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
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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.
?
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??
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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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Re: Why no AGC for digital modes, as other modes?
> have found no noticeable performance penalty ....
Would second this request. Elegant solution of the "remove digimodes from mode switch to avoid ear damage" request 2 further up
Factory/default setting would be "off", + a brief mention in the manual.
"Da Wiz", hi. We really owe Hans a lot for his little gems.
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I would be interested in this info too. I have a defective encoder.?
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Maybe digi mode should be selectable from the menu rather than the rotary knob selection? I find it a bit of an irritation that when tuning across a band that i have to cycle through digi mode (at loud volume) just to change from LSB to USB modes.?
Just an idea¡
73 Ken g4apb?
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Does anyone happen to know of a manufacturer or US distributor part number for a replacement rotary encoder switch for the QMX?? My left hand (power, band, mode)? rotary encoder switch appears to have failed. I checked the assembly manual for details, but I'm coming up short.
?
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Re: #qmx plus assembly one LP and Band filter at the time
#qmx
Azgael,
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I would expect it to transmit fine with just the one LPF installed.
Best guess is a bad solder job at T507 or no jumper at JP501.
Perhaps a bad cable from QMX out to the dummy load, or a flakey BNC connection.
You should see zero DC ohms across the dummy load with your DVM when the dummy load
is properly connected to the QMX (due to the ground on the far side of that T507 winding).
Also check the inductors in the LPF, if L511 has a bad connection in the 160m LPF,
then it may not allow much power through but C520 could be sufficient to get
enough signal for a reasonably good receive sweep (swipe?).
?
Jerry, KE7ER
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On Thu, May 22, 2025 at 09:21 AM, Azgael wrote:
Hi Everyone
I was wondering if is possible to assemble only one band filter at the time on a qmx plux rev3, this means I have assembled the all QMX leaving out only the toroids of all the filters, the LP and BP ones.
Now next I have assembled only the 160m LP and BP and test the filters. The swipes look normal on the 160m.
?
Next is to test transiting to a dummy load only this band, but I get the swr protection kicking in and no power out. voltages look normal. running a swr plot on 160m shows swr 10 on all graph.
?
The main idea is to tune filters one by one with space for the soldering iron making it easy.
?
I have reviewed soldering of transformer and swr brigde plus the jumper to the bnc is in place.
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My question is, Is it expectable that the SWR is High when only the filters for one band are on the board or this means something else is already wrong from the beginning.
?
Thank you a lot
73 Azgael
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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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#qmx plus assembly one LP and Band filter at the time
#qmx
Hi Everyone
I was wondering if is possible to assemble only one band filter at the time on a qmx plux rev3, this means I have assembled the all QMX leaving out only the toroids of all the filters, the LP and BP ones.
Now next I have assembled only the 160m LP and BP and test the filters. The swipes look normal on the 160m.
?
Next is to test transiting to a dummy load only this band, but I get the swr protection kicking in and no power out. voltages look normal. running a swr plot on 160m shows swr 10 on all graph.
?
The main idea is to tune filters one by one with space for the soldering iron making it easy.
?
I have reviewed soldering of transformer and swr brigde plus the jumper to the bnc is in place.
?
My question is, Is it expectable that the SWR is High when only the filters for one band are on the board or this means something else is already wrong from the beginning.
?
Thank you a lot
73 Azgael
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Re: SSB Cal problems with QMX (not +)
I'll bump this and see if anyone can help.
?
73,
Randy, KS4L?
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Re: Why no AGC for digital modes, as other modes?
By my understanding, DIGITAL mode is a "cheat." Note that is a SINGLE frequency mode -- thus works for FT8 <gasp>, WSPR, etc. that transmit a SINGLE frequency.?
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Thus, all you have to do is SHIFT the transmit frequency -- equivalent to a full modulation SSB SINGLE tone. Note that there is a FSK beacon mode (hiding in plain sight!).?
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So, you are just sending a CW signal -- full carrier, but just shifting the transmit frequency!
?
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Richard Dyer
jjpurdum
Daniel Conklin
Randy