A Story of Stupidity

Screen Shot 2015 11 19 at 7 58 50 AM

I am an idiot…

I was going to fire up the rig down on 75 meters last night. I switched on the TS-990, checked all the coax connections, turned on the antenna tuner, turned on the amp in standby mode. I found an empty frequency down around 3915. I put the 990 in AM mode, turned the power down to 5 watts, double checked everything, and keyed the mic to make sure the SWR and all the fun stuff was good. The PalStar’s display told me the SWR was 1.05:1 going out to the dipole and I was putting out the right power. The amplifier didn’t start on fire, always a good sign.

So I kicked the amp into ‘operate’ mode and keyed the mic again…

Now, putting 5 watts drive into that amp in AM mode will generally result in about 107 watts output when you key the mic. I looked at the readouts on the PalStar… I was putting out a whopping 10 watts…

WTF?

I looked around. Sniffed. No smoke. That’s good. Nothing exploded. So why was I only putting out 10 watts?

I bumped the output of the Kenwood up to 15 watts in AM mode and keyed. The amplifier clicked and lots and lots of red lights came on.

Oops…

The amplifier, sensing impending doom, and done what it was supposed to do and shut itself down instead of starting the office on fire or exploding or something equally annoying.

So what was going on? It will do that if there is excessively high SWR or something abnormal going on. But it doesn’t tell me exactly what happened.

Well, first thing that comes to mind is the antenna, that it fell down and was laying on the ground. And since my dipole is held up by a combination of para-cord, bailing twine (literally), a plastic fence post and a very elderly apple tree, and we’d had some pretty good winds, the possibility that the antenna was down was highly probable. So I grabbed a flashlight and went to look. Nope. Antenna is just fine.

Now what? The jumpers connecting the transceiver, tuner and amp together? That seemed highly unlikely. They were almost brand new, ultra-low loss coax with silver plated connectors. But still, such things do happen sometimes. I got out my meter, checked all of the jumpers. All were fine. I considered just replacing them all just to be on the safe side, but I am one of the laziest people I know, and the prospect of spending a half hour or more cutting coax and soldering connectors was not very appealing, especially when the cables tested OK.

So I looked more carefully. I dialed the Kenwood back down to 5 watts output to minimize the damage if something went weird, re-set the amp and tried again. The PalStar’s meter was telling me everything was fine. Power output good, SWR damn near excellent. But a quick glance at the amp’s meters everything looked okay… Kicked the amp on, edged the Kenwood up to 20 watts AM which should have given me about 700 watts output on the AMP, and keyed the mic for half a second…

Holy shit! The meter on the amp immediately jumped halfway up the scale and it immediately tripped out.

Well, that was interesting… Why was the PalStar’s meter telling me my SWR was 1.05:1 when the amp’s meter was telling me it was closer to about 7:1??? Either something inside the amp was funky or the coax jumper from the amp was bad despite what my testing had indicated…

I turned the 990 back on and…

Oh shit

Dear Lord, how could I be that stupid? I wasn’t in AM. I was transmitting in FM. Oh for heaven’s sake. The amp can handle AM, SSB and CW. Definitely not FM. It hates FM. No wonder the poor thing had been tripping out.

But what about the difference in the readings between the PalStar’s meter and the amp? I looked…

Oh no… I felt like banging my head against the wall.

The amp’s meter wasn’t set in the SWR position. It was in the power position. What I was reading wasn’t the SWR at the amplifier, it was the amount of power it was putting out. There wasn’t an SWR of 7. I was reading an output power of 700 watts…

So I’d spent almost an hour trouble shooting a problem that was due entirely to me not bothering to read the display on the 990 and seeing I was trying to transmit in FM instead of AM, and failing to notice that I’d somehow managed to change the meter on the amp from SWR to power…

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