In article ,
Roy Lewallen wrote:

Telamon wrote:
In article ,
switcher wrote:

In article

,
Telamon wrote:

It depends on what you want. Maybe the bandwidth is to narrow or
the tuning action is so sharp it is hard to peak it. You add
resistance and the peak does go down but the bandwidth also widens.
I was already thinking: if DRM is 12khz wide (am I right ?), then it
might be a tuned loop is too narrow ??

So an R might help ???

If the tuned loop bandwidth is to narrow then you can deliberately
spoil the Q of the loop by adding resistance and broaden the bandwidth.
. . .

A really quick back-of-the envelope look at the problem indicates that
adding a resistance won't make the signal any stronger when the loop is
tuned away from the peak. It'll just make the signal weaker when it is
tuned to the peak. So it's "wider", but no better at any tuning setting
but worse at and near the peak. To check on my calculation, try it:
connect and disconnect the resistor at various tuning settings, on and
off peak. Does it make the signal any stronger at any setting?

The only time there would be any advantage to adding an R to widen the
bandwidth is if it's so narrow that it distorts a modulated signal due
to uneven response across the audio bandwidth. This would mean at least
several dB variation over a couple of kHz for voice SSB or over 10 kHz
for broadcast quality AM.

I read his post correctly his concern is a 12 KHz wide DRM signal and
that the tuned loop response will be to sharp and narrow. Firstly he
needs to build the loop and sweep it to see if has a problem to begin
with. Parasitics may cause the loop response to be wide enough that 12
KHz will not be a problem. If it turns out it does he can add
resistance, which will decrease the peak response and broaden it. Adding
resistance will cause the loop to not work as well but that is the price
you pay for greater bandwidth.

--
Telamon
Ventura, California