G8 signal strength meter


Antonios Kekalos <akekalos@...>
 

Would someone mind explaining how to interpret the readings on the signal strength meter on the G8? The numbers don't really mean anything to me. Unless I missed it, the manual doesn't explain this. Thanks.

--
Tony Kekalos
Traverse City, MI
SWLR-RN072
EN74es



jim_kr1s <jkearman@...>
 


--- In ultralightdx@..., Antonios Kekalos wrote:
>
> Would someone mind explaining how to interpret the readings on the signal
> strength meter on the G8? The numbers don't really mean anything to me.
> Unless I missed it, the manual doesn't explain this. Thanks.

The decibel is a way of representing the relationship between two electrical quantities of the same type and units. For example, you may be comparing two powers, two voltages or two currents.

The meter on the left compares the voltage across the input to the LNA to 1 microvolt (uV). On AM, FM or SW, the radio's antennas are not efficient, and their response is not uniform across any band. The signal strength required to generate 1 uV on one frequency may be much different than that at another frequency. So the meter is not absolutely accurate for comparing signal strengths on different frequencies or bands. You couldn't accurately say, "WGR is 10 dB stronger than WWKB," because they are on opposite ends of the band. Thus, it's called a Relative Signal Strength Indicator (RSSI).

The meter on the right is marked "SN," an abbreviation for "Signal-to-Noise." This is a misnomer, as the proper term is "Signal-plus-Noise-to-Noise." In testing and comparing receivers, this measurement is done as follows: The receiver output is connected to a meter. With no signal applied, the noise output is measured. Then a signal of known strength is applied and the measurement is taken again. The noise measured at first is still present, thus "signal-plus-noise..."

On a PL-380 (and I assume PL-310) where you can adjust the selectivity, for a given signal strength, the SN meter reading should increase as you narrow the bandwidth. Noise is aperiodic; that is, it is random in frequency. You can hear the reduction in noise on an unoccupied channel when you decrease the bandwidth. For a given, constant signal level, reducing noise improves the "SN" result.

If you can increase the signal level without also increasing the noise, or if you use an antenna that, while it may not pick up as much signal as the internal one, reduces noise pickup even more, you can improve the SN number and make the signal easier to hear.

In actual use, however, the meters are not so helpful. That's because they don't respond quickly to changes in signal level. The reason is the need to reduce processor functions that would drain the batteries more quickly, and could increase digital noise radiated into the antenna.

Hope this helps. You can learn more about decibels from Wikipedia. To narrow the bandwidth I skipped over how they are calculated. :)

73,

Jim, KR1S
http://qrp.kearman.com/


sdwillingham
 

Jim gives an excellent explanation of the RSSI and SNR indicators.
Here are some further comments for more technical readers.

1) The abbreviation RSSI stands for "Received Signal Strength
Indicator", not "Relative . . ." Jim correctly emphasizes
that this strength refers to the LNA input voltage, not
electromagnetic field strength.

2) The signal-to-noise ratio Jim describes refers to signal strength
compared to the noise generated by the radio circuitry. The SNR
metric from the Si4734 is more sophisticated than that. If one
substitutes a short-circuit across the AM antenna terminals, he
will see the RSSI drop to 2-5 dBuV. With an antenna connected
and "between stations", the RSSI can be 30 or more dBuV. Yet the
Si4734 does not report the SNR as 25 dB, i.e. the signal strength
above the receiver noise floor. Instead, the chip reports a
metric measuring the signal strength relative to atmospheric
noise and interference. Of course, if the atmospheric noise is
low enough (or antenna gain is inadaquate), the SNR calculation
will reflect the receiver circuit's noise floor. I wish I
could give more detail about the calculation, but I believe that
is proprietary information.

