or night.
The cool thing about it, yep it was carrier current. Not sure what channel or band it was on but it was really cool. I think X10.com or another company whose name escapes me uses the same principle to remotely control devices around the home or office.
Rock95seven you may have provided the answer to my question of how to remote control several transmitters, especially the CC transmitter way down deep in the basement.
Imagine using CC to shut off the CC.
That will be a big topic on a future radio hour, but I need to search for more facts.
Submit everything you can find about X10.
EDITING MY WAY BACK IN
PAY DIRT!
YES, wikipedia has it, and the website was right... x10.com
http://en.wikipedia.org/wiki/X10_Wireless_Technology
I can say from experience that those intercoms tend to have some great range if they are on the same power lines serving i suppose the same neighborhood.
Once upon a time while doing housework i had to carry somethings into another room that had one of the intercoms (same exact model as MRAM's) installed and it was on. I heard at first what i thought was someone in trouble but i was the only person home at the time. Who could have been in distress and where were they?
As i crossed the room to where the intercom was on the dresser i quickly realized what i heard was not someone in trouble but rather uh er well a couple in the neighborhood was enjoying each others company and it didn't take me long to turn off the intercom and leave the room lol .
So the intercoms seem to have some range to them over the power lines. They had to be some distance from our house since the area i was living in at the time had acres of farm land in between homes sometimes as much as 10 acres or more.
The story of accidentally overhearing "someone out there" from your own home, reminds me of a story from 20-years ago.
A radio friend introduced me to a professional couple (both in high positions) who felt there was a chance they were being bugged. My particular experience in such things was very limited, but one thing I was able to inform them is that their intercom could possibly be monitored from elsewhere in the neighborhood without their knowledge. According to its manual it was on a low frequency, perhaps 160kHz or so.
I didn't really understood how it worked, but I knew that "it worked somehow."
Most of you know, but I'll just give a brief recap.
I have a 6 watt 1971 LPB AM vacuum tube transmitter,
model RC-6A. (It's a real joy to have this unit.)
The RF output is feeding a 10 dB pad (for isolation)
which then goes to a physically large LC, which is
tuned for max RF or minimum SWR on the transmitter
side. There is an AC extension cord feeding the
transmitter, and it is wrapped around the LC. There
is no direct connection to the A.C. line.
I did some brief experiments, because I have no desire
to break the law regarding Part 15.
There were some intermittent problems with the LC which I
discovered and fixed. That issue seems to explain why
I had some success in the beginning about 2 weeks ago,
and then had no results at all. (By success, I mean driving
under some power lines in my neighborhood and hearing
my signal.)
Although I don't have a lot of data yet, I can say this:
The set-up works better when it is loosely coupled to
the AC line. One or two wraps of AC cord around the
LC (which is about a foot square) works a lot better
than many turns of AC cord around the LC (heavier coupling.)
With loose coupling, I can hear the signal under the power lines
on adjacent streets relative to my house. Also, when the
AC is loosely coupled, I get a definite RF peak and SWR minimum
(on the transmitter side). That is - the readings are very
obvious and defined under those conditions.
With heavy coupling, such as 8 or 10 turns of extension
cord around the LC, there is no definite RF peak or SWR
minimum as the LC is tuned. Actually, that's not quite
right - there is a very very broad RF peak, and a very
slight SWR minimum, but they are so broad the reading
variations are almost not noticed. (This does not
surprise me.)
So loose coupling is better.
When I get the commercial coupler (I'm expecting),
that will be great,
but experiments with the homemade system may
continue.
By the way, I read the messages on this forum about
the LF wireless CC intercoms. Man - I wish we had
one to open up and observe how the coupling is done.
Thanks for reading this.
Bruce, DOGGRADIO STUDIO 2
This may be good news for Doggradio 2, regarding a post from MRAM giving us a pdf and illustration of a 5-Watt carrier current transmitter from 1973.
The coupling method is of special interest.
http://www.part15.us/node/3448
I'm pretty sure I was sitting in my high school
library in 1973, when somebody handed me
that article from Popular Electronics.
I remember being amazed that the 5 watt RF
energy went back into the power line via a
couple of .01 uF (?) capacitors. RF chokes were
put in front of the transmitter power supply
so the 5 watt RF AM signal would stay out of
that end of the transmitter. The RF out from
the final tube went through some kind of
transformer.
But the thing was - those caps bridging the
gap like that. I will never forget seeing that.
RFB has always said this IS NOT the way to do
it, HOWEVER, from a historical standpoint this
schematic is very interesting anyway.
i also remember that the schematic was put in
the article, but I never saw a photograph of the
actual transmitter. It makes me wonder if such
a unit was ever really built.
If I had the ability to build that thing THEN,
it would have been a really cool thing. Provided
i didn't blow myself up.
The University of Connecticut had WHUS FM/91.7 in
1973, running a little more than 3000 watts.
But WHUS AM (CARRIER CURRENT on 670 kHz (?))
was often simulcasting the FM program.
These guys at WHUS really knew what they were
doing. They would run the FM/AM simulcast, and when
a PSA was run on the FM, they would flip a switch
on the main control board, splitting the program
briefly - and run an advertisement on the 670 AM
AT THE SAME TIME.
So two cart machines were going. The PSA was on
91.7, and the commercial was on 670 CC. When
both the different carts were done, they would throw
the switch BACK, combining the AM and FM again.
It was impressive, and - it was legal, of course to
run commercials on the AM 670 CC. And they did
sell ads for 670 - for a while - I don't know how
long that worked out for them.
It was early in my radio tinkering and listening when
I realized WHUS, 91.7, at the University of Connecticut
had a 670 AM CC, and WWUH, 91.3, at the University of
Hartford, had WWUH AM CC on 640 kHz.
I didn't understand what that really meant until a
few years later.
I'll have to go back and take a look at that CC schematic
again. It does bring back memories.
Best Wishes,
Bruce, DOGGRADIO STUDIO 2