Cross posted to Tacos / Amrad and also Amsat-BB as it may interest homebrewers.

I made a ugly bug (well, The PCB was very nice when I started, and really convoluted when I finished .. ) frequency marker box (from junk parts). I will donate this to K3GWU amateur radio club and research station for general use.

I used (what I had) 3.68 MHz, 40 MHz, 50 MHz, 60MHz sealed crystal oscillator.

I used a voltage regulator and bypass caps to feed power into the units via individual switches, so I can turn on any combination manually of the oscillators, or all or some at the same time. I then combined the inputs into a common point and from that point used a 10 pF capacitor to get an output to an SMA bulkhead connector through a brass box.

Of course, I then needed a 3.3V regulated output for a microprocessor so I put in an additional 3.3V LDO as well inside the bus and all components are happy now. I even put an LED just to satisfy my curiosity and then sealed all in a box.

I do see on a simple analog scope all wave forms and my frequency counter shows the fundamental frequencies produced. A spectrum analyzer (thank you K0BRA) shows different products of the frequencies.Obviously the frequencies I saw were just whatever the crystal oscillators I had on hand, so they can be replaced, or added to.

In this line, what improvements could I do to make it an useful general purpose box for testing in the radio shack, and for AMSAT birds, is there anything of interest that might be useful to qualify a station ? One could use a microprocessor to switch in circuits, that much I can do, but which type can be used to generate accurate frequency standards ? If only a clock pulse generator (square wave) source was available, what type of circuit would allow multiple frequencies be slaved to a crystal standard ? Any old schematics reference would be appreciated.

I even saw how easy it is to use a audio transformer to modulate the power leads and transmit QRP AM on the 0.5m length RF cable. I can now use this to verify operation of the RF splitters and combiners.

73 de N3RDX @ K3GWU

if you are in Foggy Bottom area of DC and have an interest in ham radio, I'm at GWU.