22.
Measuring the notch-deepness of the completed filter.
General info.
22.1 Measuring notchdeepness without professional equipment is a tricky bussines. You are measuring at levels of abt. 100dB under the used signal generator output. It is difficult to avoid, that signal from the generator creeps directly into the sensitive detector, bypassing the filter.
22.2.1 Use, if nessasery, ferriteclamps over all the cables to prevent HF-currents on the ouside.
22.2.2 Keep generator and detector separated as far away as possible, with the filter in between them.
22.3 Notchdeepness is easy measured with a signal generator which is well shielded and filtered, has a calibrated attennuator and a max. ouput of at least 100mV.
22.4 If you are lucky to have a well shielded and filtered bandscope or spectrum analyser, you have an ideal sensitive, wide-range signal detector. Combined with a good, shielded signal generator with attennuator, you do not need extra attenuators.
22.5 If you should want to use an amateur- transmitter as a power-signal generator, use a small, well sheelded, BATTERY-powered portable of 350mW or less. Connect it DIRECTLY to the filter trough a (home made) shielded 20dB attennuator.
22.6 Avoid the use of a mains-powersupply for the transmitter, as signal will be radiated by the powerwires, and also will slip into the receiver through the mains-supply.
22.7.0 If you want to use an amateurreceiver as a sensitive detector, try to find a battery-operated one, which is very well sheelded.
22.7.1 Best use a battery as a power"supply".
22.7.2 Connect the battery directly to the receiver, or with as short as possible leads. This to avoid the pick-up of generator-signal trough the supply-wires or the mains.
22.7.3 In this case, you need further (home-build) step-atennuators with steps of 1, 2, 4, 8 and 16 dB; and some extra atennuators of 20 dB (see the ARRL-handbook how to build them). Total max. attennuation should be abt. 100 dB. They must be well sheelded.
22.7.4 Avoid long cables and unnessasery couplings.