Fusor Forums

I have seen a lot of RF attenuators on ebay and Ali Express. My only concern is the very low VSWR (~1.2:1) rating for most of the 1dB attenuators widely availabel.

https://www.aliexpress.com/item/100W-N- ... 92558.html

Low VSWR is what you want, right?

Ian,

Make a 1dB attenuator to put on the output - you lose 20% of your output at the gain of not blowing the devices
This immediately means the VSWR can not go over 8.7:1 with a dead short or open on the output (the two worst possible cases)

8.71:1 indicates the maximum VSWR the amplifier can see with a 1db attenuator on the output. Here is more info on it
(http://www.rfcafe.com/references/electr ... uction.htm). But you are right about the desired VSWR. For maximum power transfer, you want a VSWR of 1:1. However since ICP sources have been known to be very unstable. This means that the VSWR can change. Since the 1dB attenuators listed online can only withstand a maximum VSWR of ~1.2:1, I might need to build my own. There are many designs for RF attenuators however since 1dB reduction means a 20W power loss when the amplifier is at its maximum output (100W), I need to find high power carbon resistors (low reactance) which is no easy task. Does anyone know if it would be a good idea to still use the attenuator listed online?

Erik
That VSWR figure is for the attenuator it is not its with stand rating
ie the attenuator matches nearly 50 ohms resistive
more here from my web site
http://www.iel-rf.com/AttenuatorsDescription.html

all you need is a 1dB 25 watt dissipation attenuator