This is..... by far..... the most technical forum that I belong to. For that reason, I want to try a question here to see what kind of opinions I get and ... more... what kind of backing information on "why".
I have a spectrum analyzer. It's input impedance is 50 ohms and it's max input signal is +10 dBm (10 mWatts). believe me..... I have that on an RF Tap because I KNOW that if I probed a CB radio....even at 4 watts.... direct...I would smoke the daylights out of the SA's input. My thinking is that this is because it is 50 ohms impedance.... so the instant I touch it to the 4 watt signal .....the SA is going to try to pull HALF of that wattage right on in BECAUSE it is low impedance.
But let's talk about a frequency counter.....with an impedance of 1 MegOhm and a max signal input of 150 VRMS.
I think that a great many .....STILL say that this should be put behind an RF tap to keep from damaging it.
My question is..... why?
With an input impedance of 1 Meg this is a whole different animal from the SA. At 1 meg the SA is not going to pull any meaningful current from that transceiver's RF output.....it will ONLY see the voltage. RF voltage at 10 watts would only be about 22 volts or so max which is well within the range of this counter.
With this in mind..... what is a good reason that this counter HAS to be protected by an Rf tap/attenuator.... when it looks as though the counter should handle it?
IF IT TURNS OUT that it is "for safety's sake only" I can accept that! I believe in protecting one's investment. I am just wanting to understand IF it is necessary...and IF So.. why?
Thanks in advance!
Bob
I have a spectrum analyzer. It's input impedance is 50 ohms and it's max input signal is +10 dBm (10 mWatts). believe me..... I have that on an RF Tap because I KNOW that if I probed a CB radio....even at 4 watts.... direct...I would smoke the daylights out of the SA's input. My thinking is that this is because it is 50 ohms impedance.... so the instant I touch it to the 4 watt signal .....the SA is going to try to pull HALF of that wattage right on in BECAUSE it is low impedance.
But let's talk about a frequency counter.....with an impedance of 1 MegOhm and a max signal input of 150 VRMS.
I think that a great many .....STILL say that this should be put behind an RF tap to keep from damaging it.
My question is..... why?
With an input impedance of 1 Meg this is a whole different animal from the SA. At 1 meg the SA is not going to pull any meaningful current from that transceiver's RF output.....it will ONLY see the voltage. RF voltage at 10 watts would only be about 22 volts or so max which is well within the range of this counter.
With this in mind..... what is a good reason that this counter HAS to be protected by an Rf tap/attenuator.... when it looks as though the counter should handle it?
IF IT TURNS OUT that it is "for safety's sake only" I can accept that! I believe in protecting one's investment. I am just wanting to understand IF it is necessary...and IF So.. why?
Thanks in advance!
Bob