[hpsdr] PennyWhistle MOSFET's

[Riho B., ES7AAZ]

Hi Helmut,

thank you for your remarks. I'll take a look into the bifilar choke for DC
feed. This amp is designed by OH7SV, OH2NLT. It should be a working thing
and give a quite flat 22dB gain from 1 to 60MHz. The same guys who designed
the JUMA DC TRX and state-of-art LDMOS 1kW amp JUMA PA1000 -
http://www.jumaradio.com/ But yes, I built it from quite a scratch. There
was no big story about this amp - schematic, PCB 2400dpiPDF image, PCB
layout, some pictures and their measurement results on their website.

--
*73,*
*Riho ES7AAZ*

Kontakt Helmut Oeller (<dc6ny at gmx.de>) kirjutas kuupäeval T, 9. november
2021 kell 10:43:

> Hi Riho,
>
> sorry, I can't redesign your amp by email remotely :). May be the
> following remarks are helpful for you yet:
>
> 1. Acc. to the datasheet the 1 dB compression point of a RD70HVF1 is
> approx. at 45W, i.e. a push-pull  configuration should be able to
> deliver up to 90W linear power.
>
> 2. the load for each Mosfet can be calculated with R = (Ub^2)/2P. You'll
> get approx. something around 5.4 ohms for the two Mosfets together @ Ub
> = 15V.
>
> 3. A well-performing 1:9 transmission line transformer should substitute
> that simple conventional trafo for matching the 5.4 ohms to 50 ohms.
> Moreover the DC feed for the Mosfets should be done with a bifilar
> choke. This improves  IMD too.
>
> 4. These Mosfets are specified for a quiescent current of 2 A, i.e. 30W
> (!) dissipation for each Mosfet. A well-designed  bias stabilisation is
> strongly recommended to avoid thermal runaway effects and migration,
> which causes additional nonlinear distortion.
>
> 73, Helmut, DC6NY
>
>
>
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