Cheers,
Scott


Tony Germanotta
 

Thanks Jim and Scott for the info. This is fascinating stuff for a non-techie like me.  I have a question, though. When I offtune my PL-310 to one side or another of a frequency, not only does the  signal strength drop a few notches on the volume knob,  I always get a 0 SNR reading, no matter how well the station is coming through, no matter how tight the bandwidth. Does the radio somehow know the center of the signal I am shooting for? Of course, it really doesn't matter, the important thing is intelligibility. But it has me wondering just how smart this chip really is.  Is it reading my mind, or just my WRTV Handbook?
 

On Jan 26, 2010, at 11:17 PM, sdwillingham wrote:

 


Jim gives an excellent explanation of the RSSI and SNR indicators.
Here are some further comments for more technical readers.

1) The abbreviation RSSI stands for "Received Signal Strength
Indicator", not "Relative . . ." Jim correctly emphasizes
that this strength refers to the LNA input voltage, not
electromagnetic field strength.

2) The signal-to-noise ratio Jim describes refers to signal strength
compared to the noise generated by the radio circuitry. The SNR
metric from the Si4734 is more sophisticated than that. If one
substitutes a short-circuit across the AM antenna terminals, he
will see the RSSI drop to 2-5 dBuV. With an antenna connected
and "between stations", the RSSI can be 30 or more dBuV. Yet the
Si4734 does not report the SNR as 25 dB, i.e. the signal strength
above the receiver noise floor. Instead, the chip reports a
metric measuring the signal strength relative to atmospheric
noise and interference. Of course, if the atmospheric noise is
low enough (or antenna gain is inadaquate), the SNR calculation
will reflect the receiver circuit's noise floor. I wish I
could give more detail about the calculation, but I believe that
is proprietary information.

Cheers,
Scott



sdwillingham
 

Hi Tony,

I am glad you find the discussion interesting. Sometimes I
worry about alienating the non-tech group members with too
much technical stuff vs dxing strategies, techniques, and
results.

"Does the radio somehow know the center of the signal I
am shooting for?"
Actually, the problem is that it doesn't know the center you
are shooting for when you tune to a different one!

Your question is a very good one and the answer is non-obvious
to anyone without inside information on the chip's design.
Essentially, the chip needs to know the desired carrier frequency
in order to do its 'smart' SNR signal processing and calculation.
When you off-tune, the chip no longer 'sees' the carrier where
you told it to 'look'. Under this condition, the processor
considers the SNR calculation to be invalid and returns a 0 dB
result.

By the way, this is part of the issue dxer's have with soft-mute.
The soft-mute calculation is based on the measured SNR. So when
you off-tune, the SNR goes to zero and soft-mute (if enabled)
kicks in.

Cheers,
Scott


--- In ultralightdx@..., Tony Germanotta <germanotta.tony@...> wrote:

Thanks Jim and Scott for the info. This is fascinating stuff for a non-techie like me. I have a question, though. When I offtune my PL-310 to one side or another of a frequency, not only does the signal strength drop a few notches on the volume knob, I always get a 0 SNR reading, no matter how well the station is coming through, no matter how tight the bandwidth. Does the radio somehow know the center of the signal I am shooting for? Of course, it really doesn't matter, the important thing is intelligibility. But it has me wondering just how smart this chip really is. Is it reading my mind, or just my WRTV Handbook?

On Jan 26, 2010, at 11:17 PM, sdwillingham wrote:


Jim gives an excellent explanation of the RSSI and SNR indicators.
Here are some further comments for more technical readers.

1) The abbreviation RSSI stands for "Received Signal Strength
Indicator", not "Relative . . ." Jim correctly emphasizes
that this strength refers to the LNA input voltage, not
electromagnetic field strength.

