[Elecraft] Characteristic Impedance of Filters

Wed Jul 16 11:07:03 2003

Bill
A fast check is to look at the input and output capacitors of the pi
sections.
If they are the same, the filter is 50 ohms in and out, with no impedance
transformation.  That would be the job of the PA output transformer.
73, Bob N6WG

-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of William M.
Spaulding, Sr.
Sent: Wednesday, July 16, 2003 1:29 AM
To: Elecraft Reflector
Subject: [Elecraft] Characteristic Impedance of Filters

Hi All,

I'm wondering what the characteristic impedance of the bandpass filters is?
Since the switch impedance when on is probably 40 ohms or so, the filter
impedance must run in the 200 to 300 ohm area to avoid exceptional insertion
loss.

If all of that is true, then the output low pass filters make an impedance
transformation from the 50 ohms at the antenna to the 200 to 300 ohms on the
band pass side, since there are no other impedance altering circuits between
the input/output low pass bank.  Only the switches are there.

I think I need these parameters to solve my power level troubles!

Thanks,

Bill
NA7Y

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