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Old 06-25-2017, 10:13 AM
   
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Default The Schottky diode??????

I've been reading a lot about Schottky diodes and haven't found anything that explains which one is the best for use in a receiver. I know there are different preferences like the 1n5711, the 1n5817 and different "BAT" series diodes, but I can't find any info explaining WHY someone would use one over the other. All comments welcome.
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Old 06-25-2017, 1:41 PM
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In some receivers that use a diode ring balanced mixer, you may get a slight improvement in conversion loss, noise figure by going from a generic diode to a Schottky. There are many things to consider like LO drive and other levels going into the mixer before changing out diodes. Here is some info on potential improvements:http://www.hp.woodshot.com/hprfhelp/...elit/an995.pdf

Since this paper was published there have been other new mixer types introduced with even more improved performance.
prcguy
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Old 06-27-2017, 7:42 AM
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Hello All: I have read a few receiver type modifications that replace the factory diodes in a receiver, with the faster acting Schottky Diodes, and the reports are that no noticeable difference was seen. Iam not sure what function the diodes were doing in the receiver.

Iam thinking maybe a balance modulator? have always wanted to experiment around with a Balanced Modulator IC. See: http://www.onsemi.com/pub/Collateral/MC1496-D.PDF

Jay in the Great Mojave Desert
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Old 06-28-2017, 12:28 PM
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I had a couple radios done with the Schottky mod, never really could tell a difference. This was done by a very reputable tech, so I know it was done right...he even mentioned it wasn't a worthwhile mod on most modern radios. I had a PC76xl, a Grant XL, and a Cobra 25 done (all Philippine radios) and a DX959 (factory mosfet radio), no noticeable difference in any of them unfortunately.

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Old 06-28-2017, 6:28 PM
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Hello All: Yeah These diode replacement modification doesn't seem to have a noticeable difference in the receiver, these diodes I believe are in the Detector stage of the receiver.

You might need a signal generator and maybe even a spectrum analyzer to see all this on a radio if there is a difference. A lot of expensive equipment to make a measurement that isn't noticeable to the human ear. See: https://www.youtube.com/watch?v=NIb53zs-5fw

Jay in the Great Mojave Desert
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Old 07-02-2017, 7:29 PM
   
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Interesting, I replaced my galaxy Pluto's diodes and transistor and my buddy's 88 and noticed a remarkable improvement. Not sure if this was from the new transistor or if it was specific to the 3600 board. Incoming signals sure seemed better and the "white" noise was non-existant. Compared to my ham rig though, it still has a long way to go
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Old 07-03-2017, 6:23 AM
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Hello Fireguy508: What are the function of the diodes and transistor?

Jay in the Mojave
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