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Trying to diagnose my uBitx v5 #ubitx #ubitx-help #v5

columbustalley@...
 

Hello everyone.  I've assembled two uBitx v5's and was able to send and receive messages on JS8Call by putting a wire directly between the two.  I'm running the newest CEC firmware.  I also have CAT control and my audio interface is a simple USB sound card.

I purchased an antenna so I can try to receive messages in JS8Call from other hams.  The antenna is a Tram 3500 which is a CB antenna and should work fine for the 10 meter band based on my research.

I connected the shield of the antenna to the black wire, and the signal to the grey wire.  Loaded up JS8Call and nothing.  Maybe there's just nobody transmitting?

Unfortunately I don't have the second radio on hand to use for testing.

Then I disconnected the antenna and to my surprise there was no change on the waterfall.  I'm a beginner but that doesn't sound normal to me.  Here is a screenshot half of the waterfall is with the antenna plugged in and the other half is with the antenna unplugged.

https://i.imgur.com/5YfITTE.png

I guess I have two questions.

Is there something wrong with my radio?

Are these not radio signals on the waterfall?  Is it just electrical noise?

Thanks!

 

On Sun, Apr 12, 2020 at 06:03 PM, <columbustalley@...> wrote:
Tram 3500
Hi,

How are you mounting the antenna?  It will need to sit on a large, flat, metal surface so the base can couple to it and provide the ground plane for the antenna (normally this is done by the car body).  If you have nothing like that, you will need to run some radial wires out from the base.  If the antenna is sitting on the ground, radial length doesn't matter, just put a bunch 4' or longer around the base.  If the antenna is elevated, then run two or more 8' long out from the base.

How is the radio receiving other signals?  Does it sound good listening to SSB signals on 20/40/80m?

73,


Mark

Arv Evans
 

Several ideas come to mind:

"I've assembled two uBitx v5's and was able to send and receive 
 messages on JS8Call by putting a wire directly between the two."

Whoa!  Did you read the instructions where it says to use a properly 
terminated 50 ohm antenna?  First time you keyed up one rig directly 
into the other you probably burned the output MOSFET devices on 
the one transmitting, but just before it blew it probably destroyed parts 
of the receiver front-end circuitry in the receive unit.  Sending several 
watts of RF into into the receive end of a sensitive receiver cannot be 
good!

Do you have access to an SWR bridge, a dummy load, a DVM, and an 
RF detector to use with the DVM?  Normally you would not need these 
but after transmitting directly into your receiver you are probably going 
to need some test equipment and the knowledge to use it.

At this point you will have to use the schematic drawing to trace voltage 
and signal levels through the circuitry.  Start with voltages, then once 
they all look good you can start tracing signals in transmit mode.  
Since you can still tune the rig the Si5351 synthesizer is probably still 
OK.  That is good.  It also indicates that your Arduino and display are 
probably still working properly.

My guess is that these rigs are repairable, but you may need lots of help 
from the experts on this group before you have a working rig again.  
Start by measuring DC voltages at critical points (mentally divide the 
circuit into modules and check supply voltages to each module).  Make 
a list of observed voltages versus where you observed them and post 
it to this forum.  Others can tell you where these voltages look good 
and where they look strange.  

If you have a nearby ham who has several years of circuit repair 
experience, that person may be able to provide some help and make 
the repair go faster.  

Arv  K7HKL
_._




On Sun, Apr 12, 2020 at 4:03 PM <columbustalley@...> wrote:
Hello everyone.  I've assembled two uBitx v5's and was able to send and receive messages on JS8Call by putting a wire directly between the two.  I'm running the newest CEC firmware.  I also have CAT control and my audio interface is a simple USB sound card.

I purchased an antenna so I can try to receive messages in JS8Call from other hams.  The antenna is a Tram 3500 which is a CB antenna and should work fine for the 10 meter band based on my research.

I connected the shield of the antenna to the black wire, and the signal to the grey wire.  Loaded up JS8Call and nothing.  Maybe there's just nobody transmitting?

Unfortunately I don't have the second radio on hand to use for testing.

Then I disconnected the antenna and to my surprise there was no change on the waterfall.  I'm a beginner but that doesn't sound normal to me.  Here is a screenshot half of the waterfall is with the antenna plugged in and the other half is with the antenna unplugged.

https://i.imgur.com/5YfITTE.png

I guess I have two questions.

Is there something wrong with my radio?

Are these not radio signals on the waterfall?  Is it just electrical noise?

Thanks!

columbustalley@...
 

How are you mounting the antenna?
I just have the antenna sitting on the floor.  I did not know that it grounded to the car.  Duh!  I'll go attach it to the car and see if there is any change.
How is the radio receiving other signals?  Does it sound good listening to SSB signals on 20/40/80m?
Unfortunately I'm not really sure how to do that.  I don't know what frequencies to listen on and at what times.  All I ever hear is static.

columbustalley@...
 

On Sun, Apr 12, 2020 at 06:40 PM, Arv Evans wrote:
First time you keyed up one rig directly 
into the other you probably burned the output MOSFET devices on 
the one transmitting, but just before it blew it probably destroyed parts 
of the receiver front-end circuitry in the receive unit.
First of all I would like to say thank you for your help and reply it's really appreciated.  I really want to get my radio working!

I really hope that I didn't fry anything.  During that test I was using a 12v 500ma power supply.  I'm guessing that's still enough power to destroy something?
It also indicates that your Arduino and display are 
probably still working properly.
Yes the Arduino and display still work.  The CAT control is working and when tuning the audio output definitely changes.  The uBITX Manager is working as well.

My guess is that these rigs are repairable, but you may need lots of help 
from the experts on this group before you have a working rig again.
That's bad news.  I'm going to mount my antenna to my car and see if things improve.  If not then I might need to call this a learning experience and order a new v6 kit.  = (

 

Oop,

I missed how you connected the two radios to eachother and transmitted between them -- ouch!  Remember, the receiver section is made to amplify microvolt level signals from the antenna, but the transmitter section puts out at least 10,000 times that level.  But the fact that you were using an underpowered power supply and that you were able to send and receive signals, maybe your rigs are still OK.  Hopefully!

Listening: long wavelengths go better at night and short ones during the day, so 80m at night, 40m late evening/early moring, and 20m during the day are optimum times.  Of course closer stations can communicate with these frequencies at other times too.  You should look at the ARRL band plan (google it) to see what frequencies to listen on and for what.  But even with your short antenna, you could be able to hear CW and SSB voice pretty easily.

Do you have a radio license yet?  Studying for the tests should give you the background you will need to start really understanding and enjoying the amateur radio bands and practices/procedures.

73,


Mark