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Two-band QCX (20 and 17m), is it possible?

 

Hi group,

While I wait for the shipment and delivery my QCX I was wondering if someone has considered or experimented with a dual band (adjacent bands, e.g. 20 and 17m) version of the QCX.

I wonder if compromises could be made on the LP and the passband tuning filters to accommodate the 2 bands (20 and 17m). ?For the class E amp two h/w switchable L4 coils could do the trick.

Has anyone done experiments along these approaches?

Cheers,

Antonio, ea4le/kc2hax
 

Buenas tardes Antonio,

Por favor mira para ideas e información.

Luis VK5EEE
 

Gracias Luis! :) ahora mismo lo miro. 73
 

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Hi Antonio, I have a rough, untried paper design.? " bands is probably OK, as you can assign one band to vfoA, and the other to vfoB, otherwise you are in for a LOT of knob twiddling, or a factory reset when you change bands. I have settled on 2 adjacent bands, covering less than an octive. Say 30 and 40m or20 and 17m.? This allows you to use a low pass filter configured for the higher frequency.? I will make the capacitive trimmer a front panel control, and call it a preselector.? It should cover 2 adjacent bands. If you want to change the coils on each band, I would re-configure the rf input tuned circuit as a 2 torroid pair, and just change one of the torroids for each band,? The fixed torroid would be wound with say 10 tri-filiar turns. 2 of the windings are arranged as a push-pull input to the mixer. The 3rd winding connects to 10 turns on the 2nd core that is to be switched. Th e 2nd core also has a resonant winding on it, for the band in question. This eases the switching a little.? this is just a paper excersise, it will be a while before I get around to doing something about it.? It would be nice if Hans modified the software to allow larger ncremental tuning; in addition to the 10,50,100 Hz /step, we add MHz or 100KHz steps.

73

Alvey


On 04/12/17 15:28, Antonio Fernandez wrote:

Hi group,

While I wait for the shipment and delivery my QCX I was wondering if someone has considered or experimented with a dual band (adjacent bands, e.g. 20 and 17m) version of the QCX.

I wonder if compromises could be made on the LP and the passband tuning filters to accommodate the 2 bands (20 and 17m). ?For the class E amp two h/w switchable L4 coils could do the trick.

Has anyone done experiments along these approaches?

Cheers,

Antonio, ea4le/kc2hax
 

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Hi Antonio
?
You must have been reading my mind!!!
?
I thought the same thing. I have a 17mtr QCX which has had a lot of problems but I finally got the thing going. I had to change IC1 but that's another story!!!
?
Anyhow,? I set Preset memory 4 to 14.020 MHz and transmitted into a Dummy load could see? almost the same power. Stuck an aerial on it and was hearing plenty stations including HH2AA.
?
I could hear a slight peak in signal strengths? when adjusting C1.
?
Im sure RX is not optimum and not sure what the TXsignal, harmonics etc look like but it seems to work!!
?
73
?
Ian G4GIR
?
?
?
?
?

From: Antonio Fernandez
Sent: Monday, December 4, 2017 3:28 PM
Subject: [QRPLabs] Two-band QCX (20 and 17m), is it possible?
?

Hi group,

While I wait for the shipment and delivery my QCX I was wondering if someone has considered or experimented with a dual band (adjacent bands, e.g. 20 and 17m) version of the QCX.

I wonder if compromises could be made on the LP and the passband tuning filters to accommodate the 2 bands (20 and 17m).? For the class E amp two h/w switchable L4 coils could do the trick.

Has anyone done experiments along these approaches?

Cheers,

Antonio, ea4le/kc2hax
 

Hi all

The QCX may not work across multiple bands at the moment. When you set the Band menu item, this setting is used in the configuration of the Si5351A for quadrature output. If you tune several MHz away from the chosen band, it may stop producing the correct quadrature LO output. This has been reported in this group previously. I can change this in the next firmware version. The QCX is designed as a mono-band rig which is why this was not an important thing during testing. However it should be easy to change it so I will do so.?

73 Hans G0UPL

On Mon, Dec 4, 2017 at 7:51 PM, IAN FRITH via Groups.Io <i.frith@...> wrote:
Hi Antonio
?
You must have been reading my mind!!!
?
I thought the same thing. I have a 17mtr QCX which has had a lot of problems but I finally got the thing going. I had to change IC1 but that's another story!!!
?
Anyhow,? I set Preset memory 4 to 14.020 MHz and transmitted into a Dummy load could see? almost the same power. Stuck an aerial on it and was hearing plenty stations including HH2AA.
?
I could hear a slight peak in signal strengths? when adjusting C1.
?
Im sure RX is not optimum and not sure what the TXsignal, harmonics etc look like but it seems to work!!
?
73
?
Ian G4GIR
?
?
?
?
?
From: Antonio Fernandez
Sent: Monday, December 4, 2017 3:28 PM
Subject: [QRPLabs] Two-band QCX (20 and 17m), is it possible?
?

Hi group,

While I wait for the shipment and delivery my QCX I was wondering if someone has considered or experimented with a dual band (adjacent bands, e.g. 20 and 17m) version of the QCX.

I wonder if compromises could be made on the LP and the passband tuning filters to accommodate the 2 bands (20 and 17m).? For the class E amp two h/w switchable L4 coils could do the trick.

Has anyone done experiments along these approaches?

Cheers,

Antonio, ea4le/kc2hax
 

I get the point Hans and makes sense. But... tinkerers always pushing the envelope :) I was considering 17 and 20 taking into account the monoband ethos of the QCX because these bands are close. What I do not know is if this "stretch" is within the correct quadrature limits. The idea? would be 20m the primary band and 17m the secondary.
Thanks for producing things like these for us to enjoy!
73? de antonio, EA4LE?
 

Thanks Alvey, this is very useful info. I was also thinking abt the "preselector" for the front-end ;) glad to learn from Hans that he is willing to modify the software :)?

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