Re: [linrad] Homebrew Receivers

[Dan Sawyer <dansawyer@xxxxxxxxxxxxxxxxx]

All,

I am new to the concept of this radio and am having difficulty accessing 
the information. Many of the links included lead to broken links. Are 
they still available? Is there a good current starting point?

Thanks,
Dan kb0qil

w3sz wrote:

> Hello all,
>
> Just a quick note to those who might be contemplating 'rolling their
> own' front ends to use with LinRad.  The April RadCom Technical Topics 
> by Pat Hawker G3VA features a variation by I7SWX on the H-mode mixer 
> by G3SBI.  With these mixers IIP3's in excess of +40 dBm (up to +55 
> dBm!!) are reported.
>
> These are, like the mixers Leif shows on his webpages, switching 
> mixers.  What the differences are between the H-mode mixers and Leif's 
> design (if any) I am not smart enough to see, except that the 
> transformer configuration appears different with the H-mixers.
>
> These H-mode mixers mixers are also shown in the new ARRL Experimental 
> Methods in RF Design book on pages 5.15 and 5.16, and used in a 
> practical receiver on 6.48 and 6.49.  This reference describes this 
> H-mode mixer design as 'perhaps the most exciting work published in 
> the past decade in this area'.
>
> On the web they are discussed by PA3CKR at www.qsl.net/pa3ckr/himixer/
>
> The CDG2000 uses them www.warc.org.uk/cdg2000/introduction.htm
>         Slightly off this topic, you might also have a look at the LO 
> phase noise specs on that page for the CDG2000.
>
> There is an amusing rant on another list that complains that the 
> writer was able to achieve an IP3 of 'only +40 dBm' with the H-mode 
> mixer.  How sad ;)
>
> I'd appreciate any comments to the list by those who can comment on 
> whether they have had experiences with these mixers, and to compare 
> and contrast them with the switching mixers on Leif's pages.
>
> One interesting note is that PA3CKR built one version that used the 
> Minicircuits T4-1 rather than a roll-your-own transformer and the 
> FST3125, and that gave a respectible +41 dBm IIP3 (Input IP3).
>
> Thanks in advance,
>
> Roger Rehr
> W3SZ



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