Hi Jack, tank for your question.
Basically the difference between the Ring Mixer and the H-Mode Mixer is: 1) In the ring mixer the mixing is performed by the semiconductors (diodes or fets) 2) In the H-Mode Mixer the mixing is performed by the transformers. The semiconductors (FET SW) are switching one side of the windings to ground. This has the benefit of not having the RF modulating the LO signal and not requiring higher voltage to switch on or switch off the FET. This is an important aspect as it reduces the possibility of LO phase noise and, consequently, reduces reciprocal mixing. The K3 1st mixer, a FET ring mixer, and the H-Mode mixer are commutative mixer, as their operation depends on switches. The FET array ring mixer was developed in the 80s by Ed Oxner, using an SD8901, with a conversion loss of -8/-9dB and an IP3 around +30dBm. The H-Mode Mixer was invented around 1993 by Colin Horrabin, G3SBI, using the SD5000 FET array IC, presenting a conversion loss of -8/-9dB and an IP3 of around +50dBm. The “H” has no technological meaning, it is coming from the look of the circuit diagram as the original 3 transformer configuration looks like an H. It was simplified when I had the idea of using Fast Bus Switches for mixers, with particular use of FST3125, by middle of 1998. This solution presented a conversion loss of around -5dB and an IP3 of around +40/45dBm. The “H” look is lost with the 2T HM Mixer but the functionality is there. The 2T H-M M was presented by me in 2003, presenting a conversion loss of around -5dBm and an IP3 of around +40dBm. Recently, Martein, PA3AKE, implemented an H-Mode Mixer version using analog switches FSA3157, with a conversion loss around -4.5dB and an IP3 of up to +50dBm. You can read a very extensive information visiting http://martein.home.xs4all.nl/pa3ake/hmode/hmode_intro.html. A simple and easy to understand description of the H-Mode Mixer is described in EMRF Design Book, W7ZOI et al published by ARRL. Several articles were published in RadCom, in the G3VA Column Technical Topics and also in QEX. G3SBI, thanks to the H-Mode Mixer, removed the mixer from the critical stages of a receiver. Hope I have clarified your question. Best 73 Gian I7SWX -- View this message in context: http://elecraft.365791.n2.nabble.com/K3-H-Mode-Mixer-tp6889343p6895543.html Sent from the Elecraft mailing list archive at Nabble.com. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
