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Monday, 15 September 2014

To Transvert or not to Transvert

Well,

Been thinking more about my antics on 2M & 4M Meteor Scatter:

http://g0mgx.blogspot.co.uk/2014/06/cq-on-them-there-meteor-trails.html

And wondering how my TS-990 would perform with transverters for 2M and 4M.

There are many designs out there for transverters, one of the best I have found are here:

www.g4ddk.com

Sam does a transverter for 2M and 4M; I have decided to join his waiting list....

In the meantime, you may recall we had a bash at some 4M kit a while ago, so I thought I would build on that experience and have a go at making a 4M transverter myself:

http://g0mgx.blogspot.co.uk/2012/06/even-more-4m-or-70mhz.html

So here is what we have so far, the "traditional" approach would be to build an oscillator for 42MHz and then mix it with 28MHz IF. Well, I don't have such a crystal so I have started with a 20MHz crystal oscillator and a frequency tripler to give me a LO of 60MHz. This mixed with a 10MHz (30M) IF will get us to 70MHz.

Here's the LO:


It's output looks like this:


and its harmonics like this:


So I need to feed this through a low pass filter, which inits simplest of forms, looks like this:


The one I have made above sweeps like this:


So this is looking like a reasonable start.

I need to make the down converter next, this will be made with some dual gate mosfets - I've ordered some BS981s which should perform well at these frequencies. Hopefully they will drop through the letterbox any day soon.

Cat's not been helping much at all today:



Good egh?

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