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QCX-mini 20 meters RX spurs on 14.008 14.026 and 14.035 (and a way to quench them).

 

Just built a 20 meter QCX-mini and I immediately noticed garbage signals on the following receive frequencies: 14.008, 14.026 and 14.035 MHz.? I then disconnected my antenna and connected a dummy load and the problem is still present.? I then noticed that if I hit the left push button to bring up Speed or RIT the spurs in the receiver go away which is one way around the problem in a pinch.? Sure looks like the spurs are being generated by the micro-controller program.

Wonder if anyone else has noticed this with their 20 meter QCX-mini?

My QCX-mini has AGC as well as TCXO.

P.S. I now have built the QCX-mini for 40, 30 and 20 meters:)

Don (wd8dsb)
 

I should also note that I have Keying set to Iambic B.

If I change to Iambic A then the spurs move to 14.036 and 14.044 MHz.

If I change to Straight Key mode then the spurs move to 14.018 and 14.043 and 14.050 MHz.?

Also have noticed a few spurs in which the Speed or RIT trick does not work.

Just FYI,
Don (wd8dsb)
 

Don have you tried a factory reset yet??

Ron?

On Tue, Dec 6, 2022 at 13:40 Donald Kirk via <wd8dsb=[email protected]> wrote:
I should also note that I have Keying set to Iambic B.

If I change to Iambic A then the spurs move to 14.036 and 14.044 MHz.

If I change to Straight Key mode then the spurs move to 14.018 and 14.043 and 14.050 MHz.?

Also have noticed a few spurs in which the Speed or RIT trick does not work.

Just FYI,
Don (wd8dsb)

 

Hi Ron,

I did not do a "factory reset" mostly because I don't believe in them as long as the design is bullet proof and as long as I've not entered incorrect parameters.? I do a lot of assembly language programming of micro-controllers (firmware / embedded software) so my view is a little skewed, but you got me thinking and I tuned my 40 meter QCX mini to the 20 meter band, and sure enough the exact same spurs show up on 20 meters using my 40 meter QCX-mini.? I then repeated this with my 30 meter QCX-mini and sure enough the exact same spurs show up on 20 meters.? Based on my testing there is no need to do a factory reset as the problem exists on all 3 of my QCX-mini transceivers which are all basically the same except of some components in the RF stages (software is all the same regardless of what band QCX-mini you have).? The QCX-mini design (using the most current software) definitely generates internal spurs on receive up on 20 meters but since selecting different options (Speed, RIT) causes the spurs to shift, the issue is most likely related to the speed that routines are being executed within the software and/or how I/O is then being toggled, etc.? One disclaimer is that all 3 of my QCX-mini transceivers all have the TCXO option so spurs on radios without the TCXO option may be different, etc.

I'm saying everyone has this exact same issue if they are using the current version of the software which is 1.09a as long as they have the TCXO option.? I can't speak on units without the TXCO option.

Don (wd8dsb)?
 

I also don't know if the 20 meter receiver spurs are unique to units with the AGC option installed as the AGC board sits right next to the micro-controller, and I should note that all 3 of my QCX-minis have the Rev 3 PCB.? The 20 meter spurs are present with and without the AGC enabled.

It would be interesting to hear if someone has a Rev 3 PCB version of the QCX-mini without the AGC board installed and whether they hear the 20 meter spurs or not.? It would also be interesting to see if someone has the Rev 3 PCB version of the QCX-mini without the TCXO board installed and whether they hear the 20 meter spurs or not.??

Don (wd8dsb)
 

Don, my 20 meter?Mini is a Rev 1 but I have a Rev 3 that?I built for 15 meters. It has the AGC and does not have the TCXO. I set it on 20 meters and do not hear any spurious signals in the receiver.... Ron


On Tue, Dec 6, 2022 at 11:39 PM Donald Kirk via <wd8dsb=[email protected]> wrote:
I also don't know if the 20 meter receiver spurs are unique to units with the AGC option installed as the AGC board sits right next to the micro-controller, and I should note that all 3 of my QCX-minis have the Rev 3 PCB.? The 20 meter spurs are present with and without the AGC enabled.

It would be interesting to hear if someone has a Rev 3 PCB version of the QCX-mini without the AGC board installed and whether they hear the 20 meter spurs or not.? It would also be interesting to see if someone has the Rev 3 PCB version of the QCX-mini without the TCXO board installed and whether they hear the 20 meter spurs or not.??

Don (wd8dsb)

 

Forgot to say that it is is using 1.09a firmware. ... Ron


On Wed, Dec 7, 2022 at 7:34 AM Ronald Taylor via <wa7gil=[email protected]> wrote:
Don, my 20 meter?Mini is a Rev 1 but I have a Rev 3 that?I built for 15 meters. It has the AGC and does not have the TCXO. I set it on 20 meters and do not hear any spurious signals in the receiver.... Ron

On Tue, Dec 6, 2022 at 11:39 PM Donald Kirk via <wd8dsb=[email protected]> wrote:
I also don't know if the 20 meter receiver spurs are unique to units with the AGC option installed as the AGC board sits right next to the micro-controller, and I should note that all 3 of my QCX-minis have the Rev 3 PCB.? The 20 meter spurs are present with and without the AGC enabled.

It would be interesting to hear if someone has a Rev 3 PCB version of the QCX-mini without the AGC board installed and whether they hear the 20 meter spurs or not.? It would also be interesting to see if someone has the Rev 3 PCB version of the QCX-mini without the TCXO board installed and whether they hear the 20 meter spurs or not.??

Don (wd8dsb)

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