Problems with TX

General discussion and support for the Peaberry SDR V2.

Problems with TX

Postby lelazary » Mon May 27, 2013 5:34 pm

I just finished building the peaberry SDR V2 and I seem to have an issue with transmitting. The RX works good and I can pick up signals using a very simple dipole (just a simple wire cut to length). I am using HDSDR and everything seems to work when the TX button is pressed (the led blinks). However, I am not getting any RF signal on the antenna (using a dummy load and a scope). I suspect its the pcm3060 not sending the IQ data over the VOUTs.

Has anyone ran into this kind of problem? What should be the BW setting for the TX in HDSDR (I am using 96000 for TX/RX)?

Any suggestions for what to look for?

Here are some more information:
- Pin 12 (DIN) on pcm3060 is getting the digital data. When the TX button is pressed in HDSDR I can see a pulse train using a scope on that pin.
- Placing a scope on U8 it looks like the voltages on the inputs (1B1,1B4,1B2,1B3) are just staying high. The S0 and S1 are getting the QSE_Q and QSE_I signal as well as the
- I took out R17-R20 and placed a scope between VOUTL+,VOUTL-,VOUTR+,VOUTR,- and (GND or VCOM). The voltage between the VOUTs and GND is about 2.6V and seem to modulate with noise of about 200mV pk-pk (offset by a 2.6V bias). This is the same for all the VOUTs. This seems to be the case regardless if the TX button in HDSDR is pressed or not. When the TX button is pressed it looks like there some signal modulation, but it is very low and seems like noise.

-C44 junction goes from 220mV 114MHz sin wave with 0 V offset (frequency changes with the LO frequency x 4) to 300mv 110MHz at 2.15V offset then the TX button is pressed.

-Power supply goes from 0.1A to 0.3A when the TX is pressed (using 13.6V)

Any help will be appreciated,
Thanks,

Lior.
lelazary
 
Posts: 10
Joined: Mon May 27, 2013 4:37 pm

Re: Problems with TX

Postby AE9RB » Mon May 27, 2013 6:21 pm

The manual specifies 96000 as the sample rate. What mode are you transmitting?
73 David AE9RB
AE9RB
Site Admin
 
Posts: 511
Joined: Thu Nov 15, 2012 5:27 am
Location: Portland, Oregon, USA (CN85ql)

Re: Problems with TX

Postby lelazary » Mon May 27, 2013 6:44 pm

I tried all the modes, but specificity I used AM when doing the measurements (with microphone on and off).

Lior.
lelazary
 
Posts: 10
Joined: Mon May 27, 2013 4:37 pm

Re: Problems with TX

Postby AE9RB » Mon May 27, 2013 8:11 pm

If you're not seeing a carrier on the VOUT lines then the problem is with pins 9-12 on the PCM3060 and/or 3-6 on the PSoC. Also, make sure the transmit level on HDSDR didn't get turned down.
73 David AE9RB
AE9RB
Site Admin
 
Posts: 511
Joined: Thu Nov 15, 2012 5:27 am
Location: Portland, Oregon, USA (CN85ql)

Re: Problems with TX

Postby lelazary » Mon May 27, 2013 8:55 pm

I measured pins 9-12 on the PCM3060 and they all look good.
Pin 12: digital data
Pin 11: 95.7khz square wave
Pin 10: 6.2MHz square wave
Pin 9: 37Mhz which looks like a sin wav which I think its suppose to be a square wave (I am using a 100MHz 54622D scope, but I am just touching the probe to the chip).

C33-C36 junctions all show the 114MHz signal at 200mV. As soon at the TX button is pressed they go to 2.1V bias. When the TX button is releases they drop slowly as the capacitor is discharging.

Changing the tx level on HDSDR seems does not seem to do anything (except to add very little noise when the power is at the maximum).

Thanks,
Lior.
lelazary
 
Posts: 10
Joined: Mon May 27, 2013 4:37 pm

Re: Problems with TX

Postby AE9RB » Mon May 27, 2013 9:24 pm

Do you have HDSDR set to max power output?
73 David AE9RB
AE9RB
Site Admin
 
Posts: 511
Joined: Thu Nov 15, 2012 5:27 am
Location: Portland, Oregon, USA (CN85ql)

Re: Problems with TX

Postby lelazary » Mon May 27, 2013 11:51 pm

When I press the TX button in hdsdr a slider shows up indicating the power level. I have tried moving it from min to max with no effect. Is there another place to set the power level?

Lior
lelazary
 
Posts: 10
Joined: Mon May 27, 2013 4:37 pm

Re: Problems with TX

Postby AE9RB » Tue May 28, 2013 12:08 am

You should see an immediate effect on the VOUT side of R17-R20 when changing tx power. Everything points to a bad connection on the PCM3060. Even if you're measuring signal there, it could be an open connection the probe pressure is closing.
73 David AE9RB
AE9RB
Site Admin
 
Posts: 511
Joined: Thu Nov 15, 2012 5:27 am
Location: Portland, Oregon, USA (CN85ql)

Re: Problems with TX

Postby lelazary » Tue May 28, 2013 3:50 am

Thanks. That was it. I have already removed the chip once with a rework station, and it seemed like one of the leg was not soldered correctly (I went over it with a eye loupe).

Now for another question.

I built this for the 10,12,15,17 meter band. I am now measuring a 1V pk-pk on the 10m band with keying CW and full TX power (28Mhz to be exact). All the modulations modes seem to work correctly, so I tested this on CW. This was tested with a 50 ohm dummy load and the scope on the load.

A 1V pk-pk onto a 50 ohm load equates to 2.5mW of power ( (0.5/sqrt(2))^2 / 50 ). Should I expect more power on this band? is my math wrong? Should I look for other problems on the board?

Thanks again for all the help so far,

Lior.
lelazary
 
Posts: 10
Joined: Mon May 27, 2013 4:37 pm

Re: Problems with TX

Postby AE9RB » Tue May 28, 2013 4:39 am

You should get 500-800mW on 10m. Keep looking for soldering errors. Bad transformers are common too. Nobody is immune to these errors, not even me.
73 David AE9RB
AE9RB
Site Admin
 
Posts: 511
Joined: Thu Nov 15, 2012 5:27 am
Location: Portland, Oregon, USA (CN85ql)

Next

Return to Peaberry SDR V2

Who is online

Users browsing this forum: No registered users and 2 guests

cron