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On Wed, Jun 21, 2023 at 10:14 AM, Don, ND6T wrote:

If new builders want to duplicate this fix might avoid making the 19^th turn tap on L401 and not install C403. The value of the new capacitor is not critical, it just needs to block the DC bias but pass the 14 MHz receive signal when that band is selected. It could be a leaded part, placed from the hole at the input end of the C403 position to the hole where the 19^th tap was supposed to go.

Don, why not put the capacitor in place of C403 and short the L401 tap separately? Is something avoided by not using the PCB trace from the capacitor to the inductor tap?

I ask because I'm trying to do something similar on a QDX, and shorted 2 inductor holes and used an 820pf capacitor in a BPF capacitor spot, but my rf sweeps still all peak 1-2 Mhz higher than the target frequency.??

Nate
N8BTR

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Colin - K6JTH?

I very recently ordered a QDX but for the wrong frequency range. What is the best way to contact them to correct my order?

Thanks!

Received my QMX mid band yesterday and half of the box was crushed during shipping. The only "damage" ,if you would call it that, I originally saw was that one of the boards was already separated from the other so no biggie. Now I am starting the build and upon closer inspection of the main board I see all 3 of the "331" I believe inductors have the tops shattered. I remember reading, maybe on the qrp website, that if these were cracked you could glue them back assuming the wire was still intact. Problem is the missing chunks are MIA. Will this still be a viable build?

Does anyone know the rough weight of the QMX+?

I've ordered one anyway of course, I'm just interested what I'm going to be putting my back through when out and about with it...

My suspicion is that it might have something to do with your antenna system. I have had this same thing happen with multiple radios. Turned out to be connectors that tarnished and the RF reestablishes contact (at least for a while). Right now, I have a remote coax switch where one antenna will lose contact periodically but switching to another antenna works fine. Sometimes, just the exercise of switching will work, sometimes a shot of RF is necessary. I need to take the switch out and clean the contacts…

73, Kevin K3OX

Jim - congratulations!!! But not only a working QMX - also one with a PA efficiency of more than 100 %!!! ;-))
Maybe the current value is not so exact.

So, as you saw with those last sweeps, the they show that all the "sweet spots" are in the high end of the bands. How can I get them lowered?

For rf sweep the signal is going through LPF AND BPF. Which is it?
You could make a LPF sweep to check the throughput for LPF only. If the band frequencies are not attenuated so it should be the BPF. To lower the the pass trough you should increase the inductance. If possible spread the turns more over the whole toroid.

Looking at the current sweeps I think they are not all bad.

80 m: - 13 dB are not so good, but high noise on the band so maybe ...
60 m: - 7 dB are not so bad
40 m: - 2 ... - 3 dB are fine
30 m: - 5 dB is ok
20 m: - 9 dB are a bit much

Start with the highest band and with the part of the winding in use for all bands (the part direct connected to Q508, "0 - Start" I think).

Btw, thanks for the fantastic teamwork. I enjoyed all the time.

73, Ludwig

Please disregard my post. Operator error : (
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Jim?
N7RCS
Palm Bay, FL

With my HB Rev 3 HB QMX connected to N1MM I notice that the manual time I set on the QMX does not agree with what N1MM displays. The times differ by exactly 1 hour. Any idea what may be causing this issue? I'm not using a GPS for time, just setting the time manually. N1MM is working normally otherwise.

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Jim?
N7RCS
Palm Bay, FL

Hi Matteo.

One thing to try is a manually triggered factory reset if you've not already done that. Sometimes an additional reset clears up some initially seen issues.?

Using a DMM you should post your actual current readings of QMX power input which will provide a vague clue or 2.?

Also, see this recent thread titled "Re: New LB QMX RF Sweep Analysis". There's a chance that you're running into a similar issue.?
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73
de Roy - KI0ER
Littleton, Colorado USA

Karl,
I have one of these as well but it is not "quiet". There is significant switching ripple on the output which?I "fixed" with a 1000uf capacitor soldered on the top of the board.?
Gary
W9TD

I wonder if anyone has tried using a more refined encoder with the QMX, something like a 400ppr unit?

Can the QMX keep up? I don't have a QMX yet to try.

Steve G4EDG

Ludwig - T501 is back on the board, and....... SUCCESS! Key down no longer draws over an amp - closer to about 340 ma and I'm getting 4+ watts on 80-30 meters, 3.8 watts on 20 meters. The RF sweeps look almost identical to the last set I took with T501 off the board.?

So, as you saw with those last sweeps, the they show that all the "sweet spots" are in the high end of the bands. How can I get them lowered?

(By the way - thank you very much for guiding me through these issues!)

73,?
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Jim / K7TXA
Eagle, ID

SKCC 10447T
BUG 301

The dummy load seems to be working fine, as far as I can tell. My ohmmeter reads 50 ohms.?

Not sure I understand your final question?

As far as the clock is concerned I built mine in a plastic case and included an active antenna in the upper rear of the case (but saving several dBs of cable loss). ?Works well indoors?

The clock is just a UTC Ham clock?
My beacons have built in GPS modules that use a bank of active GPS antennas in the roof space which is a bit more stable than the same antenna type in the shack

Using my experience with this kit formed an opinion or few:
1. Like Clive said, don't go cheap on the solder.
? ? ?A. 63/37 Sn/Pb rosin core, NO LEAD FREE!
2. Scrape all coil and transformer leads to bright copper. DO NOT depend on?
? ? burning away the enamel. That pwr/swr transformer had to be removed,? ? ? ? ? ? rewound and re-installed and I scraped the first time. Had to reflow all
? ? ?toroids!
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73
Karl
KI4ZUQ

I got one of these and it is quiet. It is adjustable on the output connector as listed and there is a usb-A connector you must adjust the volts to 5. This usb outlet must be switched on.

The instructions are in clear english but not well organized. The illustations are great.

On Sat, May 18, 2024 at 12:51 AM, Muhsin TA1MHS wrote:

I think I will have a better result using QMX+'s BPFs and LPFs (T37-0 is great)

You cannot use T37-0 in QMX, you have to get T30-0

Hi

I experimented 40/30-20/17/15-12/11/10meters with QDX and QMX with some luck

I think I will have a better result using QMX+'s BPFs and LPFs (T37-0 is great)

73 DE muhsin TA1MHS

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