FIRMWARE UPDATES?

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W4OP
 

Posts: 15
Joined: 18 Feb 2022, 03:39

FIRMWARE UPDATES?

Post by W4OP »

I have had more time to work with the transceiver and have seen some issues that perhaps could be solved in firmware.

Is it possible to offer another AGC menu option that has a faster attack time? I am seeing a large overshoot at the beginning of a strong CW character and beginning of the 1st word (as an example) of a stong SSB.

AM mode receive is odd. I always here a heterodyne when tuning AM stations- regardless of band.
Another oddity, and I have not nailed this one down completely- when tuning with AM mode selected, the MHz position will sometimes change. This may only be an issue when the tuning rate is say at 1KHz- again, I have not confirmed the tuning rate where this problem occurs. When it occurs, I can be tuning the AM broadcast band and suddenly find the rig is on 80M.

The final issue is that the AGC appears to saturate at -50dBm. If a signal gets stronger than this, the AGC saturates at -50dBm. I guess this gets down to the dynamic range of the AGC detector.

Anyway, I am having a lot of fun with the rig and only mention these areas for possible improvement.

Thanks to the team,
Dale W4OP
pe1nnz
 

Posts: 50
Joined: 30 Dec 2021, 19:29

Re: FIRMWARE UPDATES?

Post by pe1nnz »

Hi Dale,

Great to hear you enjoying the rig and thank you for looking with more detail into the receiver behavior. This feedback is much appreciated, and I am happy to work with you to see if we can improve here.

Yes, I think the AGC can be made even faster to prevent overshoot. However, making it faster makes it also more susceptible for impulse noise, so we have to be careful here. Maybe it is possible to do some better estimations for impulse noise and signal, maybe we have to be creative here.

Yes, the AM mode is odd because when exactly tuned zero-beat, the carrier is at zero-IF and basically not detected well due to the high-pass filtering. With a slight offset (near zero-IF) the AM detection improves. I am experimenting with an AM detector that uses this principle combined with steeper IF filters. I am not aware of the tuning oddity but I will try to reproduce it.

You are correct that the AGC currently satures at -50dBc as the system has run out of dynamic range. The good news here is that before this happens we can still enable the external attenuators (-13dB and -40dB and combinations of this). So, yes it would be a great idea to incorporate this in the new AGC.

73, Guido
W4OP
 

Posts: 15
Joined: 18 Feb 2022, 03:39

Re: FIRMWARE UPDATES?

Post by W4OP »

Thank you for your kind reply Guido,

I have worked with AGC design for a couple of transceivers. My current boat anchor rig is a Cubic 102BXA.
One of its unique features is that it has a variable AGC decay time on the front panel. Here is my Swan version of the rig- the same electrically:
http://www.parelectronics.com/vintage-swan-102-BX.php

What I find is that by using a fast attack and a long decay time, fast impulse noise is pretty much disregarded. This is an excellent choice for SSB, maybe not so applicable to CW.

I know we all so much appreciate Manuel's and your time, effort and magic.

73,
Dale W4OP
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