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My low cost FM radio receiver Philips MCM129 is not receiveing some radio stations well. It has antenna made of about 133 cm long thin insulated wire which I suspect is the rason of the problem.

Can I make the reception better by making the wire longer/shorter?

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closed as off-topic by Andy aka, Leon Heller, PeterJ, Null, Daniel Grillo Nov 4 '15 at 10:21

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Questions on the use of electronic devices are off-topic as this site is intended specifically for questions on electronics design." – Andy aka, Leon Heller, PeterJ, Null, Daniel Grillo
If this question can be reworded to fit the rules in the help center, please edit the question.

  • \$\begingroup\$ What happens if you move the receiver away from walls? (Assuming it is near a wall). \$\endgroup\$ – jippie Nov 1 '15 at 10:03
  • \$\begingroup\$ How do you know it isn't the limit of operation for the radio? \$\endgroup\$ – Andy aka Nov 1 '15 at 10:17
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    \$\begingroup\$ If it has a coax connector for an external antenna, you can mount a better antenna in the attic for 10-20dB moe signal strength. \$\endgroup\$ – Brian Drummond Nov 1 '15 at 11:32
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    \$\begingroup\$ Does it have an FM mono button - if it does, press it \$\endgroup\$ – Andy aka Nov 1 '15 at 11:36
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For FM radio reception getting the antenna higher off the ground is one of the best options. Unlike AM radio FM signals are more line of sight dependent. So if you are in an area that is generally low, such as a valley, or surrounded by hills, your reception may be poor for some or all stations.

Ideally try buying a simple low cost FM antenna, see amazon for starters: http://www.amazon.com/Stellar-Labs-30-2435-Outdoor-Omnidirectional/dp/B00DHHOZBI/ref=sr_1_5/175-5135060-7871912?s=aht&ie=UTF8&qid=1446522891&sr=1-5

Here are a few links to help make your own wire antenna:

http://siber-sonic.com/FM_reception/rooftop.html

http://www.robertsewell.ca/yahoo/fmaerial.html

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  • \$\begingroup\$ I'll definitely try external antenna (unless my radio does not have socket for external one) but will this overcome what Mark Ch pointed - "Therefore, even at the ideal length, these antennas still have a very poor response" \$\endgroup\$ – Marian Paździoch Nov 3 '15 at 7:59
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the simple wire antenna is a basic monopole, and so the ideal length for the FM radio frequencies is a quarter wavelength, approximately 3e8 / 100MHz / 4 = 0.75m.

but in the reality the ground plane for the monopole is provided only by the PCB and casing of the radio and is extremely poor. Therefore, even at the ideal length, these antennas still have a very poor response.

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  • \$\begingroup\$ It's got nothing to do with FM. \$\endgroup\$ – Andy aka Nov 1 '15 at 11:19
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    \$\begingroup\$ @Andy aka yes you're right, but specifically FM radio 88-108 MHz. \$\endgroup\$ – Mark Ch Nov 1 '15 at 11:24
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    \$\begingroup\$ @vini_i I think you need to do some research here dude!! \$\endgroup\$ – Andy aka Nov 1 '15 at 11:27
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    \$\begingroup\$ @vini_i this is only true for a lossless isotropic antenna, not a real antenna \$\endgroup\$ – Mark Ch Nov 1 '15 at 11:53
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    \$\begingroup\$ @vini_i a lossless isotropic antenna is a theoretical point source, with a size of zero and therefore has no frequency response. A real antenna has physical dimensions which introduce a frequency response. The friis equations are only valid within the passband of the antenna, not outside, which for a monopole, means at the resonant frequency of the antenna (based on its length). If you do not believe this, build one and measure it. \$\endgroup\$ – Mark Ch Nov 1 '15 at 12:28

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