I'm completely new to RF design and am working on an OOK receiver for marine band VHF. The part that is stumping me is the front end channel selection filters for the 12.5KHz BW channels in the 156MHz RF band. In this case, it will need to be something like a dip switch channel selector, or possibly digital channel selection. What is the typical approach?
How to design narrow band channel selection filters for VHF band receiver
- Thread starter rolerbe
- Start date
It is normal to have a fairly wide bandwidth on the RF amplifier and mixer tuned circuits so that the cover the whole range of frequencies. The intermediate (IF) frequency is fixed (10.7 Mhz is a common IF frequency.) this is filtered by a crystal filter which defines the bandwidth of the receiver. The tuning is done by tunning the local oscillator to 10.7 Mhz above or below the frequency that you wish to receive.
Les.
Les.
Thanks Les. I'm with you up to the last sentence. Could you expound on this a little more? Thanks!
Ah. That gets it. Thanks a bunch.
With today's digital electronics......you have other options. I would first suggest buying a SDR dongle. They work extremely well and are cheap. And fun. This will give you an idea of modern radio today.
The wanted rf signal is digitally down converted to baseband and fed into a PC soundcard. If it turns out you like this kind of setup.........there are several ways to build a SDR front end. Or buy kits.
These kind of circuits do require some study. But they have many advantages and many built in features. Such as view-able, adjustable bandwidth.
I don't think you will be disappointed.
The wanted rf signal is digitally down converted to baseband and fed into a PC soundcard. If it turns out you like this kind of setup.........there are several ways to build a SDR front end. Or buy kits.
These kind of circuits do require some study. But they have many advantages and many built in features. Such as view-able, adjustable bandwidth.
I don't think you will be disappointed.
