Shalom ,
I am using the Ramsey AM25 , and a regulated 13.8 volt 2.5 amp power supply, with the antenna loaded into the power line of the building (carrier current).
Shalom ,
I am using the Ramsey AM25 , and a regulated 13.8 volt 2.5 amp power supply, with the antenna loaded into the power line of the building (carrier current).
I have the metal rack that holds equiptment (about 8 feet tall) as my ground.
Now .. where to find a good Field Strength Meter?
I have a couple of old 3 to 30 Mhz ones ..and they show activity , but still … I wanna do this right !
I started out converting old cordless phones (made before 1984) into AM radio transmitters, back in the 80’s.
I got ok results, and was amased @ how far I could hear my broadcasts.
Any thoughts are welcome
Newbie?
I started out converting old cordless phones (made before 1984) into AM radio transmitters, back in the 80’s.
Gosh – looks like you could teach some of US a thing or two 🙂
Welcome aboard!
Experimental broadcasting for a better tomorrow!
FS Meter
Welcome!
One problem we face with trying to buy or build field strength meters is sensitivity. Meters built for amateur radio use work well but they are working with fields produced by tens to hundreds of watts. The fields produced by part 15 AM transmitters are too weak to give a response from a simple meter.
My suggestion is to get an older model AM transistorized radio which does not use an integrated circuit and tap the AVC (automatic volume control) voltage from the volume control and send it to a meter. I have seen these radios at antique malls for single digit dollars.
Though they won’t provide a calibrated measurement, they can be useful for relative measurements and tuning and they are frequency selective with built in audio monitoring.
I did a bit of paper research on using my newer IC based AM receiver for this but found that the IC AVC loop gain is so high that a large change in received signal strength results in a very small change in the AVC voltage. I deemed this change to be to small to be useful
Neil
Thank You
Shalom,
That is great info.
Old Cordless Phones
Shalom,
It was 1987 when I was 15 , and was taking apart everything I owned that was electrical to see how it worked.
I noticed one day, before I had a police scanner , that I was listening to my shortwave radio, and my cordless phone that I bought @ a church garage sale a few days before – the phone when it rang , it would come blaring out of my speaker on the radio … so I experimented.
I found that I could hear my conversation clearly in the center of the AM dial as well. That makes sance to me now since I understand harmonics etc. (700 – 900 Khz is about half the frequency of the actual transmission from the base – thus being the “first hamonic frequency” ). The first (devide any frequency in half) , is always the strongest harmonic.
In the 90’s , the AM band expanded from 1610 to 1710 over a few years. By 1998 1710 was the highest frequency that was available on AM radios. Back before that time (pre 1984) cordless phones used 5 frequencies on 49 Mhz for the handset to the base, and frequencies just above 1610 AM for the base to the handset. These base units had 1 metal antenna on them that was for the receiver (49Mhz) and the antenna for the transmit on AM was using Carrier Current (loaded into the power line).
As you an see, I was able in the 90’s as was anyone else .. to hear there conversation on an old cordless phone clearly on AM radio !
So … I decided to tap the audio circuit on the base unit , and disable the receiver (49Mhz) so that I did not get baby moniters , and static etc. I did try the baby moniter idea since they used the same 5 frequencies back in the 80 ‘s – 90’s . and the sound quality was terrible( because of the base unit being designed to be a telephone – thus telephone sound quality is not very good for broadcasting ) … so I taped the audio , and then soldered an “rca ” jack into the base , and crossed two pins on the 8 pin IC that used be used back then to keep the base unit transmitting (off the hook) .
I have tons stories about how I got self tought , and if anyone has more question, I would love to share what I know.
Brandon
Converting Old Cordless Phones to AM Broadcasters
Shalom,
The way to determine if you find an old enough cordless phone base unit to convert to an AM tranmmiter , the date is almost always printed on the bottom.
Old single channel phones had the channel number on the handset and base, and anything with a number 1 – 23 and the letter “A” after it was pre 1984 ..and is exaclty what you want to use.
I can provide step by step instructions to help anyone that has experiance soldering etc.
By 1984 the FCC made the phone makers start using 46/49 Mhz, and the plan must have been to expand AM and get these phones to other frequencies .. not to meantion , the AM CC loaded antenna was to blame for the hum , and buzzing heard on the handsets back then. That was true if you were right next to the base antenna (the power lines in the house ). but if you go out into the front yard ..the buzzing went away ….. I had one old AM phone that would do 1 mile from my house …I had more trouble getting the handset(49Mhz) signal, to make it back to the base unit to “kick over” the dial tone to me … and If I got up on a hill by my house .. I could do this.
