Re: [TenTec] Tentec Orion & Oscilloscope question

[Ken Brown <ken.d.brown@verizon.net>]

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.

Have fun.

DE N6KB

>  


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