As was posted on the Amps reflector a few months back: > The LDMOS devices are designed to tolerate 65:1 SWR, 3:1 probably
> wouldn't be a problem so where is the need for a tuner? Most ham antennas don't exceed 3 to 1 SWR even on the band edges. New amps that are constructed with LDMOS finals should be able to handle nearly all antennas without a tuner. Operating a legal limit amp into an antenna with an SWR greater than 3 to 1 should be avoided for many reasons, such as: poor radiation efficiency, harmonics, RF in the shack, RFI, etc. 73, Dick- K9OM In a message dated 4/1/2017 8:48:28 P.M. Eastern Daylight Time, [email protected] writes: Date: Sat, 1 Apr 2017 12:03:01 -0500 From: K9MA <[email protected]> To: [email protected] Subject: Re: [Elecraft] Amplifier Thoughts Message-ID: <[email protected]> Content-Type: text/plain; charset=windows-1252; format=flowed On 4/1/2017 09:22, John Perlick wrote: > In the case of a solid state amp, the output is matched to 50 Ohms or so. Period. So any mismatch means that RF is reflected back into the amp....where it is converted into heat. Depending on your SWR, that could be substantial! So let's say 3:1. Then 25% of the power is reflected. Note: at 10:1 you reflect 67% of the power so that means 500 W reaches your antenna and 1000W is dissipated in the Drain-Source junctions of your expensive RF transistors! Clearly, a practical solid state amplifier capable of tolerating, say, a 3:1 SWR needs an autotuner. (Very few of us have the luxury of perfectly matched antennas across all bands.) That said, the autotuner should permit maximum flexibility, including multiple settings for the same band. There should also be an easy way to change settings, so the amplifier can be easily integrated into the station control system. 73, Scott K9MA ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
