EEVblog #1275 - Uniden UHF Walkie Talkie Teardowns

How much has UHF technology progressed in 20 years?
A teardown of a 2000 vintage Uniden 500mW UH040 UHF Walkie Talkie to a modern kids 500mW version at half the size and 1/10th the cost!
Bonus UH750 5W teardown.

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[Mobin]

"Copyright 2000" ... hold on I thought he said 20 years ago ... oh :(

[RedwoodRhiadra]

That 5-watt "professional" model might be more expensive materials, but Vietnam is where you go these days when Chinese labor is too expensive...

[VintageTechFan]

13:00 That's most likely just an RF-MOSFET. Those RF-FETs typically have the source on the cooling pad for good low-impedance grounding. I see an RC feedback network from drain to source (very common!) and a matching/filtering network to the antenna. The diode marked "W4" looks like a PIN diode for the RX-TX switching (there is a second one under the edge of the shielding can).

It's actually a quite nice design, as soon you switch on the drain voltage BOTH diodes are going to conduct and you connect the TX to the antenna, and short the RX input to ground to protect it.


The SOT23 would then be a bias regulator, since they would be using the FET in Class C there is no idle current, you just have to bias it somethat under Vth to get the right conduction angle. So no adjustment needed here.

[conodigrom]

10:30 solder balls, coming to a short near you!

[snafu]

Not sure how other countries designate bands, but CB (40 channel Citizens Band) in the USA is an AM radio using the lower HF band (26.965 to 27.405 MHz).

FRS (22 channel Family Radio Service) radios are FM, in the UHF band (462.5625 to 462.7250 MHz)

[redtails]

the remarkable thing is that the 15$ kid transceiver is 75% empty. The board is massive but there's almost nothing on it. It literally has that size so that the batteries and the LCD can fit on it without cables

[RAUK]

15:00 RDA1846 is extremely popular these days. You will find it in many inexpensive UHF/VHF radios. Baofeng radios are probably most famous. Also RDA1846 is used in some low-end Yaesu radios.

[whiskeyinthejar]

My grandparents have been using those old school Uniden uhfs daily for 16 plus years on the farm. They have held up surprisingly well.

[Zardox-The-Heretic-Slayer]

that is so bloody weird - I literately just took some of these exact same walkies apart about 30 minutes ago

[Stefan_Payne]

Nice to see a longer Teardown Video from you again!
Godspeed!

[VintageTechFan]

6:30 May be for capacitive coupling to the holding hand to use the user as a RF counterpoise. Handhelds generally do that to some degree.

[MoTheG]

I bought 866MHz radios and the worst about them was the solderless LCD connection. Soon the bars in the display went dead. The range they get depends on the battery voltage.

[Ljk]

2:38 Shoutout to Dave chortling at "People's Republic" LOL! 10 for style and finesse!

[Syntax.error.]

When I was a kid in the 90s I had a rich friend that got very fancy walkie talkies that we used to play around. I was amazed by them at the time.

[maicod]

you saved the new transceiver from an untimely death by removing that solder ball

[ingmarm]

The RDA 1846 single chip transceiver is the same chip used in most junk radios including the dual band BAOFANG VHF/UHF radios. Does the job but many manufacturers drop the ball with the band pass filter section meaning you have barely passable attenuation of harmonics.

[horiamorariu]

Hi Dave.
A very interesting teardown, thank you.
The RDA chips are also the core in Baofeng VHF/UHF transceivers.
One minor thing to clarify: all of them are PMR (446MHz), not CB (27MHz).
Cheers, take care!

[StreuB]

Videos like there, where Dave gets all hopped up and his passionate Aussie side comes out, are the best. Can always tell when he's REALLY into a topic like this one. Again, fantastic video Dave.
As for Uniden, we all remember these from the Radio Shack/Tandy store days. Always have been a high end brand, even today they stand up there with Kenwood and the lot.

[thehandyman]

Oh man I just had the exact thought about these last summer. I bought a few of these in 2001 for chatting when off-roading when we were out in our Jeeps. Fast-forward to 2019 and went shopping for some 'real walkie-talkies' for my 4 and 5 year olds to play with and to my amazement they dropped to like two for $30. They arrived and they are absolutely tiny. Blew my freaking mind. We have since bought them for all the neighbor kids and now they all play with them all the time.

[zachdemand]

It would be nice to see more teardowns of radios.