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PostPosted: 21 Feb 2016, 04:30 
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Joined: 28 Nov 2014, 15:21
Posts: 38
Location: Queensland, Australia.
G'day all, I made an interesting observation the other day about the relative 'sensitivities' of diode and simple 'transistor' AM detectors. Although I like using diode detectors in my various Hi Fi AM receiver projects, I invariably need to use an RF stage in front of the diode detector to overcome weak signal diode distortion.

However mostly by accident, the other day I realised that simple transistor based 'infinite impedance' detectors fare much better in this regard! They still require an RF stage, but seem to deliver clean and undistorted audio output at RF levels where all manner of diode based detectors simply give up and sound like an electric guitar distortion pedal!

Frankly I'm quite impressed with the weak signal performance of typical simple transistor infinite impedance detectors, and they sound very 'hi fi' too! Regards, Felix (vk4fuq).


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PostPosted: 21 Feb 2016, 17:48 
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Joined: 08 Aug 2009, 03:11
Posts: 2229
Location: Chilliwack, BC
Hi,

There is always trade-offs. Infinate impedance detectors, whether 2N2222 or 12AU7 will have really good weak signal performance, but suck totally on strong signals. The converse is true for the simple diode detector.

Balanced active detectors (1496, 3028, 602, etc.) do better as they are capable of direct AGC of 60+ dB.

Then there's the venerable 7360 which can do no wrong :D

Cheers!

_________________
-= Gregg =-
* Ratings are for transistors - tubes have guidelines*
Home: GeeK ZonE
Work: Classic Valve Design


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PostPosted: 21 Feb 2016, 18:57 
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Joined: 28 Nov 2014, 15:21
Posts: 38
Location: Queensland, Australia.
G'day mate, interesting! As the prevailing RF signal levels at this location are uniformly weak, I'll happily take excellent weak signal performance! Regards, Felix (vk4fuq).


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