Blowing Baofeng BJTs...

[needairtime]

Well, I think it's not actually a Bipolar Junction Transistor but actually a SOT-223(?) SMT MOSFET as far as I can tell in the UV82 based on the assumption it's similar to the UV5R.

I was reading in the Baofeng UV82 manual that you must make sure that the antenna's SWR is no worse than 1.5:1 ...

... 1.5 : 1 ... WOAH. That's pretty strict!

Have anyone blown a baofeng final transistor?

Accidentally transmitted without an antenna? Time to get a new baofeng?
Loose antenna? Time to get a new baofeng?

Granted, buying another baofeng is probably cheaper than replacing the final...

(Incidentally my old Kenwood HT (which does use a BJT TO-5 final) seems to have survived a really bad antenna that I hacked up, I neglected the impedance matching needed. Still seems to work at least. The transistor seems to be rated higher in terms of voltage endurance unlike the MOSFET in the baofeng?)

 

[Golay]

I'm trying to ascertain from your post.
Did you lose the final on the radio? Or are you just pondering what to do if it was to happen?

 

[needairtime]

No, I was wondering how many people have blown them already -- curious about how well designed/overdesigned the output stage is.

The manual (UV82, F8HP, and probably all of them) states 1.5:1 SWR for external antennas or expect damage -- some people would die for that low of an SWR, and end up transmitting on 2.0:1 to 2.4:1.

Plus transmitting without an antenna typically means instant final death. I just wonder because baofeng usually means "cheap" and overdesigning an output stage to prevent output death from SWR mismatch isn't "cheaping" it out.

As far as I can tell, the cheap baofeng HTs do not have SWR protection circuitry that looks like the protection circuits on my higher power radios (but not much higher!), hence the curiosity. I'd imagine the output need to be able to survive spikes of near 60V to deal with bad SWR.

 

[khaytsus]

Pretty sure you could transmit with no antenna on a Baofeng and it'd be fine. I wouldn't do it intentionally, but they certainly aren't going to die because your rubber suck antenna is 2:1. Unless the thing is a dummy load, most of them are high SWR anyway.

 

[needairtime]

thought most rubber ducks were fairly decent SWR-wise but do not radiate in the best pattern for distance.

It looks like someone has tried transmitting on a missing antenna on a UV-5R and it survived... Good job Baofeng, alas, left a bit to be desired for that 2.5mm jack...

 

[khaytsus]

thought most rubber ducks were fairly decent SWR-wise but do not radiate in the best pattern for distance.

It looks like someone has tried transmitting on a missing antenna on a UV-5R and it survived... Good job Baofeng, alas, left a bit to be desired for that 2.5mm jack...

Most rubber sucks are low SWR indeed.........because they're a dummy load. But a lot of them are still high SWR.

And the 2.5mm jack is a standard that Kenwood came up with. Why is it an issue?

 

[needairtime]

Most rubber sucks are low SWR indeed.........because they're a dummy load. But a lot of them are still high SWR.

This is incorrect. It radiates much better than a dummy load, just that it's more like an omnidirectional radiator and has no additional gain in desired directions. Go ahead and take apart a dummy load and compare it to the rubber duck, they are not the same at all. If you have a dummy load that works as well as a rubber duck, you have a bad dummy load.

I get where you're making this conclusion from SWR measurements of bad antennas, but you can't make the inverse conclusion.

And the 2.5mm jack is a standard that Kenwood came up with. Why is it an issue?

The 2.5mm jack in my baofang broke, the 2.5mm jack in my Kenwood did not.

 

[KD8DVR]

I've sent aprs bursts on a baofeng with no antenna. No harm done. I've got several and never have had an issue with output transistors failing with several years of owning them.

 

[needairtime]

Nice!!! I've seen a bunch of people abusing their baofengs and they survived.

I'm kind of surprised that it survives even long transmits, the baofeng uses a SOT89 OPT and is effectively only heat sinked by whatever copper is on the PCB. There is a poor silicone heat pad that's really thick and thus won't conduct heat effectively to the metal backing plate in the radio which would otherwise function as a very nice heatsink...

 

[scanmanmi]

Most rubber sucks are low SWR indeed.........because they're a dummy load. But a lot of them are still high SWR.

Some of my friends think it true and some think it isn't, and I always agree with my friends.