[minima] Re: Rx only minima for swl
- From: "Joe Rocci" <joe@xxxxxxxxxx>
- To: <minima@xxxxxxxxxxxxx>
- Date: Thu, 20 Mar 2014 14:47:35 -0400
"Use relays or active device switches to decrease capacitor values
in the crystal filter"
Arv
Keep in mind that anything you do to change the filter bandwidth will also
change the characteristic impedance. Impedance mismatch in bandpass filters
usually results in distorted passband shape and increased loss. I think the
second approach is better.
Joe
W3JDR
----- Original Message -----
From: Arv Evans
To: minima@xxxxxxxxxxxxx
Sent: Thursday, March 20, 2014 2:31 PM
Subject: [minima] Re: Rx only minima for swl
Cor
It really depends on whether one wants a general coverage communications
quality receiver or a broadcast quality receiver. If wider IF bandwidth is
needed then there are at least two approaches to achieving it.
a.. Use relays or active device switches to decrease capacitor values
in the crystal filter.
b.. Add a second wider bandwidth IF filter and switch the filter in
or out using relays or active device switches.
Changing bandwidth of the IF filter also could be applied for CW or other
narrow bandwidth modes.
Arv K7HKL
_._
On Thu, Mar 20, 2014 at 12:22 PM, dx11 <dx11@xxxxxxxxx> wrote:
It crossed my mind as well to make a Rx only version with AM added. I did
not yet come to a solution how to widen the Xtal filter to an AM value.
Cor Beijersbergen
It appears from a quick look at the schematic that you should be able to
add an AM detector and switch the audio amplifier input between outputs
of SSB and AM detectors. To avoid interference you might want to switch
the BFO oscillator power off when listening to AM.
I like your idea of using this design as a general coverage receiver. May
have to try that myself.
Arv K7HKL
_._
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