I posted the following question to Yahoo’s HamRadioHelpGroup:
I’ve heard this talked about a lot – but don’t really understand.
What is a “final”?
What causes one to “blow the finals”?
How do you know if you have “blown finals”?
73 Scott KD7PJQ
Final output transistors. They are what generate the power going to the antenna. If the radio is in TX mode for too long or transmitting into an improper load for too long they will get hot from the SWR or just the power dissipation and can get damaged or “blown”.
Inside a transistor package there is small silicon die that is the actual transistor. Gold or aluminum wires connect the connection pads on the transistor to the leads on the package. These are usually what gets “blown”, and they heat up and the attachment points let go, although it’s not uncommon for the actual silicon crystal to melt across the junction. The attachment if usually done by ball bonding or wedge bonding, which is just to smash the end of the wire which is shaped as a ball onto the aluminum pad on the silicon.
> What is a “final”?
Short for “final amplifier” (tube or transistor) in your transmitter.
> What causes one to “blow the finals”?
Some combination of output power level and antenna mismatch.
> How do you know if you have “blown finals”?
Transmitter not transmit.
73 de W3GERry