Our Field Day group has a set of these filters, like this 40 meters one,
https://www.dxengineering.com/parts/lbs-pb-f200-7
In the back of my mind I have two ummm "Specifications" That in the back
of my mind are true,
But I can not find any documentation to verify what I am thinking is
actually true.
It all has to do with SWR.
1- To have the filters provide the ultimate best rejection they can
provide the impedance must be as close to 50 ohms as possible.
Is this true? If it is, is there any published data showing how much is
lost on performance due to "X" SWR?
2- This one is even more important. They are rated 200 watt units. "At
50 Ohms"
Now SWR that is NOT 50 Ohms Can make some pretty high voltages true?
And I am assuming these voltages are what gives each unit it's power rating.
Go too high and fry a cap.
Now Our Station, (The only CW station) will be running a K3 with the
Roofing filters. My Partner in this station says,,,,,
Picking up a K3 tomorrow.
We will be using it at field day. It has a 400 Hz roofing filter, 100 Watts,
internal tuner, USB interface, upgraded synth and the nice IO board.
Should be on the air for SST Sunday night.
Jim
Now I know we will be clean on Transmit, To an OCFD.
That 400Hz roofing filter, How much will that protect US, see we will be
surrounded by several IC-7300's
Would like to use the Band Pass filters to help but not sure if they can
handle the not perfect SWR that a typical OCFD will give us.
I assume if we had to we can add an external manual tuner, to make the
SWR flat then go to the filter and rig.
And the external manual tuner would also add in some band pass filtering
effect too.
Joe WB9SBD
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