Thanks to all of you for the suggestions . I'll take some test and let you know.
Dario. --- In [email protected], "Jose A. Amador" <[EMAIL PROTECTED]> wrote: > > > 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 >
