layout. The first thing I noticed is that the drawing has I&Q carrier
balance trimpots and the pc board does't have these parts.
Now for the results, all the same audio problems with with PC sound
cards that cause trouble when using them with receivers show up again
with the transmitter. Transformers are required between the PC and
the transmitter to remove common mode hum also the quality of the
sound card is important in reducing hum and noise on the transmitter
output.
When using DL6IAK two tone I/Q test program which has a phase delay
option along with the amplitude balance it's possible to null a single
tone unwanted sideband about 50db.
At a output frequency of 10mhz. the max undistorted output is -2.5
dbm. at 2.5mhz it's about zero.
I find that cxr leakage is about 50db at 2.5mhz and tends to get
worse as output frequency is increased this leakage isn't caused by
the 4066 switches it's present with the chips removed. I used sockets
on my board and this may be causing the problem. I have been able to
reduce the cxr leakage by about 10db adding a 2-8pf trimmer cap.
between pins 5&6 of IC1 to ground. A double sided board with a ground
on top side my help also. A good bandpass filter is required following
this board for a to remove unwanted mixing products and LO products.
Since most of my test equiptment is homebrew your results may vary.
Joe wa9cgz
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