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Author Topic: 2 meter band pass for broadband noise?  (Read 149 times)

KK4GMU

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2 meter band pass for broadband noise?
« on: June 11, 2022, 04:10:45 PM »

I'm wanting to clean up received FM audio on 2 meters on my Icom IC-7100.

The noise is continuous, broadband, across several bands and records a consistent S9 on my meter.

Voice is barely audible over the noise from repeaters 12 to 15 miles.

To what extent, if any, would a 2 meter band pass filter reduce my noise?

I understand I would need a relay to bypass the filter when transmitting to maintain my transmit power.
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WB2VKL

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Re: 2 meter band pass for broadband noise?
« Reply #1 on: June 11, 2022, 06:02:48 PM »

I found that LED bulbs (screw in, medium base) wiped out 2M in the way you have described. There is a switching power supply inside each bulb. These were in my ceiling fixtures. Replaced with incandescent.
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AF5CC

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Re: 2 meter band pass for broadband noise?
« Reply #2 on: June 11, 2022, 11:22:25 PM »

One of the main reasons I have no LED lightbulbs in my house. 
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KK4GMU

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Re: 2 meter band pass for broadband noise?
« Reply #3 on: June 12, 2022, 07:03:08 AM »

Has anyone used a 2 meter band pass filter to suppress noise?  I've been discussing potential sources in other threads.  Just want to know if this sort of filter has been used to suppress noise.
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G8FXC

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Re: 2 meter band pass for broadband noise?
« Reply #4 on: June 12, 2022, 08:26:16 AM »

One of the main reasons I have no LED lightbulbs in my house.

You are lucky to have the choice - incandescent bulbs are now banned oer here and impossible to buy!

Martin (G8FXC)
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K7NI

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Re: 2 meter band pass for broadband noise?
« Reply #5 on: June 12, 2022, 10:15:45 AM »

I don't think a bandpass filter will help, because it sounds like the noise would be within the passband of the filter. You'll have to kill it at the source.
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K6JH

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Re: 2 meter band pass for broadband noise?
« Reply #6 on: June 12, 2022, 11:54:23 PM »

Does the noise show up all across the band on your handheld also?

I believe I was the one who suggested a filter, but that was when I thought it was just the one frequency, not all across the band. These kind of filters are really only effective if the problem is intermodulation, and you can filter out one component. If the noise is broadband, and present on two different receivers, it’s extremely unlikely to be a mix. These kind of filters will accomplish nothing with on channel noise.

Three such manufacturers:
http://www.ocicom.com/index.php/amateur-radio/products/2-meter-bandpass-filter
ARRL review https://www.ocicom.com/images/OCI/PROD-REV-OCI.PDF
http://dcifilters.com/?Section=Products&SubSection=Amateur
http://www.parelectronics.com/amateur.php
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73
Jim K6JH

K0UA

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Re: 2 meter band pass for broadband noise?
« Reply #7 on: June 14, 2022, 04:31:38 PM »

Fact 1:   Installing a 2 meter bandpass filter will not help in the slightest.
Fact 2:   I have a house full of LED bulbs that put out NO noise on any frequency (Cree brand)
Fact 3:   You must find the noise at its source and eliminate it. Start by flipping the main breaker to your own house. Shut down the entire house, including anything that is running off of any UPS. Shut down EVERYTHING. Is the noise still there? If not, praise Jesus. It is in your own house. Something you can do something about. If it is still there. You are in trouble. If it is gone, start by turning OFF every breaker in the box, and flip ON the main breaker. Still gone? Start flipping on the breakers one by one until you find the breaker or breakers that cause the noise to return. Now go to the room/rooms that the offending breaker powers. Start disconnecting everything in that room until the offending device/devices is found. Take a hammer to that device, and pulverize it until it is no longer recognizable.   It goes without saying that you power the rig from battery during all of this time.
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73  James K0UA

KK4GMU

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Re: 2 meter band pass for broadband noise?
« Reply #8 on: June 18, 2022, 08:10:17 AM »

Quote
If it is still there. You are in trouble.

I'm in trouble.  I cut of all power, UPS, while radio connected to lead acid battery.  Still there.  Moved the antenna a few feet in several directions.  Still there.  Tried a J-pole instead of my vertical ground plane.  Still there.  Separated each antenna from metal pole with pvc stand off.  Still there.  Applied multiple chokes to antenna cable.  Still there.
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WA3SKN

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Re: 2 meter band pass for broadband noise?
« Reply #9 on: July 12, 2022, 02:36:12 PM »

Are you ready to build a direction finding antenna yet?

-Mike.
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