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QMX+: low RX sensitifity @ 6m / 22 dB noise floor / 1500 Hz wistle

 

Hello Dan,
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firmware Vers 2 is installed,
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Several resets to factory serttings didn?t solve the problem. Wistle is still present.
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During reset I hear the 1500 Hz wistle in my headphones.
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vy 73 Michael
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Hello Don,
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in USB and Digi 1500 Hz wistle is dominat in audio, but also in LSB and CW wistle is present.
At 6m band additional digital noise is present.
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vy 73 Michael
 

Hi Ken

Using SSB without calibration is perfectly acceptable, the audio is still good. Calibration just makes it even better.

73 Hans G0UPL


On Thu, May 8, 2025, 19:54 KEN G4APB via <lfoofui.nbz42=[email protected]> wrote:
On Thu, May 8, 2025 at 04:50 PM, Daniel Conklin wrote:
Since factory resetting a couple of times and installing the latest SSB firmware, the noise has mostly disappeared from my QMX+. My QMX HB never had the problem. It appears to be solvable.
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73, Dan - W2DLC
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?Thanks Dan but I am reluctant to install the latest SSB firmware as it seems to be bring in other as yet unsolved problems (PAs failing during calibration). I also am not happy with problems that just ¡®go away¡¯ without explanation. The SSB firmware is not listed as tackling this issue. I will just be patient until someone finds the cause (and a cure hopefully).?
73 Ken G4apb?
 

On Thu, May 8, 2025 at 04:50 PM, Daniel Conklin wrote:
Since factory resetting a couple of times and installing the latest SSB firmware, the noise has mostly disappeared from my QMX+. My QMX HB never had the problem. It appears to be solvable.
--
73, Dan - W2DLC
?
?Thanks Dan but I am reluctant to install the latest SSB firmware as it seems to be bring in other as yet unsolved problems (PAs failing during calibration). I also am not happy with problems that just ¡®go away¡¯ without explanation. The SSB firmware is not listed as tackling this issue. I will just be patient until someone finds the cause (and a cure hopefully).?
73 Ken G4apb?
 

Since factory resetting a couple of times and installing the latest SSB firmware, the noise has mostly disappeared from my QMX+. My QMX HB never had the problem. It appears to be solvable.
--
73, Dan - W2DLC
 

Are you hearing the whistle on all modes? I only hear it on the upper bands when in LSB.
 

Hi Michael, there is already a thread covering this ¡­..

QMX+ with ~1000 tone on 12M & 6M

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I did sent it to Hans direct some time ago but so far no response. I also see the poor sensitivity on 6m.
No-one on the forum seems to have come back with a solution yet.
73 Ken G4APB
 

Hello,
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I? recently build QMX+ and noticed a huge
noise floor and wistling a 6 m.
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Therfore I measured sensitifity using a signal generator.
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Band [MHz] Sens [dBm]@Noise+10dB Noise [dB]
1,85 -100,0 0
3,65 -106,0 0
5,35 -107,0 6
7,07 -107,0 0
10,14 -110,0 2
14,23 -107,0 1
18,1 -103,0 4
21,04 -99,0 9
24,9 -97,0 7
28,1 -103,0 5
50,5 -79,0 20
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Method: injection of signal Rx frequency + 1,1 kHz Mode: Digi
Noise: signal detected by WSJT-X
Sens: Noise floor + 10 dB
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Noise floor is increasing by frequency, but at 6 m wistling and digital noise make RX unusable.
Output at 6m is about 2 W at 9V Vbat (12V Version)
1,5 kHz wistle starts at 20 m and is increasing by frequency
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Using wsjt-X i evalating waterfall diagram: (QMX+ at 50 Ohm)
AVE:1, cumulative
Noise [dB] : signal by WSJT-X
?signal in waterfall diagram AU?
QMX+ ? ? freq [Hz] freq [Hz] freq [Hz] freq [Hz] freq [Hz] freq [Hz]
Frequency [MHz] Noise [db] Noisefloor 500 1000 1500 2000 2500 3000
1,84 0 0,2 0,2 0,2 0,8 0,2 0,2 0,2
3,57 0 0,3 0,3 0,3 0,7 0,3 0,3 0,3
5,3 1 0,5 0,5 0,5 1 0,5 0,5 0,5
7,04 5 0,8 0,8 0,8 1,1 0,8 0,8 0,8
10,1 1 0,5 0,5 0,5 0,5 0,5 0,5 0,5
14,1 1 0,5 0,5 1,3 2,8 2,1 0,5 1,5
18,1 5 0,8 1 1,8 2,3 2,1 1,1 2
21,1 7 1 1 2,1 2,6 2,1 1,1 2,1
24,9 7 1 1,2 2,7 2,8 2,7 1,3 2,5
28,1 7 1 1,2 2 1,5 1,5 1,2 2,2
50,3 22 1,8 2,5 3,8 4,2 3,9 2,8 3,8
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At higher bands 1,5kHz signal is constant and independent from RX freuqency.
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At 6m additional audio signals are appearing.?
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6m RF Filter seems to be ok.
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Any suggestions to detect cause?
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vy 73 Michael (DF6TV)
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