Topics

uBITX woes, feeling disheartened. #ubitx

Nick VK4PP
 

HI Group.
I have completed the install of my uBitx into a case but have several issues which effectively makes the radio useless, I am writing to seek advice on how to solve these issues. here they are:

1: Very loud pop on power on, and when TX initiated.
2: Constant broadcast QRM, at least twice as loud as the background static.
3: Very low audio when I do find a signal, I have to turn up the volume past 1/2.
4: Then I try TX I get MASSIVE feedback and have to turn the volume down to almost nothing else it just screeches.

Thanks in advance, I'm hoping to get this sorted, really love this little rig, cant wait to get out and do some portable HF work...
73, Nick, VK4PLN

Gordon Gibby
 

​Well, besides checking your wiring once over, 


you might tell us what happens when you 

a) disconnect the antenna

b) transmit into a dummy load


Then there's a video of tests to run on the receiver that MIGHT be appropriate depending on the above.


Is there a very strong broadcast station quite near you?


Cheers!


Gordon 



From: BITX20@groups.io <BITX20@groups.io> on behalf of nickpullen@... <nickpullen@...>
Sent: Thursday, January 4, 2018 6:01 PM
To: BITX20@groups.io
Subject: [BITX20] uBITX woes, feeling disheartened. #ubitx
 
HI Group.
I have completed the install of my uBitx into a case but have several issues which effectively makes the radio useless, I am writing to seek advice on how to solve these issues. here they are:

1: Very loud pop on power on, and when TX initiated.
2: Constant broadcast QRM, at least twice as loud as the background static.
3: Very low audio when I do find a signal, I have to turn up the volume past 1/2.
4: Then I try TX I get MASSIVE feedback and have to turn the volume down to almost nothing else it just screeches.

Thanks in advance, I'm hoping to get this sorted, really love this little rig, cant wait to get out and do some portable HF work...
73, Nick, VK4PLN

Nick VK4PP
 

Hi,
a: When disconnecting the antenna the QRM goes away, but the noise floor also drops, right off, as expected?
b: Still get massive feedback into a dummy load., no QRM though

Thanks.

Gordon Gibby
 

Making progress.   Others here may have much more knowledge than I.


1.  The QRM:   is it recognizable voices?   Are you able to recongize the station and thus tell us the frequency they are on?


2.  Were there strong broadcast stations near you, or some other strong transmitter?


3.  You said the feedback when transmitting goes away when you turn down the volume control.   Does it last for more than 3 seconds?   If so, then it is either coming from Q70 or from "CWTONE".   You could disconnect the wire from the Raduino that goes to CWTONE in the schematic to eliminate that input and see if it remains, which would mean it comes from Q70.   Next you could measure the collector voltage on Q70 in transmit to see if for some crazy reason it is still getting power (which it shouldn't).   That would begin to allow you to work your way back on why the audio stages are still giving you signal when you shouldn't be hearing any in TRANSMIT.


If you're able to answer #1 above or help us know the FREQUENCY of the interference that would help.


Cheers!


Gordon




From: BITX20@groups.io <BITX20@groups.io> on behalf of nickpullen@... <nickpullen@...>
Sent: Thursday, January 4, 2018 6:16 PM
To: BITX20@groups.io
Subject: Re: [BITX20] uBITX woes, feeling disheartened. #ubitx
 
Hi,
a: When disconnecting the antenna the QRM goes away, but the noise floor also drops, right off, as expected?
b: Still get massive feedback into a dummy load., no QRM though

Thanks.

M Garza <mgarza896@...>
 

There have been several threads discussing BCI filters that can be added to block the AM broadcast interference.  Search the messages, there have been suggested filters and schematics.

Marco - KG5PRT 

On Jan 4, 2018 5:53 PM, "Gordon Gibby" <ggibby@...> wrote:

Making progress.   Others here may have much more knowledge than I.


1.  The QRM:   is it recognizable voices?   Are you able to recongize the station and thus tell us the frequency they are on?


2.  Were there strong broadcast stations near you, or some other strong transmitter?


3.  You said the feedback when transmitting goes away when you turn down the volume control.   Does it last for more than 3 seconds?   If so, then it is either coming from Q70 or from "CWTONE".   You could disconnect the wire from the Raduino that goes to CWTONE in the schematic to eliminate that input and see if it remains, which would mean it comes from Q70.   Next you could measure the collector voltage on Q70 in transmit to see if for some crazy reason it is still getting power (which it shouldn't).   That would begin to allow you to work your way back on why the audio stages are still giving you signal when you shouldn't be hearing any in TRANSMIT.