These old phones were kinda neat … You could hear the handset ring for long distances …you just couldn’t answer them !
Brandon
Old Cordless Phones and Harmonics
Brandon,
Thanks for sharing your “war stories” about the old phones. My first was a Uniden and I think it was all 49 MHz. We had another which was somewhere around 27 MHz but I never dug deep enough into its specs. to say for certain.
Your understanding of harmonics differs from mine in that harmonics are multiples of a fundamental frequency. For example, if the fundamental is 1000 kHz then the second harmonic is 2000 kHz, the third is 3000 kHz, and so on. There are no “sub-harmonics” such as 500 kHz since this would make 500 kHz a fundamental and 1000 kHz would be the second harmonic.
Maybe you were able to receive your signal on a lower frequency because of the superheterodyne receiver’s image frequency. This frequency is usually 910 kHz higher than the tuned frequency. For example, if your phone was transmitting on 1800 kHz this would be the image of (1800 kHz – 910 kHz =) 890 kHz and it could be heard at 890 kHz.. This could easily be the case when the receiver is close to the transmitter. What do you think?
Neil
Harmonics
Shalom,
Absolutely makes sence!
I have no degree , but what you said makes perfect sence …. I used to be able to find my 900 Mhz corldess phone on uhf around 450 Mhz if the units were close together.
I may have called it the wrong thing then … I again have no formal degree.
Brandon
Neat stories
I am also self-taught in electronics and have made it my lifetime career! I started messing with radios at age 7 and at age 16 had a part 15 am station and studio. I worked in commercial radio as a Dj and later as an engineer,then moved on to 2-way radio,paging and microwave. I have added IT and VoIP with new projects I am involved with,I love this stuff! I should point out to you,Neil,that the third harmonic would be 4000 -not 3000. And welcome to Brandon with a caution about using 1710khz,it is NOT a part 15 authorized frequency! The band stops at 1705khz,I would hate to see you get fined! When you are bored and have nothing better to do,sit down and read part15 FCC rules,its an eye opener!
Regards,Lee,RadioFreeErie,AM/FM and SW
http://www.freewebs.com/wilcomlabs/index.htm
Harmonic
Lee,
Lee wrote:
… I should point out to you,Neil,that the third harmonic would be 4000 -not 3000…
Actually, it is 3000 kHz. It would make sense that it would be 4000 kHz if you look at the harmonics as being only the multiples of the fundamental but that is not how this is done. The fundamental is considered to be the first harmonic by definition so it then becomes a simple matter of multiplying the fundamental by the harmonic number to get the harmonic frequency. Though perhaps not 100% right in terms of language it does make calculations very simple.
Neil
Also Mostly Self-Taught
I’m also mostly self-taught. Started with a crystal radio kit and then went on to building some of the Radio Shack “Science Fair” kits, where you used the plastic box it came in as a sort of perfboard to build the circuit on. The “Wireless AM Microphone” kit from that line was my first transmitter. I’d never soldered anything before except a few leaky plumbing joints, and I used the “soldering iron” that fit on a propane torch cylinder to build it. That was a mass of poor wiring and dripped solder joints but it worked! Well, sorta. The only way you could say it had a range of 10 ft was if you stretched the 9 ft of wire out on the floor and put a table radio within a foot of the end of the wire. And the frequency was touchy, about as stable as Charles Manson sitting on your front porch eating Froot Loops.. But it was a first taste. It had a horrendous little mic and so the sound was awful, but I messed with it a bit.
I fumbled my way though learning a bit about electronics as a teen by trying to fix things like table radios gone wrong and etc. Got my share of “Shazam!” moments from touching the wrong things in old TVs and old tube radios. When I got into music and playing guitar, the only place to get parts was a TV repair shop in a town a few miles away. I’d bike over there and spend the day asking questions and buying a few parts and sometimes learning a trick or two for troubleshooting. My first FM “station” came from that.. The guy who ran the shop showed me how to check the oscillator in an FM radio by tuning another FM radio about 10 mhz below it. Then one day I was poking around the innards of a radio with a little one transistor audio oscillator I’d made as a “signal injector” and rather than coming out of the speaker of the radio I was working on, the tone came out quite loud on the radio I’d tuned to check for the oscillator and forgotten I’d left on. Well, that was interesting. I pretty much immediately thought of putting in some more interesting audio and used the speaker output wires of a small cassette tape player that was handy. Lo and behold, on the air!
