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Microphone pre-amp

 

Hello,
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Has anybody tried this microphone preamp :
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Evaluation boards can be found for about 5€ looks good to me but I am no expert !
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73,
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Yannig - F4IUJ
Re: Release of version 1.2 of ABS solution for QMX+ (Automatic internal antenna tuner, internal battery and internal speaker with audio amp) #ABS #ATU #PSU #QMXplus

 

Me too! Ordered a qmx+ kit at Dayton.

Thanks

Raj, N2RD

¡ª Sent from my mobile
Rajiv Dewan
rmdewan@...
Re: Dreaded dead transmit from SSB Calibration routine

 

Thats strange that you get 4w+ at 60m??? Reset factory defaults to erase calibration??
Re: Dreaded dead transmit from SSB Calibration routine

 

Ludwig,
Thank you for your reply. Please note my amended post above. I ran Diagnostics in Putty and see the following RF Output:
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  • 60m - 4.3W
  • 40m - 0.6W
  • 30m - 0.5W
  • 20m - 0.2W
  • 17m - 0.1W
  • 15m - 0.0W
The SMPS appear normal and other conditions on the Diagnostic screen appear normal (unless I'm missing something). I've checked all 1N4007 diodes as well as several others on the board - all check out OK.
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73,
Robert VE7ZN
Re: QMX Microphone capsules in EU

 

Perhaps you could buy a quantity, get a small discount and share the shipping cost with other hams.
73, Don N2VGU
Re: Dreaded dead transmit from SSB Calibration routine

 

Revision to original post...
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I just checked again and I'm actually getting about 4W on 60m but then it drops to 350mW on 40, ~100mW on 20m, 75mW on 17m and 0mW on 15m.
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Help!
73,
Robert VE7ZN
Re: Mini Microphones for QMX SSB

 

hey eric,
I'd like to buy a fully assembled mic.
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please and thank you.
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Brett/K5BEZ
K5bez1 (at) Gmail.com
Re: QMX short during SSB calibration?

 

Chris, G5CTH <chris.rowland@...> wrote:

One theory is that there is no envelope shaping on the SSB calibrations
and this can generate voltage surges which causes some BS170s to fail.
Hans has said that he will add envelope shaping to the SSB calibrations.
This is interesting. QDX has the same transistors in the PA, doesn't have
envelope shaping by design, and typically doesn't routinely damage the PA.
Re: Dreaded dead transmit from SSB Calibration routine

 

Robert, maybe this document from the QRP Labs Wiki is helpful.
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73 Ludwig
Dreaded dead transmit from SSB Calibration routine

 

On my mid-band QMX ....I wasn't going to do it. I'd read several horror stories but then, as an "experimental amateur radio station operator" I couldn't help myself. The SSB calibration routine was a disaster. Blew the 2A inline PSU fuse, and took out the BS170s.?
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I replaced the BS170s with new ones on hand and applied enough heat, visually checked for other damage (none found), then sparked it up. Receives fine and all functions appear to work (Mode, Volume, Step, Band etc). However, when I try to transmit on CW into a dummy load, I'm only seeing about 340mW on 40m and progressively less as I go up in frequency...
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Any ideas as to where to turn to next would be very much appreciated...
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73,
Robert VE7ZN
Re: I made a protective cover for the QMX+ which also doubles as a stand and storage!

 

Looks nice; well done! From the photo, have you also added a heatsink?
Re: New QMX+ Calibration victim

 

On Mon, May 19, 2025 at 09:52 PM, Jonas Sanamon wrote:
Guess next is to start checking LPF selection BSS123's and PIN diodes??
Jonas, for this you may use this document from the QRP Labs Wiki.
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73 Ludwig
Re: QMX Microphone capsules in EU

 

You can find it also at Farnell.
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73 de 9A7AM
Re: New QMX+ Calibration victim

 

Update:

Managed to remove L101 by cranking up the temperature on the hot air station.
I created a new L101 by putting 29 turns of magnetic wire on a FT37-43 core to get ~300uH as a temporary fix until i receive?my Digikey shipment?
That worked while on the HW-diagostic?screen, but PSU limited on current when TX Bias was enabled.
Replaced all 4 BS170s and the SMPS seems happy again!?
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I now have (good) output power on 160m, 80m & 60m, but next to nothing on 40m and even less going up in frequency.?