If you're able to answer #1 above or help us know the FREQUENCY of the interference that would help.


Cheers!


Gordon




From: BITX20@groups.io <BITX20@groups.io> on behalf of nickpullen@... <nickpullen@...>
Sent: Thursday, January 4, 2018 6:16 PM
To: BITX20@groups.io
Subject: Re: [BITX20] uBITX woes, feeling disheartened. #ubitx
 
Hi,
a: When disconnecting the antenna the QRM goes away, but the noise floor also drops, right off, as expected?
b: Still get massive feedback into a dummy load., no QRM though

Thanks.

Nick VK4PP
 

Hi, thanks,
1: Its appears to be a local broadcast station, its on 837khz, also on 710, 630, 540, I can pick it up[ on all 4 of those frequencies with my FT-450D,

2: as above its ABC Capricornia on 837khz....

3: The squeal is only if the volume is up high, if i turn the volume to 1/4 it is ok, no feedback, but at 1/4 I cant hear anything, its a HIGH pitch squeal and a POP from the speaker..

I am might try knock up a high pass filer....

Jim Sheldon
 

Nick & possibly others,
I have a similar problem now with my uBITX.  It was working just fine with no BCB interference and great audio volume.  I was trying to refine the CW transmit frequency and get the BFO set on the filter (note to Ashhar, this procedure needs to be addressed in a bit more detail for those with digital signal generators and other more sophisticated tools, perhaps in a manual appendix.)

All of a sudden I got a huge POP in the speaker as I accidentally overloaded something with too high a signal level input at the antenna from my signal generator (about +5dBM, maybe even higher) and from that point on it only had about 1/3 to 1/2 the audio output it previously had and several close in AM broadcast stations had taken over the radio completely.  I was thinking I might have damaged the TDA2822 audio amp so I ordered a handful, but there my be something else that popped.  

Anyone have any ideas?  I have a half dozen other projects on the bench and had to put this one back for a bit so I'm asking the group.

Jim Sheldon - W0EB

------ Original Message ------
Sent: 1/4/2018 7:48:35 PM
Subject: Re: [BITX20] uBITX woes, feeling disheartened. #ubitx

Hi, thanks,
1: Its appears to be a local broadcast station, its on 837khz, also on 710, 630, 540, I can pick it up[ on all 4 of those frequencies with my FT-450D,

2: as above its ABC Capricornia on 837khz....

3: The squeal is only if the volume is up high, if i turn the volume to 1/4 it is ok, no feedback, but at 1/4 I cant hear anything, its a HIGH pitch squeal and a POP from the speaker..

I am might try knock up a high pass filer....

Nick VK4PP
 

Also, the feed back is non existent if i unplug the MIC and use a CW key to trigger the TX/... but is still get a loud POP on tx... So its definitely Audio feedback... wonder if its related to the QRM...

Nick VK4PP
 

HPF worked, no more QRM, but still cant TX, 

https://groups.io/g/BITX20/attachment/37197/0

Jim Sheldon, your situation is interesting, sounds exactly like my symptoms...

Nick VK4PP
 

HPF

 

Your  K3 may not be ok.if M1 M2 does not disconnect then you will get the mic
signal going to the amp and speaker resulting in feedback.

Check contacts with multimeter. Check if the coil is getting voltage..

Raj


At 05/01/2018, you wrote:
HPF worked, no more QRM, but still cant TX,

https://groups.io/g/BITX20/attachment/37197/0

Jim Sheldon, your situation is interesting, sounds exactly like my symptoms...

Gordon Gibby
 

Great work, gang!!
Fast turn-around on that high pass filter!!!!!

Suggest checking audio transistor collector voltage in TX. to verify relay operation -

Sent from my iPhone

On Jan 5, 2018, at 00:21, Raj vu2zap <rajendrakumargg@...> wrote:

Your  K3 may not be ok.if M1 M2 does not disconnect then you will get the mic
signal going to the amp and speaker resulting in feedback.

Check contacts with multimeter. Check if the coil is getting voltage..

Raj

At 05/01/2018, you wrote:
HPF worked, no more QRM, but still cant TX,

https://groups.io/g/BITX20/attachment/37197/0

Jim Sheldon, your situation is interesting, sounds exactly like my symptoms...

