For clarification, adding an attenuator doesn't guarantee a 50ohm load
to the rig regardless. An attenuator makes VSWR lower, the amount of
improvement related to the value of the attenuator.
For example, using the 2dB value featured in the link Mike gave, in
round numbers, a 3:1 VSWR upstream will look like 2:1 at the rig; 2:1
upstream will look like 1.5:1 at the rig and so on.
A higher value attenuator gives greater reduction in VSWR at the rig side.
The trade off for improved VSWR is that attenuator will dissipate power
and need heatsinking - at least 37% of what you feed in for 2dB value
and higher for higher values.
It's a good way to reduce interactions between amplifier stages and many
professional designs build them in to deal with awkward problems.
Steve G8GSQ
For an input SWR when using a solid state amplifier against a PT2500 Amplifier,
why not use something like this? It will provide a 50hom load to the
transceiver input regardless of the band exercised. They offer 1db, 2db on up
of attenuation, and are matched at 50ohms to the Transceiver input of the amp
all the way to 1Ghz or better. The point being here the transceiver will always
see a ~50ohm load. Just a thought.
https://www.ebay.com/itm/370603866564?hash=item5649b639c4:g:s2sAAOSwLzdWRTy4
Thank you,
Mike
W5CUL
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