Simple Spot Frequency Marker.         All photos copyright John Mills, last updated 4 January 2010 Here is a useful spot frequency generator based around a programmable CMOS Frequency Divider made by KSS Kinseki (Now part of Kyocera) type KSS-EXO-3C. The unit is a 8pin DIP package, originally designed to be used as a single frequency CMOS clock. Besides having a Fundamental output (Fo), the unit has a built in divider allowing a further 8 divided frequencies to be obtained (Fo/n) The unit requires a power supply of 3 - 6 vdc. I soon realised that with the addition of a switch, and some diodes and pull down resistors, the unit would be a good, cheap spot frequency source suitable for checking valve receivers etc. The frequency accuracy is quite good, but not to exacting standards, however for quick alignment checks it is fine. In fact the stated accuracy is +/- 100ppm, and checks on my own unit showed the frequencies to be very near the expected, certainly more accurate than the frequency resolution needed for valve receivers. I built my unit onto a small piece of copper stripboard, and with the inclusion of a 5v regulator this allows it to run from a PP3 type 9v battery built into the case. As can be seen from the Standard Frequencies Table, the most useful original (Fo) frequencies are 12MHz, 16MHz or 20MHz as these divide down nicely for at least 4 or 5 divisions. However I found that supply of the 12MHz version is limited, but the 16MHz and 20MHz versions are available easily from Rapid, from where you can also download the full data sheet. I settled on the 16MHz for this build, but plan a second one soon using the 20MHz chip. The case used was an OKW type A9406344 which has a built in 9v Battery compartment. I have shown the top and bottom stripboard layouts and along with the pictures this should be all you need to duplicate this project. I took the precaution also of adding a 10nF cap to each output from the IC to be safe. However if fed into an antenna socket this should not prove a problem. Since there is no easy way to attenuate the signal, in a lot of cases the unit only needs to be in close proximity to the receiver. Harmonics appear usable to many hundreds of MHz as well. My unit has two outputs, one being Fo = 16MHz, the other being switch selected for 8MHz, 4MHz, 2MHz, 1MHz, 500kHz, 250kHz, 125kHz and 62.5kHz.  Using the 20MHz version will output at traditional standard frequencies of 10MHz, 5MHz and 2.5MHz, so anyone able to receive WWV can check accuracy if required. Click on either picture above for a larger view All diodes 1N4148 or 1N914 general purpose silicone C1 must be as close to IC1 as possible Note: A wire jumper must connect the +5v from the 78L05 to the +5v pin at the top left hand of the board. Earlier version without 78L05 Click for larger image Click for larger image Stripboard layout designed using LochMaster3 from Abacom software Black rectangles are breaks in the copper track Circuit & design © John Mills.