Hi.

After I successfully built the QDX I asked to myself: Can we implement 15m/10m on the QDX v2? At first it's a matter of lpf. Yes. Beside this: Is the firmware prepared to switch to this frequencies? Is it possible in general?

Hans,

Oh yes, I’d buy a QDX kit for 10/12/15/17 :-)   With an original doing 20/30/40/80– that’d be a nice pair of digital transceivers!  Suspect it’d sell like hotcakes, too, especially if the sun cooperates! 

Mark N8MH 

The Sun cooperates more than expected! A possible 10/12/15/17m kit would be a hit.

Kind regards

Janez, ON/S58J

Yes, a QDX for 15m and 10m would just be perfect! You'd have my custom. Even better would be one single QDX for the whole range 80m to 10m. 73 de HA7RJA

That would be nice to have, but would most certainly require a larger
circuit board for the QDX, as well as a separate board for the LPFs.

For now, maybe we could live with the original 80-20M QDX, and a new
QDX that covered up to 10M or maybe even 6M. 15-6M is five bands, and
I'm not sure if that would fit on the existing PCB.

73
Jim N6OTQ

I misspoke -- I said "15-6M" when I should have said "17-6M", the
complete band plan for USA.

I am not familiar with the band allocations for non-USA hams.

N6OTQ

On Wed, Sep 28, 2022 at 3:10 PM Jim Strohm via groups.io
<jim.strohm@...> wrote:

That would be nice to have, but would most certainly require a larger
circuit board for the QDX, as well as a separate board for the LPFs.

For now, maybe we could live with the original 80-20M QDX, and a new
QDX that covered up to 10M or maybe even 6M. 15-6M is five bands, and
I'm not sure if that would fit on the existing PCB.

73
Jim N6OTQ

On Wed, Sep 28, 2022 at 1:14 PM <ha7rja@...> wrote:

Yes, a QDX for 15m and 10m would just be perfect! You'd have my custom. Even better would be one single QDX for the whole range 80m to 10m. 73 de HA7RJA

I have now finished my QDX for 20m, 17m, 15m, 12m and 10m.
Work on the project was delayed by the event that occured in the UK recently, I was too upset and unable to concentrate on the technical aspects.
Main change is L12 changed to a T50-6 toroid, 20m is on the old 80m connection to keep the BPF switching correct, Other bands are using the remaining taps.
Receive is a delightlful less than 1 micro-volt on all bands, some are less than half a micro-volt.
Transmit power is down from the 5 Watts on the lower bands but still over 1 watt on 10m. Still too much for use on WSPR so I will only use on FT8 and FT4.
DC input is 8.6 Volts.
Don't know about the firmware not working, all OK here. Just changed the band config to cater for the new bands.
All filters designed with help from Elsie and the calculator from DL5SWB and tested on a breadboard with a N2PK VNA.

I would love to see a QDX V2 that included 10M and ^ Meters...I work some 10 Meters now.2 Watts

L12 is now wound on a T50-6 toroid with 20 turns for 20m, 13 turns for 17m, 12 turns for 15m, 5 turns for 12m and 10m.
C30 ( 20m ) is 68pF, C28 ( 17m ) is 100pF, C31 ( 15m )is 100pF, C29 ( 12m & 10m ) is 68pF.
I used the method described as before. Reducing the signal input from generator until it is not discernable on the WSJT-X waterfall. The old Marconi generator is scaled in milli-volts and micro-volts and not dBm as most modern generators seem to be. 1 micro-volt being negative 107dBm which is plenty sensitive for the HF bands where band noise usually exceeds that figure, at least it does at my location.
I am running at the lower voltage DC input as I don't want the higher power, the U3S running 100mW is my preferred TX signal for WSPR but for FT8 etc. I shall be using the QDX.

Thanks, I'll see if I can do something to help my red L12 without ruining the lower band performance. I'm guessing it will work just as well except for 80 meters.

M

I should have mentioned before with the values I listed for L12 and associated capacitors that these were for the LPF's I used. The LPF has  an effect on the L12 and C28-31 values. These were all "tweaked" on the test setup with the VNA before installation on the board. I built the LPF's first and then added the BPF components for each band.

Yes, I realized that myself - the LPF must be optimized first.

WRT your measurements, I've checked my mods using the method of minimum signal detectable on the waterfall, and I'm getting results similar to yours.

While that method works well, it's dependent on the waterfall settings being exactly the same all the time.

It also makes the measurement across an unusually narrow passband. I don't know the size of the bins in the WSJTX FFT, but they are well under 10hz for most settings. That accounts for the difference we are seeing in measurements. I'm taking mine across the full QDX passband of about 3khz...

Of course, the narrow passband is also what makes WSJT-X work so well!

I'm still going to explore different toroids in my QDX. I'm suspicious of the QSD input transformer. I've ordered another QDX so I don't have to worry about destroying this one - when it comes I'm going to make a few more mods.

I also find the QDX internal noise seems to be higher above 15mhz. It's possible that weak signals are being covered up by power supply and cpu noises. I think that later versions of the QDX are better about this. My version 2 board may be much noisier than the ones that came later. Hans made a number of changes, I believe...

In practice, I agree with you that the current mods are working well enough for the output power level. I can't usually work any "normal" stations weaker than about -3 in WSJTX due to the power imbalance anyway. Most of them are running 50-100 watts!

I do feel that my receiver is not quite at that level at 12 meters, however - probably due to rising noise.

I've never really been much of a 12 meter fan in the past, so I'm not too worried about it right now.

I've been operating this thing a lot and even had it on two trips to the local park with great results so this project has definitely given a great return on the money and time invested!

M