I lived out in the country, it didn’t even cover the yard, but the sound was nice in my bedroom with the receiver not 20 ft away. LOL I had microphones and eq and a small home-made passive mixer from my musical interests, and it was fun when friends would come over.
Then I started college in about ’79 and got into the college radio station. Little class “D” 10 watter and we thought we was something. LOL Dropped out of college after a year, and the station was shut down anyway because some of the student admin of it didn’t bother with keeping the required logs and the college wasn’t particularly supportive of the station anyway.
A couple years after that, I had one of those old “100 in 1” electronics project kits with the little spring terminals and where you build circuits by putting jumper wires between the parts. I built the little AM transmitter in the project book but wasn’t very pleased with the sound, and rigged an old FM receiver up as a transmitter instead. I tried boosting the range by probing around inside it with a piece of wire and figured out that tack soldering on a loop of one of the coils did the trick. The range was still about 2 rooms, so I got the idea of an outdoor antenna. Cobbled one together out of an old plastic pill bottle and some pieces of aluminum tubing off an old TV antenna cut to length for the frequency and about 20 ft of old rg-8 CB coax between the “transmitter” and the antenna.. Blew something in the “transmitter” in about 30 seconds. I guessed that the hopefully more resonant antenna had been too much load on the circuit compared to the little piece of wire I’d used at first..
So, I got another old receiver out of a console system a neighbor was throwing away and this time added a trimpot in series between the antenna and the tap on the coil and carefully creeped it up until it sounded clear on a receiver on the front porch. The antenna was mounted on a window frame at the back of the house, so it also covered most of the back yard. Set up a little studio just for fun out of mostly band sound gear. It was nice for kicking back and being able to hear tapes all through the house without having a stereo outside the basement turned up loud, and fun for parties. Until the first time it rained.
The first time it rained, then that transmitter also went to the big scrapyard in the sky. I decided at that point that a circuit actually designed to transmit might cope a bit better. I went to the library and found a circuit in a book for a little one transistor FM transmitter and built it. Then the range was about to oh.. the sidewalk across the street. But having weatherproofed the antenna and connections this time, it survived things like rain and with a guitar effect compressor and an old 5 band eq sounded like pretty much any station on the air other then being mono. Played a lot of early electronica. Rick Wakeman, Jon Anderson, etc. Also rehearsal tapes and gig tapes from my band and friends’ bands (punk) and some classical (yeah, quite a mix there). I’d been reading Phillip K. Dick’s novel “Radio Free Albemuth” and remembered the “Radio Free Europe” ads on TV and REM had a song I liked out by that name. I called that project “Radio Free Arcturus” because.. well.. I didn’t want to call it Radio Free Albemuth, but I liked the sound of the name. Arcturus is a star, like Albemuth. No other connection, really. LOL
No great range, might have even actually been within FCC limits, but I wasn’t sure, so I ran it cautiously and mostly at night and on weekends. Sometimes friends who had been DJs on the old college station would come in to take an evening, but no real schedule. Had the “ID” on a loop on a small reel-to-reel tape machine that had a sensor for the metallic bit of tape so it’d play once and then stop, and it could be just punched in like a cart machine loaded with a short ID. I usually would record a show to tape while doing it live so other times I could sit back and relax with friends and listen. Just a fun station, it didn’t go much past the yard and it didn’t need to.
That was in the early 80s, and I gave my station gear to an interested friend when my wife and I moved out of state. Inside of a week he let somebody tinker with the transmitter to “tweak it up” and blew it out. So far as I know, that was the end of it.
No other stations until the past couple years. In the meantime I took a basic correspondence course in electronics, which was enough to get a job as an assembler in a little company out west, moved back east and got another job in electronics for a few years.. That’s about as close as I’ve gotten to a formal education in electronics. But about 4 yrs of putting in overtime weeks schlepping boards and assemblies together is great experience for a hobbyist and to any newbies out there, if you can even get a temp gig doing it for a month or few it’s the *best* way to get your soldering skills and etc.. There’s nothing like your good friends at the quality control station for getting you to where you can handle an iron good.
