8x Jumpers, Pl259's, Too Much Heat?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by K0DUC, Sep 14, 2021.

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  1. K0DUC

    K0DUC Ham Member QRZ Page

    Bought a 500 foot roll of Tram 8x coax for jumpers and other miscellany. Especially after using LMR 400 and 8u for jumpers, which is unecessary and stubborn.

    Finally got around to putting ends to some wires today. Very delicate, especially compared to LMR 400. Slow and careful work with the knife and razor, then the crimper, they first part looked very good. Then I set about soldering the center conductor.

    Instead of the usual old worn out solder gun, I decided to try my brand new American Beauty 60 watt solder machine. With some help, got the solder to flow pretty good, with the only thing I noticed was excessive smoke on a few. Especially one end that really smoked for a while after I put it in the coffee can to cool.

    Quick final check with the Hioki 3030 confirmed clean jumpers.... except for one. Center and shields showed continuity every which way you touched them. A complete failure and dud. After spending all that time being careful!

    Thinking of what could have gone wrong, I'm about completely certain I did not have any possible contact between the shield and center through loose wire, I was clean, slow, careful. On inspection I found that the PL259 on one side had a brown burn looking ring around the center. I make the assumption that with that bigger solder chisel and maybe too much solder flow, that I ended up burning through the foam and created a complete connection?

    CB radio with dummy load and SWR meter showed the rest are totally fine. I don't want to risk blowing up my Galaxy on a coax I know is bad. So....

    Am I right in my assumption? Did I burn through the dielectric? Or was I sloppy afterall? Before I keep making (and wrecking) jumpers, what other possibility am I missing, what mistake did I make, and how can I do better?
  2. W1VT

    W1VT Ham Member QRZ Page

    RG-8X and RG-174 are very prone to shorts resulting from the dielectric melting. It doesn't take much. Unlike Teflon coax, which can stand a lot of heat.

    RG-8X has a foam dielectric that melts easily. RG-174 is very thin coax.

    I use crimp connectors with 8X.
    AK5B, W7UUU and W9IQ like this.
  3. KP4SX

    KP4SX Premium Subscriber QRZ Page

    60w isn't much with PL259s. Its doable, though. Just last night I put on a PL259 on RG8X with my 40w Weller. It would have been easier/quicker with more heat but once the solder begins to flow to the braid and adapter then you're in business.
    Keep everything still in case the dielectric begins to melt. Tin the center conductor before starting.
  4. KA9JLM

    KA9JLM Ham Member QRZ Page

    You need more than 60 Watts.

    Quick on Fast off is the key that works for me.
    W9WQA and AK5B like this.
  5. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    IMO it's not the "watts" so much as the thermal mass of the tip.

    A 60W iron should work if it has a massive tip that can store a lot of thermal energy. It takes about a 250W soldering "gun" to do this job because the tip doesn't store anything so you have to keep pumping power into it to keep it hot.

    I use a Weller SP-120 (I have a few of them, all 20-30 years old but it's still a current model) which has a large, heavy barrel and a 1/2" plated copper tip that can store lots of heat, so once it's at 900F (which takes about five minutes after plugging it in), it can heat a PL-259 to soldering temperature in about 2-3 seconds and the solder flows easily onto the connector body, through the holes, and into the braid.

    Whole operation to solder through all four holes takes maybe 15 seconds. Maybe slightly less.

    Then, as stated, "don't move anything" for a minute or so. I cool off the connector by gently pressing a wet sponge against it, otherwise it would be too hot to pick up for a couple of minutes.
    K9XR, W9WQA and W9IQ like this.
  6. K4SAV

    K4SAV Ham Member QRZ Page

    It was unclear if the shield was crimped or soldered. There are different sources for coax with foam dielectric and the melting point of the dielectric varies a lot with the manufacturer. It is possible to solder the shield on some of them (if you are very good at soldering) but on others it is impossible. I consider myself pretty good at soldering (been doing that for 64 years) and I tried one of the low melting point dielectric coax cables and I could not do it. As an experiment I did it several times and every time was a failure. Even the tries that did not show a direct short broke down at a very low voltage using a hypot tester.

    Jerry, K4SAV
    Last edited: Sep 14, 2021
  7. KA9JLM

    KA9JLM Ham Member QRZ Page

    That iron is a good choice.

    I got spoiled using Butane for field work. It is Weller as well.

    I mostly crimp now. The $300 in proper tools only hurts once.
    AK5B, KP4SX and K0UO like this.
  8. AI5DH

    AI5DH Ham Member

    Why would anyone use solder connectors? Just asking for trouble and you found it.
    W1PEP and K0UO like this.
  9. K0DUC

    K0DUC Ham Member QRZ Page

    In the long winded description, I stated I crimped the shield. I only soldered the center, which is absolutely necessary.

    That's why I was surprised. All the heat and hot solder was at the tip, nowhere near the crimp. But I held it there for a long period while more solder kept dripping in, and I probably did it way too long.

    I'm used to a worn out low power solder gun and letting things warm up for a long time before pushing solder in. And since I didn't get the nice slight overfill round end, I kept feeding more solder in.
  10. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    If you use coax with a stranded (not solid) center conductor like RG8X, there are crimp connectors available where you crimp the center pin as well.

    Those don't work well at all with solid conductor cable, but with 8X they're okay.

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