Nobody else is complaining of the same problem, so, were
I in your shoes, I would look for a systemic problem in the
way I assembled my QMX+.
Several thoughts:
1) perhaps you chronically miscounted the turns on your toroids?
2) perhaps you chronically scrambled toroids when you installed them?
3) there are some test points in the LPF that seem to attract thru hole
capacitor leads (assuming you have a version 2 or older board).
4) bad solder joints on toroid wires are so common as to be a cliche.
About the only thing I can tell you for certain is the radio doesn't
do this when built correctly with good parts.
What I would not do, is transmit to anything other than a dummy load
until this is fixed.
-Chuck Harris, WA3UQV
On Thu, 03 Apr 2025 22:17:52 +0000 "WB9YXA" <ahoffman1@...>
wrote:
I have assembled and have working a QMX+, with one caveat;? all of
the LPF sweeps are bad.
The audio filter sweeps, RF filter sweeps, image sweeps, and SWR
sweeps look reasonable, although on a couple of bands the SWR sweeps
aren't flat across the entire bandwidth swept, but were always good
in the ham band frequencies.? The I/Q sweeps all looked good except
for 160 Meters where the phases were in sync for some reason.? Not
really a problem for me, I don't own that much wire. Here's the real
problem.? All of the LPF sweeps are bad.? For example: 0 ?|
* .* ?* ?* ?* .* ?* ?* ? ? . ? ? ? * ?* .* ?* ?* ? ?. ?* ?* ?* ? . |
* ? ?* ?* .* ?* ?* ?* .* ?* ?* ?* ?* ? ?* ?* ?* .* ?* ?* ? ?* ?* ?*
* ?*. | ?* ?* ** * .* ?* ?* ?* .* ** ** ** ** ** ** * ?* .* ?* ?* ?*
** * ?* ?* ?** | ** ** ** **.* ?* ?* ?* ** ** ** ** ** ** ** ** * .*
* ** ** ** * ?* ?* * * | ** ** ** **.** * ** ** ** ** ** ** ** ** **
** **.* ** ** ** ** ** * ** * * | ** ** ** **.***|*** ** ** ** ** **
** ** ** ** *** *** ** ** ** **** ** * * | ** ** ** *** **|** *** **
** ** ** ** ** ** *** ** *** ** ** ** *** *** * * | ** ** *** **
**|** ** ** ** ** *** ** ** *** ** ** ** ** *** *** ** ** ** * | *
*** *** ** **|** ** ** ** ** ** **.*** *** ** ** ** ** *** *** ** **
** * | * * ?* ?* ?* **|** ** ** * ?* ?* ?* .* ?* ?* ?* ** ** ** * ?*.
* ?* ** ** * | * * ?* ?* ?* ?*|* ?* ?*. * ?* ?* ?* .* ?* ?* ?* ?* *
* ?* ?*. * ?* * ?* ?* | * * ?* ?* ?* ? |* ?* ?*. * ?* ?* ?* .* ?* ?*
* ?* * ?* ?* ?*. * ?* * ?* ?* |* ?* ?* ?* ?* ? | ? * ?*. * ?* ?* ?*
.* ?* ?* ?* ?. ? ?* ?* ?*. * ? ?* ?* ?* |* ?* ?* ?* ?. ? | ? ? ?*. *
* ?* ?* .* ?* ?* ?* ?. ? ?* ?* ?*. * ? ? ? * ?* |* ?* ?* ?* ?. ? |
?*. * ?* ?* ?* .* ?* ?* ? ? . ? ?* ?* ?*. * ? ? ? * ?* |* ?* ?* ?*
. ? | ? ? ? . ? ?* ?* ?* .* ?* ?* ? ? . ? ? ? * ?*. ? ? ? ? * ?* |*
* ?* ? ? . ? | ? ? ? . ? ? ? ? ?* .* ?* ? ? ? ?. ? ? ? ? ?*.
?* |* ? ? * ? ? . ? | ? ? ? . ? ? ? ? ? ?. ? * ? ? ? ?. ? ? ? ? ?*.
? ? ? ? ?* |* ? ? ? ? ? . ? | ? ? ? . ? ? ? ? ? ?. ? ? ? ? ? ?.
? ? . ? ? ? ? ? ?. |* ? ? ? ? ? . ? | ? ? ? . ? ? ? ? ? ?.
