Issue with NFM Reception on DV10 Receiver

[fafax]

Hello everyone,

I have been experiencing an issue with my AOR DV10 receiver, specifically concerning the NFM reception quality. I have observed a significant degradation in the voice reproduction quality, particularly between the 60MHz and 80MHz frequency range when using the default narrow band filter settings.

Interestingly, I've found that when I switch to a wider filter setting at 100KHz, the signal appears much cleaner. This is a bit puzzling as one would expect the narrower filter setting to provide better signal isolation and hence better quality.

Even more paradoxical is the fact that some signals, which are completely undetectable when using the 12.5KHz filter setting, become faintly audible when I switch to the 100KHz filter. Despite the volume being extremely low, it's quite surprising that these signals can be picked up at all with such a wide filter setting.

Has anyone else experienced a similar problem? And does anyone have any suggestions on how to improve NFM reception quality on the DV10? I'm hoping there might be some kind of workaround or setting adjustment that I haven't thought of yet. Any advice would be greatly appreciated.

Thanks in advance for your time and assistance.

Best regards,
Fafax

 

[G7RUX]

Hello everyone,

I have been experiencing an issue with my AOR DV10 receiver, specifically concerning the NFM reception quality. I have observed a significant degradation in the voice reproduction quality, particularly between the 60MHz and 80MHz frequency range when using the default narrow band filter settings.

Interestingly, I've found that when I switch to a wider filter setting at 100KHz, the signal appears much cleaner. This is a bit puzzling as one would expect the narrower filter setting to provide better signal isolation and hence better quality.

Even more paradoxical is the fact that some signals, which are completely undetectable when using the 12.5KHz filter setting, become faintly audible when I switch to the 100KHz filter. Despite the volume being extremely low, it's quite surprising that these signals can be picked up at all with such a wide filter setting.

Has anyone else experienced a similar problem? And does anyone have any suggestions on how to improve NFM reception quality on the DV10? I'm hoping there might be some kind of workaround or setting adjustment that I haven't thought of yet. Any advice would be greatly appreciated.

Thanks in advance for your time and assistance.

Best regards,
Fafax

I haven't used a DV10 but this sort of behaviour is indicative that the unit may be off-frequency enough that the standard filter puts the wanted signal significantly out of the passband.

 

[fafax]

I haven't used a DV10 but this sort of behaviour is indicative that the unit may be off-frequency enough that the standard filter puts the wanted signal significantly out of the passband.

Hello G7RUX,

Thank you for your response and for sharing your thoughts on this issue.

Your suggestion regarding the possibility of the unit being off-frequency is intriguing. However, if that were the case, I would expect to eventually intercept the signal when moving around the frequency band. But the reality is that there seems to be no audible signal at all in these circumstances.

Moreover, anything below the 100KHz filter setting results in a significant increase in noise, which makes the listening experience rather unsatisfactory. Therefore, I believe there might be other factors at play affecting the reception quality.

I appreciate your contribution and I'm hoping others might have encountered similar issues and possibly have some insight or solutions. Please let me know if you have any other suggestions or thoughts.

Thanks again for your time.

Best regards,
Fafax

 

[palmerjrusa]

Hello everyone,

I have been experiencing an issue with my AOR DV10 receiver, specifically concerning the NFM reception quality. I have observed a significant degradation in the voice reproduction quality, particularly between the 60MHz and 80MHz frequency range when using the default narrow band filter settings.

Interestingly, I've found that when I switch to a wider filter setting at 100KHz, the signal appears much cleaner. This is a bit puzzling as one would expect the narrower filter setting to provide better signal isolation and hence better quality.

Even more paradoxical is the fact that some signals, which are completely undetectable when using the 12.5KHz filter setting, become faintly audible when I switch to the 100KHz filter. Despite the volume being extremely low, it's quite surprising that these signals can be picked up at all with such a wide filter setting.

Has anyone else experienced a similar problem? And does anyone have any suggestions on how to improve NFM reception quality on the DV10? I'm hoping there might be some kind of workaround or setting adjustment that I haven't thought of yet. Any advice would be greatly appreciated.

Thanks in advance for your time and assistance.

Best regards,
Fafax

Try tuning to one of the WWV frequencies:

Radio Station WWV

Notice: Since November 15, 2021, WWV and WWVH has been broadcasting a test signal on minute 8 of eac

www.nist.gov

Evaluate how the signal sounds when your DV-10 is tuned to the official frequencies and tuning around them.

