3609	2009-10-12 22:45:46	Vincenzo Calandra	A question abot level
Message	Date	From	Subject
Hi all, i've learned from EMRFD that the correct level of the LO to drive a simple double diode mixer (like SBL-1 or homemade mixer with 1N4148 or similar) in the first stage of a RX is +7 dBm. But: 1) What happens if the LO level is greater of +7 dBm. And is more under like +2 - +3 dBm? 2)If the same mixer is the first stage of a TX CW chain? What's the level correct level of the BFO and the LO? 3) What's about the same questions if the mixer is a simple two diode mixer? Many thanks in advance for all reply and... apologize me for my bad english. 73 de IZ5GVP Enzo (vcalandra@libero.it) [Non-text portions of this message have been removed]
3613	2009-10-13 14:11:54	w7zoi	Re: A question abot level
Hello Enzo and group, Generally, the conversion gain does not change much for a diode ring with hot carrier diodes (like the MiniCircuits mixers) if you drop the LO drive to +2 dBm. It decreases more if you go to 0 dBm. The same is true with silicon switching diodes, although they often require a dB or so more LO. The intercepts drop significantly with reduced LO sine wave LO drive. It is not as severe with square wave drive. It is generally not a problem to increase LO drive, although there is not a great deal of advantage either. I often end up with +10 dBm or so with a TUF-1 and similar parts. The same general rules apply for transmitters, even if they are just for CW. The reason is that when distortion becomes bad with two tone signal input, the spurious responses also increase. There is no difference between a BFO and a transmit mixer. They are really all the same thing so far as distorti
3614	2009-10-13 16:50:59	w4zcb	Re: A question abot level
These arguments are mere "Rules of Thumb" and as you have read, EMRFD is not about rules of thumb. Indeed, we have tried to avoid such things, replacing them with measurements. There is nothing to replace a measurement, especially when designing a piece of gear. Good luck. 73, Wes w7zoi Or, as W3AU was always fond of saying, "One experiment is worth a thousand expert opinions". Regards to the group W4ZCB
3615	2009-10-14 06:58:31	Tim	Re: A question abot level
Go to the "files" section of this board, and look at W7ZOI's "diode ring mixer measurements.pdf". This may work as a direct link: http://f1.grp.yahoofs.com/v1/UMvVSt8Jz6d-6UhTd1dqm0vcNS7vXAZtkSiHnYWp-kGMg5_bvjDZx6VPkaAw8CNTJ_ffYQoHYdSBUURxgMjPpctA4yifB3hQ/diode%20ring%20mixer%20measurements.pdf I think between the graph and his comments all your questions are answered. If EMRFD is ever updated with new content, I think this would be a perfect thing to put in. It exalts how design is directly related to measurement.
3617	2009-10-14 10:07:12	Vincenzo Calandra	Re: A question abot level
Il giorno mer, 14/10/2009 alle 13.58 +0000, Tim ha scritto: :-( :-( The link is broken.... > > > Go to the "files" section of this board, and look at W7ZOI's "diode > ring mixer measurements.pdf". > > This may work as a direct link: > http://f1.grp.yahoofs.com/v1/UMvVSt8Jz6d-6UhTd1dqm0vcNS7vXAZtkSiHnYWp-kGMg5_bvjDZx6VPkaAw8CNTJ_ffYQoHYdSBUURxgMjPpctA4yifB3hQ/diode%20ring%20mixer%20measurements.pdf > > I think between the graph and his comments all your questions are > answered. > > If EMRFD is ever updated with new content, I think this would be a > perfect thing to put in. It exalts how design is directly related to > measurement. > > > > > 73 de IZ5GVP Enzo (vcalandra@libero.it) [Non-text portions of this message have been removed]