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Old 01-25-2018, 8:17 PM
Join Date: Feb 2006
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Default RSP1 Play MW interference

I recently added an RTL-SDR .com MW filter to the RSP1 but I am still receiving a local MW broadcast on 1450. The xmitter is only a couple of miles away. Its a lower power station, especially at night, although I don't know the specifics off hand. Since I am seeing a lot of strange signals across large junks of other bands, I'm guessing this MW station is the culprit. Any ideas how I can mimimize the signal from this broadcast?
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Old 01-26-2018, 8:32 AM
Flatliner's Avatar
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Location: UK
Posts: 390

If you're using a MW filter and you're still getting good MW signals, then either the filter doesn't have a high rejection, or/and the signal on 1450 in phenomenally strong. A MW transmitter at two miles... you could power an LED on that from your antenna. Worth a try!

Also 1450 is getting towards the end of MW so the attenuation skirt may not be very steep.

Worth noting the RSP1a has a MW built in filter. You could add your filter to that also, if need be.

Edit: That RTL filter claims 60db of suppression, which is pretty respectable, though, again, if you still have very strong signals, the above still applies.

Also... that filter may be reaching saturation and not actually blocking that signal. It could even radiate from the input to the output, inside the housing and miss the filtering completely, due the signal strength. Make sure that your radio is well-grounded. you could be getting that very strong signal over the shield too. Remember that you're dealing with electricity.
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Last edited by Flatliner; 01-26-2018 at 9:03 AM..
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Old 01-26-2018, 12:18 PM
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Did you try cutting your gain down? Sounds like you're running into an overloading issue.

Also it would be helpful if we knew the make/model of your filter to look at its response curve (if it has one)...Mike
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Old 01-26-2018, 12:30 PM
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I also use the MW broadcast filter with my RSP2. When tuning the actual AM broadcast band, you would still expect to receive some stronger AM stations. However, that's not really the purpose to the filter. What you are trying to do is to remove the effects of strong AM stations overloading and appearing on the HF bands as images of the original frequency. To that extent, the filter does what it's designed to do, at least for me.
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Old 01-27-2018, 1:18 PM
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Posts: 122

At 1450 your attenuation with that filter should be around 63-65 db.

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Old 01-28-2018, 3:44 AM
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Join Date: Jul 2010
Location: Cheshire, England
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You've also got to consider pickup on the general wiring and the effect of earth loops. Try connecting your various items together with a short wire to bypass any RF that may be getting in directly. We have a 2KW station about 2 miles away and several 50-200KW stations about 15 miles away and they put in huge signals here. Careful grounding and bonding completely stopped the unwanted pickup.
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