How do you tune cb radio 75wx st
Not sure what you mean by tune.
If you mean peak and tune, where in you increase the internal power output of the radio, then the quick and dirty way of doing it is, turn VR4 all the way to the left and take the tank slug out of L14. HOWEVER, I prefer to use a watt meter on avg power to adjust L14 to peak, and no more as not to over bias the final. But typically nothing will happen if you do. This will give you full modulation, and full carrier.
If by tune you mean, Tuning the SWR. Then that is a whole different topic.
In this case you don't actually tune the radio. You tune the antenna. If the antenna is not the correct length, relative to the wave length, Frequency of transmission..... then you will have a high SWR and this means more of your RF energy is not leaving the antenna, and going back into the radio. This is bad. this kills radios.
So to tune it you must make the antenna the right length. Here is how to check SWR.
Tune the radio to ch 20. Put the rf/SWR/CAL switch to CAL.
Turn the CAL knob all the way to the left.
Key the radio, and turn the CAL knob to the right until the needle of the meter is at the CAL mark, on the top line of the meter indicated by a little upside down triangle. That is the cal mark. The needle should be on it.
Flip the RF/SWR/CAL switch to SWR while holding the key down.
The meter is now showing your SWR. If it is under 2 you are not real good, but not gonna kill the radio. If you are 1.5 or less you are good to go. Ideally you want to be 1.5 or less if you can.
If it is over 2 you should try to get it lower.
here is how to find out if the antenna is too long or too short.
Turn to ch 1, repeat the steps to check SWR. Then do the same thing on ch 40. Compare the reading. If the reading is higher on 1 then on 40 the antenna is too short, and you need to make it longer. If it is higher on 40 then 1, it is too long and you need to make it shorter.
All antennas have a way of adjusting the length.
Hope this helps.
Aug 10, 2012 |