I have a hard time wording stuff, So bare with me
Do they have like a transmitter to send out the Jamming?
Do they have like a transmitter to send out the Jamming?
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AM Jammers
- Thread starter MarioMania
- Start date
Yes, just as the stations being jammed have transmitters. That's how radio works: Receivers receive what transmitters transmit. Silly question, unless your difficulties in "wording stuff" are obscuring your true meaning.
I think it's an issue where english may not be @MarioMania's first language, but he has a serious question nonetheless.
I believe he's asking about frequency jammers, like those used to prohibit cell phone reception and use in certain locations, or the jammers used for instance by Cuba to "block" incoming transmissions from the USA and elsewhere. He's trying to better understand how they work.
I believe he's asking about frequency jammers, like those used to prohibit cell phone reception and use in certain locations, or the jammers used for instance by Cuba to "block" incoming transmissions from the USA and elsewhere. He's trying to better understand how they work.
On MW, a jamming signal is just a bunch of transmitters on the same frequency that targets one particular station, resulting in a bunch of noise, or they might even broadcast something. It kind of all breaks down to two or more stations on the same frequency, therefore when KMXA Denver forgets to power down at night, they are technically "jamming" KAAY Little Rock. However, we only really use the word jamming if it was intentional, such as what Cuba and the Koreas do.
Well 1st I'm handicap have a learning disability, speech problem to try to get words out..
So bare with me if I can't come up with something intelligent
So bare with me if I can't come up with something intelligent
Of course! 🤗
Think ZantennaG1's explanation is spot on. "Jammer" always has struck me pretty much as noise or broadcasting intentionally aimed at preventing an area from hearing a certain broadcast. Radio Marti stands out to me in that respect. Cuba doesn't have to have a flamethrower shooting north on 1180, but they do it purely so listeners in their country can't hear Marti.
There are actually several jamming techniques for an Amplitude Modulated signal, whether it be Long Wave, Medium Wave or Short Wave.
First is noise on channel. In this case some kind of hash, tones or garbage is broadcast to make listening unbearable. Warble tones seem to make it very difficult and were used a lot by the Soviets during the Cold War era. In a few cases, repetitive Morse code is used to make listening to the "other" station most annoying.
Second is just to put another station on the same channel, with regular local programming. In the areas with such a station's "local" quality signal, the station that is not wanted is blocked.
Third is a slightly off channel station, typically 1 kHz above or below the station that is to be blocked. This causes a heterodyne which squeals so badly that listening to the distant station is unbearable.
Cuba mostly does the second option, with many stations on the channels it wishes blocked... 1180, 670, 710 for example; because Cuba is so wide, it takes many transmitters to block a medium wave station they don't want heard. But in the past, Cuba used the third option with a station just off 1140 to block WQBA in Miami when that station was virulently anti-Castro; they did the same to block Radio Swan / Radio Américas in the 60's.
Thanks David
Thank you David, you put it better than I could've. So does that mean the "Warbler" on 870 that everyone is talking about could be a jammer?
He does expain it better
The Wobbler on 870 is a Jammer
We don't know why
The Wobbler on 870 is a Jammer
We don't know why
It could be, but why? There is nothing worth jamming.
I believe it is a low frequency heterodyne from one or more very unstable Cuban stations.
You're doing great, Mario. I think it's safe to say all of us on this board are glad you're here, and appreciate your comments.
My youngest son also has a learning disabity. He's, 38 years old and doing great also! He's tought me and his mom, along with his brothers and sister, that those with learning disabilities are special persons....and awesome!
I've come to the exact same conclusion. Which also explains why in the past we've heard something similar on 930 and other frequencies where there's "nothing worth jamming".
Thanks Mario for starting this thread. I've learned something!
One thing David said got me thinking. He described 3 ways used for amplitude modulation jamming. How would you go about jamming FM stations? For example, I imagine there are a lot of Seoul FM's that could be heard in North Korea. Does North Korea just put NK stations on the same frequencies, or are there other methods used there?
One thing David said got me thinking. He described 3 ways used for amplitude modulation jamming. How would you go about jamming FM stations? For example, I imagine there are a lot of Seoul FM's that could be heard in North Korea. Does North Korea just put NK stations on the same frequencies, or are there other methods used there?
And a het of two local stations would only be heard at some distance from the primary coverage area of either, so the local engineers would not be aware of the issue unless they had a frequency monitor for each station. I suspect that today's very stable technology leads broadcaster to not install monitors for each station.
FM can easily be "jammed" by installing more powerful co-channel stations on the same channels. FM, unlike AM, does not easily "mix" multiple signals on a receiver. Power wins. That iis why during ducting situations, a distant station may be heard while the local one is 100% gone.
But North Korea has "mental jamming" where listening to a Southern Korean station can result in loss of rights, imprisonment or even death.
Mostly they use high-power transmitters to put a loud pulsing, bleeping noise over the outside broadcast, exploiting the capture effect to jam outside FMs. It's been speculated that terrestrial FM is mostly used in North Korea to feed remote MW, cable and business music systems and isn't actually intended for direct listening. Simple, highly effective and feasible given that the regime basically has no budget and operates on an isolationism ideology (Juche).
Several years ago, Mark Fahey did an approximately hour-long presentation at an Hackers of Planet Earth convention in New York that extensively discussed North Korean propaganda media (and received a standing ovation), and included an analysis of the radio situation there. It's on Youtube:
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World Radio Handbook, which seems to get accurate data from the North Koreans, shows 12 "Pyongyang FM Pangsong" FMs in the larger cities all at 1 kw to 20 kw power as well as one People's Army station in Pyongyang.
They have 8 "Joson Jung-ang Pangsong" AMs, ranging from a 2 kw secondary service in Pyongyang, to 500 kw. There are two 500 kw station, 3 with 250 kw and 2 with 50 kw on AM.
They also have a bunch of domestic SW station, mostly on the 3 mHz band.
They have 8 "Joson Jung-ang Pangsong" AMs, ranging from a 2 kw secondary service in Pyongyang, to 500 kw. There are two 500 kw station, 3 with 250 kw and 2 with 50 kw on AM.
They also have a bunch of domestic SW station, mostly on the 3 mHz band.
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