Greater love than this no man hath, that a man lay down his life for his friends.
Catholic Hams have fondly and unofficially taken St. Max on as our patron saint, the patron of Amateur Radio operators, worldwide.
St. Max, ora pro nobis!
They say that confession is good for the soul - so I will confess. Yesterday, I replaced the coax running out to my Butternut HF9V. The coax has been there for umpteen years since I put the vertical in place in 1999, about a year before my son Joey was born. It's been a while now that I've wanted to replace the coax and last Autumn, I purchased some 9913 from DX Engineering, My good intention was to run that coax out to the antenna before last Winter began. You know what they say about good intentions.
Yesterday, the weather for the chore was about as near perfect as it gets. It was sunny, warm, but not hot, with a slight breeze and low humidity. I began by putting on the work gloves and pulling up the old coax. It's been such a long time since I put that coax down; and I was mortified by what I discovered.
Connected to the Butternut's matching stub was a barrel connector and then a 100 foot run of LM-213. At the end of the 100 foot run was another barrel connector and a 25 foot run of some more LM-213. Then, as if that wasn't bad enough - there was yet another barrel connector and a final 25 foot run of RG-8X leading directly to the operating bench.
What the heck was I thinking?!? This was coax hack job of the century! I still can't believe that I did this; and if I hadn't seen it with my own eyes, I would never have believed that I could do such a sloppy, piecemeal job. The only thing that I can think of was I was so tapped out after purchasing the Butternut, that I just used whatever coax I had on hand to get the job done.
All those barrel connectors! All that loss! I must have had an ERP of about 2.5 Watts! It seems a miracle that I made any QRP contacts at all, let alone all the DX and states I have worked with that cockamamie set up. I am truly amazed at what a lousy job I did - EXCEPT in one respect.
When I removed the electrical tape covering up those barrel connectors and their accompanying PL-259s, they were as shiny and new looking as Day One. And I owe that to an article I read somewhere, way back when, maybe it was on QRP-L. When I made those connections, I first wrapped the coax and the connectors with electrical tape. Then, I covered that with a layer of plumber's putty. The plumber's putty was followed by a final layer of electrical tape. After some 18 years, the connections were bright, shiny and there was NO sign of any water intrusion, whatsoever. And considering the coax was laying on the ground through some very harsh Winters and at least three major Hurricanes, Floyd, Irene and Sandy, that's pretty darn good.
There was one section where the jacket of the LM-213 got chewed up pretty badly from lawn mower hits. To prevent that, this time I elevated the coax as it ran along the back fence.
I used garden fencing stakes, spaced out at about 5 foot intervals and I cable tied the coax to the stakes to keep it off the ground and away from the angry blades of my coax eating lawn mower. Once I got to the chain link fence running along the side perimeter of the yard, I then cable tied the coax to the top tube. My new run of one piece of 150 feet of RG-9913 is safe and sound from gasoline powered lawn tools! There's only one barrel connector, where the terminus of the coax meets the Butternut's matching stub. and you can see that little lump in the picture, above. Now maybe I'll get a bit more of that precious 5 Watts into the antenna and out into the aether.
Later on, in the afternoon, after getting home from my monthly volunteer stint at the soup kitchen, I soldered on the PL-259 to the radio end of the coax. I plugged it into the KX3 and was happy to see a VERY easy match made by the autotuner on all bands. Maybe a 1/2 to one second "BRRRRP" by the relays in a few cases, and in the rest, there was no match needed at all.
There's peace of mind knowing that I now have a proper run of low loss coax out to my vertical. I'm also going to change out the coax to the W3EDP. That's a straight forward exchange, and I figure that as long as I'm doing one, I might as well do both. I'm happy to state that the coax currently running to the W3EDP is not a hack job conglomeration like what was running out to the vertical !
I'll NEVER do that again and like they say on all those shows on TV = "Don't try this at home!"
72 de Larry W2LJ
QRP - When you care to send the very least! (using good coax!)
I hope you haven't thrown away the old caox and the barrel connectors. If you still have them, let me suggest that you terminate the coax run in a good 50 ohm load, send some RF in at the other end, and measure the loss as well as the SWR. If the coax has become contaminated to a significant extent then there will be loss, and to the extent that the lossy sections and the barrel connectors provide impedance bumps, the SWR may be other than 1.0. Do this on all bands on which you used the vertical. Repeat the experiment with the individual sections of coax, without using the barrel connectors.
ReplyDeleteI see that the antenna is rated for use on all bands 80 m through 6 m. My guess is the barrel connecors aren't that bad, even on 6 m. I don't see whey they should be inherently lossy. If their characteristic impedance is other than 50 ohms then they will put a bump on the line but slight increases in SWR won't raise the loss that much. Now up on 2 m it's likely another story.
If you run the experiments, let us know what you find.
David Ryeburn VE7EZM and AF7BZ
In the words of Hans Solo....Never tell me the odds!! Sounds to me like your coax job has been working just fine for the last 17-18 years.
ReplyDeleteAs David suggests above, your loss from the barrel connectors at HF frequencies should have been negligible, especially since you did a very good job of sealing them.
ReplyDeleteMark AI4BJ