Hi folks,
In the order received, this radio will be quite a bit better than the
Winradio. Mr. Starman, the Sync detector will be available as an
outboard accessory.............I just am not sure when. I did release
the detector design to one of the US radio manufacturers (don't ask me
who!), so it should show up in the next version of that manufacturer's
radio.
Oh, that image problem..............I was receiving Radio Bejing's
9790kHz frequency. I solved the problem in two ways. First of all, I
shielded the TDA1572 by covering it with a strip of copper tape,
soldering both ends of the tape to the ground plane.
The image occured because of this reason............with a 10.7MHz 1st
I.F. and a 455kHz 2nd I.F. I decided to use a 2nd LO injection frequency
of 10.245MHz. Since this is a low-side injection scheme, the radio can
respond to the 10.7MHz upper sideband response of the mixer (the desired
one) and the 9.790MHz lower sideband response (the image). Once I
identified this mechanism, I was able to solve the problem by inserting
a low-pass filter between the JFET source follower and the wideband
MMIC. With my Boonton Model 103D RF Generator set at a 1V output level,
radiating directly into the loopstick antenna, the response is down
-70dB. Problem solved.
Now, if I could only get those softward people at
work...................this unit will also have RS-232 control, and we
will have some sort of Windows based GUI program to control the radio.
For you Linux folks, we will be releasing the protocols, so you will be
able to write your control code.
Overall, I am happy with the design, and I think that all of you will
like it. I talked to the boss about releasing a barebones, portable
version of this radio, with only a preselector control, volume control,
and tuning control, but he didn't go for it. Too bad............it would
have captured the under 150 dollar market.

Pete