Radio attenuation with resistors

[Andrew Howard]

I was just wondering, if you have a high frequency radio with an
antenna, what would happen if you put a resistor before the antenna (in
parallel and/or series with).
Would it just attenuate it, or are there other effects as well?
Would doing the reverse (removing a resistor) stuff any thing up?

Thanks
Andrew Howard

 

[Andrew Holme]

Andrew Howard wrote:

I was just wondering, if you have a high frequency radio with an
antenna, what would happen if you put a resistor before the antenna
(in parallel and/or series with).
Would it just attenuate it, or are there other effects as well?

Yes, a large resistor in series, or a small resistor in parallel, would
attenuate the signal. Small / large in this context is relative to antenna
impendance which is normally pretty low e.g. 50 ohms.

Would doing the reverse (removing a resistor) stuff any thing up?

It depends. If the resistor is acting as an attenuator, then removal might
cause overload.
If the resistor was biasing the gate of a JFET pre-amp then removal would
stop if from working.

 

[Andrew Howard]

Andrew Holme wrote:

Andrew Howard wrote:
I was just wondering, if you have a high frequency radio with an
antenna, what would happen if you put a resistor before the antenna
(in parallel and/or series with).
Would it just attenuate it, or are there other effects as well?

Yes, a large resistor in series, or a small resistor in parallel, would
attenuate the signal. Small / large in this context is relative to
antenna
impendance which is normally pretty low e.g. 50 ohms.

Would doing the reverse (removing a resistor) stuff any thing up?

It depends. If the resistor is acting as an attenuator, then removal
might
cause overload.
If the resistor was biasing the gate of a JFET pre-amp then removal would
stop if from working.

Thanks for the info.

Andrew Howard