Michael Dunn wrote:
Thanks to all so far for the various comments. I guess i should have
explained my design philosophy for this a bit.

What is your reception goal for this receiver?

- High fidelity?

- High sensitivity?

- Adjacent-channel rejection?

- Overload tolerance?

- Low cost?

(or of course, some combination of the above?)

I think the best way to do it will be VERY dependent on what you're
trying to accomplish.
--
Doug Smith W9WI
Pleasant View (Nashville), TN EM66
http://www.w9wi.com

In article ,
says...

PLLs are feedback loops. Feedback loops are driven by error. In this
case error would show up as distortion.


Well, that's a pretty extreme oversimplification.

Error above the loop bandwidth shows up as distortion. To use a PLL to
recover FM, you use a wide bandwidth that covers the entire baseband
spectrum of interest. That way, the error *is* the signal. Very
standard technique.

-- jm

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http://www.qsl.net/ke5fx
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In article , Doug Smith W9WI
wrote:
What is your reception goal for this receiver?

- High fidelity?

- High sensitivity?

- Adjacent-channel rejection?

- Overload tolerance?


Pretty much all of the above. Cost is secondary. Though I do like
simple elegance, and I'm not going to go as far as the SUPRX mentioned
by Bob, though it must be a fine rcvr.

Mark mentioned:
could design not only AFC, but also automatic tuning of an RF
preselector and perhaps even an antenna tuner, that would be tres
cool.

Signal strength is a different signal from AFC. AFC comes after the
signal has been limited, so that's sort of information is lost.

Yes, I know. I was just conceptually linking AFC to "AAT" and
"APS". The latter two would be a lot trickier I think since we're not
dealing with a monotonic function, but one with a peak. Might need a
uP or some overly complex analog circuits...


Speaking of quadrature demods, wouldn't best performance be had by
using a 23.3ns ) wideband delay instead of a single or
double-tuned LC. I just found one with 30MHz BW...

Michael

Speaking of quadrature demods, wouldn't best performance be had by
using a 23.3ns ) wideband delay instead of a single or
double-tuned LC. I just found one with 30MHz BW...

Probably not, unless there's something I'm missing. You don't want a
wideband circuit here -- the quadrature detector takes advantage of
phase shift through the passband. Basically it uses a mixer to compare
a signal with a phase-shifted version of itself, with the output being
proportional to the actual phase difference. With a single-tuned
circuit, the 3 dB point corresponds to 45 degrees of phase shift, and
that's where you center the quadrature coil.

-- jm

------------------------------------------------------
http://www.qsl.net/ke5fx
Note: My E-mail address has been altered to avoid spam
------------------------------------------------------

"Michael Dunn" wrote in message
.. .
In article , Doug Smith W9WI
wrote:
What is your reception goal for this receiver?

- High fidelity?

- High sensitivity?

- Adjacent-channel rejection?

- Overload tolerance?


Pretty much all of the above. Cost is secondary. Though I do like
simple elegance, and I'm not going to go as far as the SUPRX mentioned
by Bob, though it must be a fine rcvr.

Mark mentioned:
could design not only AFC, but also automatic tuning of an RF
preselector and perhaps even an antenna tuner, that would be tres
cool.

All of my older FM tuners have a three-gang "bread slicer", A.K.A. variable
capacitor. It tunes (1) the LO, (2) mixer input, (3) RF stage input. Since
the OP wasn't interested in a synthesized LO, a multigang capacitor would
seem to make sense.

With some imagination, one could arrange a scheme so that the LO would lock
to
a synthesized signal every 200 kHz step. Thus one-knob tuning of multiple
stages, yet with synthesizer stability. Details are left as a student
exercise.

73 de bob w3otc

"R J Carpenter" wrote in message ...

All of my older FM tuners have a three-gang "bread slicer", A.K.A. variable
capacitor. It tunes (1) the LO, (2) mixer input, (3) RF stage input. Since
the OP wasn't interested in a synthesized LO, a multigang capacitor would
seem to make sense.

With some imagination, one could arrange a scheme so that the LO would lock
to
a synthesized signal every 200 kHz step. Thus one-knob tuning of multiple
stages, yet with synthesizer stability. Details are left as a student
exercise.

73 de bob w3otc

You'd also probably get higher Q with air var. cap.
But everything else is more complicated with this approach

SioL

In article , John
Miles wrote:

Speaking of quadrature demods, wouldn't best performance be had by
using a 23.3ns ) wideband delay instead of a single or
double-tuned LC. I just found one with 30MHz BW...

Probably not, unless there's something I'm missing. You don't want a
wideband circuit here -- the quadrature detector takes advantage of
phase shift through the passband. Basically it uses a mixer to compare
a signal with a phase-shifted version of itself, with the output being
proportional to the actual phase difference. With a single-tuned
circuit, the 3 dB point corresponds to 45 degrees of phase shift, and
that's where you center the quadrature coil.

Phase shift = delay for a given frequency of course. 90deg at
10.7MHz is 23.3ns. Being wideband means the delay and amplitude change
over a 150kHz BW are MUCH less than with a single LC. Seems to me that
would give the best performance and lowest distortion...

Michael