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Re: 7.277 Anyone

 

Too bad Evan. Your loss.
Re: Changing out L5 & L7 in UBitX for Spur Fix

 

Your question made me go back and look at the picture.? L5 looks correct, as it is in the circuit as was the original (L5 and C215 in series with the filter).? L7 is directly connected to T4, removing C211 from the circuit.? Not sure if that is intentional, so good question!

Hopefully someone can answer your question, I do not know for sure.? Based on the values, I would assume that it is for DC blocking that may not be needed on both sides of the filter.

Evan
AC9TU
Re: 7.277 Anyone

 

I tested with an RF Explorer SA and found that I had the harmonic issue on 40m, even on ssb.? I did not see the issue on 20m or 10m.? I have not had any success with those bands, mostly due to conditions.

I need to replace the relays and verify again before I use 40m.? I do not have an antenna for 80 (MFJ-2010 40, 20, and 10 only).? I could do 20m, however the band has been pretty bad over the past month, so now is the time to replace the relays.

73
Evan
AC9TU
Re: Tracing receive signal for low signal

 

Dave,
By the time the signal from the antenna gets to TP17, it has been converted to the audio on a 12mhz carrier.? Said another way, the signal by now has been converted to 12mhz +- the audio tone, not the base? original received frequency.

Injecting a pure 12mhz signal at TP17 (or TP16) should produce an audio tone that is 12mhz - the BFO frequency at TP20 (input to the audio amp).? From previous posts I believe that you stated the BFO as 11.996 mhz so you should have an audio tone of 4khz at TP20.

Evan
AC9TU
Re: Tracing receive signal for low signal

 

AT 60mV you should a really loud sound from your speaker. Check all the resistors and report on
DC voltages at the audio transistors.

Raj

At 24-12-18, you wrote:
Also interesing at the base of Q71 injecting 1khz signal at 60mv gave a .1 mv peak to peak signal but I could not hear any tone on the speaker. It wasn't until injecting 300mv could I faintly hear the tone and that produced 444mv peak to peak.
Re: Tracing receive signal for low signal

jim
 

TP 16/17 should be around 12 Mhz regardless of the frequency setting on th ubitx ...all else is filtered out by the 12 Mhz crystal filter

Jim


On Sunday, December 23, 2018, 6:19:42 PM PST, Dave Space <davesspacebar@...> wrote:


Redid TP17 at 19.26 MHZ (should have been 19.15 (12MHZ+7.15) put in 3.5v to get 80mv p-p out but even though it showed 80mv I could barely hear a tone through it.

This may be a hint TP16 at the same frequency (injection frequency) produced 80mv with a much louder tone.
Re: Tracing receive signal for low signal

 

Injecting 1khz tone 2.4v at pin 3 of q71 (should feed into q72 and q73) produced .1v p-p
Re: Tracing receive signal for low signal

 

Also interesing at the base of Q71 injecting 1khz signal at 60mv gave a .1 mv peak to peak signal but I could not hear any tone on the speaker.? It wasn't until injecting 300mv could I faintly hear the tone and that produced 444mv peak to peak.
Re: Tracing receive signal for low signal

 

I checked the boards solder joints with a magnifying glass but it's really hard to tell.? probably need to find a way to test specific suspect points.

I tried to check the toroids in the load pass filter I think they all look good from what I can tell.
Re: Tracing receive signal for low signal

 

K3 pins 12 and 14 get a tone for continuity.


Tp21 shows 10.85k ohms to ground.
Re: Quick question

 

The Koss cs100 has an electret element and works well. I have one that I have used. Someone else on this board put me on to it. They are now about $20, but not long ago were much cheaper.?
Re: Tracing receive signal for low signal

 

Sorry that was for Q70
Re: Tracing receive signal for low signal

 

Q&0 pin 1 is 0.65v pin 2 - 0 volts pin 3 1.7 v


Pin1 seems lower than the 1.3 expected in the diagnostic manual and pin 3 seems higher which was supposed to be 0.2v
Changing out L5 & L7 in UBitX for Spur Fix

Guy WB7SZI
 

just desoldered L5&7 to get ready for the placement of the SMD inductors.?
From the image I can see where to solder the inductors to where the toroids were but can¡¯t see where to solder the other ends. It looks like the traces below L5 & L7 were exposed to solder the other side. Is this right?
thanks

Guy WB7SZI?

4789CA44_F5D9_4798_BA87_C2B343760644.jpeg

Re: Tracing receive signal for low signal

 

Also FYI just checking maybe not such a great deal on my scope the signal generator definitely has some differences compared to volt amplitude.

I checked at 60hz AC volts with my multimeter and when I had 3.5v set on the signal generator it showed 2.4v on my multimeter.? Since the scale of the differences between your numbers jim and mine? are pretty large I don't think that changes the net relative difference that would change the direction of this investigation.
Re: 7.277 Anyone

Jack Purdum
 

Evan:

Maybe...maybe not. My ?BITX is legal on 80M and 40M, and spot on for 20M, so I can use it on two bands and be within spec. Right now, 20M is out.

Jack, W8TEE

On Sunday, December 23, 2018, 5:41:11 PM EST, Evan Hand <elhandjr@...> wrote:


I was till I noted that my uBitx is not legal, so until I get the parts and install I am off the air.

73
Evan
AC9TU

Re: Tracing receive signal for low signal

 

I didn't hear a tone at 19.15, adjusting the signal generator up? to 19.26? I got that barely perceivable tone at 3.5v on tp17 and a much louder tone with 3.5v in on tp16.
Re: Tracing receive signal for low signal

 

Redid TP17 at 19.26 MHZ (should have been 19.15 (12MHZ+7.15) put in 3.5v to get 80mv p-p out but even though it showed 80mv I could barely hear a tone through it.

