Saturday, August 29, 2020

QO-100 A1A up-link idea

This is something I had in mind for quite some time by now. What about an A1A only up-link for QO-100?

This is an old idea. At the time, this idea was to create a CW transmitter for 70cm based of a 2m signal. I have seen similar attempts to get something transmitting on 3cm. So, why not on 13cm?

Having done some "maths", I came up with a carrier of 96MHz, which is available as a regular crystal.

With a factor of 25, this will result in a 2.4GHz frequency.

Now, why is that interesting? The multiplication of 25 can be achieved with 5 x 5 .... dahhhh. Yes, sounds simple enough. Here is the interesting thing, it should be easy with a square-wave oscillator to generate 480MHz. At this frequency, it is pretty easy to build a strip-line filter or cavity resonator to clean the signal. Now, we just have to multiply the signal again. So, we might want to use a non-linear amplifier again, in order to create all the wonderful harmonics. Again, a 2.4GHz resonator should not be to hard to build.
And here is the idea. What if we used a rather high powered amplifier at 480MHz, which is easy to build, and a non-linear element to generate all those harmonics at decent power.

With a VTCXO of 96MHz, slightly pulled by a few kHz, one should be easily creating a signal in the CW band of QO-100, using the above mentioned method.