RF In The Shack

blog/_posts/2023-01-20-sudden-rf-in-the-shack.md

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+---
+title: Sudden RF In The Shack
+layout: post
+date: 2023-01-20 16:21:22
+tags: Ham-Problems
+excerpt_separator: <!--more-->
+---
+
+We all hear about it, we've probably experienced it, and we've all done our fair share of fighting with it.
+So what happens when RF decides to suddenly appear in your shack? How did I solve this latest problem? How
+the hell did I even notice it in the first place?
+
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+
+Last night while on a weekly video chat with some other hams, I decided to fire up the rig and run some FT8.
+Everything seemed normal until I went to tune my antenna. I was greeted with funky operation from my rig, and
+the sudden death of everything plugged in to that USB hub. That one was easy; turns out the shield connection
+to the USB Hub (which has seen much much better days) had broken from the board. The solution was a 40 minute
+operation where I removed the old, short, flat USB cable; and replaced it with a spare. Nothing complicated
+here, just a simple cut and solder job. Being essentially a glorified electronics technician by trade for 
+almost 20 years, I learned my way around a soldering iron. The tight quarters of a small "travel" USB hub did
+add to the difficulty, but I've got the small tips needed for the job.
+
+This went smoothly. After wiring up the new cable I plugged everything back in and not only did it work; but
+no more cutting out on TX. But there was a new problem, one that most hams probably don't have in their shack.
+
+I was getting RF in to the audio system.
+
+My shack does double duty; it's both a shack and an office. Since I'm an audio guy at heart, I keep my "good" 
+sound system down here. Sometimes it's nice to listen to something while working FT8. But during the test TX
+for the hub, I noticed the other RF problem. My audio was buzzing before cutting out. It will do this on 17
+and 15m; due to the fact I do have an antenna practically running over my head. But not on 40m; and not enough
+to make the audio cut completely out. It wasn't a problem the other week, so I knew something had changed.
+
+My first step was trying to see where the problem was coming from. Was it the headphone amplifier, the pre-amp, 
+the DAC, or the EQ? I turned volume knobs down and quickly determined it was either the EQ or the DAC; and
+watching the status of my devices along with the DAC display told me it wasn't that. It left one culprit, my
+Sansui SE-8 Graphic Equalizer. This thing has had it's issues in the past; both from RF and age. I blew the 
+spectrum analyzer circuit years ago with a 10m FM transmission; watching all the bars max out and blink before
+dropping silent. No big deal. It was also the source of some of the buzz on 15m when TXing; since that's one of
+the few times the spec-an on it registers any activity. But this buzzing and going in to it's power-on-reset was new, 
+especially on 40m. 
+
+I checked a few things inside, rearranged some wires, and verified I still had ground connections. All of that was
+fine, no change there. But what changes had I made since putting the antenna back up and getting the FT-1000MP on the
+air? Well, nothing; at first. But I recalled some behavior that lead me to my next path, the antenna. I had noticed
+that when my tuner wasn't properly tuned; I'd get more buzz. I run a balanced-line fed doublet; and then I remembered
+I had risen and lowered the antenna due to bouts of wind recently. I went to the "interconnect" I have from the tuner
+to the feed-line coming inside. The level of noise was not dropping nearly as much when both sides were connected. 
+AH-HA. I bet one of my solder joints broke. 
+
+I wish I could explain why I soldered my feed-line vs crimping it; it was just something I felt like doing. I've
+actually built two versions of this doublet, my original from 2015 and a replacement in 2018; but I kept all the
+balanced line. Sure it might look rough and be kinked in spots; but it's still perfectly usable. In 2018 I had one
+solid un-spliced run on my antenna; it performed no better or worse than the previous one with splices everywhere.
+I had once read the most important thing when working with this stuff, aside from keeping it away from metal, is to 
+maintain the spacing of the conductors. This was one of the reasons I stuck with the stuff; not only was it's 
+performance suited for the application, but you can actually splice it back together. There's no worry about water
+ingress damaging it like coax, so even the old pieces I tossed under the shack for storage were easily able to be
+put back in to service. 
+
+How do I keep it from falling apart and stranding my antenna in it's raised position? Zip-ties. I run a couple of 
+zip-ties through the "windows" to act as somewhat of a physical strain relief, but mostly backup support. If things
+broke at a splice...the ties would still allow me to lower the antenna. 
+
+So, I went outside, loosened one leg of the antenna, and began lowering it via gentle tugging on the feed-line. It
+was then I saw it; one of the splices had broken. "This explains everything," I thought to myself. The one side's
+solder joint was still strong, only the one had failed. It was the last one of the repair job, so I was likely
+tired and having issues getting it to flow; that solid core just sucks up the heat and the flux core in my "antique"
+solder probably isn't much good anymore. 
+
+I cut the wire from the center insulation enough to jam a crimp splice on to it, making sure to keep the overall
+length matching the good leg and crimped it down. 
+
+Of course, while doing this; the wind decided to blow the feed-line out of reach while working on it. It was probably
+too windy to safely keep the antenna up, so I'll have to wait and confirm my repair worked. However, I'm *really*
+confident it will do the job. The other splice was still intact and since the radio was still receiving things; I
+knew the patched-up leg wasn't an issue.