Re: Why no AGC for digital modes, as other modes?
Could have AGC (or just some crude clipping) on data to the DAC for the QMX headphone jack
Jerry
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On Thu, May 22, 2025 at 06:27 PM, ajparent1/kb1gmx wrote:
or digi modes no agc helps.? Reason is that if a strong signal appears
in the pass band it pumps the agc and all signal are reduced by that
amount.? ?So a digi band has a couple of very strong signals it tends
too make the weak ones impossible to detect.? ?It was a big problem
with early receivers with a strong agc system rather than large
dynamic range.
?
?described differntly AGC when it operated it does so by
making the radios gain lower to correct the excessive
level.? Good for the ears but it also is making the radio
less sensitive to accomplish that.
?
--
Allison
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Texas Instruments often skips the "74" in front of the chip name, so 74ACT08 is actually what you need to look for...
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Nothing fancy on these connections. Top layer and bottom layer traces only. I just checked with the meter and all is well. My question really was about the diodes. Where do you get 1n4007 diodes with .3mm leads?
Tony
AD0VC
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Tony,
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The QMX series of radios uses a 6-layer PCB. Making the drilling hole larger could cause gaps in the internal layers. It would be better to use a thin lead and solder the fat lead above the board. Look at the board trace pictures and the schematics to
verify that the connections are still there.
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73
Evan
AC9TU
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You can either measure continuity from top to bottom, or solder both top and bottom. Whether the via is needed depends upon which or both have connections.?
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Don't think that the lead must go through the hole. It doesn't. Note all the surface mount parts without any leads (-:
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Tony,
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The QMX series of radios uses a 6-layer PCB. Making the drilling hole larger could cause gaps in the internal layers. It would be better to use a thin lead and solder the fat lead above the board. Look at the board trace pictures and the schematics to verify that the connections are still there.
?
73
Evan
AC9TU
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I needed to replace one of the 1n4007 diodes in my QMX (I cut the lead for an experiment) so I went looking for a replacement. None of the 1n4007 diodes at Mouser have the small diameter leads like the ones from QRP Labs. They are all about .7mm diameter where the QRPLabs diodes are more like .3mm. I ended up ordering Vishay diodes with the fat leads.
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I had cleared the holes with the solder sucker but the leads still did not fit so I used some PCB drill bits to clear the holes and finally got the diode in there. Hopefully the via barrel is still intact. I am waiting for some caps to put it back together and try it.
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Any discussion about these diodes? My experience is that 1N400x diodes all had fat leads.
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Thanks,
?
Tony
AD0VC
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Re: Tune SWR on QMX+ always shows SWR <1.05
Excellent!? I'm glad you got it going!? And this is the Nth time (N large) that someone who was sure the soldering was good fixed the problem by reflowing the solder yet again.? That's why I recommend to carefully scrape or burn/sand off the enamel before soldering the coil wires, which avoids much of this issue.
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Thu, May 22, 2025 at 04:15 AM, SA6ZGM Arne wrote:
find a way to have the esp32 that controls the motor for the magloop tuner stop excactly at the point where the QMX's SWR measurement is the lowest.
The release software now has a CAT command to read the SWR value, and extra virtual serial ports, so everything is there that is needed on the QMX side to make this happen - good luck, and let us know how it goes.
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Re: QMX+ Pulse in headphones on TX UPDATE !!
So I replaced the suspect Q516 and seems I have a happy QMX+ woohoo.
No more fluctuating bias current and silence in the headphones on key up.
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Thanks a heap for the help guys. You got me on the right track.
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Cheers
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Ian ZL1HIM
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Hans says his rigs in the lab with BS170's seem to survive just fine,
even when he accidentally fails to hook up an antenna or dummy load.
So his opinion is that TN0110's are not needed.
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If yours blow, you may be of a different opinion.
Could be process variation between different manufacturing lines for the BS170?
Could be variations in cap and inductor impedances for the LPF?
Could be dumb luck?
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It has been found that the BS170 Vds-max of 60 Volts is exceeded on 160m and 80m
even with a 50ohm dummy load on the QMX/QMX+, can be far exceeded with bad SWR.
The TN0110's are good for a Vds of 100 Volts.
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There are tens of reports here in the forum of blown BS170's.
But then we're approaching ten thousand QMX/QMX+'s out in the world.
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I have some TN0110's on hand to try if these BS170's blow.
But I have not seen any reports yet of intermodulation measurements
after switching from BS170's to TN0110's when operating SSB.
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Jerry, KE7ER
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On Thu, May 22, 2025 at 05:01 PM, Stan Dye wrote:
On Thu, May 22, 2025 at 04:38 PM, Eugene Pressley wrote:
Are their any drawbacks to using the alternate mosfets?
