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Re: [linrad] Homebrew Receivers
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?
> 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