Monday, July 20, 2015

Trevo bandpass filter - I

Slowly I'm getting the "Trevo" transceiver built.

I'm trying to get now the bandpass filter to some usefull state.

Here's the progress with the inclusion of relays for switching.

...decision that I already regretted after soldering all those small relays, each one is an inverter, so it takes two for each band, and I'm also grouping two separate sets (one for the low bands, the other high bands)...and still missing almost all the coax from the filters to the relays!

General schematic is this one:

...adapted from the "Speaky" transceiver without the diode switching part.

The filter includes a tuning voltage that is applied to C21, kind of pre-select with varicaps, input is applied on L2(3,4), output goes on L3(3,4) or vice-versa if you care....

The varicaps are going to be changed to diferent type from the ones in the "Speaky" because they are made of un-obtanium so I expect to do some changes in the filter componentes values.
The baseline is the following:

I never testes this configuration for the 160m band so I might have to change design for that band. Will probably include also one option for VLF bandpass or a filter bypass.

Still a lot to be done.

Have a nice week!