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“NORSAT convertor”

On AMSAT-BB I often seen that amateurs having problems with their 13cm down convertors. I had also some problems with getting the local oscillator correctly tuned. The problem is that not everyone has expensive frequency counters till the 2400 MHz area.

I have here an self-made frequency counter, but is stops till 1800 MHz. Measuring the crystal was what I wanted to do, but it gave to less signal to drive my counter L Then I thought out some even more simple and more easier way to measure the oscillator frequency.

The frequency of the oscillator is 8.8125 MHz. When we take the 49^th overtone, then we have 49 x 8.8125MHz = 431.8125 MHz !!!!

When we use an reciever that can measure the center-frequency, than we can also measure the local oscillator of the NORSAT (Or maybe other) convertor. I have tuned my NORSAT convertor by using my FT847. The 2m can be used to feed the convertor with 12Vdc via coax. At the 70cm I connected an portable 70cm antenna and placed it close to the crystal of the convertor. The signal is weak but well detectable by the FT847. An FT726, FT736 can also be used, and many other types what are able to measure centre-frequenty. Below you can see an simple drawing how it can be done :

Making the LO more stable:

Below you can see how I made the local oscillator more temperature stable. It is done by using an MURATA heat-clip. The heat-clip is an metal clip that can be put over the crystal. At the metal clip an PTC resistor is glued. When an stabalised voltage is supplied over the PTC, it will warm up to an constant temperature. I used the 9V internal stabalised voltage of the NORSAT.

Here an close-up of the heat-clip:

This page is designed and created by PE1RAH. (William Leijenaar).