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I have a few baofeng UV5R handhelds sitting around that only transmit, the receiver is damaged.

What I would like to do with these is build a foxhunt transmitter. Sure, I could set it to low power (1 watt) and put it through a less efficient antenna, where it will radiate less ERP wise, but it will still get quite hot and waste the battery.

Does anybody know of any way to decrease these Chinese handhelds transmit power below 1 watt? Maybe destroy the final amplifier? Give it less voltage on the input? Change resistor values? I don't care if I fry the radio in the process, I have nothing else to do with it.

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    $\begingroup$ Have a look a the schematic here. It's a highly optimised diagram and hard to read. Q8 is the final PA transistor, top left corner. Perhaps remove it and see if you can pick up lower power RF somewhere near Q6? $\endgroup$
    – tomnexus
    Aug 31, 2015 at 5:52
  • $\begingroup$ Is "optimized" really what people call this style of schematic? Yuck. :( $\endgroup$
    – Phil Frost - W8II
    May 22, 2017 at 12:45

3 Answers 3

Reset to default
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As per tomnexus answer above but consider if you can pick up the trace to Q8 and add a variable resistor to lower the bias.

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Put a dummy load in stead of the antenna; that will attenuate the signal.

It won't solve your "heating up" problem, nor your "battery drain", but it will reduce the output EIRP quite a bit.

I ran a fox hunt with a Baofeng, tested on 1 W, sending out morse (over FM, hihi) every 15 minutes; the battery lasted 16 hours, more than enough for a day's fun.

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Have you tried adjusting VR2? That looks to control the bias for Q3 and Q5 which are both common before the VHF and UHF final transmit section splits off to each respective final amplifier circuit. VR2 looks to be an adjustment setting for the APC line. Top right corner of schematic, sorta.

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