In article ,
Patrick Turner wrote:
On Jul 8, 8:51*am, John Byrns wrote:
In article
,
*Patrick Turner wrote:
On Jul 6, 10:07*am, John Byrns wrote:
*What do you gain by adding the cathode follower to the
circuit? *What is wrong with simply choosing the diode load to reflect
the
desired load to the secondary of the IFT, 100k or whatever? *
Better sound. Try it sometime. Then you'll know.
OK, I'm sensing a challenge here, similar to Danger Dave's assertions that
resulted in the ³Power Amplifier Without Power Transformer². *The problem
is
that with respect to Danger Dave's assertions, SNR was an easy to measure
parameter. *Unfortunately your claims for the benefits of using a cathode
follower to buffer the IFT from the detector diode, is ³Better sound², a
sort of
vague standard.
Before I take up my soldering iron to demonstrate that an AM detector the
equal
of yours can be built without the cathode follower between the IFT and
detector
diode, I will need to know how to measure ³Better sound². *Can you suggest
some
valid objective measurements I can use to measure ³Better sound²?
I suggest you renovate your distortion measuring capabilities,
OK, you seem to be saying that it isn't "Better sound" that counts, that it is
measured "distortion" that counts?
I have next to zero interest in "renovating" my distortion measuring
capabilities, how good do my distortion measuring capabilities have to be to
adequately measure the performance of your AM detector?
What is the measured distortion performance of your AM detector circuit as shown
at the following URL?
http://www.turneraudio.com.au/am-fm-...iles/schem-tun
er-am-tuner-dec-05.gif
At what IF signal level, into the detector, did you measure its performance?
This is important since I do not intend to try and duplicate your entire tuner,
just the detector.
and then compare an average AM adio performance
Why do I care about the performance of "an average AM adio", why do you even
mention it?
to something designed on the principles I recommend which bean
counters in 1950 were likely to say were "uanaffordable".
All I am interested in comparing is "something designed on the principles you
recommend" vs. something designed on the principals I have recommended.
http://www.turneraudio.com.au/am-fm-...ex-decoder.htm
On your web page above, that describes your AM tuner design, you say about the
detector, "The grid of the IFT2 sec is biased at +31V to give some idle current
in the cathode R9, and to trickle a small current in the 1N914 diode via
R16&R17, so that the non-linear turn on character of the diode is avoided, since
it is always slightly turned on by the idle dc flow." Can you explain how this
bias avoids the "turn on character" of the diode, given that to function as a
detector the diode must turn off?! Bias, if correctly applied, will help reduce
the slew rate limiting at high modulating frequencies.
An interesting web page describing a number of AM detectors used in broadcast
modulation monitors and ham radio receivers can be found here.
http://www.tonnesoftware.com/appnote...iodedemod.html
[Much off topic drivel snipped]
--
Regards,
John Byrns
Surf my web pages at,
http://fmamradios.com/