2) The signal-to-noise ratio Jim describes refers to signal strength
compared to the noise generated by the radio circuitry. The SNR
metric from the Si4734 is more sophisticated than that. If one
substitutes a short-circuit across the AM antenna terminals, he
will see the RSSI drop to 2-5 dBuV. With an antenna connected
and "between stations", the RSSI can be 30 or more dBuV. Yet the
Si4734 does not report the SNR as 25 dB, i.e. the signal strength
above the receiver noise floor. Instead, the chip reports a
metric measuring the signal strength relative to atmospheric
noise and interference. Of course, if the atmospheric noise is
low enough (or antenna gain is inadaquate), the SNR calculation
will reflect the receiver circuit's noise floor. I wish I
could give more detail about the calculation, but I believe that
is proprietary information.

Cheers,
Scott


Tony Germanotta
 

So would you avoid the soft mute or the zero reading by merely keying in 1209 instead of 1210, for instance? Or by setting the step to 9Khz rather than 10 for transatlantic stations? It doesn't seem to do anything for me, but that would be a rather simple way to eliminate the soft mute, which doesn't seem to bother me nearly as much as most folks here. I am still amazed at what this little chip can do.


On Jan 27, 2010, at 12:51 PM, sdwillingham wrote:

 



Hi Tony,

I am glad you find the discussion interesting. Sometimes I
worry about alienating the non-tech group members with too
much technical stuff vs dxing strategies, techniques, and
results.

>> "Does the radio somehow know the center of the signal I
>> am shooting for?"

Actually, the problem is that it doesn't know the center you
are shooting for when you tune to a different one!

Your question is a very good one and the answer is non-obvious
to anyone without inside information on the chip's design.
Essentially, the chip needs to know the desired carrier frequency
in order to do its 'smart' SNR signal processing and calculation.
When you off-tune, the chip no longer 'sees' the carrier where
you told it to 'look'. Under this condition, the processor
considers the SNR calculation to be invalid and returns a 0 dB
result.

By the way, this is part of the issue dxer's have with soft-mute.
The soft-mute calculation is based on the measured SNR. So when
you off-tune, the SNR goes to zero and soft-mute (if enabled)
kicks in.

Cheers,
Scott

--- In ultralightdx@yahoogroups.com, Tony Germanotta tony@...> wrote:
>
> Thanks Jim and Scott for the info. This is fascinating stuff for a non-techie like me. I have a question, though. When I offtune my PL-310 to one side or another of a frequency, not only does the signal strength drop a few notches on the volume knob, I always get a 0 SNR reading, no matter how well the station is coming through, no matter how tight the bandwidth. Does the radio somehow know the center of the signal I am shooting for? Of course, it really doesn't matter, the important thing is intelligibility. But it has me wondering just how smart this chip really is. Is it reading my mind, or just my WRTV Handbook?
>
> On Jan 26, 2010, at 11:17 PM, sdwillingham wrote:
>
> >
> > Jim gives an excellent explanation of the RSSI and SNR indicators.
> > Here are some further comments for more technical readers.
> >
> > 1) The abbreviation RSSI stands for "Received Signal Strength
> > Indicator", not "Relative . . ." Jim correctly emphasizes
> > that this strength refers to the LNA input voltage, not
> > electromagnetic field strength.
> >
> > 2) The signal-to-noise ratio Jim describes refers to signal strength
> > compared to the noise generated by the radio circuitry. The SNR
> > metric from the Si4734 is more sophisticated than that. If one
> > substitutes a short-circuit across the AM antenna terminals, he
> > will see the RSSI drop to 2-5 dBuV. With an antenna connected
> > and "between stations", the RSSI can be 30 or more dBuV. Yet the
> > Si4734 does not report the SNR as 25 dB, i.e. the signal strength
> > above the receiver noise floor. Instead, the chip reports a
> > metric measuring the signal strength relative to atmospheric
> > noise and interference. Of course, if the atmospheric noise is
> > low enough (or antenna gain is inadaquate), the SNR calculation
> > will reflect the receiver circuit's noise floor. I wish I
> > could give more detail about the calculation, but I believe that
> > is proprietary information.
> >
> > Cheers,
> > Scott
> >
> >
>



jim_kr1s <jkearman@...>
 


--- In ultralightdx@..., Tony Germanotta wrote:
>
> So would you avoid the soft mute or the zero reading by merely keying in 1209 instead of 1210, for instance? Or by setting the step to 9Khz rather than 10 for transatlantic stations? It doesn't seem to do anything for me, but that would be a rather simple way to eliminate the soft mute, which doesn't seem to bother me nearly as much as most folks here. I am still amazed at what this little chip can do.