Recent years, before the internet streaming stations started being charged for using copyrighted material I was asked to do shows on an internet station that’s now defunct. Got the “DJ bug” back again and was having fun with it.. But I got real tired of having to sit at the computer when on the air, so I looked into current part15 and built a little FM kit. Which took a fair bit of tinkering and modding to get clean and fairly stable. Originally just wanted it for around the house, but some of the nearest neighbors liked to listen. Then I quit streamcasting and went to indie/original format. My station isn’t on 24/7. A couple hours in the early morning until the kids are off to school to share talk some music and weather reports and etc.. then a few hours after supper which are mostly stories read from classical literature or OTR radioplays from Project Gutenberg. Late night is mostly calm instrumentals (again indie) that can be neoclassical or electronica or whatever.
I replaced the kit FM with a nicer sounding Maxell FMT-1 that has an FCC ID#, and use a SStran indoors with the wire antenna for AM. I mostly only run the AM for the evening story/OTR programming, since there’s a neighbor across the street with an antique radio who likes being able to use it.
I call the current project “Radio Strange”.. Originally because I couldn’t think up a spiffier name, and now because that’s what my IDs are recorded as saying. LOL And it’s strange enough, since the music can vary from things that sound sort of pop or rock to folk to Native American flute or whatever other musicians send me to play with my own music or I can get artists’ permission to run.
I don’t have an interest in being at all commercial in my programming and don’t see my station as being in competition with local commercial stations. Even if anybody was crazy enough to want to buy ad time on a station with a range that’s less than most people could throw a baseball, I wouldn’t do it. I don’t *like* commercials, and what’s more I have old friends that work at the local stations and they have families to feed just like anyone else. I view part15 as a hobby interest that lets me have radio be the way I like it, and sometimes also entertains next door neighbors who think it’s neat. I don’t like the corporate trends in programming, so I do it for my household and my neighbors the way I wish it was when I turn on a radio.
When weather gets warm and I get an outdoor antenna set up for the SSTran, It *might* have enough range that I may find neighbors a little further out who are interested. Which would be fine, but I won’t be changing the programming to “be popular”.. This town already has Top 40 stations, Oldie stations, Classic Rock stations, Country stations.. No point in my mind duplicating that, and I prefer to remain an alternative rather than trying to do what they do.
Not to say it’s not of use or interest to the few people outside my household who make it a point to tune in. For example, even the time announcements in Zara are for times when somebody needs to get up or start looking for the schoolbus or head out the door for work or when somebody’s youngsters are supposed to get ready for bed.. It’s community of a sort, just an a bit smaller scale than I think most people on this forum are working towards.
Anyway, so I’m mostly self-taught as well and learned more electronics from tinkering and fixing band gear and working in electronics factories than I did by formal education.
Daniel
That reminds me …
Shalom,
I did alot of the same things .
I used to wait until my Step Dad was watching the “big game” on TV.
I would tune my old tube type shortwave radio unit I got the harmonic just right and then fine tune until I got the sound of static over the TV from down the hall …….. Yikes!
I was a bad kid. I got shocked a few times as well.
Thanks
Shalom,
I have been looking at some things on the FCC site and I see that 1705 is the, “last stop” so to speak …but the 1710 and up to the next “stopping point” in the rules does not seem to have anything much differant in way of power output , needing a smaller than 10′ antenna etc.
Seems to me like the AM broadcast band has the most restrictions in comparison to the others (excluding FM). So if that being true , wouldn’t is be more likely that 1710 and up to eht enext point , would be less restricive?
If there is a link , or a specific violation anyone can think of with this set up on 1710 , I would love to learn about it ..in the mean time just to be safe , I am switching back to 1610.
Thanks
Brandon
Operation on 1710 kHz
Brandon wrote: If there is a link , or a specific violation anyone can think of with this set up on 1710 , I would love to learn about it ..in the mean time just to be safe , I am switching back to 1610.
TITLE 47–TELECOMMUNICATION
CHAPTER I–FEDERAL COMMUNICATIONS COMMISSION
PART 15–RADIO FREQUENCY DEVICES–Table of Contents
Subpart C–Intentional Radiators
Sec. 15.219 Operation in the band 510-1705 kHz.
(a) The total input power to the final radio frequency stage
(exclusive of filament or heater power) shall not exceed 100 milliwatts.
(b) The total length of the transmission line, antenna and ground
lead (if used) shall not exceed 3 meters.