 

[G7RUX]

Hello G7RUX,

Thank you for your response and for sharing your thoughts on this issue.

Your suggestion regarding the possibility of the unit being off-frequency is intriguing. However, if that were the case, I would expect to eventually intercept the signal when moving around the frequency band. But the reality is that there seems to be no audible signal at all in these circumstances.

Moreover, anything below the 100KHz filter setting results in a significant increase in noise, which makes the listening experience rather unsatisfactory. Therefore, I believe there might be other factors at play affecting the reception quality.

I appreciate your contribution and I'm hoping others might have encountered similar issues and possibly have some insight or solutions. Please let me know if you have any other suggestions or thoughts.

Thanks again for your time.

Best regards,
Fafax

Indeed, that does sound odd...as you increase the filter bandwidth you would expect an increase in noise level. However,this might not occur using an FM discriminator so I would still be suspicious of frequency error, especially given that this is a known weakness of the DV10. I would suggest it's not a bad idea to check it anyway since it would eliminate one possibility.

 

[fafax]

Indeed, that does sound odd...as you increase the filter bandwidth you would expect an increase in noise level. However,this might not occur using an FM discriminator so I would still be suspicious of frequency error, especially given that this is a known weakness of the DV10. I would suggest it's not a bad idea to check it anyway since it would eliminate one possibility.

Thanks for your valuable input. I understand your point regarding the possibility of a frequency error, considering it's a known issue with the DV10.
Could you possibly provide an estimate of what the range of this frequency error might typically be? Knowing this could greatly aid me in methodically checking a narrower range around the expected frequency.

Thanks again for your time and assistance.

 

[fafax]

Thanks for your valuable input. I understand your point regarding the possibility of a frequency error, considering it's a known issue with the DV10.
Could you possibly provide an estimate of what the range of this frequency error might typically be? Knowing this could greatly aid me in methodically checking a narrower range around the expected frequency.

Thanks again for your time and assistance.

I've checked it and appears to be centered...

 

[fafax]

Try tuning to one of the WWV frequencies:

Radio Station WWV

Notice: Since November 15, 2021, WWV and WWVH has been broadcasting a test signal on minute 8 of eac

www.nist.gov

Evaluate how the signal sounds when your DV-10 is tuned to the official frequencies and tuning around them.

Hello, I'm in Europe, I'm not sure if it will work. Thank you

 

[G7RUX]

Thanks for your valuable input. I understand your point regarding the possibility of a frequency error, considering it's a known issue with the DV10.
Could you possibly provide an estimate of what the range of this frequency error might typically be? Knowing this could greatly aid me in methodically checking a narrower range around the expected frequency.

Thanks again for your time and assistance.

From memory it was rather variable but could easily be 5+kHz if the unit is operating higher up in it's range.

 

[palmerjrusa]

Hello, I'm in Europe, I'm not sure if it will work. Thank you

It should work, grew up in the UK building and listening to shortwave radios!

Try 5 kHz, 10 kHz and 15 kHz and the Canadian equivalents = 3330 KHz, 14670 kHz and 7850 kHz

 

[fafax]

It should work, grew up in the UK building and listening to shortwave radios!

Try 5 kHz, 10 kHz and 15 kHz and the Canadian equivalents = 3330 KHz, 14670 kHz and 7850 kHz

Ok thanks!

 

[fafax]

I want to express my gratitude for all your responses, and I would like to update you on yet another test that I've conducted. I tried recording onto an SD card with and without using the Discriminator. Unfortunately, this feature on the DV10 is not accessible for standard listening and therefore it is only possible to hear the result in a recording. In every available option, the signal was not audible.

However, during the recording test, I noticed something interesting. The option to apply or remove a filter is only accessible with the filter set up to 30kHz. For example, this option is not available with the 100kHz filter. This probably implies that the signal is processed differently depending on the filter bandwidth. I'm now wondering whether the radio operates in SDR mode when the filter is set up to 30kHz, and switches to analog mode when it is set to 100kHz. Does anyone have any thoughts on this?

In the meantime, I have an update on the advice given and the listening to the Radio Station WWV. Although the signal is quite noisy, it is audible.

Thank you all for your support.