The soft mute really gets annoying when there are two signals on the same frequency but slightly out of phase. If you're tuned to the station's frequency, whether on 9- or 10-kHz channel, and it's strong enough, the soft mute won't be a problem. But it can turn on even when you're right on the frequency if the station fades. Just as they ID, on the downward slope of a fade, the bloody soft mute turns on and makes it even harder to hear. Arrrrggggh.

When DXing splits I start on-frequency, but sometimes go up or down 1 kHz to get away from interference. I always use headphones, so even if the s-m goes on, there's usually enough audio. I find it more of a problem on crowded channels, like the Graveyards. Sounds like a steam locomotive high-balling it.

Because I have the radio on a turntable I can't see the meters much of the time anyway, so I rarely bother with them when DXing. In fact, lately I've been keeping the display set to show UTC time, as my little UTC clock found its way back to the portable ham station container! (I've always logged in GMT/UTC.)

73,

Jim, KR1S
http://qrp.kearman.com. 


Roy <roy.dyball@...>
 

Jim you would really love the USB mod on the G8. You can completely turn the soft mute off and select the filter you want then disconnect it from the computer and use it in a normal manner away from the computer till power down and with good rechargeable batteries you can leave it on for days.

In some ways the G8 is superior to the PL-380 when set up on the computer. The Pl-380 still has a touch of soft mute. I turn the soft mute completely off with the software and the 1Khz filter sounds a bit clearer on the G8 as it has a different audio stage configuration and seems to be more punchy with a higher tone. I am really looking forward to trying out the 1.8Khz bandwidth and the 2.5Khz bandwidth, gradual roll off selections in the new Si4734-C40 ver40 firmware. I think the new PL-380 2009.9 ver2 may have the new chip but I don't think they have the new filter selection available.

You are probably better off with the clock selected because if you listen carefully on certain frequencies when you have the meter selected you can hear the local MCU perform the Received Signal Quality (RSQ) update. This is more noticeable with a larger loopstick.

Cheers Roy. 

 

 

--- In ultralightdx@..., "jim_kr1s" wrote:
>
>
> --- In ultralightdx@..., Tony Germanotta
> germanotta.tony@ wrote:
> >
> > So would you avoid the soft mute or the zero reading by merely keying
> in 1209 instead of 1210, for instance? Or by setting the step to 9Khz
> rather than 10 for transatlantic stations? It doesn't seem to do
> anything for me, but that would be a rather simple way to eliminate the
> soft mute, which doesn't seem to bother me nearly as much as most folks
> here. I am still amazed at what this little chip can do.
>
> The soft mute really gets annoying when there are two signals on the
> same frequency but slightly out of phase. If you're tuned to the
> station's frequency, whether on 9- or 10-kHz channel, and it's strong
> enough, the soft mute won't be a problem. But it can turn on even when
> you're right on the frequency if the station fades. Just as they ID, on
> the downward slope of a fade, the bloody soft mute turns on and makes it
> even harder to hear. Arrrrggggh.
>
> When DXing splits I start on-frequency, but sometimes go up or down 1
> kHz to get away from interference. I always use headphones, so even if
> the s-m goes on, there's usually enough audio. I find it more of a
> problem on crowded channels, like the Graveyards. Sounds like a steam
> locomotive high-balling it.
>
> Because I have the radio on a turntable I can't see the meters much of
> the time anyway, so I rarely bother with them when DXing. In fact,
> lately I've been keeping the display set to show UTC time, as my little
> UTC clock found its way back to the portable ham station container!
> (I've always logged in GMT/UTC.)
>
> 73,
>
> Jim, KR1S
> http://qrp.kearman.com.
>


Gary Kinsman
 

Hi Scott,

How hard would it be for Tecsun to modify the firmware of their radios so that soft mute can be turned off with a combination of key presses? Ideally this change should be retained through a power cycle.

