CRT SS6900n
The CRT SS6900n
The CRT SS6900n is a cheap/entry level CB/10 meter radio with FM, AM, SSB and CW modes, frequency display, SWR meter, variable output and more than enough power output (around 12W/AM, 40W/FM and 30W/SSB).
This version is V6 of the famous Anytone AT5555 wich is comercialized under several brands, like K-PO, Maas, Intek and CRT. I don't know if they are exactly the same but I'm shure the base is the same. There are some cosmetic changes (like the blue leds and display) but all functions are the same, at least to my knowledge.
Despite beeing a simple and inexpensive radio, I think it's a very good investment for a beguinner. I've made lots of contacts with it around europe and usually get good reports.
Board version
Board version is only identifiable by opening the radio. It is printed on the board.
(Re)programming
Communication with the radio is done by an internal serial port (located on the board). To connect it to a computer you can buy a programming cable or use a FTDI adapter. I went with this last solution has I had a cheap FTDI adapter around waiting to be used. By the way, I also tried to use a Baofeng UV5R programming cable with success (Baofeng cable has internally a FTDI or similar adapter and uses a Kenwood connector - see pictures for the correct connections).
The major dificulty is getting the right connector for the board. It's a JST-PH connector (JST-PH has 2 mm spacing between pins) that can be found on e-bay. You need the female connector.
Having an FTDI adapter and the right connector, you only need to wire it correctly (TX to RX and GND) and fire the software. If you can't communicate with the radio (it must be turned on, obviously) try swapping TX with RX. Usually solves the problem.
One last note regarding TTL levels used by the FTDI adapter: in mine I can select 3.3v or 5 volts. I tried with 3.3v and it worked fine so Ieft it that way. I don't know the levels used by the Baofeng cable but it worked also.
CRT SS6900 COM port. To see it's location on the board, please see the board picture.
FTDI adapter.
All set. I didn't built a cable. Just connected everything with wires and alligator clips.
Baofeng UV5R programming cable.
Connecting headphones to external speaker output
CRT SS6900n has an output for an external speaker, as almost every radio. It's possible to use it to connect stereo headphones, cutting the internal speaker and using the headphones for listening. Despite some users connect the headphones directly, it's better to make a simple adapter so we get better volume control and avoid getting damage done to the headphones.
The adapter is very simple and only uses a 330 ohm resistor to drop output voltage and two 2.5 mm jacks. A stereo female to connect the headphones and a mono male to connect to the radio. See the images on this section. They are self explanatory.
Power supply
CRT SS6900n specifications state that it should be powered by a PSU of 13.8V. I'm using my radio with a PSU of 12V without any problem detected. Regarding power consumption, it needs around 9.5A transmiting in FM (it needs less in AM and SSB). I've found that using a cheap 13.8V PSU that I have lying around, I've got a around 10A current draw. I was expecting a lower current consuption with 13.8V than with 12V but the realityt is this smalI increase. I don't know if that translates to more output power as I don't have a meter but since this PSU produces more noise than my 12V PC converted PSU, I don't use it.
Issues
- NB/ANL only works in AM;
- Clarifier adjustments are memorized. When you adjust and change the channel, the radio keeps the adjustment made for that channel;
- When programming Uk FM frequencies (or others that end in 50 Hz), despite inserting in the software the correct frequency, like Uk FM channel 1 27.601250 MHz, after programming, the radio is set to 27.601200 MHZ. You must manually, using the clarifier, set the correct frequency (27.601250 MHz). Of course you only need to do this one time because the radio memorizes clarifier adjustments;
- Busy channel: the usual factory programming set channel 9 as emergency and make it "busy". That means that when you try to transmit with squelch open the radio beeps and the disply says "BUSY". When you close squelch you can transmit normally. You can change this behaviour only by reprogramming the radio;
- Standard microphone: there are some users that complain about the standard microphone. I set gain on mine to 50 (ICG or IC9). I usually get good radio reports but I try to talk a little louder (and very close to the microphone) than normal. A power microphone or even a KPO DMC-110 can solve this problem;
- Programming software: you must use the software version that matches the board version.