 

[Ubbe]

One thing to remember are that a standard FM discriminator will give less audio level at lower modulation levels and usually the logic changes the audio gain to get equal sound levels at different bandwidth settings. A 100KHz filter setting are expecting a high modulations level and when you switch to 30KHz it's expecting a low modulation and will set a higher audio gain. If you then listen to a clean carrier without modulation that has some background noise it will be much more noise in the 30KHz setting. A NFM setting usually use a 15KHz bandwidth and needs even more audio gain and the noise level will be much higher compared to the modulated signal, worse signal noise ration when using smaller bandwidth filters, but selectivity will be better to attenuate other adjacent frequencies.

Also a SDR receiver like Unidens SDS scanners has a high level of modulation noise. The closer the modulation levels reaches the filter limits the more noise it produces. Sometimes you get a better signal quality when selecting the wider FM filter even when monitoring NFM signals.

To check frequency accuracy you can listen to a data signal in the 800MHz range with open squelch. Set the step size to 1KHz and listen to how far you can tune down in frequency until you hear distorsion and then do the same when going up in frequency, and go back and forth a couple of times. If you can go the exact same amount of KHz in both directions then you are spot on in frequency calibration. Double check with another transmitter.

/Ubbe

 

[G7RUX]

Hello, I'm in Europe, I'm not sure if it will work. Thank you

Whereabouts in Europe are you? There may be a suitable beacon nearby that you could make use of, or indeed someone with suitable equipment might be able to generate a test signal for you with which you can test the frequency accuracy of your receiver.

 

[imago01]

Bojour, il parle du filtre ou du step ? Filtre 12.5 il n'y a pas sur le dv10 ! Ni de nfm d'ailleurs.

 

[fafax]

Bojour, il parle du filtre ou du step ? Filtre 12.5 il n'y a pas sur le dv10 ! Ni de nfm d'ailleurs.

Filtre.

 

[fafax]

Whereabouts in Europe are you? There may be a suitable beacon nearby that you could make use of, or indeed someone with suitable equipment might be able to generate a test signal for you with which you can test the frequency accuracy of your receiver.

I'm located in Italy. I finally managed to run a test using NFM transmission, and indeed, the issue is confirmed. I reached out to AOR support, but they only provided vague answers without offering a clear solution. It's quite disappointing and, in my opinion, ridiculous that a brand of this stature has such an issue.

 

[fafax]

Hi all, just an update. I have written again to AOR support.
In my opinion, assuming that is true the fact the DV10 is a SDR based equipment, this issue can be solved with the firmware.
The point I cannot understand is why there is complete silence on this issue by AOR support...

 

[G7RUX]

I'm located in Italy. I finally managed to run a test using NFM transmission, and indeed, the issue is confirmed. I reached out to AOR support, but they only provided vague answers without offering a clear solution. It's quite disappointing and, in my opinion, ridiculous that a brand of this stature has such an issue.

What did you confirm the issue to be?

If it is frequency error then this may or may not be fixable if firmware, depending on the actual source of the problem and whether it is a stable error or drift.

 

[fafax]

What did you confirm the issue to be?

If it is frequency error then this may or may not be fixable if firmware, depending on the actual source of the problem and whether it is a stable error or drift.

I don't believe it's a frequency error based on the tests I've conducted.
Let me try to explain better: let's imagine we take a frequency, purely as an example: 50 MHz.
We apply an IF of 100 kHz to this. A very distant signal is heard, and there's absolutely no noise. Turning up the volume to the maximum and artificially raising the gain, the voice is perfectly audible. This happens because the filter on the voice reception frequency is too wide, and the signal isn't distributed over the entire area of the filter. There's no noise because the spectrum is clean. By narrowing the filter first to 30 kHz and then gradually down to 6 kHz, the sound becomes increasingly louder. This is what happens with any other receiver and other SDR (Software-Defined Radio) receivers.
However, inexplicably with the AOR DV-10, as soon as you switch from the 100 kHz filter to the 30 kHz filter, the sound paradoxically becomes inaudible, and the background noise increases inexplicably.
Various tests around the frequency change practically nothing, and there's no noticeable frequency shift or similar problem.
The problem is only evident when the signal is very low.

This description suggests that the issue might not be a simple frequency error but could be related to the specific characteristics or limitations of the AOR DV-10's filtering and gain control system. The behavior of the device, especially the increased background noise and loss of audio clarity when switching from a 100 kHz to a 30 kHz filter, could indicate a problem with how the device's filtering system processes weaker signals. This issue might not be prevalent in other receivers or SDRs due to differences in their design or filtering algorithms.