[hpsdr] 100W PA for Hermes

[Kjell Karlsen]

Hi Helmut.

I have measured the IM3 on several commercial transceivers (Icom, Kenwood  
etc.) and the IM3 at maximum PEP is always specified at -30 dBc.  Only the  
most advanced and costly transceivers have better IM3 values at 100W PEP.  
Take a look at the tests done by ARRL.

At 12-14 Volt VDD it is very difficult to achieve better IM3. If you  
increase the voltage to 28, 48 or even >100 volt, the results are much  
better. I am looking at a solution using a high voltage MOSFET pair to get  
300W PEP. If this is a success, it will be a simple and low cost solution.  
The only drawback is the PSU but they are sold cheap on e-bay.

Normally a Power Amplifier is delivering the maximum legal power at a  
lower output than 100W from the transceiver and then the IM3 is better.

73, Kjell






På Sun, 13 Nov 2011 20:03:22 +0100, skrev Helmut Oeller <dc6ny at gmx.de>:

> Hi,
>
> is it right that IM3 is only -30 dBc? For my impression too bad when  
> driving a power amp.
>
> 73, Helmut
>
> -----Ursprüngliche Nachricht-----
> Von: hpsdr-bounces at lists.openhpsdr.org  
> [mailto:hpsdr-bounces at lists.openhpsdr.org] Im Auftrag von Kjell Karlsen
> Gesendet: Sonntag, 13. November 2011 19:28
> An: hpsdr at lists.openhpsdr.org
> Betreff: Re: [hpsdr] 100W PA for Hermes
>
> ***** High Performance Software Defined Radio Discussion List *****
>
> Hi Jeff.
>
> As Abhi say, I have constructed a 100W PA and I am finishing the final  
> PCB
> layout now.
>
> One lab model and 2 Beta boards have been built and tested and soon I  
> hope
> to get the results from two other builders in DL.
>
> After the modification of the output transformer the results are very
> good. Power output is > 100W PEP with >-30 dBc IM3 on all bands.
>
> I´ll post the measured results on
> http://openhpsdr.org/wiki/index.php?title=MUNIN soon.
>
> 73, Kjell
>
>
>
>
>
>
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