I was wondering if anyone has or had these intercoms and could you tell me if they were true FM or actually just great sounding AM?
Would be an easy hack to add audio to one of these for an in-house broadcast on the longwave band. Which brings me to another question I guess, are all of the older radio shack intercoms in the longwave band? Or did i just imagine all this? Hmm ...
Barry of Blue Bucket Radio 1520 AM
I actually was paying attention at some point in time.
Here is a thread about easing up on the longwave part 15 rules and MRAM mentioned he has this model of intercoms in the LW band doing CC.
Answers most of my question.
We we smart in those days, when that thread was written.
Look at us now.
Since then I finally found the section of Part 15 that applies to carrier current outside of the regular medium wave band, let me find it again and link to it here.
Keep waiting, I'm looking it up.
Alright... I'm back.
Here it is:
15.109 Radiated emission limits.
(e) Carrier current systems used as unintentional radiators or other unintentional radiators that are designed to conduct their radio frequency emissions via connecting wires or cables and that operate in the frequency range of 9 kHz to 30 MHz...
To see the rest of the text consult the FCC Part 15 Rules.
I wonder if it broadcasts in the band of 160-190 Khz? If so you could do a LW Radio station and I know it will go the length of a neighborhood. It will even travel the length of a school campus as well. You should be able to strip off the mic element and then attenuate it and add a 1/8th inch jack. Then its plug into your computer and use a good automation program and a mic and you can start a Radio station. Too bad its hard to find receivers that will do LW.
There are LW radios out there, they cost a little more but not much.
Often if radios have shortwave they also have long wave.
I have four long wave radios, some of them cover a larger number of frequencies than the others.
Soon we'll be getting back to the designing of a longwave transmitter that got started a few years back here at this site. There's a link to it somewhere on my website.
The only interest I have in running a longwave transmitter is for local casting to my property which is why I have expressed interest in obtaining a set of these intercoms.
After struggeling to build the second SStran AMT3000 I have realized that my tremors are much worse than I thought. Precise soldering is a bit difficult when your hands shake, still I managed to build the kit and it works so that must count for something.
As MRAM noted in that thread i linked here, there is are at least 3 frequencies the Realistic intercoms use and that is indicated by the model numbers. One is on 160 khz, but since I don't plan on modifying the antenna section at all, the carrier current mode will work just fine for me.
An estimated range of 300 feet is fine with me, i just want to hear it on a Grundig G3 GlobeTraveller that does LW. Modifying the audio section of these intercoms should be pretty easy.
p.s. I was coming home a while ago from the grocery store and was about 1/4 mile from home, despite my antennas being inside the house and the power line noise, i managed to hear both of my AM stations under the noise. I call that progress.
Barry of Blue Bucket Radio 1520 AM
WXW 530 AM - All of the weather, all of the time.
When I saw this thread it reminded me... I have a pair of "wireless" intercoms sitting right here! One is down here in my office, the other is up in the studio. They haven't been plugged in for years. Of course they're not actually "wireless". They have power cords, and the audio is transmitter through the house wiring. I never gave them a thought.
These have a choice of three channels -- you would buy more than one for the "receiver" end, and the "main" unit could then call whomever they wished by choosing the channel for that particular receiver. Bottom says they are "Model 30-6027" and the frequencies for channels A, B, and C are 230, 260 and 290 KHz.
They're not new. They don't have a polarized plug and not a mention of meeting part 15 rules on them anywhere.
Curious indeed.
TIB
When I saw this thread it reminded me... I have a pair of "wireless" intercoms sitting right here! One is down here in my office, the other is up in the studio. They haven't been plugged in for years. Of course they're not actually "wireless". They have power cords, and the audio is transmitter through the house wiring. I never gave them a thought.
These have a choice of three channels -- you would buy more than one for the "receiver" end, and the "main" unit could then call whomever they wished by choosing the channel for that particular receiver. Bottom says they are "Model 30-6027" and the frequencies for channels A, B, and C are 230, 260 and 290 KHz.
They're not new. They don't have a polarized plug and not a mention of meeting part 15 rules on them anywhere.
Curious indeed.
TIB
If you could find some that have 160-190 Khz they probably could be modified to be max legal and actually get some range. But even for your own property they could really have some great uses. It would make a great STL and you could put your AM TX up high. One way I could put my Talking House up in the attic. Now the range would greatly increase. Hmmm I may be able to find some. And if I'm already using 160-190 Khz I could even get listeners of a greater range.
TheLegacy wrote:
" Hmmm I may be able to find some. "
That won't be hard, I did a search today on Ebay and there were pleanty of these units for sale. Some with free shipping and priced reasonably. Just need to filter out the one's you are looking for according to frequency.
Yup and then have someone help solder an 1/8 in jack into it and of course make it so I can plug the patch cord into it. Plug my computer into it and see if I'd actually get any range with it if I was to somehow modify it to transmit to an antenna. Or maybe Carrier Current would go further in my case. It would be fun to try it. If you do this let me know your range I'd love to know what happens and how clear it is.
Wait I got an idea. I always wanted to try carrier current AM on 1630 Khz. Well how hard would it be to change the crystal or whatever to make it transmit on 1630 Khz? I wonder if I'd get 1-2 miles with that? Anyone near me who plugs their Radio into the same power line connected to the same transformer could hear The Legacy right? OK there is the Library, 2 law firms and even a bar and a school where some people do listen to Radio. Some buildings may have material that would normally attenuate an AM signal maybe FM too. But a modified intercom to transmit on 1630 Khz and just plugs into the wall? Its been what I wanted. Someone who has sight please try this and tell me what happened I got to know. I'd buy one of these and have you modify it for me. At least I'd have a long range station till Station8 has his antenna done. Or maybe the circuit could be modified to allow my Talking House to transmit carrier current with part of that circuit. I could use their coupler to do it somehow. All of this gives me ideas.
The plug and play intercoms are FM , not trying to burst your bubble just saying that the circuitry will only allow FM mode unless a complete re-work of the transmitter was perfmormed on the plug n play.
Hard to say how difficult that would be to modify without a schematic.
Well the only way this would be any good would be to reverse engineer the coupler that is inside the wireless intercom system so that you could somehow use an existing AM Transmitter like the Talking House. Since there is a 75 ohn F connector and no tuner you could somehow figure out a coupler that would allow a connection to a standard plug. I don't know if the signal would actually get out because the Talking House AM Transmitter only has 100 mW, but you don't know till it has been tried. Different houses may or may not be suitable on count of how the wiring is configured.
Both of my AM stations, one being a talking house v5 and the other the SSTran AMT3000 are on the indoor antenna's but in different rooms.
The other day I was able to hear both signals (530 khz and 1520 khz) as long as the power lines followed the road. Once the power lines slipped into the woods and climbed the mountain my stations were no longer detectable.
It was nothing but static until I turned onto the road to my house.
There is a an outlet close to both antennas with wiring running from the outlets down the wall and under the house to the breaker box.
Both signals were just barely above the noise level which is amazing since the TH is in a back room with a mobile home no more than 9 feet away from that room at my neighbors property line. The AMT3000 is in the living room in front of the house by a window.
With a coupler of any kind, i think 100mW probably could cover 1/4 or a bit more, I have heard tales of 100mW transmitters wired to home made ATU's and a long wire up in a tree covering 4 miles.
Not sure really without trying it myself, but i am thinking 1/4 mile over power lines would be the max before the signal ran out of energy and is consumed by power line noise.