I don't have any antenna or RF impedance bridge that I trust. So the 50 ohm termination and "infinite" impedance test is all I have.
Regards.
Max. K 4 O DS.
Email: max@...
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----- Original Message -----
From: "Patrick Wong" <patwong3@...>
To: <hp_agilent_equipment@...>
Sent: Tuesday, December 25, 2012 9:16 PM
Subject: [hp_agilent_equipment] Re: 608 output attenuator.
Hi Max,
I'm not sure how this proves the attenuator is OK. If you use an oscilloscope with the option to select between a 50 ohm input and a 1M ohm input, the 50 ohm input will typically result in vertical deflection ~50% of the high impedance input.
The use of a 50 ohm passthrough adapter on a 1M ohm input, is a reasonable equivalent of selecting a 50 ohm input on the scope's vertical channel, at least until you reach a sufficiently high frequency so the passthrough adapter starts to display a reactance component.
If you have access to an antenna analyzer like an MFJ259B or MFJ269, then you can measure the VSWR of the 608 antenna output. I would say that is a reasonable test if you do not wish to remove the attenuator to physically inspect and measure the resistor(s).
Patrick Wong AK6C
--- In hp_agilent_equipment@..., "Max Robinson" <max@...> wrote:
...Today I checked it again the way I had calibrated it
with a short cable and a pass through 50 ohm termination at the scope end.
I set the frequency to 10 MHz and the attenuator to 100 mV to be sure there
would be no proximity effect between the pickup coil and the output tuned
circuit. With the scope reading 100 mV within accuracy spects I then
removed the termination and measured 200 mV within accuracy spects. From
this I conclude that my output attenuator has not been damaged by someone
transmitting into it.
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