(c) All emissions below 510 kHz or above 1705 kHz shall be
attenuated at least 20 dB below the level of the unmodulated carrier. Determination of compliance with the 20 dB attenuation specification may be based on measurements at the intentional radiator’s antenna output terminal unless the intentional radiator uses a permanently attached antenna, in which case compliance shall be demonstrated by measuring the radiated emissions.
Sec. 15.223 Operation in the band 1.705-10 MHz.
(a) The field strength of any emission within the band 1.705-10.0
MHz shall not exceed 100 microvolts/meter at a distance of 30 meters. However, if the bandwidth of the emission is less than 10% of the center frequency, the field strength shall not exceed 15 microvolts/meter or (the bandwidth of the device in kHz) divided by (the center frequency of the device in MHz) microvolts/meter at a distance of 30 meters, whichever is the higher level. For the purposes of this section, bandwidth is determined at the points 6 dB down from the modulated carrier. The emission limits in this paragraph are based on measurement instrumentation employing an average detector. The provisions in Sec. 15.35(b) for limiting peak emissions apply.
(b) The field strength of emissions outside of the band 1.705-10.0 MHz shall not exceed the general radiated emission limits in Sec. 15.209.
//
1710 Khz
Shalom,
thanks you … I have set the transmitter back to 1610 AM .. it is clear here, and not other station is heard ever – even @ night.
That will solve any question.
Thanks Again – better to be safe than sorry !
Now I have to change my nickname here LOL!
carrier current
Shalom,
Another exception to the above rules pertains to Carrier Current broadcasting. This involves coupling a radio signal into the powerlines, and using that as your “antenna”. Carrier Current carries a different limitation: the field strength must be less than 15uV/m from the power line, measured at 47,715/(frequency in kHz) meters from the transmitter. This means that if your station is broadcasting at 540kHz, the test point would be at a power line 88.4 meters (292 feet) from the transmitter. If conditions are right, this can go significantly farther than a Part-15 antenna signal.
Unfortunately, Carrier Current is a very erratic system. I’ve heard stories of carrier current stations going several miles, and some that won’t even go across the street. One of the biggest problems with Carrier Current signals is the power line transformers. They are designed to zap and RF going through them, which will effectively stop any carrier current signals.
One idea I’ve heard for getting around this is to attach the RF feed to the return wire instead of the hot wire. This might work better. Another idea I’ve heard is to bypass the power line transformer itself by attaching a very high voltage coupling capacitor between the input and output of the power line transformer. This is extremely dangerous, and should only be attempted by a qualified linesman. And unfortunately, it is very doubtful that the power company would agree to make any such modification.
This was found on page 20 of the “Low Power Broadcasters Handbook.” I seem to having better luck with CC Antennas … I hope this is ok to use … I need to find out what the FCC would recognize as a “college campus. ” We have teaching here @ the office, but I wonder what the FCC wants that to be defined as.
Any thoughts are welcomed !
Posting while tired
You are right Neal,dont know where that came from. The harmonics are integers of the fundamental. Also on some heavy meds for pain management….disregard my babblings! I’ll be quiet over here in the corner,LOL
Regards,Lee
http://www.freewebs.com/wilcomlabs/index.htm
Carrier Current Antenna Load
Shalom,
Well , I setup the carrier current antenna load here @ my office and I have been able to get close to 1 mile ,3 directions from the office on my car radio on 171o am ( I did not check the 4rth because the traffic was so bad ).
I am pleased with the results …. I did have to experiment with grounds though.
I now use the metal shelves @ 8 feet tall ad my ground, and the CC Antenna together …. Works Well !
No Degree
Brandon,
You say you have no degree….so what? I was on the air with part 15 AM and FM while I was still in highschool. I learned by reading and experimenting. Your willingness to experiment and learn as you go will serve you well in this great hobby.
I appreciate your willingness to share your escapades and I hope you will continue to do so. Don’t be shy about asking questions on this board. There are a lot of friendly folks who are glad to help. Keep in mind that I and others here will learn from your reports. We are all in this together.
Neil
No Degree
Shalom,
Thanks.
I got my job here at a full power radio station on what I know and I am seeing that is true. I volunteer some, and get paid some, but it has been a blessing anyway.
I will update when the actual station engineer gets back from vacation, and helps me set up an outdoor antenna and goud system … I will let folks here know how it goes.
I will also be setting up an FM soon
Brandon