majoco
Stirrer
Now that we've been off-topic for so long, has anyone heard from the OP "snapperq" since we re-started this topic? 
MW DXing- what's the best receiver?
- Thread starter snapperq
- Start date
- Status
- Joined
- Jun 13, 2018
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- 869
My interest has been spurr'd- there seems to be a number of radio anomalies that occur at the equator. To be truthful, I never really gave them much thought- but working in the central and south Pacific, something changes at the long waves. Different magnetic fields, ocean currents, atmospheric layers?.. I'm sure if I search there will be a plethora of information... how could the military's not have look'd into this in depth?
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That multi-path delay is fun to observe- and a pain sometimes. - I can often hear it on HF when signals are arriving both long and short path- that hollow echo'ing sound to a voice is unmistakable-
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I have actually had to change (this is all work related stuff)- beam patterns when using full-same frequency HF duplex, to eliminate it. The multi-path delays and phase distortion have made my voice practically unintelligible.
.......Such a good lesson why the really accurate time signals, like WWVB broadcast on LW.
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Trying very hard to stay on Topic- ...........
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So, here is my favorite consumer grade MW/LW receiver. It a strange bird-- called an AquaMeter. I pick'd it up years ago at a flea market. It was made for boaters- dating pre-GPS days. The receiver covers 150-400, and 500-1700Khz. It has a rotatable ferrite loop antenna with a 360 degree scale to use in triangulating positions from various stations. It is extremely sensitive, and has a good ANL function. I built an internal 12VDC full wave conventional power supply into it (don't even THINK anything like a switching Pwr supply for a low frequency receiver...; ) )
I use it all the time near Santa Fe NM to listen to KTNN -AM, 660Khz. from Window Rock, Arizona.... "The voice of the Navajo Nation."
I can't understand a word of Navajo, but they play neat country/western music- and AM radio music listening is now such a dying beast.
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Lauri
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That multi-path delay is fun to observe- and a pain sometimes. - I can often hear it on HF when signals are arriving both long and short path- that hollow echo'ing sound to a voice is unmistakable-
.
I have actually had to change (this is all work related stuff)- beam patterns when using full-same frequency HF duplex, to eliminate it. The multi-path delays and phase distortion have made my voice practically unintelligible.
.......Such a good lesson why the really accurate time signals, like WWVB broadcast on LW.
.
Trying very hard to stay on Topic-
............
So, here is my favorite consumer grade MW/LW receiver. It a strange bird-- called an AquaMeter. I pick'd it up years ago at a flea market. It was made for boaters- dating pre-GPS days. The receiver covers 150-400, and 500-1700Khz. It has a rotatable ferrite loop antenna with a 360 degree scale to use in triangulating positions from various stations. It is extremely sensitive, and has a good ANL function. I built an internal 12VDC full wave conventional power supply into it (don't even THINK anything like a switching Pwr supply for a low frequency receiver...; ) )
I use it all the time near Santa Fe NM to listen to KTNN -AM, 660Khz. from Window Rock, Arizona.... "The voice of the Navajo Nation."
I can't understand a word of Navajo, but they play neat country/western music- and AM radio music listening is now such a dying beast.
.
.
Lauri
.
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majoco
Stirrer
CF - your DF receiver seems to work very well......
https://www.youtube.com/watch?v=62YdmSWXjwo
Yours is not the auto version but the guts are probably the same.
https://www.youtube.com/watch?v=62YdmSWXjwo
Yours is not the auto version but the guts are probably the same.
Last edited:
w2xq
Mentor
Yes, MW is the same as AM. Internationally, the MW term may be more universally understood and used in the 9 kHz spacing found in Europe or 10 kHz in NA and elsewhere. This https://www.mwlist.org/ website might be of interest to you. HTH.
majoco
Stirrer
Well, not to be too pedantic, but we need to examine the truth here. AM is a form of modulation, it has nothing to do with the carrier frequency. Almost all shortwave band broadcasts intended for Joe Public to receive on his portable radio are Amplitude Modulated, even Single Sideband transmissions are amplitude modulated, just one sideband and the carrier have been removed.
When 'Frequency Modulated' transmissions came into vogue in the mid 30's in the US, manufacturers proudly printed "AM" or "FM" on their radio dials. Once again "FM" is not a band, it's a form of modulation, you can have frequency modulation on any "carrier" frequency you like - you might annoy lots of people but it can be done.
On many small and even larger radios, there may be only two bands, the "Broadcast Band" from say 520 to 1710kHz which is broadcast in "Amplitude Modulation" - the bandwidth expected from these stations is expected to be no more than +/-5kHz from the allotted carrier frequency in the US so that the next station along the dial does not (hopefully) interfere with your favourite local station.
However, to get a good frequency response and signal-to-noise ratio, frequency modulation requires a far greater bandwidth. Also to reduce background noise, a limiter circuit in the receiver clips off any amplitude variations in the signal, so all we are left with is frequency variations, no amplitude variations from thunderstorms or car ignitions etc. AND we get stereo broadcasts too! This requires a bandwidth of at least +/-100kHz - try this in the 520 to 1710kHz band and you would wipe out a heap of local stations!
So the FM band is proposed to around 45MHz initially and later to 88MHz to 108MHz in the US and most of the world. Now you can fit 100 channels of FM stereo into this one band - receivers have the ability to reject any interference and also reject the next door transmitter - the capture effect.
So amplitude modulation is used in the medium frequency broadcast band but not exclusively - and frequency modulation is used in the VHF broadcast band but also not exclusively, so to call them them the "AM"' band and the "FM" band is just a matter of convenience to Joe Public.
When 'Frequency Modulated' transmissions came into vogue in the mid 30's in the US, manufacturers proudly printed "AM" or "FM" on their radio dials. Once again "FM" is not a band, it's a form of modulation, you can have frequency modulation on any "carrier" frequency you like - you might annoy lots of people but it can be done.
On many small and even larger radios, there may be only two bands, the "Broadcast Band" from say 520 to 1710kHz which is broadcast in "Amplitude Modulation" - the bandwidth expected from these stations is expected to be no more than +/-5kHz from the allotted carrier frequency in the US so that the next station along the dial does not (hopefully) interfere with your favourite local station.
However, to get a good frequency response and signal-to-noise ratio, frequency modulation requires a far greater bandwidth. Also to reduce background noise, a limiter circuit in the receiver clips off any amplitude variations in the signal, so all we are left with is frequency variations, no amplitude variations from thunderstorms or car ignitions etc. AND we get stereo broadcasts too! This requires a bandwidth of at least +/-100kHz - try this in the 520 to 1710kHz band and you would wipe out a heap of local stations!
So the FM band is proposed to around 45MHz initially and later to 88MHz to 108MHz in the US and most of the world. Now you can fit 100 channels of FM stereo into this one band - receivers have the ability to reject any interference and also reject the next door transmitter - the capture effect.
So amplitude modulation is used in the medium frequency broadcast band but not exclusively - and frequency modulation is used in the VHF broadcast band but also not exclusively, so to call them them the "AM"' band and the "FM" band is just a matter of convenience to Joe Public.
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