Saturday, 9 April 2016

Inside the Baofeng BF-888S Radio itself

Yesterday I took a look inside the desk charger that came with these radios. Today, lets see whats inside the handhelds themselves!

The first thing I will say is - Dont Try This At Home!

(unless you are, like me, a time served RF engineer with 25 years experience of servicing handhelds!)

Getting into these is pretty simple, although the manufacturers have opted for a pair of hex screws to keep out the idle curious.  Removing the hex screws from the bottom, and the three nuts holding the antenna sockets and controls, the radio body eases out. Care is needed as the loudspeaker is hard wired rather than having a connector.

With the case removed you can see that there is very little on this side of the PCB. There is however the one and only adjustable device, a single surface mount potentiometer. It will be interesting to discover what this controls, it could be the VCO reference, the Tx deviation, the low battery threshold. Is it too much to hope its the Tx output power?

I opted to desolder the wires at the loudspeaker, as this was less risky than at the PCB. To remove the PCB required removing five cross head screws, and unsoldering the +ve power terminal and the antenna socket pin.

On the other side of the PCB is where its all happening. You can easily see why these are known as 'radios on a chip'. There does at least seem to be some proper filtering at the antenna connector. Build quality wise, the board was soldered ok, I found a small solder splash which I brushed off.

Putting it back together is simply the reverse of taking it apart, with a bit of care to ensure the antenna pin and the power terminal solder back properly.

You will notice that there is no seal between the case and the chassis! Dont get these wet! But, for around £8 each, they are ok for what they are - cheap UHF walkie-talkies.


Anonymous said...

so, what is that potentiometer for?

Zak The Rabbit said...

You know, I never did find out!