Please search prior messages for TN0110.? Not everyone has the same opinion regarding their use - some are big proponents, others, including Hans, do not recommend them or see any need for them.
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Re: Why no AGC for digital modes, as other modes?
For digi modes no agc helps.? Reason is that if a strong signal appears
in the pass band it pumps the agc and all signal are reduced by that
amount.? ?So a digi band has a couple of very strong signals it tends
too make the weak ones impossible to detect.? ?It was a big problem
with early receivers with a strong agc system rather than large
dynamic range.
?
?described differntly AGC when it operated it does so by
making the radios gain lower to correct the excessive
level.? Good for the ears but it also is making the radio
less sensitive to accomplish that.
?
--
Allison
------------------
Post online only,?
direct email will go to the bit bucket.
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We need a "good things to order and keep on hand from Mouser if you are going to place an order" Sticky?
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On Thu, May 22, 2025 at 04:38 PM, Eugene Pressley wrote:
Are their any drawbacks to using the alternate mosfets?
Please search prior messages for TN0110.? Not everyone has the same opinion regarding their use - some are big proponents, others, including Hans, do not recommend them or see any need for them.
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Hi Eugene,
Nothing other than mounting them upside down (flat side up) because the outside leads are reversed from BS170.
Tony AC9Q
On Thu, May 22, 2025 at 6:38?PM Eugene Pressley via <me.e2p2= [email protected]> wrote: Are there any drawbacks to using the alternate mosfets? Anything that needs to be altered to use them??
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Eugene,
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You might want to also consider ordering some TN0110 FETs, a BS170 alternative, to have on hand if you decide you'd like to experiment with a hardier device.
I'd also suggest order a few 5ft. rolls of Solder Wick and a ChipQuik SMD removal kit.
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73 de WD4AH
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Are their any drawbacks to using the alternate mosfets? Anything that needs to be altered to use them??
?
Eugene,
?
You might want to also consider ordering some TN0110 FETs, a BS170 alternative, to have on hand if you decide you'd like to experiment with a hardier device.
I'd also suggest order a few 5ft. rolls of Solder Wick and a ChipQuik SMD removal kit.
?
73 de WD4AH
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Re: Pop! Oops, blew a BS170 in my QMX, my fault. Lesson learned
On Wed, May 21, 2025 at 07:15 PM, KF0OUH wrote:
?I did have SWR protection on and set at 3 but it didn¡¯t stop the pop.
This surprises me.? I have my swr protection set at 3, and it has triggered every time it should.? I have several times forgotten to attach the dummy load before tx, and it saves me every time.? And when I forget and transmit on 12m or 17m on my 20/15/10 antenna, or outside the narrow passband on my 80m dipole, each time the swr protect triggers and saves me from damage.
Maybe you were at 2.9:1 during a FT8 transmit and that was enough to cause the damage...
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Re: Pop! Oops, blew a BS170 in my QMX, my fault. Lesson learned
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Re: Pop! Oops, blew a BS170 in my QMX, my fault. Lesson learned
When I damages my QMX+ finals, only 2 of the BS170s were bad. See my post on diagnosing which ones are bad and how to replace them safely without damaging your PC board.
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Perhaps my suggestion was without enough detail and I assumed too
much.
In my experience, the suggestion to "just turn down the volume" is
no substitution for AGC, and the multiple reasons that it was
invented.
If my reasons to want? and use "unnecessary" AGC, in single tone
digital modes, make me a technical dufus, so be it.
If I requested Hans to do something extraordinary, or difficult,
or time consuming, or contrary to his vision - to make AGC
available for all modes -
I hope he will offer something more sensible than "turn down the
volume".
wa4hei
Re: Audio level request
From: Daniel
Conklin
Date: Thu, 22 May 2025 12:33:39 EDT
Fred,
AGC is not necessary with the Digi mode because the audio is
always at 100%. You don't even need to listen to it since it's
encoded ad interpreted by the computer. If you do want to listen
to it, then just turn down the earphone volume.?
--
73, Dan - W2DLC
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New Information site on T41 SDR and DSP with microprocessors.
Hi Everyone,
I have created, with Jack's help, a new site all about the T41-EP at:
This is an 'information and background site" for the T41, not
an open forum - the SCHR is the place for posting
comments/suggestions about the T41.It also has general info on SDR radio design and DSP.
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I intend to post lots of photos of user-built T41 rigs. I
have a few already included, but would like more. If I get enough, I
will create a separate gallery page of just T41 builds.
Photos should be sent to me directly at albertfpeter@... with a brief explanation. I reserve the right to edit any comments for brevity.
Let me know what you think.
Regards,
Al Peter
AC8GY
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Richard Dyer
jjpurdum