Questions tagged [mf]

Medium Frequency: The frequency range from 300 kHz to 3 MHz

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Ferrite unun transformer to match antenna resistance loads of <50Ω?

For LF/MF (2200m/630m), I am interested in the situation of a vertical antenna with capacitance hat top-loading, where the vertical antenna is VERY short compared to wavelength, and the antenna is ...
photosynthesis's user avatar
5 votes
1 answer

MF band mixer - feasible parameters

Trying to build an homebrew receiver for MF band broadcast (Navtext). Usually working on VHF, where all parts are easily found as an IC, but here I'm trying to get back to roots, so I may be missing ...
gusto2's user avatar
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3 votes
1 answer

Why is QRN so bad on the low HF and MF bands?

If one tunes an HF/MF radio at night, the lower the frequency (or the longer the wavelength) of the band, the more QRN (static and atmospheric noise) there is. 80m is noisier than 40m, and 160m is ...
rclocher3's user avatar
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4 votes
1 answer

Commercial Loopstick Antenna Manufacturers?

I am an electrical engineer working on a product that needs a loopstick antenna. I had thought that AM radios were so commoditized that I'd be able to find an off-the-shelf vendor. However the closest ...
Aaron's user avatar
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3 votes
2 answers

Supershield or Superscreen coax: Does it exist? What is its common name?

I'm sure this seems like a Google question, but I've BTDT and come up empty. The problem I'm trying to solve is to obtain cables that are as "leak proof" as possible. Tried Pasternak "...
user103218's user avatar
2 votes
1 answer

How much field strength to blow out a receiver?

I was wondering what calculations would need to be performed to find out if a receiver will blow out in the given conditions. Portable AM receiver with ferrite rod antenna 200 ft away from MW antenna ...
Synaps3's user avatar
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5 votes
1 answer

How should two loopstick antennas be placed w.r.t each other to maximize transmission?

An engineer working in the RF industry told me something which left me very confused: He said that a pair of emitter-receiver beacons get the clearest signal when loopstick antennas in the receiver ...
Dugas's user avatar
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9 votes
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How can I do direct digital synthesis of a 630m WSPR signal?

I want to do direct digital synthesis of a 630m band WSPR signal. Specifically I'd like to use an Atmega 328 chip running at 20 MHz to produce such a signal. I will use standard phase accumulator ...
Eric Urban's user avatar
4 votes
3 answers

What are the technical reasons that there are no FM transmissions on the long, medium, or shortwave?

Why are there no frequency modulated broadcasts on the long/medium/short wave, but only on VHF? I'm sure there are many historical and political reasons (long/medium/short wave were already in use for ...
JanKanis's user avatar
  • 405
1 vote
1 answer

Receiving medium - low frequency CPU signal

I'm trying to listen to the CPU freq's my PC produces (kinda similar to what was done here: I do see a clear signal that comes from the CPU (I know ...
George Lashenko's user avatar
1 vote
1 answer

Utility pit MW/LW omnidirectional antenna

I am looking at antennas for a rather unusual application: mounted under a utility pit lid (manhole cover). The goal is to receive commercial MW/LW stations. The antenna has to be attached to the ...
user1211's user avatar
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3 votes
1 answer

Can one send data over Short-wave frequencies?

I have an inkling of an idea- a modem system communicating over Short-wave. I know that WiMAX already exists, but the difference is that, while WiMAX works on the Gigahertz frequencies, and most ...
Rory Yammomoto's user avatar