Topics

Low power output on ubitx

Mike R.
 

First post - be gentle :)
I have been playing around with the ubitx for about a week now. Pretty cool radio and I like the idea of modifying the software.
Installed Ian's version of the software v1.04 and even added a menu entry on my own to display the current version which normally only appears at power up. Still have a ways to go in fully understanding the software for the rig.
To the point...I was listening to some FT8 the other night and enjoying the decoding on the computer screen from the ubitx. I thought it might be nice to see if I could transmit. So, I connected a dummy load and wattmeter to see if the rig was putting out power. I tried CW first.
I had VERY low power out, in the range of milliwatts.
The numbers:
Frequency: 7.150, antenna connected to a dummy load.
Power supply set to 12.5 volts. Using a key to send CW.
Output was nil on 40m. Didn't make the meter move on the WM-1.
So, I did the bias adjustment thing that everyone says to not do. Adjusted the bias for the 510's at 100ma each and then set RV3 max clockwise (how it was received, actually).
Output on 40M was about 400mw after adjusting the bias and RV3.
Started to dig into Glenn's post where he made measurements of the PA section. Everything was nominal to his
numbers except for the collector voltages on Q92-93 and 96-97 where they were 12V vs. the 2.8v he measured.
I get 12v on the "TX" side of R961 and 11V on the junction of R961 and C92.
Receive current is about 160ma and transmit current is around 720ma for an output of about 400mw.
I'm thinking there is something amiss with T10.
Any comments for anyone that has had the same issue and found a resolution?
Thanks, Mike W1USN



Conrad San Diego
 

Hi Mike I had the same problem.  I checked Q90 and found E & B are shorted. I replaced 2N3904 with a regular type transistor Instead of the SMD type. I get 30 W but I tuned it down to 15 W.


On Fri, Mar 16, 2018, 17:20 Mike R. <ubitx@...> wrote:
First post - be gentle :)
I have been playing around with the ubitx for about a week now. Pretty cool radio and I like the idea of modifying the software.
Installed Ian's version of the software v1.04 and even added a menu entry on my own to display the current version which normally only appears at power up. Still have a ways to go in fully understanding the software for the rig.
To the point...I was listening to some FT8 the other night and enjoying the decoding on the computer screen from the ubitx. I thought it might be nice to see if I could transmit. So, I connected a dummy load and wattmeter to see if the rig was putting out power. I tried CW first.
I had VERY low power out, in the range of milliwatts.
The numbers:
Frequency: 7.150, antenna connected to a dummy load.
Power supply set to 12.5 volts. Using a key to send CW.
Output was nil on 40m. Didn't make the meter move on the WM-1.
So, I did the bias adjustment thing that everyone says to not do. Adjusted the bias for the 510's at 100ma each and then set RV3 max clockwise (how it was received, actually).
Output on 40M was about 400mw after adjusting the bias and RV3.
Started to dig into Glenn's post where he made measurements of the PA section. Everything was nominal to his
numbers except for the collector voltages on Q92-93 and 96-97 where they were 12V vs. the 2.8v he measured.
I get 12v on the "TX" side of R961 and 11V on the junction of R961 and C92.
Receive current is about 160ma and transmit current is around 720ma for an output of about 400mw.
I'm thinking there is something amiss with T10.
Any comments for anyone that has had the same issue and found a resolution?
Thanks, Mike W1USN



Mike R.
 

Hi Conrad and thanks for the reply.
I just shootgunned and replaced Q90 with a non-smd part and have exactly the same problem.
So replacing Q90 doesn't seem to be the cure.
In reading the posts I see where 12v on the collector of Q90 could be a bad thing. I get 11.7v on the collector,
3.7v on the base, and almost 3v on the emitter. I'm thinking I might have an issue further down the transmit chain.
The 12v I'm seeing on the collectors of Q92,93,96,and 97 are concerning as Glen's measurements has them at 2.8v.

sdr freak
 

Hi Mike, 

How did you get the issue away and what was the main issue or main reason for your low output ?

This is an very difficult thing in same style problem what i have with my ubitx and i dont find a way to become more than 4-5 Watts on 80m an on each other it was evertime less with higher frequency.. on 10m only 1 Watt and this is not the real way to operate with this low output, so i was very thankfull for any answer, thanks !

MVS Sarma
 

what is version # please?

On Sun, May 5, 2019 at 7:50 PM sdr freak <sdrfreak55@...> wrote:
Hi Mike, 

How did you get the issue away and what was the main issue or main reason for your low output ?

This is an very difficult thing in same style problem what i have with my ubitx and i dont find a way to become more than 4-5 Watts on 80m an on each other it was evertime less with higher frequency.. on 10m only 1 Watt and this is not the real way to operate with this low output, so i was very thankfull for any answer, thanks !

sdr freak
 

I have V3 and i have an idea to rise up the output with an mic amplifier but i want look for an simple homebrew mic amp, but i think the problem is the voltage on mic cable for the amp, i read here in the forum of an simple 2N3906 amp directly after the mic capsuale and without any voltage from battery, only the voltage on the mic line should work, but i have built this and my first usage of it have no output, anything wrong in the circuit i solder or it is the voltage on the mic line that is not enoug.. but i think an mic amp is the first what i need..

My power output with cw is more than ssb on 80m i habe test, on other band i dont have testing cw against ssb power output. But it look like anything is wrong..

