Radioberry with QRP-Labs 10w Linear amplifier

[G4ZAL]

I have built the QRP-Labs 10w linear amplifier to use with my radioberry.
I've measured the Radioberry output into my nanoVNA and it is pretty flat from 160-10m at around 12dbm output.
When connected to the 10w amp, I see on 80/40/20m around 20w output, but from 17 to 10m it tails off to around 4w on 10m (with 13.8v to the amp).

Does anyone else see this who has built the QRP-Labs 10w amp?

I understand the 10w amp has an input of ~200-400ohms and wonder if there is a good way to modify this to better suit the RB?

73
Nigel

[Wim Gmail]

Hi Nigel.

The use of a irf510 mosfet wil drop down at high frequency. Til 20m its oke. Above It have the same experience. Not enough power on 10m.

Wim PE1PWR 73s

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Op 6 jan 2026, om 12:24, G4ZAL <devon...@gmail.com> schreef:

[Wim Gmail]

And the reason of a lower power on 10m is that the irf510 capacity is to high for use on 10m. For lower frequentie is there no problem. Better is to use real high frequency MOSFETs like de RD100 or RD70VHF.

Wim PE1PWR 73s

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Op 6 jan 2026, om 12:24, G4ZAL <devon...@gmail.com> schreef:

I have built the QRP-Labs 10w linear amplifier to use with my radioberry.

[G4ZAL]

Hi Wim,
I also posted about the amplifier in the QRP-Labs forum on groups.io and got some useful replies.
I have rewound the input transformer (T210) for the BS170's that form the drivers for the IRF510 finals.
The original transformer winding is 6:3:3 (6 turn primary and 3 turn bifilar wound secondary).
It is now 3:3:3 (3 turn primary and 3 turn bifilar wound secondary).
This has now made the overall performance flatter from 160-10m and I think I will settle on this solution.

The QRP-Labs thread...
https://groups.io/g/QRPLabs/topic/10w_linear_amplifier_input/117104424

Nigel, G4ZAL

[Ravi Miranda]

Hi
As another alternative, you can use Dr. Bill Schmidt's 20W Amplifier
which uses RD16HHF1s.
I'm going to test mine with something similar and can report back in a few days.

Best 73,

Ravi/G1RVI

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[G4ZAL]

Hi Ravi,
I have seen Bill's 20w amp on the groups.io builders group he runs.
Interested in how you get on with it and I thought it was only available in the US as nobody was offering the kit in the UK/EU?

AFAIK it's similar to the openHPSDR PennyWhistle 20w amp, of which I have but I built it into my openHPSDR Hermes rig.

https://openhpsdr.org/pennywhistle.php

https://openhpsdr.org/hermes.php

Nigel, G4ZAL

[Wim Gmail]

Hi all.

I got the same amplifier with RD16. Works great performance is much better.

With itf510 something go wrong with your impedance they blow up. RD16 is more forgiving with a fault

Wim PE1PWR 73s

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Op 8 jan 2026, om 21:39, Ravi Miranda <ravim...@gmail.com> schreef:

[Jörg Uthoff]

Hello Nigel,

I have PCBs for the K9HZ (Bill Schmidt) PA left over (no kit).

I could send you one, if you take over the shipping costs. 

You might also want to check before with Andy Rutter G8HCK before,  as he was handling kits for UK and Europe.

Vy 73, Joerg -DB2OO

[G4ZAL]

Hello Joerg,
Thank you for your kind offer, I will let you know as I have pinged G8HCK an email as you suggest to see if he has any kits available.
I'll let you know how it turns out, but please hold a PCB for me for now.
My problem is obtaining all the parts for completion as getting them from many sources becomes expensive with postage etc.

73

Nigel, G4ZAL