On Thu, 27 Mar 2025, 12:20 Bob D., <ajamas.rn@gmail.com> wrote:
> Thanks for info Lukasz. I'm not surprised the 3809 died. Looking at the
> data sheet Vcc spec is 8V.
>
Indeed. I wish I looked at the datasheet instead of believing what the
Aliexpress seller page said.
> It is only a 2W part with adequate copper and via density on the PCB.
>
> Are you playing with Analog Devices Pluto?
>
I'm playing with Lime SDR. A somewhat similar device to Pluto. After I
spent a couple of months using my HF SDR (Hermes Light 2) that is connected
to my "big" HF amp. I wanted to have a similar experience for UHF (and
maybe microwave in future). I've bought a couple of LimeSDRs (one USB 3 and
one mini) back in the day when they were being crowd funded (and were alot
cheaper). So it made sense to use it.
The problem is that the output is approximately 7dBm or 5mW. (Hermes Light
is 5W). So I'm struggling to amplify it sufficiently to feed it into any
"big amp" or even just to use as is. I need a couple of watts. 1W at the
minimum. I can amplify it to 100-200mW with cheap "20dB modules". But
getting from 0.1W to 1W or 2W seems very challenging.
There seem to be zero DIY designs (for 70cm) I can find and these Chinese
amps are rubbish (maybe not the one I overvolted, that was my fault - but
it does a max od 29dBm with 17dB gain - no better than these 0.8W
Mitsubishi mosfets).
I ordered a bunch of these transistors to hopefully fix the amps.
I've found one potentially promising device I could use. It is Mitsubishi
rd06hhf1. For some reason it it being marketed as HF device, but the
datasheet publishes S parameters for up to 1Ghz (and it is cheap! $10 or
so). I've never designed input/output matching for a transistor based amp,
but perhaps I'll have to try if none of these readymade amps work.
If anyone knows any diy designs that use a cheap part that can work on 70cm
(23cm a bonus, but I doubt it'll come to pass) please let me know.
73, Lukasz
>
>>>
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