How can this less power output have any reason, which reasons there to look when receive is 160mA and ptt only 450mA and with adjust the rv2 and rv3 to each 100mA to the 450mA so i have made, the ubitx have 650mA pttonly by 12V and with say Haaaallloooo it have 1A but only 4-5W on Dummy on 80m and on Dipole 80m it have onmy 4W too.. 

There is the mic amp i look for the next step to rise up power in ssb mode.. but the mic amp should be self made because i have not much money for buy an mic amp module in online shop, and i have many items at home like Transistor,R,C,L,ICs and many messuaring Tools so it should be an ubitx mic amp for homebrew and the circuit i only found of this kind doesnt work..

If any Ideas for an mic amp shematic for the ubitx 3 or any help to me to become more power i would be proud!

Arv Evans
 

Overdriving the mixer/modulator is not a good idea because it can cause higher level of spurious output.
_._


On Tue, May 7, 2019 at 10:08 AM sdr freak <sdrfreak55@...> wrote:
I have V3 and i have an idea to rise up the output with an mic amplifier but i want look for an simple homebrew mic amp, but i think the problem is the voltage on mic cable for the amp, i read here in the forum of an simple 2N3906 amp directly after the mic capsuale and without any voltage from battery, only the voltage on the mic line should work, but i have built this and my first usage of it have no output, anything wrong in the circuit i solder or it is the voltage on the mic line that is not enoug.. but i think an mic amp is the first what i need..

My power output with cw is more than ssb on 80m i habe test, on other band i dont have testing cw against ssb power output. But it look like anything is wrong..

How can this less power output have any reason, which reasons there to look when receive is 160mA and ptt only 450mA and with adjust the rv2 and rv3 to each 100mA to the 450mA so i have made, the ubitx have 650mA pttonly by 12V and with say Haaaallloooo it have 1A but only 4-5W on Dummy on 80m and on Dipole 80m it have onmy 4W too.. 

There is the mic amp i look for the next step to rise up power in ssb mode.. but the mic amp should be self made because i have not much money for buy an mic amp module in online shop, and i have many items at home like Transistor,R,C,L,ICs and many messuaring Tools so it should be an ubitx mic amp for homebrew and the circuit i only found of this kind doesnt work..

If any Ideas for an mic amp shematic for the ubitx 3 or any help to me to become more power i would be proud!

sdr freak
 

Why overdrive? I have not overdrive when clockwise the rv2 and rv3 is 450mA and i give 200mA with anticlockwise screwing to this, and so 100mA at each PA how it was sayed i  HF Signals, but i have the 1A when i ptt and speak loud hallo but only ptt is only 650mA.. and now it was really less with 4W on 80m or not?

What can i do and what about the mic amp to become more power?

MVS Sarma
 

Are you using electret mic as the mic pin is having dc bias voltage?
Generally we provide a 1nF  cap across the electret. That filters rf induced on the mic cable.

Reg ver 3 drawing 650mA on Rx with volume control at minimum, please check whether the audio amp is landing into oscillation. You could place a 1nF at  Vol mid pin close to the tda2822 and gnd. If the chip is too hot oscillation could be suspected. 
Once the Rx  current comes down to expected standard, you can adjust the mos fet currents one  by one after making the gate bias as zero at first stage.

Perhaps you might have already exercised all above steps.

  He k once whether the bias regulator output is dropping down not allowing needed Id  for the IRF510s.

Hope to see you solving out the issues.
Regards 
sarma   u3zmv

On Tue, 7 May 2019, 9:38 pm sdr freak <sdrfreak55@... wrote:
I have V3 and i have an idea to rise up the output with an mic amplifier but i want look for an simple homebrew mic amp, but i think the problem is the voltage on mic cable for the amp, i read here in the forum of an simple 2N3906 amp directly after the mic capsuale and without any voltage from battery, only the voltage on the mic line should work, but i have built this and my first usage of it have no output, anything wrong in the circuit i solder or it is the voltage on the mic line that is not enoug.. but i think an mic amp is the first what i need..

My power output with cw is more than ssb on 80m i habe test, on other band i dont have testing cw against ssb power output. But it look like anything is wrong..

How can this less power output have any reason, which reasons there to look when receive is 160mA and ptt only 450mA and with adjust the rv2 and rv3 to each 100mA to the 450mA so i have made, the ubitx have 650mA pttonly by 12V and with say Haaaallloooo it have 1A but only 4-5W on Dummy on 80m and on Dipole 80m it have onmy 4W too.. 

There is the mic amp i look for the next step to rise up power in ssb mode.. but the mic amp should be self made because i have not much money for buy an mic amp module in online shop, and i have many items at home like Transistor,R,C,L,ICs and many messuaring Tools so it should be an ubitx mic amp for homebrew and the circuit i only found of this kind doesnt work..

If any Ideas for an mic amp shematic for the ubitx 3 or any help to me to become more power i would be proud!

sdr freak
 

Ok thank for the fast answer, i would make the things you say and then i post in thd next hours again, for the first time i say very much thanks, 

Greetz DD1FK

sdr freak
 

I have check all again, and the rv1 at 2/3 was best modulation but the output doesn't get higher than 4-5W on 80m an 3W on 40M.. the other Bands still get 1-2 on 15M or 10M

THIS CAN NOT BE THE UBITX OUTPUT THAT SHOULD BE THE RIGHT ONE , WHAT CAN I CHECK IF Q90 IS NOT SHORTET I REALLY GONE CRAZY..

sorry this makes real bad vibrations everytime i get outdoor for testing on lagre antenna in the nature and everytime there is no way, or even when have luck it really strong to get qso with this.. and this issue should be able to find but i'm doesn't find till now 

Hope for any idea