|Subject:||Re: [TenTec] Tentec Orion & Oscilloscope question|
|From:||Ken Brown <firstname.lastname@example.org>|
|Date:||Tue, 23 Nov 2004 18:11:33 -1000|
I'd like to know the better way to take the "modulated signal" to inject
it into an oscilloscope ?|
Someone already suggested a 30 dB 100 watt (or greater) rated attenuator. This is probably the best method if you only want to monitor while you are not actually radiating a signal. Remember though, that a Tektronix 453 (and most oscilloscopes) has a 1 megohm input impedance. If you really want an accurate voltage measurement, and an accurate 30 dB loss through the attenuator, then the output of the attenuator needs to be terminated with a 50 ohm load. If you monitor the voltage at the output of the attenuator, across the 50 ohm load, with the 1 meg input of the scope, the effect of the 1 meg paralled across the 50 ohms will be insignificant, and the measurement will be quantitatively accurate.
On the other hand if you are more interested in a qualitative measurement of your modulation waveform, without much importance attached to the absolute amplitude measurement, there are much cheaper ways to do it, that can also allow you to monitor while you are transmitting into an antenna (without 30 dB attenuation of your radiated signal).
If you were to thread a short piece of insulated wire, say about 22 AWG or smaller, a few inches long, inside the sheild of one of you coax jumpers, perhaps between you transceiver and your antenna tuner or antenna switch or other accessory, it could be used as a signal sampler. one end of the wire would connect to the shell of a BNC female connector and the other end to the center pin. Then a BNC to BNC cable from there to the o'scope input would do it.
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