Dario, I have almost the whole collection by YU1LM on my HD.
The ADTRX1 uses 70AC74's as digital phase shifters, and your receiver works OK, so, I have two things on my mind: 1) Check that both I and Q modulators are receiving RF from the phase shifter. A bad solder link or bad resistor can do that. 2) Check that both I and Q audio amplifiers have EQUAL gains. The easiest way is to feed I and Q with the same audio signal, and adjust R51 for equal audio levels on R21 and R32. Then, you should have EXACTLY the same levels on R28 and R33. The level on R32 is fixed, and variable on R21. When you have the same voltages on pins 1 and 8 of the TL084, you should check that the audio voltages on pin 7 and 14 also are identical to that of pin 8. The balance condition requires that ideally, those voltages are identical, and there is a 90 degrees phase shift between pins 1 and 7 relative to pins 8 and 14. The voltages between pin 1 and 7 are 180 degrees out of phase. The same occurs between pin 8 and 14 of the TL084. Check that the 74AC4053 are OK. A friend of mine has built a receiver that still does not work because of some undetermined problem with the 4053. The easiest way is having the IC on a socket and substituting it. There is software available for the tests. One that I remember is IQGEN. You have received other suggestions as well on this list as I see this morning. Check your hardware and make sure all the connections are are good, don't discard the possibility of a micro crack on the PC board tracks, that may look OK but does not actually connect its ends. A single bad component can create a nightmare for you. Don't get discouraged by this. Identify and substitute it, and you will be "on business". The good news is that your receiver already works well. Good luck checking the TX side. 73, Jose, CO2JA PS: And your qustions are not silly. Silly would be to remain silent and stay with the problem. You will need an audio voltmeter, or preferably an oscilloscope. Even better, a dual channel oscilloscope with A-B function, so you can check the equality of levels by means of an A-B null, which is a much sharper indication of balance. ---- dario_matteo wrote: > Jose, > > thanks for your response. > I'm trying to use the ADTRX1 hw by YU1LM. > The schematics are on his web pages : > http://yu1lm.qrpradio.com/homebrew.htm > > I've no problem with the RX part. > I'm in trouble with the TX part. No way to suppress the image. > The sound card used is a 16 bit. > I'm quite new in sdr, sorry for this silly questions.. > > Dario. __________________________________________ Participe en Universidad 2008. 11 al 15 de febrero del 2008. Palacio de las Convenciones, Ciudad de la Habana, Cuba http://www.universidad2008.cu