Regards,
Gary

--- In ultralightdx@..., "sdwillingham" <sdwillingham@...> wrote:
Hi Tony,

By the way, this is part of the issue dxer's have with soft-mute.
The soft-mute calculation is based on the measured SNR. So when
you off-tune, the SNR goes to zero and soft-mute (if enabled)
kicks in.

Cheers,
Scott


jim_kr1s <jkearman@...>
 



--- In ultralightdx@..., "Roy" wrote:
>
>
> Jim you would really love the USB mod on the G8. You can completely turn the soft mute off and select the filter you want then disconnect it from the computer and use it in a normal manner away from the computer till power down and with good rechargeable batteries you can leave it on for days.

You also could make a regulator that would power the radio off a larger battery or line-operated supply. The PL-380 soft-mute setting isn't too bad. You can see why some people would think it was disabled.

> the 1Khz filter sounds a bit clearer on the G8 as it has a different audio stage configuration and seems to be more punchy with a higher tone.

I listen through the MP3 recorder, which has some audio-tailoring options. These Far Eastern gadgets are wearing me out. The ICD UX-70 manual also covers the -60 and -80 models, which I was led to believe only differed in memory capacity. So yesterday I finally got some AAA rechargeables for it and tried to charge one in the unit via the USB port. Except the option to turn on the charger (so you don't try to charge an alkaline) is not in the menu of my -70!

The world's gone mad. I found a AAA charger for less than USD2.00 including postage from Hong Kong. It may send the cells into low-earth orbit, but for that price it's worth a try. I like China's postage rates even better than their radios.

> I think the new PL-380 2009.9 ver2 may have the new chip but I don't think they have the new filter selection available.

Speaking of that. We probably don't want a thread where everyone reports their version number, but my -380 shows a November build date, yet there's no version number on the end flap of the box!

> You are probably better off with the clock selected because if you listen carefully on certain frequencies when you have the meter selected you can hear the local MCU perform the Received Signal Quality (RSQ) update. This is more noticeable with a larger loopstick.

The meters were useful when it was in the Faraday box, but I wasn't tuning around. Otherwise they just have limited entertainment value. Now, if we could tie that RSSI signal into a motor driving the turntable....

73,

Jim, KR1S
http://qrp.kearman.com/ 


sdwillingham
 

Gary,

There is no technical difficulty in changing the soft-mute
parameters, which are documented in the chip's programming
guide. In software, it's no more difficult than changing
the channel.

The main question is what settings and features are
marketable for them to add to their interface. In general,
defeating the soft-mute is mostly a DXer feature -- not a
big market. They have, however, backed off on the feature
in the PL-380, so maybe they've been listening to the
criticisms. Or maybe they've come to their own conclusions
about the advantages of soft-mute versus the artifacts (in AM).

We'll have to wait and see if it comes back in newer models.

-Scott-

--- In ultralightdx@..., "gkinsman1" <gkinsman@...> wrote:



Hi Scott,

How hard would it be for Tecsun to modify the firmware of their radios so that soft mute can be turned off with a combination of key presses? Ideally this change should be retained through a power cycle.

Regards,
Gary

--- In ultralightdx@..., "sdwillingham" <sdwillingham@> wrote:
Hi Tony,

By the way, this is part of the issue dxer's have with soft-mute.
The soft-mute calculation is based on the measured SNR. So when
you off-tune, the SNR goes to zero and soft-mute (if enabled)
kicks in.

Cheers,
Scott