Page 1 of 1

cze 7w transmitter

Posted: Tue Sep 18, 2018 1:21 pm
by radionortheast
I got this transmitter lately just to mess about with, comparing to my pcs stuff I don’t hear anything extra, checking carriers that where out of band and that they didn’t have any range, I mostly went above the fm band with my little scanner. While the power dose seem decent, its unforunately ruined by really bad squelch, it will go really low on a car radio, the signal is I think too wide (i didn’t get anymore range than my 3w) don’t know if there is anyway to defeat this, I suspect there isn’t, it sounds like the stereo might be unflitered, it can’t operated close to other radio stations as the pcs stuff.

Re: cze 7w transmitter

Posted: Wed Apr 01, 2020 9:34 am
by djdavis526
Is there a way to add rds???

Re: cze 7w transmitter

Posted: Wed Apr 01, 2020 11:00 am
by Polecat
The chinese rigs operate on super wideband fm.

Some chips are better than others and some have better filtering. Have you checked 2nd and 3rd harmonic freqs?

The rds question is on another thread.

Re: cze 7w transmitter

Posted: Wed Apr 01, 2020 11:26 am
by teckniqs
I've never tried it myself as I would never use one, but I've seen RDS added to them before.

Re: cze 7w transmitter

Posted: Wed Apr 01, 2020 11:37 am
by g33ky
Polecat wrote: Wed Apr 01, 2020 11:00 am The chinese rigs operate on super wideband fm.

Some chips are better than others and some have better filtering. Have you checked 2nd and 3rd harmonic freqs?

The rds question is on another thread.
I haven't seen any harmonics on my rig.

Re: cze 7w transmitter

Posted: Thu Apr 02, 2020 4:55 am
by Albert H
I can guarantee that the thing will be spewing spurs either side of the main carrier. They will be big enough to cause interference to your neighbours.

These rigs use "audio sender" ICs as their exciters. Whilst this is a cheap and easy way to generate stereo FM, they're simply not clean enough to amplify. There's also no way to introduce RDS into the modulator. You'd also need to synchronise the 57kHz RDS carrier with the 19 kHz stereo pilot to prevent nasty whistles and other corruption.

I found two good things about these nasty little transmitters - the box they're in is quite high quality, and the PA part of the rig is actually pretty decent. I stripped out the nasty "audio sender" IC out of one, and built a proper exciter. When completed, it had a stereo coder, audio limiter and clean exciter (using the original 7-segment displays to show frequency). It did about 6 Watts, and has been in use in a village in Eastern Europe for a couple of years. I wouldn't recommend doing the re-build, though. It was just done to see if it was possible!