elchupacabras said:
Well at least we finally found a use for LW ;D
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Long Wave DX - anyone here do it?
- Thread starter markwooldridge
- Start date
Well at least we finally found a use for LW ;D
elchupacabras said:
LibertyNT said:
These are almost certainly called Image Interference:
Image = Signal +/- 2 * I.F. or Signal +/- I.F.
so if your the station you say that you're hearing on the LW band is your local "AM 1300"
it could end up on 2200, 1750, 850 and 400 kHz
1300 + 2 * 450 = 2200 kHz and/or 1300 - 2 * 450 = 400 kHz.
1300 + 450 = 1750 kHz and/or 1300 - 450 = 850 kHz.
(I used 450 kHz in the example for the I.F. since most of the digitally tuned radios use that I.F., older non-digital radios use 455 kHz, or other frequencies near 455 kHz, and then there's double and triple conversion receivers (better for suppressing images and spurs, but more expensive too!)
If it's not a frequency that can be easily added or subtracted by a multiple of the Intermediate Frequency, the inductor(s) used to help demodulate an AM signal, then it's probably a spurious signal, caused most likely by overloading from too much signal strength arriving at the receiver's tuner, either caused by a very strong signal from the station, a very sensitive radio or an additional antenna which overloads the tuner (or a combination of several of these) and causes the RF circuitry to operate in a "non-linear" fashion, therefore images of the station appear elsewhere on the dial than could be explained by the Intermediate Frequency sum and difference, or a harmonic of the radio station itself. Sometimes a nearby AM radio has circuitry that is so RF "leaky" you might be able to hear its images! I have no idea why one would be getting images with no strong local stations nearby, if someone knows let us know!
http://bahrambaba.persiangig.com/pdf/reading30.pdf
Very cool. Thanks trusty.
crainbebo said:
How close are you to their towers?
crainbebo said:
This one surprises me. Yes, I pick up harmonics on my E5 and G5 (and on other radios) from local AMs on the LW band. However, not once have I picked up a harmonic from a MW station in the MW band on my E5 or G5 (I have both). Not even when I am very close to the transmitter site. And, I've never had such a problem on the same frequency as a beacon - though that may just be good luck. Like your example, the harmonics seem to be limited to 4 or 5 higher frequency MW signals. And, they aren't necessarily that strong.
I have a Sony ICF SW-7600GR, which is the only radio I have that never offers spurious MW signals on the LW band. It's awesome with LW, AM and SW and is a highly rated receiver for this reason. However, the purely digital tuning (push button, push again, again, etc.) and the poor FM reception that this radio offers makes it one of my least favorite to play with. Even though it was the most expensive.
I didn't think in-band spurious MW emissions were that uncommon. Within a few miles of a 50 kW stick on 690 I was always able to hear them clearly on 1380, and this was on multiple radios.
There's no MW near where I live now, so the only spurious emissions I hear is a beacon that I get off-kilter on 1230 kHz on a car radio.
There's no MW near where I live now, so the only spurious emissions I hear is a beacon that I get off-kilter on 1230 kHz on a car radio.
Zach said:
A lot of it has to do with how sensitive and how many IF stages your tuner has. Sounds like you need a better radio.
elchupacabras said:
Agreed.
The better radios won't throw spurious signals all over the MW band. But, for some reason, most of the portables (even better ones) do have the issue of MW signals invading the LW band. My thought is that LW is an afterthought to a lot of these manufacturers.
BRNout said:
In this part of the world definitely.
Well, most of the portable receivers that we are able to buy are made in China now. All of the Eton/Grundig models and many of the others (like the CC Radio models) are designed there as well. And, there's little LW usage in China. So, it's not a major priority for them. They've also had to play catch-up with SSB because it's not generally used over there.
They include LW on most international multi-band radios because the European, Middle Eastern and north African markets demand it. But a lot of their low-end models don't even offer it.
I will say that my radio worked fine when I was in the UK and all I got on LW was LW. But here, where there's almost nothing on the band, you get the IF signals.
They include LW on most international multi-band radios because the European, Middle Eastern and north African markets demand it. But a lot of their low-end models don't even offer it.
I will say that my radio worked fine when I was in the UK and all I got on LW was LW. But here, where there's almost nothing on the band, you get the IF signals.
BRNout said:
When I was in the UK about 30 years ago there was plenty of activity on LW and no IF problems even around London & the big signals.
Yeah the radio in question is one of those Sangean-made and RS-rebranded deals. Not a great unit by any stretch, but it does have RDS on FM.
Those of you who've been overseas, what the LW reception like over there? Do they cover a lot of territory? Do they suffer even more from noise and interference than MW?
Those of you who've been overseas, what the LW reception like over there? Do they cover a lot of territory? Do they suffer even more from noise and interference than MW?
Zach said:
I was in the UK over 30 years ago, but I remember during the day the LW stations had very good range if you were out in the countryside. However, if you were near power lines or in cities it could be quite noisy.
Yes, imagine if you had a very low frequency AM (like 540 or 550) with super power - then exaggerate those characteristics. Meaning, a large geographical range for groundwave and a fairly stable signal, but.....very prone to electrical noise. Also, the largest component of these signals is the groundwave. Not much skywave, normally. Which makes them very stable.
I was in Leicestershire, UK 3 years ago and was able to pick up oodles of longwave stations there. Broadcasters tend to battle the electrical noise issue by cranking up the power to high levels (250 kw and higher). It does seem to work in suburban areas, but I did not have much luck with LW at my hotel in London. Too much noise and concrete.
When I was Japan in 2000, I had a cheap Radio Shack portable. The LW band provided a lot of those spurious signals, but there was one Russian LW station that came in loud and clear and which was not an image from MW. In east Asia, Russia is pretty much the only country that uses LW - which is because it's also a European country.
Oh how I wish I had something like the E5 in Japan back then!
I was in Leicestershire, UK 3 years ago and was able to pick up oodles of longwave stations there. Broadcasters tend to battle the electrical noise issue by cranking up the power to high levels (250 kw and higher). It does seem to work in suburban areas, but I did not have much luck with LW at my hotel in London. Too much noise and concrete.
When I was Japan in 2000, I had a cheap Radio Shack portable. The LW band provided a lot of those spurious signals, but there was one Russian LW station that came in loud and clear and which was not an image from MW. In east Asia, Russia is pretty much the only country that uses LW - which is because it's also a European country.
Oh how I wish I had something like the E5 in Japan back then!
BRNout said:
Years ago I remember a weather station on the LW band up in central Wisconsin. It put in a good daytime ground wave signal into the Chicago area.
The G5 is a great radio for traveling. I use it regularly for that purpose.
F
frcradio
Guest
Do they cover a lot of territory?
- - - While on vacation in Morocco, North Africa in 1969 I remember listening to the BBC on 200 kHz.
in the middle of the day. So yes, Longwave stations do cover a lot of territory, and because it propagates primarily
by ground wave, its not as affected by the Sun as skip propagation on higher frequencies.
- - - While on vacation in Morocco, North Africa in 1969 I remember listening to the BBC on 200 kHz.
in the middle of the day. So yes, Longwave stations do cover a lot of territory, and because it propagates primarily
by ground wave, its not as affected by the Sun as skip propagation on higher frequencies.
frcradio said:
That is good coverage!
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