Panadapter level reading when using "tune"

AB2EZ
Posts: 89
Joined: Sun Apr 09, 2017 2:29 pm
Location: Princeton, NJ

Panadapter level reading when using "tune"

Postby AB2EZ » Sat Jul 21, 2018 7:43 pm

Just a reminder of a problem that first came up several HPSDR releases ago... and still remains in release 3.4.9. I am using an ANAN-10E, but I believe this problem exists on other models as well.

In "tune mode" (but not in other modes such as two tone, or normal transmit operation), with DUP on, and a known/fixed output power sample being provided as a Pure Signal input... the panadapter displays a carrier power reading that is about 10dB low on 40 meters. It is also incorrect, by various amounts, on other bands.

However, the output power is correct, and the S-ATT setting is correct.

Stu
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DL2XY
Posts: 18
Joined: Sun Jul 30, 2017 9:47 am

Re: Panadapter level reading when using "tune"

Postby DL2XY » Sun Jul 22, 2018 11:06 am

If it helps, the correct display is restored when changing ATT during TUNE.
This is not persistant, on the next tune the error comes up again.

Walter
AB2EZ
Posts: 89
Joined: Sun Apr 09, 2017 2:29 pm
Location: Princeton, NJ

Re: Panadapter level reading when using "tune"

Postby AB2EZ » Sun Jul 22, 2018 7:08 pm

Walter

Thanks... that works! While in "tune" mode... I changed the S-ATT setting from 19dB to 20dB... and the panadapter reading changed from about 10dB too low to the correct reading.

Yes... if I cycle tune off and back on... then the panadapter reading returns to about 10dB too low.

Interesting...

Stu
AB2EZ
Posts: 89
Joined: Sun Apr 09, 2017 2:29 pm
Location: Princeton, NJ

Re: Panadapter level reading when using "tune"

Postby AB2EZ » Sun Jul 22, 2018 10:18 pm

Based on the behavior that I am observing... I suspect that the step attenuator's actual value (independent of the S-ATT setting shown on the GUI) is being set to 31dB when you first select tune mode. Then, when you change the S-ATT setting (while still in tune mode), the step attenuator 's actual value is set to whatever S-ATT is set to. While the step attenuator's actual value is set to 31dB (before you change the S-ATT setting), the part of the HPSDR application that controls the GUI display is "assuming" that the step attenuator is set to the S-ATT setting. That is why the panadaptor displays a carrier power value that is too low.

Example

S-ATT is set to 20dB... but the actual value of the step attenuator is 31dB. The HPSDR application thinks that the step attenuator's actual value is 20dB (i.e. what S-ATT is set to). Therefore, the panadaptor reading (calculated based on the assumed 20dB step attenuator value) is 11dB too low.

Stu

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