I recently got a Yaesu FTDX-3000. It's an amazing radio. The DSP and filtering are extremely effective, and it almost makes the FT-991A feel like a toy, which is most definitely is not.When the radio arrived I carefully installed Anderson power poles to the factory DC cable and applied power. The radio came to life.
A bit of background. For roughly the last year I've concentrated on FT8, with the exception of Field Day, which was done outdoors using SSB on the FT-891 (yes, I like Yaesu equipment). In the shack, which is on the second floor of my home, 98% of my operating has been on digital at powers not exceeding 30 watts. My radios are powered from one of two Astron RS-35 linear power supplies, using cables that I carefully made with eye hooks and power poles. Being on the second story raises the specter of effective grounding. I had strung a copper wire down to the grounding rod associated with a whole-house 30KW generator, which was itself bonded to the house entrance ground. It all seemed fine.
After spending some time marveling at the FTDX-3000 receiver, I tried transmitting at CW signal at 100 watts. I keyed down and WHAM -- the rig rebooted! Was this a bad unit? I tried again and WHAM -- the rig rebooted again. I tried a different band. WHAM -- reboot. I tried reducing the power to 50 watts. WHAM! Reboot! I shut down and went to bed, sorely disappointed.
The next day I suspected grounding issues. Specifically, I wondered if I had a good DC ground but a poor RF ground. After putting in a much more respectable ground with a shorter path to a cold water pipe and bonding to the house entrance, I tried again. WHAM! Another reboot.
Well, I thought, maybe RF from my end-fed long wire is dumping RF into the shack and affecting the sensitive electronics in the '3000. I lowered the power to 20 watts and was able to transmit. I increased the power to 30 watts and was able to transmit. At 40-50 watts, however, the radio rebooted. So I tried winding some feedline chokes, and it seemed to make a little difference in that now I could transmit a little over 50 watts before encountering problems.
I ordered a common mode feedline choke from MyAntennas and that seemed to help a little -- and my noise floor decreased, which was nice -- but the radio still wouldn't get much above 50 watts before rebooting.
I tried disconnecting everything from the radio and transmitting; the problem persisted. I tried cleaning oxidation off fuses; the problem persisted. I disconnected all other radios from the RIGrunner power distribution system I use; the problem persisted. I put ferrites on all the power and other cables; the problem persisted.
A local amateur with whom I had been discussing the problem suggested shortening the power cables, which come from the factory very long. I didn't do that, but I did try a new power supply, figuring that the higher current drawn on the higher power might have uncovered some instability. When I went to remove the eye hook connections on the power supply, I saw that the positive power cable was brown and stiff -- charred, in fact -- around the eye connector.
It turns out that the eye hook I had installed was not heavy enough to carry 20 amps. The rig was rebooting because it couldn't draw sufficient current to transmit. Because I had operated at lower power levels until now, the issue had never surfaced.
I felt like such a rookie.
There a many lessons here, but perhaps the most fundamental is that, when encountering such problems, always start with the power. If I had simply looked at the power cables at the power supply unit source, maybe it wouldn't have taken three weeks to identify the root problem, which was easily solvable.
Of course, my station is now much better for all the things learned and steps taken to harden my setup. This hobby is so great that teaching lessons.
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