tag:blogger.com,1999:blog-6865153472775099637.post4397316452518260326..comments2022-12-12T20:04:19.488+00:00Comments on Radio Adventures @ G4GUO: MRF300AN 71.5 MHz amplifierG4GUOhttp://www.blogger.com/profile/15634884412587660320noreply@blogger.comBlogger4125tag:blogger.com,1999:blog-6865153472775099637.post-84387076792281644252022-12-12T20:04:19.488+00:002022-12-12T20:04:19.488+00:00If you are using the application note and are oper...If you are using the application note and are operating in the frequency range specified by the note, then you can assume the impedance is 50 ohms.I didn't use the app note but used an inductor and a couple of mica trimmers on the input and output, that way I was able to retune it to a different frequency. The idea was to match it at 71 MHz, then measure the conjugate match at both ports. From that, I was going to build a custom matching section that did not require the variables. I never got around to the 2nd part of my plan. G4GUOhttps://www.blogger.com/profile/15634884412587660320noreply@blogger.comtag:blogger.com,1999:blog-6865153472775099637.post-77730015856036365262022-12-11T23:22:13.472+00:002022-12-11T23:22:13.472+00:00I just start experimenting with MRF300AN. Would yo...I just start experimenting with MRF300AN. Would you inform me about input and output impedance ?<br />If I make the circuit according to application notes, can I connect 50 ohm impedance signal source directly to the circuit input ?<br />ThanksAsep Jagawanahttps://www.blogger.com/profile/10590083755687829901noreply@blogger.comtag:blogger.com,1999:blog-6865153472775099637.post-78523321291152225832018-10-25T09:15:26.051+01:002018-10-25T09:15:26.051+01:00Hi Steve, the amplifier shown was a test jig for c...Hi Steve, the amplifier shown was a test jig for characterising the large signal parameters at 71 MHz. I blew one device up through inadequate cooling but the forced air cooling cube seen above is adequate to cool the device @ 250 Watts with no drift in bias etc as it heats up. I thought the whole idea of the plastic package was to remove the need for a copper carrier. The final amplifier will run at about 40 watts so cooling won't be an issue.G4GUOhttps://www.blogger.com/profile/15634884412587660320noreply@blogger.comtag:blogger.com,1999:blog-6865153472775099637.post-52331762639611692442018-10-24T15:08:17.392+01:002018-10-24T15:08:17.392+01:00Yours is the first PA work I have seen using this ...Yours is the first PA work I have seen using this interesting device. I'm interested to know what approach you find adequate for heatsinking...it looks like you haven't used the suggested method of soldering to a copper carrier.Steve VE3SMAhttp://www.qsl.net/ve3smanoreply@blogger.com