EMRFD Message Archive 12092

Message Date From Subject
12092 2015-12-28 07:07:02 Ravi Miranda OT-Switching ceramic filter+additional stage
Hi everyone

Seasons Greetings!!

Now sure where to find the answers to decided to start here.

I have two questions that I'm looking for answers to and hopefully someone can point me in the right direction.

1. I would like to switch ceramic filters of various bandwidths in an IF stage, how would this be possible? For example, one bandwidth for WFM reception and another for NBFM reception. Would this be via a switched method or under uP control?

2. In this link; http://onetransistor.blogspot.co.uk/2014/08/design-of-tv-tuner-based-radio.html
I could get FM reception, and a tap from the 455 Khz detector leading to a AM detector IC, as shown here http://www.qsl.net/sv1bkg/super_scanner/

But how do I add a Product detector for CW, USB and SSB, preferably under uP control.

Thank you all for reading and for your help in advance.

Wishing you all a Happy New Year 2016!!



I'm here to add more value to the world than I'm using up.
12094 2015-12-28 13:26:40 kerrypwr Re: OT-Switching ceramic filter+additional stage
We had a discussion on this subject some time ago;


Kerry VK2TIL.
12095 2015-12-28 13:45:57 Will Re: OT-Switching ceramic filter+additional stage
Hi Rav,

I think you need to first separate the switching, relay, pin diode, diode, mechanical switch, from the control system physical switch, computer, micro processor.

Once you have decided on how to switch then work out how to control it.

Again with SSB/CW you need to work out how you want to do the process, then work out the controlling system.

Of course you could do it the reverse way but that might limit you options as to quality of switching.