Re: Soundcard based Noise Figure Alignment aid
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One thing RSGB need to do as part of their revamp is to place past copies of RadCom on the website - and not just the previous year's.
They can't, surely, expect us to pay for stuff we've already read once and 99/100 times have no further interest in.
Needless to say I chucked out all magazines before 2008 :-) Who wants paper copies of stuff now.
Hopefully my Rad Club library cupboard will go back that far
Tried to find that design on the website you list, but he only shows circuit diagrams in the native .SCH form - which is most definitely not readable by my EasyPC which what .SCH and .PCB files load into here.
Why authors cannot give circuit diagrams on web sites as .GIF or whatever I just don't know. They're just asking not to be found or looked at.
As for the two current sources in series by the way: I did that deliberately. When feeding a separate I-source, the PNP transistor one which is set to a higher current (20mA) just saturates and delivers an on-off switched 28V or whatever. Teh main reason for doing it like that is, since teh PNP is needed anyway as a switch, all it wanted was another resistor and a zener to give a nice current protected output.
My MaCom noise diode does not have its own integral current source, but does have the value of 12.3mA engraved on it which is what I set the separate LM317 source to deliver. Homebrew ones can probably work just with the PNP source adjusted appropriately.
On 25 November 2011 21:49, Ian White GM3SEK <gm3sek@...> wrote: