Russell McMahon wrote: >> "Get an amateur license", >> "Get a Spectrum Analyser"... >> > > A remarkably good indication re spurious output level can be obtained with > one of the el-cheapo manually tunable black & white tvs. > > If you can place one of those near a radiation source and tune it over all > its bands without any audible or visual indication that the device is > transmitting (except on its fundamental) then you quite probably have a > clean signal. > > Not as good, but still useful, is to tune a portable radio aross AM and FM > bands and listen for any signals. > > Sensitivity is very high when very close so you can usually manage "spuries" > when the received is ON the tx that vanish at very short distances. > Good also for devices that are not intended to be transmitters, but are. > > Indeed there are several designs for simple spectrum analyser for 42MHz to 870MHz using a I2C controlled TV tuner and a PIC. With KS0108 128 x 64 panels now about 12 Eur, you can even build a hand held portable model. 10KHz to 45MHz can be added by using 25MHz or 50MHz crystal based 50MHz L.O. Mixer to up convert to 50.01 to 95MHz you can cover 870 MHz to 2100 MHz with a Satellite receiver Tuner I2C controlled (old stock Comtech under $10) and use the UHF tuner as 480MHz IF for it. My own spectrum Analyser is only got a 110Mhz plug in. (HP141T). I'm on the look out for a 18GHz plug in. But meanwhile I can put an old TV tuner with manual hand calibrated pot for tuning 85 - 300 and 410 - 880 (depending on band switch) and Spectrum Analyser set approximately 34MHz to 40MHz. Gives 10MHz bandwidth on analyser. I have a converted MMDS (2.5GHz) receiver as a front end for 2.4GHz band and can connect LNB and other Microwave receivers for 10GHz to 12GHz. Old VHS or TVs or analog Sat receivers are good source of free parts for such simple projects. You can even simply diode detect analog tuned (0.5V to 20V often) non- I2C old tuners with X-axis sweep of scope and feed diode to Y axis for a really basic analyser. Sweep rate needs to be quite slow. There is a good reason why the old HP141T has a storage tube. However in storage mode you can get down to less than 300Hz resolution and viewing 19KHz to 60KHz to see multiplex + RDS is possible, with 100K Ohm to 50 Ohm opamp buffer. I have a spare KS0108, 128x 64 and a 20x4 text and a nice box. Plus an LMX2430 synth with 400MHz to 800MHz and 800MHz to 1600MHz VCOs. by adding mixer and two filters that will give 10KHz to 2400MHz. I'll stick the UV917 I2C TV tuner, 50MHz converter, and comtech 900MHz to 1700 MHz I2C tuner in the box with batteries, keypad and the two displays to have a cheap portable signal generator / tracking generator and spectrum analyser. Also I have 100MHz to 3GHz noise gen I built. So connectors for external RF bridges too are in order to measure return loss/VSWR/Impedance of filters and aerials with tracking generator and detectors or noise gen and spectrum analysers etc. I have nice pair of drum attenuators from a scrapped piece of gear 1dB and 10dB steps that are good to 1GHz and a DC switched attenuator good for up 6GHz... But not today. Maybe in the Autumn. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist