Saturday, May 19, 2007
For the past year or so I've known my station is somewhat deaf. My antennas are less than stellar, my terrain is horrid, and I've got nasty noise.
Frequently I'd see spots of this or that DXpedition saying "loud in N CA" but not be able to hear them. I can't hear the late night state/county hunter net on 40m, etc...
So I decided to measure it.
The Northern California CX Federation (NCDXF) maintains a world-wide set of HF beacons running on 20, 17, 15, 12 and 10 meters. These beacons are ordered so that you can check how well you hear them from around the world on a single band in 3 min and all 5 bands in 15 min.
Link to NCDXF beacon page
I used a piece of software called Faros (Faros web page) to control my radio and chart how well I was hearing the beacons. It provides a SNR rating for each received signal.
I compared this against a propagation prediction for what I *might* be hearing. For prediction I used the HamCAP, IonoProbe, and ITS HF combination.
This story is a bit better when you add pretty pictures...
First, here is an output from Faros. It shows all 18 NCDXF beacons for 24 hours for all 5 bands. It reads from left to right with 00:00Z on the left and the vertical lines are 3 hour increments. Black means no signal received. The other colors are "the hotter the better." Green is better than blue. Light blue is better than dark blue, etc.
So, I can hear the UN station in New York from about 21:00Z to 04:00Z.
Hawaii kicks in about 03:00Z for about 5 hours, then comes back about 16:00Z for another 3 hrs.
New Zealand comes in from about 02:30Z until about 05:00Z.
All of these are on 20 meters, except a brief blip for 4U1UN and ZL6B on 18 meters.
So, the above represents the "reality" of what I'm (not) hearing.
Here is the theory of what I "should" be hearing from those stations... The vertical axis is frequency, the horizontal axis is time from 00:00Z to 23:59Z and "lighter is better" in terms of SNR. Note the text at the bottom of the screen as it shows the "peak" measurement time and value. Those should correlate to the actual measurements.
(Measurements are SNR as measured by Faros and predicted by HamCAP/ITS HF using propagation parameters updated for the current conditions by IonoProbe. All results are at 20m.)
For New York:
4U1UN:
Best measured: 14.4 dB
Prediction at that time: 37 dB
Difference: 23 dB
For Hawaii:
KH6WO:
Best measured: 3.2 dB
Prediction at that time: 51 dB
Difference 48 dB
For New Zealand:
ZL6B:
Best measured: 8 dB
Prediction at that time: 43 dB
Difference: 35 dB
You can see that the results grossly resemble the predictions... But you need to subtract, oh, 30 to 40 dB to get the "reality" from the predictions...
So, it seems that I'm spotting the prediction 23 to 48 dB of signal to noise.
Ugh! As JV said after listening to the noise "It's a wonder you ever work anybody."
"Agn?"
Frequently I'd see spots of this or that DXpedition saying "loud in N CA" but not be able to hear them. I can't hear the late night state/county hunter net on 40m, etc...
So I decided to measure it.
The Northern California CX Federation (NCDXF) maintains a world-wide set of HF beacons running on 20, 17, 15, 12 and 10 meters. These beacons are ordered so that you can check how well you hear them from around the world on a single band in 3 min and all 5 bands in 15 min.
Link to NCDXF beacon page
I used a piece of software called Faros (Faros web page) to control my radio and chart how well I was hearing the beacons. It provides a SNR rating for each received signal.
I compared this against a propagation prediction for what I *might* be hearing. For prediction I used the HamCAP, IonoProbe, and ITS HF combination.
This story is a bit better when you add pretty pictures...
First, here is an output from Faros. It shows all 18 NCDXF beacons for 24 hours for all 5 bands. It reads from left to right with 00:00Z on the left and the vertical lines are 3 hour increments. Black means no signal received. The other colors are "the hotter the better." Green is better than blue. Light blue is better than dark blue, etc.
So, I can hear the UN station in New York from about 21:00Z to 04:00Z.
Hawaii kicks in about 03:00Z for about 5 hours, then comes back about 16:00Z for another 3 hrs.
New Zealand comes in from about 02:30Z until about 05:00Z.
All of these are on 20 meters, except a brief blip for 4U1UN and ZL6B on 18 meters.
So, the above represents the "reality" of what I'm (not) hearing.
Here is the theory of what I "should" be hearing from those stations... The vertical axis is frequency, the horizontal axis is time from 00:00Z to 23:59Z and "lighter is better" in terms of SNR. Note the text at the bottom of the screen as it shows the "peak" measurement time and value. Those should correlate to the actual measurements.
(Measurements are SNR as measured by Faros and predicted by HamCAP/ITS HF using propagation parameters updated for the current conditions by IonoProbe. All results are at 20m.)
For New York:
4U1UN:
Best measured: 14.4 dB
Prediction at that time: 37 dB
Difference: 23 dB
For Hawaii:
KH6WO:
Best measured: 3.2 dB
Prediction at that time: 51 dB
Difference 48 dB
For New Zealand:
ZL6B:
Best measured: 8 dB
Prediction at that time: 43 dB
Difference: 35 dB
You can see that the results grossly resemble the predictions... But you need to subtract, oh, 30 to 40 dB to get the "reality" from the predictions...
So, it seems that I'm spotting the prediction 23 to 48 dB of signal to noise.
Ugh! As JV said after listening to the noise "It's a wonder you ever work anybody."
"Agn?"
Labels: Faros, HamCAP, NCDXF, QRM
