even the commercial radio can't pick up a distant station too well

Discussion in 'Wireless & RF Design' started by mik3ca, Mar 12, 2008.

  1. mik3ca

    Thread Starter Active Member

    Feb 11, 2007
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    Ok,

    So after building and giving up with my superregen for one night, I decided to use a commercial radio, the same one I used before that was able to pick up the station 80km away from me.

    What happens? the station STILL does NOT come in clear! The commercial radio is a GE Confetti. Yes, It shows confetit in capital pink letters. the best I get on a commercial radio when it is at the farthest point away from interference is a flickering stereo light.

    In both tests (one with the best version of my homemade receiver, and the other with the commercial receiver), I have the receiver connected to my computer through a 3ft speaker extension cable so that I can listen to music through my laptop. I get pretty much the same results from both receivers.

    I'm beginning to think that something else is causing interference. I wonder if I should clamp a whole bunch of chokes around my laptop power cord. I took the one that came with it off before because I had to fix the cord and reduce the cord length.

    so maybe it is NOT my receiver that is at fault now that I have done tests.
    I think my laptop is the likely culprit since it is the closest piece of active electronics. I have a desktop computer that is closer to the radio, but it is completely turned off, and plugged in during all tests.

    I have an incadescent light that is on during all tests, but that appears to do no interference. There is nothing else nearby (at least within 5 meters) that can cause interference.

    Does it come down to choking the wires coming out of my laptop? and how carried away should I get with them?
     
  2. Audioguru

    New Member

    Dec 20, 2007
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    Google and I have never heard of a GE Confetti FM stereo radio.

    The "radios" I got for free for subscribing to a newspaper are sold for $1.00 at The Dollar Store and have terrible reception. They pickup strong local stations sometimes.

    My pretty cheap Sony Walkman FM stereo radio has a local-distant switch because its RF amplifier is not tuned and doesn't have automatic-gain-control. It picks up some distant stereo stations perfectly. Local stations are all over the dial unless it is switched to Local but then it can't pickup distant stations.

    My cheap clock radio picks up local stations but not distant stations.

    My home stereo and my car radio pickup local and very distant stations perfectly.

    Try your radios with headphones if you think your laptop is causing interference.
     
  3. SgtWookie

    Expert

    Jul 17, 2007
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    So, your laptop cord originally had a ferrite or a choke on it, and you removed it?

    Computer manufacturers don't install parts unless they are needed.

    If you still have the original part, then reinstall it.

    If you don't, order a complete new cord.
     
  4. thingmaker3

    Retired Moderator

    May 16, 2005
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    Do I understand you correctly? You are trying to pick up an FM station from 80km distance?
     
  5. mik3ca

    Thread Starter Active Member

    Feb 11, 2007
    189
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    something like that.

    I'm in Hamilton, and the station's tower is in Orangeville, so it is about 80km.
     
  6. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
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    FM signals are of high enough frequency they do not reflect off the ionosphere. They are "line of sight" only.

    Your broadcasting tower is right on the horizon. Try taking your receiver up on the roof for better reception. Exercise all appropriate safety measures when climbing up on the roof.
     
  7. JoeJester

    AAC Fanatic!

    Apr 26, 2005
    3,373
    1,159
    I have built a horizontal polarized half-wavelength antenna and placed it about 30 feet above the ground, feeding an old car radio, to pick up a radio station approximately 101.03 miles from my location ... well outside the "fringe" as defined by the coverage area map. I used the audio output [attenuated ...] to feed the PA system in my building. The half-wave had a feed impedance of about 72 ohms, so the cable from the antenna [about 50 ft] was a typically 75 ohm RG cable.

    Now if that doesn't work, you can purchase a commercial FM antenna and a signal booster [probably 28 dB], to improve your chance of reception.

    TV antenna's typically cover the FM band, so you could get a directional yagi to solve your problem.

    I guess it depends on how you want to address the solution.
     
  8. mik3ca

    Thread Starter Active Member

    Feb 11, 2007
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    Just to let you know, the broadcasting tower belongs to the people who own Z103.5.

    I don't think I'll take that chance. I'm already on the second floor of my house.
     
  9. Audioguru

    New Member

    Dec 20, 2007
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    The broadcasting antenna is 554m above mik3ca's elevation. Their power is 30.7kW. The reception contour shows a pretty strong signal (-54dBu) at its red circle where a very poor quality FM radio might not have good reception. Mik3ca is a little farther than the red circle.
     
  10. thingmaker3

    Retired Moderator

    May 16, 2005
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    I apologize for my ambiguity. When I typed "your tower" my intent was "the tower generating the signals you are attempting to receive.

    It's too far away from you. The distance between you and the tower is such that you won't be able to receive it well.

    The earth is round. Radio signals travel in a straight line. Signals of some frequencies bounce off the ionosphere, so you can tune in "over the horizon." Signals of other frequencies do not bound off the ionosphere. The radio station you do not own - the one with the tower I refer to as "yours" (even though it is owned by someone else) - uses one of the "non-bouncing" frequencies.
     
  11. SgtWookie

    Expert

    Jul 17, 2007
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    Ok, so if you want to optimize reception for 103.5MHz, tune your antenna for that frequency.

    Commercial radios are supplied with fixed-length antennas (or "wound" antennas on ferrite rods) - however, you aren't making a commercial radio, so you're not that limited.

    A standard FM antenna in the USA is usually 34" - but that's a compromise between the high and low ends of the FM band. You'll get better results on 103.5MHz by using a somewhat shorter antenna. 27" works pretty well for the aircraft communications band, which is above the commercial FM radio band.

    If you are serious about getting good reception, try building a Yagi antenna.
     
  12. mik3ca

    Thread Starter Active Member

    Feb 11, 2007
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    I guess I will have to start playing with my antenna.

    Thank you.
     
  13. Audioguru

    New Member

    Dec 20, 2007
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    Hi Mike,
    There are so many local FM radio stations and TV stations in our area that an untuned "signal booster" will be seriously overloaded and won't work.

    There is another super-regen radio thread recently on this website and it stops working when its antenna is longer than a short amount, probably because it interferes with itself or because it becomes overloaded by all the local stations.
     
  14. SgtWookie

    Expert

    Jul 17, 2007
    22,182
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    Mike,
    If you want to learn a good bit about antennas, here's a really good resource for you:
    http://www.armymars.net/ArmyMARS/Antennas/Resources/usmc-antenna-hb.pdf

    It's the USMC Field Antenna Handbook, in .PDF format. If you're in a hurry to skim through and start trying stuff, I suggest reading through chapters 2 and 4.

    Your experimental antennas don't have to be fancy or made of expensive components; you could use magnet wire, salvage wire from an old doorbell, whatever scrap wood, old fishing poles, salvaged PVC pipe or whatever you might have around to experiment with.

    Actually, 1/2" PVC pipe is a great material to work with, and very inexpensive. If you don't glue the fittings, you can easily take your assembly apart to try different configurations. Just use a bit of masking tape to attach your antenna wires.
     
  15. arthur92710

    Active Member

    Jun 25, 2007
    307
    1
    Is that 80km driving? Or by air? It can be even closer then 80 by air.
     
  16. Audioguru

    New Member

    Dec 20, 2007
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    The tall antenna of the transmitter is about 70km to 80km away from Mik3ca.
    I don't know if an obstruction is in the way.

    The radio station says they have good coverage in the city of St. Catharines which is much farther than Mik3ca.
     
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