Vince Vielhaber
 

check for solder bridges on board along M1 M2 paths.

Vince.

On 01/05/2018 12:17 AM, Raj vu2zap wrote:
Your K3 may not be ok.if M1 M2 does not disconnect then you will get
the mic
signal going to the amp and speaker resulting in feedback.

Check contacts with multimeter. Check if the coil is getting voltage..

Raj

At 05/01/2018, you wrote:
HPF worked, no more QRM, but still cant TX,

https://groups.io/g/BITX20/attachment/37197/0

Jim Sheldon, your situation is interesting, sounds exactly like my
symptoms...

Nick VK4PP
 

I'm about to go examine K3.
Just to confirm, when in TX there should be NO mic audio at all from the speaker?

If I turn down the vol, initiate TX, then turn up the vol, I can hear any tapping or blowing on the mic from the speaker... It seems to be the initial TX pop the starts of the feedback, 
but yeah, if the Mic is supposed to be completely muted, I have an issue there, as it is not....

73 Nick, VK4PLN

Gordon Gibby
 

So, there will be an initial pop but it is loud but not unbearable and then I think it quietens a lot quicker than the Bitx40 did (that one took about 2 seconds to completely quieten).  I haven't really noticed it AT ALL


I'm really a fan of having the radio tell you where the problem is, instead of just striking out and checking a whole lotta things....unless there is a really well known fault.    It sounds like your relay is staying in, but an easy way to check that is is to simply put a voltmeter on the collector that I earlier suggested.  I don't know how intimate you are with schematics, but all the parts are marked and there will be additional parts connected to that collector that make it easy to probe its voltage.   It should have voltage in RX and not in TX....and then you would be able to move a step back and see if the relay controlling that had voltage to its coil at the proper time and so on......


​The schematic is like anatomy, and your knowledge of electronics is like physiology and the things you measure and observe are symptoms and using all that you can diagnose the problem without a huge amount of guesswork.....


Since you built that high pass filter in nothing flat, you must be pretty good at this, so I don't know why I'm telling you this.


Cheers


gordon



From: BITX20@groups.io <BITX20@groups.io> on behalf of nickpullen@... <nickpullen@...>
Sent: Friday, January 5, 2018 3:33 PM
To: BITX20@groups.io
Subject: Re: [BITX20] uBITX woes, feeling disheartened. #ubitx
 
I'm about to go examine K3.
Just to confirm, when in TX there should be NO mic audio at all from the speaker?

If I turn down the vol, initiate TX, then turn up the vol, I can hear any tapping or blowing on the mic from the speaker... It seems to be the initial TX pop the starts of the feedback, 
but yeah, if the Mic is supposed to be completely muted, I have an issue there, as it is not....

73 Nick, VK4PLN

Nick VK4PP
 

Thanks Gordon,

Yes, I should know better... Ill print out a nice large copy of the schematic and have a probe around... but thank for confirming at least that K3 and that area with M1 M2 is likely where the issue is...

Ill, keep you all informed.

73, Nick VK4PLN

James Lynes
 

Take the pdf to Staples or Office Depot and you can get a D size print for about $3.50.

James
KE4MIQ

Nick VK4PP
 

On Fri, Jan 5, 2018 at 03:56 pm, James Lynes wrote:

Take the pdf to Staples or Office Depot and you can get a D size print for about $3.50.

James
KE4MIQ


 Ok, so, results of testing. In RX the collector of Q70 is 12v and at TX drops to 0v so this tells me that K1 is switching. I can hear it,

Also tested M1-M2 at relay side of R70 and C51, in RX there is continuity, but in TX there is still continuity! So I'm thinking K3 is faulty... Farhan did mention issues with relays.... What a PITA to change, 8 legs to de-solder... I'm thinking just crush the relay in situe and then remove one leg at a time.

73 

Nick VK4PP
 

well,  replaced K3, and still the same.. i dont get it?!?!, Why would there be continuity between R70 and C51? I have check and get voltage at the coil of K3. but the contacts dont seem to be switching....


Eish...

73 VK4PLN

Gordon Gibby
 

What has what voltage in TX?



Sent from my iPhone

On Jan 6, 2018, at 04:53, "nickpullen@..." <nickpullen@...> wrote:

well,  replaced K3, and still the same.. i dont get it?!?!, Why would there be continuity between R70 and C51? I have check and get voltage at the coil of K3. but the contacts dont seem to be switching....


Eish...

73 VK4PLN