From: [EMAIL PROTECTED]
> The way I understand it, > > The infinite impedance detector is a device such as a tube or FET that > normally draws output current unless reversed biased. The device is > reversed biased to cutoff and then input signal turns it on like class B > service but the input does not draw current. The output is taken from the > cathode, or source in the case of a FET, in follower fashion. > > I am not sure how this is going to correct the slew distortion that is > caused by the RF filtering and discharge rate of the output. Perhaps it is > because of the follower effect of having a low Z output with no diode at the > output. This may mean that the discharge is at the same rate as the charge? I've recently been working on a quasi-restoration of a National NC-156 (like the NC100XA with a 1500Kc IF and a few other differences). This particular one uses one half of a 6C8 dual triode as an infinite impedance AM detector. I don't know why they did this, as it is immediately followed with a series-diode noise limiter which I would think would introduce more distortion than a simple diode envelope detector, even when "disabled" (diode biased fully "on"). The cathode-grid terminals of the other 1/2 of the 6C8 is used for this diode. This is the 1st BA receiver crossing my bench employing an infinite impedance detector, and only some of the NC-100 variants used this circuit. Other versions used the common "plate detector" (triode or sharp-cutoff pentode cathode-biased to near cutoff, with the IF ripple filtered in the plate circuit and audio taken from the "far-side" of the filter). 73, -Larry/NE1S ______________________________________________________________ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/[email protected]/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:[email protected] To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