This may be a hint TP16 at the same frequency (injection frequency) produced 80mv with a much louder tone.
Re: Tracing receive signal for low signal

jim
 

One thing at a time ...one stage at a time ..Lets get the audio stage working first
then ...

Jim


On Sunday, December 23, 2018, 6:03:14 PM PST, Bob Lunsford via Groups.Io <nocrud222@...> wrote:


Jim, all you mention is good for this problem and then
I thought of something else: What if it's not just one
thing on that list but a couple of them at the same
time? In this case, it's not so much looking for a problem,
it's making sure all is well at all those points before
proceeding to the next one. Gray line here but it is
sometimes better to verify circuits are working properly
instead of concentrating on what may be wrong. At
least this will provide some encouragement as you
go along the circuit path. And, also, when you find one
problem, it may "fix" the problem to some degree while
another problem is waiting to be found.

Bob ¡ª KK5R

--------------------------------------------

On Sun, 12/23/18, jim via Groups.Io <ab7vf=[email protected]> wrote:

Subject: Re: [BITX20] Tracing receive signal for low signal
Date: Sunday, December 23, 2018, 1:39 PM

Well ..so far, at least you
have something on al the test points ...useful for reference
if for nothing else ...
the situation
at TP 17 indicates to me

bad/misaligned 12 mhz filter? or
defective 12 mhz mixer? or
messed up clk0? or
defect in Q70 stage or
open contacts M1/M2 or
Q74 shorted/turned on (conducting)?? or
....??

One step
at a time progressing at this point from front to back ..
I prefer going back to front but we are
where we are

Jim


? ? ? ?



? ? ? ?
? ? ? ? ? ?

? ? ? ? ? ? ? ?
? ? ? ? ? ? ? ? ? ? On Sunday, December 23, 2018, 8:21:06 AM
PST, Dave Space <davesspacebar@...> wrote:
? ? ? ? ? ? ? ?
? ? ? ? ? ? ? ?

? ? ? ? ? ? ? ?

? ? ? ? ? ? ? ? Thanks
I'll try those new measurements tonight.? Do the
measurements so far say anything?? Seems like it's
taking a lot more to get .1 vp-p output than jim's board
from all test points.? The weird thing though is it mostly
gets worse (requires more power to get .1v p-p audio)
further along the receive path.?


For those other questions:
Yes everything on the radio seems to work,
display, etc.? Tapping on components doesn't seem to
change anything connections at least seem stable.? before
changing the BFO I could hear only the strongest of signals
but they were so faint and almost completely
unintelligible.? Changing the BFO I can now pick up only
really strong signals faintly and they are a bit more
intelligible.? It's clear from the signal tracing it is
taking a lot more power to get my audio to .1v p-p so
clearly something interesting is going on here.? The real
interesting part is the farther away from the antenna on the
board the more power it takes to produce a .1v p-p audio
output for the most part.

I
have a tiny bit of experience using my signal generator /
scope on a working fm/am radio kit I built recently?

(An nice little kit building the radio in
sequence and testing each stage, teaches quite a bit)






? ? ? ? ? ?
? ? ? ?



Re: Tracing receive signal for low signal

 

Jim, all you mention is good for this problem and then
I thought of something else: What if it's not just one
thing on that list but a couple of them at the same
time? In this case, it's not so much looking for a problem,
it's making sure all is well at all those points before
proceeding to the next one. Gray line here but it is
sometimes better to verify circuits are working properly
instead of concentrating on what may be wrong. At
least this will provide some encouragement as you
go along the circuit path. And, also, when you find one
problem, it may "fix" the problem to some degree while
another problem is waiting to be found.

Bob ¡ª KK5R

--------------------------------------------

On Sun, 12/23/18, jim via Groups.Io <ab7vf@...> wrote:

Subject: Re: [BITX20] Tracing receive signal for low signal
To: [email protected]
Date: Sunday, December 23, 2018, 1:39 PM

Well ..so far, at least you
have something on al the test points ...useful for reference
if for nothing else ...
the situation
at TP 17 indicates to me

bad/misaligned 12 mhz filter? or
defective 12 mhz mixer? or
messed up clk0? or
defect in Q70 stage or
open contacts M1/M2 or
Q74 shorted/turned on (conducting)?? or
....??

One step
at a time progressing at this point from front to back ..
I prefer going back to front but we are
where we are

Jim










On Sunday, December 23, 2018, 8:21:06 AM
PST, Dave Space <davesspacebar@...> wrote:





Thanks
I'll try those new measurements tonight.? Do the
measurements so far say anything?? Seems like it's
taking a lot more to get .1 vp-p output than jim's board
from all test points.? The weird thing though is it mostly
gets worse (requires more power to get .1v p-p audio)
further along the receive path.?


For those other questions:
Yes everything on the radio seems to work,
display, etc.? Tapping on components doesn't seem to
change anything connections at least seem stable.? before
changing the BFO I could hear only the strongest of signals
but they were so faint and almost completely
unintelligible.? Changing the BFO I can now pick up only
really strong signals faintly and they are a bit more
intelligible.? It's clear from the signal tracing it is
taking a lot more power to get my audio to .1v p-p so
clearly something interesting is going on here.? The real
interesting part is the farther away from the antenna on the
board the more power it takes to produce a .1v p-p audio
output for the most part.

I
have a tiny bit of experience using my signal generator /
scope on a working fm/am radio kit I built recently?

(An nice little kit building the radio in
sequence and testing each stage, teaches quite a bit)
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