SFI > 250 or bust!

I might have enough coax cables at hand for Field Day. But it feels like I don’t. Never enough, right? I have a long stretch of coax that needs plugs. I plan to bury it in a tube along with some other cables in a few weeks. So I soldered the PL plugs to this forty meter long stretch of Ecoflex 10 coax cable. I have another fifty meter run of RG213 in stock that has N plugs. That should do to connect the antennas to the transceiver.

I also have a presumably fifty meter length of RG217 cable. That ½” low loss HEAVY stuff. It’s hard to find plugs for that since it’s quite an obsolete cable. I purchased a complete ‘now old stock’ drum when we bought the house. I found matching N plugs from a renowned RF brand but they were ridiculously expensive in 2002-2003. So I didn’t buy those. I found a batch of used but good N plugs when attending a ham fest in 2003 and I used these for the fixed feed lines from shack to various junction boxes outside. Once I managed to make a homebrew PL style socket by modifying a regular PL plug and using brass plumbing reductions. K1TTT’s idea.

But for the 2011 edition Field Day I bought plugs for Ecoflex 15 type cable. Expensive enough but within reason. These plugs do not fit 100%. But it worked and got tested before taking it to OT1A’s field day site.

50m of RG217 with DC bias T’s (@ON5ZO 2011)

This virtually lossless cable below 10 MHz turned out to be faulty. It took some time to realize and admit that. It got tested here before hauling it to OT1A’s but antenna SWR was way up when deployed. We lost quite some time because of that. We checked everything from antenna to TRX except the part in between: this coaxial cable.

Back home I hung it on a hook where it has been for five years until two days ago. I put in on the antenna analyzer with the other end connected to a dummy load. Sure enough the screen showed SWR bumps of 4:1 and more from 1.8 MHz to 52 MHz. Visually the cable was OK, so I suspected the plugs. I removed all the PVC tape from one of both plugs and unscrewed the nut. The center pin came off too so the problem revealed itself without further inspection. True Ecoflex 15 has a much thicker center conductor than RG217. In 2011 I filled the cup with solder tin but it didn’t hold up.

I cleaned the cup with desoldering wick. Then I made a sleeve of desoldering wick. I used that as a spacer between the center conductor and the plug’s pin’s inside. I pulled and twisted the PL center pin but it didn’t release so I guess this time it’s a better connection. The antenna analyzer then showed a flat SWR plot from Top Band to Magic Band. R = 46 ohm on 30 MHz with X = 0 ohms at 0°. Not bad for a homebrew dummy load. And with low loss coax cable…

I also found two short runs of Aircell7 in my pile of junk/parts/miscellaneous stuff. Too short to be useful, too long to throw away. I made N-to-PL adapters from it, coiling them up so they will act as a current choke. I have many N-type plugs and sockets in use so these adapters always come in handy.

And along the way I discovered I have another length of what looks like 20 – 25 meter of RG213 with male and female N type plugs. I really have tons of stuff, so much I don’t always remember I have it. Or I can’t remember where I put it.

But for field day, the coax needs should be covered.

2 Responses to Field Day Frenzy Part 2: coax cables

  • That was a nice competition, but last 2 hours I had to leave. Congratulations, and hope to find you next year!
    Mikel EA2CW ED2C in the contest!

  • Congrats on #1 Restricted, Franki! We had a blast operating ON4NOK/P OAB 24h.
    De Glenn ON4WIX

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