HFU HF Underground
Technical Topics => Equipment => Topic started by: Dude111 on December 31, 2019, 0055 UTC
-
Im not sure if this is the right base for this or not,maybe Chris can move it if its not the best place....
There is a station in my area who must have ice on thier tower or something.... For the last week they are spewing out severe harmonics!!
They are at 1160 and I can hear them from about 1010 to about 1320!!!
I have left a message with them about getting this fixed before the FCC hears of it,I dont think they would be happy........
I havent heard a station with this bad harmonics in along time!!
Makes it hard listening to other stations within that range I tell ya!! (All you hear is garbled crap from them)
uugghh
-
You sure it's them and not your station?
-
If their fundamental frequency is 1160 and you are hearing them from 1010 to 1320, then “harmonics” is the wrong term. Harmonics will be heard at integral multiples of the fundamental frequency (2320 kHz, 3480 kHz, etc).
It sounds more like InterModulation Products (IMP). While it could be a problem at the station, it is more likely due to something in your receiver or your antenna system. Is this the strongest station at your location? Do you hear the same problem on different radios or using different antennas? If you drive to a location further away, do you still hear the same problem? Do you hear just that station, or do you hear other stations mixed together too?
-
Agreed, if what you hear is evenly distributed around the carrier frequency, it is spurious emission. Any chance of a screen grab of what it looks like? The frequency range in question makes me guess PWM switching trash is somehow making its way through the PA's output network, assuming its a solid state transmitter. In a tube rig, a failure of just about anything in the power stage can cause gross spurious emission.
+-RH
-
Ya I guess its intermodulation then.......
I hear it on multiple radios,in the car,etc............. So its def a problem with them...........
Im sorry for the wrong term.........
-
First off is the noise blanker on? If so, that may be causing imd from strong signal overload. To test for this simply disable the nb and see if the issue is resolved or reduced.
If it is and you still need the nb in operation, what i do is find about the strongest am sig I can and tune like 3kc up or down from the carrier so you're in the splash. Then enable the nb and adjust the level until there's no imd, then you should be in good shape with regards to imd caused by the nb on just about any sig level.
If the nb isn't at fault, perhaps the preamp is on and is causing imd? Disable it to test. If using a sdr, reduce the gain however one does so, and check for imd. If it happens regardless of acceptable gain settings, a ambc highpass filter may be the only thing you can do to remedy the issue.
Also test via another radio, if present on both then it may well be the station having spurs. In that case time to make a phone call.
-
Ya I guess its intermodulation then.......
I hear it on multiple radios,in the car,etc............. So its def a problem with them...........
Im sorry for the wrong term.........
If you hear the same problem you described in your original post on multiple radios then the problem
obviously is not in your shack but rather elsewhere.
Intermodulation is the mixing of usually strong signals from two (or more) frequencies which combine to produce
an unwanted signal on yet another frequency. Generally something in your antenna set up or receiver front end
causes the external or internal mixing to produce intermodulation.
Again, since you hear the problem on different radios and even in the car it has nothing to do with your equipment
so you can rule out intermod.
Therefore the problem is elsewhere. The fact that what you are hearing is evenly distributed either side of the
center frequency seems to indicate spurious emissions by the transmitter.
-
Yup its all fixed........ I got a hold of someone who contacted the engineer and she sounds excellent now and no problems.....
I like to help others....... (Not many today do)
-
Good, nice to have a story with a happy ending to start the new year. :)
-
uugghh its back again!!
All I can do is hope that now they are aware of it,it will be fixed soon!!! (Very annoying when trying to listen to a side freq (1110 for example))
EDIT:
They seem to have gotton on it quicker this time.... Its fine now and hopefully will stay clean!!!!!!!
-
Nice that they got to it. Shows they care. There was an AM station on the other side of my state that had an audible ground loop on their signal for over a year.
-
Ya it seems like more people do not care how they sound these days but something like this I think they have to!!
The FCC wont stand for blatant interference being caused.... (Although they did allow IBOC to interfere)