|SSA.||Simple Spectrum Analyser (SSA).||13/5/07|
|VHF.||VHF Comms based Analyser.||-|
|HP 141.||8552B, 8553B + TG & 8555.||-|
This is a low cost design by Roger, based on an original idea by K2BLA in QST November 1985 with later modifications. The operating range was 1 - 90 MHz and uses an oscilloscope as the display. Components were conventional and readily available at the time.
I bought the 3 PCBs and assembled them according to my own requirements. For instance, I decided to use a first IF of 170MHz instead of 145MHz. I considered that running an IF on 2 metres might cause confusion if a 2m TX was being tested! The 3-section helical bandpass filter on 156MHz was harder to source and more expensive than the specified Toko one on 145MHz.
As can be seen in the photo the project is not really finished - I still have to apply front panel markings. I would also like to do more performance testing and circuit adjustments.
Left to right (5x Control knobs):
Bottom row(Coax Socket & Switches):
Top left (2x switches):
Top right LED:
Marker area at the bottom (10MHz xtal osc and divide by 10 IC)
Note the long shiny multi-turn pot on the front panel for Coarse Frequency Control.
This was rather an ambitious design by DB1NV published in VHF Communications. The series of articles started in about 1989 and with additions and updates, ran on for many years. Luckily, I was able to buy the main PCBs from the publishers; gradually I managed to obtain most of the required components or near equivalents. Some crucial parts were not available so I had to do some of my own design and evaluation to arrive at a usable system. I failed to finish building it before my retirement. However, later on, I did get the chance of completing and testing some of the important units using testgear, during visits back to work. I think the last time I worked on it was in 1994. This is why it looks so unfinished!
Most of the project seemed to be working in 1994 to some extent. However, at this stage of build, what is needed is a good spectrum analyser, a high frequency scope, a stable signal generator and external regulated power supplies. More important still is time and a good active brain!
The miniature socket between the two BNC sockets supplies DC power for an active probe. I bought an old Tektronix probe that works well to at least 100MHz. The isolation it provides often makes it very useful for in-circuit testing.
Space for Marker & Input RF Filter boxes *
Input Mixer, IF (465MHz & 10.7MHz), Log Amp Variable Bandwidth Xtal Filter (10.7MHz)
Phase Locked Loop (0.465-1465MHz)
Space for Pre-Regulator box * (+20v, -20v, -9v, and +35v)
Space for Precision Regulators box * (+15v, -15v, and +30v)
Microstrip VCO (0.465-1465MHz)(1st LO)
* = Circuits designed but not built
|Internal view - top.