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Where can I find a diy-type Propeller AM radio transmitter project? — Parallax Forums

Where can I find a diy-type Propeller AM radio transmitter project?

AwesomeCronkAwesomeCronk Posts: 1,055
edited 2019-07-03 01:56 in Propeller 1
Looking to make a short range transmitter, ideally with variable frequency. Spin/Pasm code is preferred.

Comments

  • BeanBean Posts: 8,129
    Are you looking to transmit data or audio ?

    Bean
  • TheTech69TheTech69 Posts: 51
    AwexomeCronk,

    Did you happen to find this?

    http://forums.parallax.com/discussion/105674/hook-an-antenna-to-your-propeller-and-listen-to-the-radio-new-shortwave-prog#latest

    It might be a good starting point for the receiver side of the AM radio transmitter project you are working on. If you're going to transmit a signal, I suspect you will need a receiver.
  • AwesomeCronkAwesomeCronk Posts: 1,055
    I planned to make a transmitter to send audio maybe 20 feet to a quarter mile. Maybe prop speech synthesis. I have an am radio and have found quiet spots around 520 kHz and 1 MHz. So I figured the prop could use a cog to mime the oscillator and use another to provide audio. @TheTech69 that thread I saw a while back and is why I figured a prop could do it.
  • YanomaniYanomani Posts: 1,524
    If are there no nearby HVAC transmission lines, perhaps you could use that 1 MHz "quiet spot" you've found.

    Otherwise, your transmissions/receptions could experiment a lot of interference, due to gap discharges, commonly present at the insulator spacers, near each of the wire-holding metal towers that route HVAC trasmission lines (a extremmely commom phenomena, at least in my country).

    There are also the possibility of HVDC power transmission systems, with totally different parametrization and behaviour, but they are not directly connected to commercial/residential areas; they must be converted to HVAC before routing to the consumers.

    https://electrical-engineering-portal.com/7-bad-effects-corona-transmission-lines#electromagnetic-interference
  • YanomaniYanomani Posts: 1,524
    Just in time, the other "quiet spot" you've found (520 kHz) is too near AM IF frequency (455 kHZ), so you can expect a good bunch of "mostly innaudible" interference at that region of frequencies.
  • AwesomeCronkAwesomeCronk Posts: 1,055
    I think that the 1.7 MHz option is my go-to. Weird phonomenon, I can hear the vacuum over the AM lines if I tune into the 1.7 MHz range.
  • AwesomeCronkAwesomeCronk Posts: 1,055
    Silence in my area from 1620-1710 kHz, also at 520, 560, and 570 these three receive nasty amounts of scattered transmissions, though.
  • RS_JimRS_Jim Posts: 1,773
    AwesomeCronk wrote: »
    I think that the 1.7 MHz option is my go-to. Weird phonomenon, I can hear the vacuum over the AM lines if I tune into the 1.7 MHz range.
    Typical of AM radio. The Vacuum is probably using a brushed type motor and you are hearing a harmonic of the brushes arcing.
    Jim

  • jonesjones Posts: 281
    If you want your transmitter to operate at night, be sure to check for noise/signals then as well. Medium wave propagation can open up at night and stations can appear that you can't hear at all when the sun is up. Not that you really want to be up all night, but the best time for long distance MW reception is typically after midnight. Back in the old days, there were 50 kW "clear channel" stations that could often be received many hundreds of miles away. I think some of those still operate, so they might give you trouble, particularly when the separation between your transmitter and receiver are greatest.

    If your operation will be limited to daytime or early evening, you probably don't need to bother.

    Bob
  • Peter JakackiPeter Jakacki Posts: 10,193
    edited 2019-07-04 01:11
    Nobody has mentioned FCC regs so far, have they? I'm fairly certain that unless your AM broadcast band transmitter only works at arms length, then it probably isn't legal. Somebody who is in the know can correct or dispute this.

