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Re: #qmx mid-band receive
#qmx
#troubleshooting
Thanks Stan. I did not realize that the RF dB values are using a common offset. That means that the RX performance on 17 isn't that different between BPF1 and 0 - only about 3dB. I decided to try removing one more turn from 401a, and here are the results (after a few different attempts at bunching/spreading:
Looks basically the same to me. I did try a version with very close bunching of the turns, but that only gave me 1db more of peak at 15m and moved the top of the curve to the left of 21mhz. I am kind of surprised that the BPF shape and amplitude are relatively insensitive to the number of turns on L401a. Makes me think there might be some other factor at play that's driving the filter response. In any case, I think I'm ready to chalk this up to issues with using a Rev 1 board in a different manner than intended. Unless, of course, you and/or others on the forum have any ideas about how I could squeeze a bit more performance out of 15/17m receive. Either way I appreciate your help and the wealth of knowledge on this forum
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Alex N7ADH
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CW Practice / Rag Chew
开云体育On
4/08/25 I had a CW practice / rag chew session on 30
meters. I worked three stations:
Conditions were
OK. 30 meters seemed to be better than what I have been
experiencing on 20 . SSN = 167, SFI = 162, A = 13, K =
2.
My next CW practice session will be April 11 at 09:00 EDT / 13:00 UTC on 30 meters.?Anyone and everyone is welcome. This practice is intended for operators who are new to CW or they need some practice. IT DOES NOT MATTER HOW POOR YOUR CW IS. Mistakes are OK. Poor fists are OK. Slow speed is OK. Really slow speed is OK. This practice is meant for you to improve your CW. I will do my best to adjust to your skill level. Operate at any power level. If several stations show up, I will operate as a round-table control station. I will do it as a round-table so everyone gets a chance to transmit. Please listen to my directions. Details: Date
- April 11 2025
Time - 09:00 EDT ?13:00 UTC Band - 30 Meters How to find me - I will find a clear frequency and call CQ. Go to the Reverse Beacon Network and search for my call sign AB8DF. That will tell
you what frequency I am on. Tune your station to
that frequency and if you hear me give me a call. If
there is a QSO in progress, please wait for a break
in the action. Then send your callsign. If I hear
you, I will invite you to join the QSO and start a
round-table QSO.
Reply to this email if you have questions. IT DOES NOT MATTER HOW POOR CW IS Ed AB8DF |
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Re: QMX+ T507 winding direction?
There is some small interaction between the two windings on a binocular core which ultimately limits the directivity of the coupler, but it is not at all an issue for the QMX.
I would usually include a URL to Owen Duffy's website at this juncture, but sadly, it was shut down ? 72 de Russ, va3rr |
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Re: QMX+ T507 winding direction?
It won’t make any difference. I tested one wound in the same sense and again in the opposite sense and no difference. These are two independent windings. As long as you put the wires in the circuit board hole on the same side of the core where the wire exits, it will work. If you cross the wire under the core and connect to the board hole near the other end of the core you will have problems.? Ron On Tue, Apr 8, 2025 at 16:23 Dave WD8CIV via <dhinerman=[email protected]> wrote:
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Re: Thank you
Hear here!? Absolutely.? This group is one of the best I've ever found for people helping each other.? My home built QMX worked fine from the first power-up, but I visit everyday to learn more about Han's great products. Even with a running radio, there is a lot to learn here about various settings: filters, AGC, test sweeps, etc.
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Many thanks to all who help!
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Off to smoke test a QMX+.
--
72 de N4REE, Bob Easton - QRP CW forever |
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Hi All,
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Just wanted share my experience with you.
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I have experimented with 3 electret mic capsules so far. 2 that I scrounged off of other boards and one utilising the mic from my PC gaming headset.
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The mic from the head set resulted in low volume and unsatisfactory modulation. When I turned up the mic gain on the QMX+, the QMX also amplified internal noise creating unacceptable background noise in the modulated output.
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The other two capsules were a little better but still unsatisfactory.
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One of the capsules that I had took off was from a MAX9814 Arduino mic amplifier module.?? I thought, "Hey, why not use the amplifier module to use with my headset!"
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Well, I did just that. I wired up 2 x 1.5v AA's in series to power the board with and wired the mic from the headset as the input to the amp. I then wired the output of the amp to the mic input of the QMX via a 1uF capacitor to block the 3.3v dc from the QMX.
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Well, that done the trick! I'm getting much better results now. But I did have to reduce the mic amp module gain as it was way too high.
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As it currently stands, I am unable to achieve a satisfactory calibration with any of the bands on my QMX+.? As a result of this, my QMX+ is in default calibration settings.
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The mic gain on my QMX+ is now set at 35 and have made a few contacts with good reports with this setup.
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Now, the question is, how do I wire up the mic amp module to the QMX using the 3.3v supply on the TRS rather that using batteries?
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I? did try taking the 3.3v via 2k ohm resistor from the QMX TRS terminal to the vdd of the mic amp module, and connect the output of the module back to the same TRS terminal via a 1uf dc blocking capacitor, but sadly that didn't work. I'm clearly missing something...
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Cheers,
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Mel. M0KMD.
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va3rr
Braden Glett
Ronald Taylor
N4REE - Bob