?. ? ? ? ? ? . ? ? ? ? ? ?. -8 |* ? ? ? ? ? . ? | ? ? ? .
. ? ? ? ? ? ?. ? ? ? ? ? . ? ? ? ? ? ?.
----------------------------------------------------------------------------
6 ? ? ? ? ? 9 ? ? ? ? ? 12 ? ? ? ? ? 15 ? ? ? ? ?18 ? ? ? ? ? 21 0
|. ? ? ? ?*. * ?* ? ? . ? ? ? ? . ? ? ? ? . ? ? ? ? ?. ? ? ? ? .
? . |.* ? ? ? *. * ?* ?* ?. ? ?* ?* . ? ? * ?*. * ? ? ? *. * ? ? ? *
?* ? ? ?.* |.* ?* ? ?** * ?* ?* ?. * ?* ?* .* ? ?* ?*. * ?* ? ?*. *
* ? ?* ?* ? ?* .* |.* ?* ?* ** * ?* ?* ?. * ?* ?* .* ? ?* ?*. * ?*
*. * ?* ? ?* ?* ?* * .* |** ** ** ** **** ** ** ** * ?* ** ? ?* ?*. *
?* ? ?*. * ?* * ?* ?* ?* **.* |** ** ** ** **** ** ** ** * ?* ** **
** *.** ** ** ** * ** ** ** * ** **.* |** ** ** ***|*** ** ** ** ****
** ** ** *.** ** ** ** * ** ** ** * ** **.* |** ** ** ***|** *** **
** **** ** ** *** *** ** ** **** ** ** **** ** **.** |* *** *** .*|**
*** ** *** *** ** ** *** *** ** ** *** *** ** *** *** *** * |. ***
*** .*|** ** *** *** ** *** *** ** ** *** *** ** *** ***.** *** *** *
|. ** ** * .*| ? * ?*** *** ** ** **** ** ** *** *** ** ** ****.**
*** *** ** |. * ?* ?* .*| ? * ?* ** ?* ** ** ** * ?* * ?** ** * .* *
* ?*.** ** * ?* * |. * ?* ?* .*| ? * ?* .* ?* ** *. * ?* ?* * ?* ?*
* .* * ?* ?*. * * ?* ?* * |. * ?* ?* . | ? * ?* .* ?* ? ?*. * ?* ?* *
?* ?* ?* .* * ?* ?*. * * ?* ?* * |. * ?* ?* . | ? * ?* .* ?* ? ?*. *
* ? ?* ?* ?* ?* . ?* ?* ?*. * * ?* ?* |. * ?* ?* . | ? ? ?* .* ?*
*. * ?* ? ?. ?* ?* ?* . ?* ?* ?*. ? * ?* ?* |. * ?* ?* . | ? ? ?* .*
* ? ?*. * ?* ? ?. ?* ?* ?* . ? ? * ?*. ? * ?* ?. |. ? ?* ?* . |
* .* ? ? ? *. * ?* ? ?. ?* ?* ?* . ? ? * ?*. ? ? ?* ?. |. ? ?* ? ?. |
? ? ?* .* ? ? ? ?. * ?* ? ?. ? ? * ?* . ? ? * ?*. ? ? ?* ?. |.
. | ? ? ? ?.* ? ? ? ?. * ? ? ? . ? ? * ? ?. ? ? * ? . ? ? ?* ?. -7
|. ? ? ? ? . | ? ? ? ?.* ? ? ? ?. ? ? ? ? . ? ? * ? ?. ? ? ? ? .
* ?.
----------------------------------------------------------------------------
16 ? ? ? ?24 ? ? ? ? 32 ? ? ? ?40 ? ? ? ?48 ? ? ? ? 56 ? ? ? ?64
?72 All of the other bands exhibit a similar pattern. I tried
looking for something common to all of the filters, but nothing I
came up with made any sense given that the other sweeps were
'normal'. Since everything looked OK except for the LPF sweeps, I
decided to perform a smoke test.? I hooked it up to EFHW at 20 feet
and worked Oklahoma on 40 Meters FT8, so the transceiver is working.
I don't have the necessary test equipment to check the spectral
purity of the output signal so I'm hesitant to continue using it on
the air until I resolve this problem. I tried searching for a
solution both here and with Google, read a lot about fixing issues I
don't have but nothing that pointed me in the right direction. Thanks
all for the great ideas I'm about to receive. Andy WB9YXA
