Re: Upconverter not working?

[Opendous Incorporated]

  With the Upconverter powered up (USB plugged-in, LED next to USB connector lit) and the switch in Upconvert mode you should see a signal peak at 125MHz if you tune your RTL dongle to 125.1MHz or so with a 0.5MSPS sampling rate on the RTL dongle.  This is the natural LO bleed.  It should disappear when the switch is in Passthrough Mode.

  If you do not see any such signal, that means the LO is not getting to the mixer (or the mixer is broken).

  Please check with a multimeter the DC voltage across R2 (to right of the X1 oscillator can) when in Upconvert mode.  It should read near 1V.  This means the oscillator is fine and the problem is either in the LO filter or mixer.

  If there is no voltage across R2, do you happen to have any Half-DIP 4-pin oscillators around?  If yes, please try plugging one in and seeing if you get any DC voltage across R2 in Upconvert mode.  If yes, it means the original 125MHz oscillator is broken.

  If the oscillator is fine and you have the time, please try soldering a wire from R4 to L13 to bypass the LO filter and see if you get a signal at 125MHz.  This would mean the LO filter is broken.  Please contact the seller for an RMA.

> Tried inputting a 10 K Hz signal of 200mv into the front end

  You should see a signal peak at 125.01MHz in Upconvert Mode about 10dB lower than the input 10kHz signal.  200mVpp is about -9dBm so it should show up at about -20dBm.
http://ifmaxp1.ifm.uni-hamburg.de/DBM.shtml

  It is unlikely to get through in Passthrough mode as the Upconverter conversion losses dive below 50kHz.

  If you are interested in pursuing the issue further, please contact me with any more readings and observations you make.

  The easiest to source replacement oscillator is the DigiKey-stocked programmable SGR-8002DC which you can ask DigiKey to program for you:

http://www.digikey.com/product-detail/en/SGR-8002DC-SCB/SGR-8002DC-SCB-ND

[Ariel Pimentel]

Hi,
 
I a few days a go i received the Ham it up v1.2  (125MHZ) upconverter. I plug it to the dongle ( switched 0t upconvert) an try to tune HF frequencies and nothing happend.
When i power up the upconverter an tune 125mhz i see a peak no matter if the switch in  passthough or upconvert position, the peaks goes when is no power to the circuit.

''Please check with a multimeter the DC voltage across R2 (to right of the X1 oscillator can) when in Upconvert mode.  It should read near 1V.  This means the oscillator is fine and the problem is either in the LO filter or mixer''

Found cero voltage  at R2 in upconvert mode.

I will appreciate your help.

Thanks

[Ariel Pimentel]

El sábado, 8 de marzo de 2014 19:45:58 UTC-4, opendous escribió:

[opendous]

> When i power up the upconverter an tune 125mhz i see a peak
> no matter if the switch in  passthough or upconvert position

  Please tune to 125.01MHz or so.  Due to how I/Q demodulation works there will always be a peak at the center frequency.  The LO bleed should appear near the tuned frequency at around 125MHz.

> Found zero voltage at R2 in upconvert mode.

  You also mention just one peak which means there is likely a problem.  The LO is never exactly at 125MHz so it would not overlap the tuned frequency exactly.

  If the LED is on then power is available.  Please try removing the oscillator and cleaning the contacts with alcohol.  After the alcohol dries, please firmly press the oscillator into its socket.  It sticks out a bit above the socket but the contact should be firm.

  If you still do not get a second peak near 125MHz in your SDR software and there is zero voltage across R2, contact NooElec for a replacement.

[Ariel Pimentel]

Hi,

  I cleaned the oscillator  pins and see no voltage at R2.
  I do see the second peak (i forgot to mention in my first question,please see attached pictures.) The second peaks stay no mater the switch position, it only goes when power    of   the converter.

There is any voltage to measure at the witch pins in order to verify it working correctly ?

 Is this a malfunction of the 4 pin Crystal oscillator ?

Thanks for  your help.

Saludos

[phase2682]

I have the same failure mode as Ariel.  May I get a replacement or is there a simple fix?

 

thanks for your assistance

[Opendous Incorporated]

  There are some simple checks that can be performed with a multimeter.  The voltage between pin 1 (EN) and pin 4 (GND) of the oscillator should be 3.3V when in Upconvert mode (0V in Passthrough).  Voltage between pin 4 (GND) and 5 (VCC) of the oscillator should be 3.3V.  The voltage across R2 (next to the oscillator) should be about 1V (0.7V-1.3V depending on multimeter).

  In Passthrough mode the voltage between the pin closest to the board edge and the other pins of the switch should be 3.3V.  In Upconvert mode, the center pin of the switch should be 0V relative to the top pin.

  In Upconvert mode you should see a spike at ~125.01MHz in your SDR software.  This is the LO bleed.  Switching to Passthrough mode should make it dissappear.

  If everything seems to work but you cannot pick up any MF/HF frequency bands, try a larger antenna or connect to a large metal object like a water pipe or radiator.  If you have a proper HAM antenna, then please check all connections before contacting the seller for a replacement.

[opendous]

  The Upconvert to Passthrough switch in SDR software image shows 100MHz but that should read 125.06MHz.