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Date:01/01/70 Time:01:00
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UKHASnet

Recently i built another 2m Amplifier using the RD70HVF1, it is relatively cheap at under 20 GBP each but only available on ebay form far east!
I ordered two for 36 GBP, ebay item 191149037109.

This device is rated at 70W CW so was a good candidate for getting more 'clean' power on 146MHz Digital ATV.

Initial tests show very good results at up to 5W output, -55dB IMD3. I can get about -58dB with some tweaking but not very repeatable!, using the amplitude only pre-distortion in the DATV Express i can manage 6W at -60dB IMD3.

The design is extremely close to the RD06 and RD15 devices but with a couple of value changes in L/C.

I have used trimmers for a few caps during testing but the values which i found to do the job are shown below.
I have very little knowledge on amplifier design, i just twiddled a bit until i got what i needed, i'm sure someone else could do a better job!

The device is biased up well so you do need to get the heat away from the device well, i used a copper spreader to move the heat and it works very well, a fan is a must on 5"x4"x1" heatsink!

I think the best way to drive this amp is using an RD06 device which has very clean output at 50mW level, you then need ~1mW drive from the modulator.

Here is an updated schematic and photo: (fixed cap values added 18/9/15)

RD70HVF1 Amp V3



RD70HVF1 Amp Photo



RD70HVF1 Spectrum 5W












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