Author Topic: Care and Safety for Spectrum Analyzers  (Read 87 times)

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Offline guitar_199

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Care and Safety for Spectrum Analyzers
« on: July 15, 2019, 10:16:51 PM »
Somewhat depressed.  :)

I picked up an older Hameg Spectrum Analyzer at a hamfest back in May.    I know very very little about them but I am learning fast.  Catching up on dBs, dBms, attenuation.....but the big thing I am concerned about is the safe handling of what I stuff in to it.   I know that you have to attenuate the transceiver down to a safe level but it seems that there are a number of ways to do this... and all of them appear to be in the thousands of dollars.  Not only that, I have not found any place that discusses just HOW you set them up.

Some say "use attenuators".   A nice 100W 40db would knock most low powered transceivers down (thinking 5 - 10 watt, I still love CBs!!!!!)  BUT here is the question.... if you go from the radio to the attenuator and the attenuator to the SA...... does the attenuator serve as a dummy load for the radio?  It says it is 50 ohms input and can handle 100 watts.... so I would think so...BUT I can't find a place that discusses it.

Others use samplers.   I have seen some that tap off of the RF on the way to or IN a 50 ohm dummy load.  They just tap resistors off...more or less a voltage divider... and take that point out to the sample port and feed it to the SA.     Is this calibrated enough to allow measurements?  And....the dummy load is dissipating all of the power...and the resistors seem to be high enough that they don't pull a lot of current....so they don't have to be very high powered themselves.   Again, I have found no place to discuss it.

Other people I see use directional couplers.   They seem to be a pass through for the main RF line that you might connect up to a dummy load AND they have a sample port that is some number of dB down.  If the dummy load is dissipating all of the power..... how much power handling does the directional coupler have to account for?   It doesn't seem to me like it would be much..... the dummy load is doing the real work.....but, again, I have found no place to discuss it.

From what I have splattered here.... does anyone know of a resource that offers this kind of info....    I really want to learn what options are for connecting these things up so I don't destroy it on the first go round.

Any ideas?

I would most certainly appreciate it.