    Mind you, as a teenager I would ride on the bus with my AM transistor radio, except I wasn't listening to it, I'd just sit near someone who was listening to theirs and with the volume down I'd turn the tuning dial until the local oscillator would start to interfere with the station that they were listening to. Amid their confusion as to why their radio was playing up I'd have my silent little geek giggles :)

    But that makes you wonder about all the inadvertent transmitters such as electrical equipment and HV power lines that interfere on that band.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    Peter Jakacki wrote:
    Nobody has mentioned FCC regs so far, have they? I'm fairly certain that unless your AM broadcast band transmitter only works at arms length, then it probably isn't legal.
    True enough. You need to check the FCC's Part 15 regulations for "intentional radiators":

    https://www.fcc.gov/oet/ea/rfdevice

    Across the room may be okay. A quarter mile? Not so much.

    -Phil
  • AwesomeCronkAwesomeCronk Posts: 1,055
    edited 2019-07-04 03:36
    Didn’t find anything there that tells me “no-no”, but that may be because I didn’t read in depth through the rest of the page.

    Range wise, if I can reach the car out front and the radio on my desk, I’m good!
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    AwsomeCronk wrote:
    Didn’t find anything there that tells me “no-no”, but that may be because I didn’t read in depth through the rest of the page.
    That page is just a summary. You have to follow the links to get to the real meat.

    -Phil
  • twm47099twm47099 Posts: 867
    Here's a link with more info (including penalties)

    https://fcc.gov/media/radio/low-power-radio-general-information

    And here's some highlights from that page:

    "Part 15 Devices
    Unlicensed operation on the AM and FM radio broadcast bands is permitted for some extremely low powered devices covered under Part 15 of the FCC's rules. ... On the AM broadcast band, these devices are limited to an effective service range of approximately 200 feet (61 meters). See 47 CFR Sections 15.207, 15.209, 15.219, and 15.221. These devices must accept any interference caused by any other operation, which may further limit the effective service range.

    Prohibited Forms of Low Power Operation
    A license or a construction permit is required for all forms of operation in the AM and FM radio broadcast bands which cannot be classified as Part 15 or Carrier Current or Campus Radio Stations.

    Penalties for Operation Without A Permit or License
    The Commission considers unauthorized broadcast operation to be a serious matter.
    Presently, the maximum penalty for operating an unlicensed or "pirate" broadcast station (one which is not permitted under Part 15 or is not a Carrier Current Station or Campus Radio Station) is set at $10,000 for a single violation or a single day of operation, up to a total maximum amount of $75,000.
    Adjustments may be made upwards or downwards depending on the circumstances involved. Equipment used for an unauthorized operation may also be confiscated. There are also criminal penalties (fine and/or imprisonment) for "willfully and knowingly" operating a radio station without a license. sort by DON'T DO IT!
    See recent Enforcement Bureau orders for unlicensed operations.
    "
    There is more info on that page at at the links on it.

    Tom

  • AwesomeCronkAwesomeCronk Posts: 1,055
    Well, it was a fun idea!
  • RS_JimRS_Jim Posts: 1,773
    Go get yourself a technician class amateur radio license and then you can legally broadcast in the specified bands with all kinds of modulation techniques. I got my start in electronics with a novice license at age 13.
    Jim
  • kwinnkwinn Posts: 8,697
    edited 2019-07-04 21:25
    Peter Jakacki wrote: »
    .............

    Mind you, as a teenager I would ride on the bus with my AM transistor radio, except I wasn't listening to it, I'd just sit near someone who was listening to theirs and with the volume down I'd turn the tuning dial until the local oscillator would start to interfere with the station that they were listening to. Amid their confusion as to why their radio was playing up I'd have my silent little geek giggles :).............
    Similar to what I did with a 555 timer when a group of teens would have an AM station (CHUM 1050 in Toronto) blaring near my bedroom window. Desperately needed my sleep as I was working evenings full time while going to university all day.
  • tomcrawfordtomcrawford Posts: 1,129
    edited 2019-07-05 16:45
    Back in the day, the assembly girls liked to listen to an AM station he hated. So one night, he took a center punch and put dents in two opposing plates of the tuning capacitor on their five-tube superhet such that they lined up at the station he hated.
    220px-Variable_Capacitor.jpg
    220 x 173 - 15K
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