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#1
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Transmitter splatter
I find that the Radio Marti tx from Greenville (I think) on 6030 in the
evenings NAm time really plays havoc with BBCWS West Africa stream on 6035 which is on between 0300-0400 UTC. Officially, it's not a problem because the two stations are broadcasting to totally different areas, but that's my best chance to get BBC news since the Americas schedule was eliminated. The other option, 7160, is plagued by Cuban bubble jamming meant for Radio Republica which was there B05. John Plimmer wrote: Many of you are unaware that transmitters emit splatter. A bad transmitter on the HF shortwave spectrum can emit 12 kilohertz of splatter, that is 6 kilohertz of splatter either side of the centre frequency. Since the shortwave band has a channel separation of only 5 kilohertz, that means that such a transmitter will obliterate and interfere with signals either side of it on the 5 Khz separation. Many of you may think that this interfering splatter is a result of poor filters on your portable radio, but this is not so. Even very expensive professional grade receivers with top of the line filters cannot get rid of the splatter, as it is inherent and is on the band. On the BCB AM mediumwave band the situation is even worse as many transmitters will occupy a massive 30 Khz of space, severely disrupting reception of other stations either side of it. It is possible to observe such effects with the modern receivers that have spectrum scopes and also the new breed of computer radio's such as the Winradio G3 series. What can be done to remove this splatter? Very little I am afraid. One of the only possibilities is to "phase" out the splatter with a device such as the MFJ 1025/6, but these devices also have severe limitations and will not work in every circumstance. Despite the glowing reports of some users with these phaser's, they will only work if the station you want to phase out is not too strong and also that the offending transmitter is at right angles to the transmitter you are trying to receive. Secondly, the phasing works better the lower down the frequency spectrum you are, so on the mediumwave band it can be quite effective, but as you go up the band the effect is less noticeable, so that by the time you get up to about 6 Megahertz the phasers become almost ineffective. The idea that antenna tuner's and antenna matching units will improve matters relating to removing splatter is also wrong. They will not improve that situation at all. A better bet than tuner's and matching units for optimising signal strength is the simple 9:1 or 4:1 magnetic matching transformer. The 9:1 is suitable for the lower reaches of the spectrum and the 4:1 if you do more listening above 10 Mhz. I am sure RHF will rush to give you lots of leads on these very effective devices that do not require endless knob twiddling. |
#2
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Transmitter splatter
In article ,
running dogg wrote: I find that the Radio Marti tx from Greenville (I think) on 6030 in the evenings NAm time really plays havoc with BBCWS West Africa stream on 6035 which is on between 0300-0400 UTC. Officially, it's not a problem because the two stations are broadcasting to totally different areas, but that's my best chance to get BBC news since the Americas schedule was eliminated. The other option, 7160, is plagued by Cuban bubble jamming meant for Radio Republica which was there B05. Snip For 6030 where I'm located the bubble jamming of Radio Marti from Cuba is the problem. Radio Marti itself is not very strong at my location. I have to listen upper sync selective sideband on 6035. There is another station near but not on channel that plays havoc with the BBC on 7160. The carrier off something like 1 KHz is the main problem. I again have to listen sync selective sideband on 7160 or use the notch filter. -- Telamon Ventura, California |
#3
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Transmitter splatter
Telamon wrote:
In article , running dogg wrote: I find that the Radio Marti tx from Greenville (I think) on 6030 in the evenings NAm time really plays havoc with BBCWS West Africa stream on 6035 which is on between 0300-0400 UTC. Officially, it's not a problem because the two stations are broadcasting to totally different areas, but that's my best chance to get BBC news since the Americas schedule was eliminated. The other option, 7160, is plagued by Cuban bubble jamming meant for Radio Republica which was there B05. Snip For 6030 where I'm located the bubble jamming of Radio Marti from Cuba is the problem. Radio Marti itself is not very strong at my location. I have to listen upper sync selective sideband on 6035. There is another station near but not on channel that plays havoc with the BBC on 7160. The carrier off something like 1 KHz is the main problem. I again have to listen sync selective sideband on 7160 or use the notch filter. My Yaesu is currently casters up so I'm forced to rely on my Degen 1102, which simply isn't up to this sort of challenge. I had a little extra dough left over this month after bills so I may pack the Yaesu up and ship it to LA for repair. |
#4
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Transmitter splatter
In article ,
Telamon wrote: There is another station near but not on channel that plays havoc with the BBC on 7160. The carrier off something like 1 KHz is the main problem. I again have to listen sync selective sideband on 7160 or use the notch filter. I think that's the second harmonic of the TV color burst frequency. A lot of consumer electronics run their micro/TV video chips on 7.15909, or 14.31818 MHz resonators or xtals. And since the damn things are always on to "listen" for remote control commands... Mark Zenier Googleproofaddress(account:mzenier provider:eskimo domain:com) |
#6
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Transmitter splatter
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#7
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Transmitter splatter
In article ,
David wrote: On Sat, 29 Apr 2006 19:48:31 GMT, (Mark Zenier) wrote: In article , Telamon wrote: There is another station near but not on channel that plays havoc with the BBC on 7160. The carrier off something like 1 KHz is the main problem. I again have to listen sync selective sideband on 7160 or use the notch filter. I think that's the second harmonic of the TV color burst frequency. A lot of consumer electronics run their micro/TV video chips on 7.15909, or 14.31818 MHz resonators or xtals. And since the damn things are always on to "listen" for remote control commands... Mark Zenier Googleproofaddress(account:mzenier provider:eskimo domain:com) 3.579? Yea, but they run the microprocessor/video processing combo chip on a multiple of that to simplify the chroma processing. (Or maybe they're just cheaper). And anything digital, like the satellite systems the Mon wrote about another post or DVD players, will have a video display generation hardware that uses the color burst frequency in there somewhere, if it's designed to feed an older TV set/analog video. Mark Zenier Googleproofaddress(account:mzenier provider:eskimo domain:com) |
#8
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Transmitter splatter
In article ,
(Mark Zenier) wrote: In article , David wrote: On Sat, 29 Apr 2006 19:48:31 GMT, (Mark Zenier) wrote: In article , Telamon wrote: There is another station near but not on channel that plays havoc with the BBC on 7160. The carrier off something like 1 KHz is the main problem. I again have to listen sync selective sideband on 7160 or use the notch filter. I think that's the second harmonic of the TV color burst frequency. A lot of consumer electronics run their micro/TV video chips on 7.15909, or 14.31818 MHz resonators or xtals. And since the damn things are always on to "listen" for remote control commands... Mark Zenier Googleproofaddress(account:mzenier provider:eskimo domain:com) 3.579? Yea, but they run the microprocessor/video processing combo chip on a multiple of that to simplify the chroma processing. (Or maybe they're just cheaper). And anything digital, like the satellite systems the Mon wrote about another post or DVD players, will have a video display generation hardware that uses the color burst frequency in there somewhere, if it's designed to feed an older TV set/analog video. Mark Zenier Googleproofaddress(account:mzenier provider:eskimo domain:com) You are probably right about the source since it is prolific. Digital chips make things worse by using square waves and the resulting increase in odd harmonics. -- Telamon Ventura, California |
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