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Author Topic: Winradio Noise Blankers?  (Read 10918 times)
KD9VV
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Posts: 26




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« on: November 21, 2013, 06:12:51 AM »

Curious if there are any technical discussion on how these (2) noise filters are supposed to work?

1) Enable DDC Averaging
2) Enable ADC Threshold

Either I live in a low RF noise area or they do not work effectively.

My average noise floor seems to hover around 125-130 dbm.

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K0OD
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Posts: 2556




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« Reply #1 on: November 21, 2013, 06:53:49 AM »

Quote
My average noise floor seems to hover around 125-130 dbm.

On what band and with what antenna?
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KD9VV
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Posts: 26




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« Reply #2 on: November 21, 2013, 08:25:46 AM »

Quote
My average noise floor seems to hover around 125-130 dbm.

On what band and with what antenna?

Pretty much all bands from 500Khz to 30 Mhz.

Using a 80/40/10 Par EndFedz.

I've opened the breaker to the mains in my home and saw no discernible diff in noise floor
or any external interference.

I'm beginning to believe -125 to -130 dbm is a norm in ambient atmospherics?
This equates to approx S5 to S7 noise.

 Watching several you tubes from ppl with the same receiver, I see their noise floor is also about the same.
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KB4QAA
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« Reply #3 on: November 21, 2013, 10:18:04 AM »

-125db noise floor?  Yeah thats pretty quiet.  Like middle of the desert with only battery power noise.

Noise Blanker function in typically intended to work against 'pulse' noises like auto ignition, not atmospheric noise.   Your specific question doesn't quite make sense to me.

DDC would refer to Digital-Digital Conversion

ADC would refer to Analog-Digital Conversion.

I would interpret these as options of two different signal processing methods and paths.
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K0OD
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« Reply #4 on: November 21, 2013, 11:05:03 AM »

Quote
I'm beginning to believe -125 to -130 dbm is a norm in ambient atmospherics?
This equates to approx S5 to S7 noise.

That dBm level amounts to a lot less than S5 to S7. That would be remarkably low on the lower ham bands and about right for the highest ones. I'd look on my Flex-5000 to make sure, but my antenna is disconnected now due to storms.

My normal band noise around 5 MHz (where I've kept records going back three years) is about -88 dBm using my 43' vertical and in a 2.4 KHz bandwidth and normal AGC. That level is about S6 or S7 on the calibrated S-meter of my Flex.  The lowest nighttime noise I've ever encountered is about -96 dBM or S5. I know my station hears DX very well on the 60 meter ham band.

The Flex noise blanker (there are actually two) works great, but like KB4QAA said, it doesn't reduce atmospheric noise. I don't usually keep the NBs on.

Isn't there a Winradio Yahoo group or such where you can ask that precise question? 
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KD9VV
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Posts: 26




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« Reply #5 on: November 21, 2013, 12:02:20 PM »

[quote
Isn't there a Winradio Yahoo group or such where you can ask that precise question? 

There may be..I'll have to check.

Thanks
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K0OD
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Posts: 2556




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« Reply #6 on: November 21, 2013, 08:04:24 PM »

Rain has stopped. Was curious to see the nighttime noise baseline on my Flex-5000 and 43' vertical fed via an in-shack tuner to 1:1 swr. Mode USB and 2.4 kHz bandwidth. med agc:

60 meters  -87 dBm
40 meters  -91
20 meters  -103
15 meters  -115 (band dead)
10 meters  -111 (band dead)

No antenna  -119

Note that Flex meter readings are independent of settings such as pre-amp and RF gain.

If your SDR is -125 to -130 dbm everywhere, the noise blanker is probably the last thing you should be worried about. I'd try another antenna, maybe about 30' of hook up wire running out a window.
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KD9VV
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Posts: 26




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« Reply #7 on: November 26, 2013, 09:42:27 AM »


If your SDR is -125 to -130 dbm everywhere, the noise blanker is probably the last thing you should be worried about. I'd try another antenna, maybe about 30' of hook up wire running out a window.

Something is not quite right here..perhaps our reference values we are looking at.

All the You Tube videos I look at concerning the G31 are all showing about the same noise floor. (-125 to -135) which is obviously extremely low. My guess is that these are relative values on the G31, not absolute calibrated values.

Recently I put up the Par Endfed EF-SWL....Hugh difference in quieting the noise with fantasic ability to receive wek sigs...but still, the "Noise Floor) visually indicated on the G31 is averaging -130dbm.

As reference only, Radio Havana signal on 6 Mhz is peaking around -60 to -70. Monster signal obviously.

Hopefully we are all on the same page as s/n are concerned as 0/dbm would represent s/n= 100/0
« Last Edit: November 26, 2013, 09:45:46 AM by KD9VV » Logged
KD9VV
Member

Posts: 26




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« Reply #8 on: November 26, 2013, 01:20:19 PM »




If your SDR is -125 to -130 dbm everywhere, the noise blanker is probably the last thing you should be worried about. I'd try another antenna, maybe about 30' of hook up wire running out a window.

Really?
Sounds like you might want to find another place for your antennas.
Your figures show extreme noise....I'm surprised you are able to dig anything out with level you are reporting.

http://www.flickr.com/photos/proshoot/sets/72157638091930455/
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KI6LZ
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« Reply #9 on: December 05, 2013, 05:48:42 PM »

Be careful with SDR noise values. Lets say your SDR FFT bin is 1 Hz, what you see is noise voltage/power in that 1 Hz bin. If you used a 1000 Hz bandwidth you would have to add 30 db to those values. Thus the -130dbm in 1 Hz would become -100 in a 1000 Hz bandwidth. It also get a little complicated using RMS or peak values. Also some algorithms account for this, some don't.
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