Guess next is to start checking LPF selection BSS123's and PIN diodes???
(strange error though, as there are many LPFs and none above 60m is working. Only one LPF is enabled at a time, right?)

Regards, Jonas
Re: QMX Microphone capsules in EU

 

Hi Kiril,
There is always the option to using a mic preamp with the capsule at hand, which is what I did.
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Mel. M0KMD.
Re: QMX+ LCD blank on new build

 

Thanks Stan!
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Even though I had looked at that long connector multiple times and could not see a problem, I took out the soldering iron and reflowed all of the solder joints on the front of the display pcb and now I have a display!? The radio type needed to me changed to QMX+ to see all the bands so I changed that and found the encoder buttons are a bit bouncy.? I also found all 10 bands.
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I guess next thing is to connect a dummy load and see if I can get the whole radio calibrated.? I'm crossing my fingers, hoping that it doesn't croak like some have had happen.
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Thanks
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Lincoln
N9IN
Re: QMX+ LCD blank on new build

 

Next check is to make sure both ends of each pin are correctly soldered in that long connector between the LCD module and the LCD mount board.? It is easy to miss one, or short two together?
Re: Release of version 1.2 of ABS solution for QMX+ (Automatic internal antenna tuner, internal battery and internal speaker with audio amp) #ABS #ATU #PSU #QMXplus

 

I just purchased a complete at FDIM vendor night. I would also like to be added to the group buy of V2.
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How will the information be delivered if a buy is happening, costs and timing?
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Joe N7QPP
Re: Difficulty with the SSB compressor

 

Thanks guys. Yes I am working into dummy load and I have run the mic calibration (seems like 40 to 55 all sound good until I turn on compression). I'm pretty satisfied these aren't variables in the problem, but will check both again. What bugs me is that it seems like the compressor is working properly while in the terminal mode if I transmit to test settings, it is when I leave the terminal and try to start a real QSO that the problem starts. Almost like the wrong (super high) compression level was saved...?
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Regards,
Earle KC0KVR
Re: U3S andLPF Relay Sw board

Steve Shuff
 

Hi Guys, Thanks for the replies,

Firstly, I was unaware?that depressing the "Edit" button while?the U3S is in idle mode (awaiting the start of the WSPR transmission)
puts the U3S in transmit mode. If I have 6 relays and LPF installed can I choose which relay to fire up ?
I have not read this information anywhere so I am missing something, please point me in the right direction to gain access to this info.

I have come to the conclusion that I am incorrectly programming the U3S because now when the WSPR transmission starts it only transmits on band 1,?
yesterday it was only transmitting on band 0. (yes, I have been meddling?in the menus)
I can confirm the tx frequency along with the corresponding? relay/LPF combination is working and I have 200mw RF flowing into the power meter.
I am sure I have set all 6 channels correctly and depressed the "Edit" button twice to make the band active, (No ---- symbols between?
? ?WSPR--------23? (disabled mode setting)
Definitely?a programming issue on my part,?
Any help would be appreciated?






On Sun, May 18, 2025 at 10:31?PM Bruce Akhurst via <bruce=[email protected]> wrote:
For each of the mode Index entries, The following 'band' number is programming the relay and LPF paths while the frequency in that memory is setting the exact TX frequency for that 'RF route' and when that TX memory is selected/enabled it should all work. For digimodes you need to make sure the start & Frame figures make sense too?

Most likely it's going to be your programming, or errors in links, wiring relay ID numbers etc.? ?e.g. verify if the right relays clicking as you select transmit on each of the bands.?



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Steve Shuff.
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