[hpsdr] Norton CBTF rf amp

[Ken Klein]

I posted the following message today on the Flex site.  I thought it might
be of interest to the HPSDR folks.  It certainly is an interesting little
amp, and might find its way into the projects over here.  Let me know if you
find it helpful.

 

 

Recently I built a couple of wide-band common-base transformer feedback
(CBTF) amplifiers as described by Dallas Lankford in this article :

[<http://www.kongsfjord.no/dl/Amplifiers/Ultralinear%202N5109%20And%202N3053
%
<http://www.kongsfjord.no/dl/Amplifiers/Ultralinear%202N5109%20And%202N3053%
25> 

20Amplifiers.pdf#search=%22dallas%20lankford%20CBTF%22
<http://www.kongsfjord.no/dl/Amplifiers/Ultralinear%202N5109%20And%202N3053%
25> >]

 
<http://www.kongsfjord.no/dl/Amplifiers/Ultralinear%202N5109%20And%202N3053%
25>  

 
<http://www.kongsfjord.no/dl/Amplifiers/Ultralinear%202N5109%20And%202N3053%
25>  

I built the push-pull version with 2N3053's in the 1 :11 :4 ratio which gave
me 16 db gain across the HF bands, and used it as a rf preamplifier ahead of
the SDR-1000, just to see how well it would work.  I haven't exhaustively
tested it yet, but my early impression is that it improves small signal
reception quite a lot, especially when trying to separate low level signals
very close to higher power interference.  The IP2 and IP3 specs on this
amplifier are pretty awesome.  In almost all cases, signal readability is
improved significantly.

 

So I thought that I'd pass along the suggestion to those who like to
experiment with this kind of thing.  The amp is cheap and dead easy to build
and a lot of fun to play with.  I'm building another now for lofer work, and

I even use one as a preamplifier for my oscilloscope!   I'm not suggesting

that the SDR-1000 needs this kind of amp, but at my QTH and with my antenna,
the improvement is certainly noticeable, very welcome, and it seems to
benefit all modes of operation.  

 

Even if you don't want to build the amp, the article is well worth reading.

Just don't flame me for actually suggesting that our SDR needs more
hardware!

 

Thanks,

 

Ken WR5H

 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openhpsdr.org/pipermail/hpsdr-openhpsdr.org/attachments/20060926/0a1a6bd9/attachment-0003.htm>