Icom IC-7300 4m RF Overshoot

[@mikewillis1592]

Hi Tim, The answer is to use a power attenuator rather than power control to set the drive for the linear. That applies on all bands because even if there were no overshoot, one day you will forget to turn it down and send full power into the amplifier.

[@hamtek]

Luckily the amp has an AGC so it backs off the radio output if I forget! (It has protection as well apparently but I’ve never tested it). I used to use an attenuator but it was a pain to take in and out (to run 100W without the linear) and reduced the RX as well as TX. I suppose I could have come up with a switch or used a pre-amp, but I chose to control the audio and connect it directly. Are you surprised by the amount of overshoot? I supposed it could just be a fault in my radio.

[@ok2it]

@@hamteki agree with Mike. Even back in days when I ws running QROO on VHF and used Javornik Transverters and FT1000MP, I opted out for 100W into 30dB 100W ATT as I got the best results. Now when I need AMP to be driven, I usually go with dedicated setup. I saw simillar behaviour with other rigs, including IC756PRO3

[@TonyLing]

I wonder if this problem being only observed on 4m is as a result of the 50W reduced power output on this band.

[@hamtek]

I'm not sure, I haven't investigated it further. If the power limit is controlled by the AGC then it could well be. If I ever get around to working it out I'll post it here 😀. Thanks for your comment.

[@johnsonimagineering]

The problem is "ALC" overshoot on that particular radio. I've experienced the same problem on the 40 meter band. The gentleman who made the following video has correctly pinpointed the problem cause and has come up with a novel solution: kzbin.info/www/bejne/rJewnGyGrdWCrdU I hope you find this helpful. I did and was able to correct the issue on my Icom 7300 this morning by using the ALC interconnect between the radio and the ALC linking circuit on a Palstar LA-1k amplifier by providing the 7300 with a reference voltage. That seems to prevent the spike. Gaines Johnson N8FSD.