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Signal loss at a union at 2m

Discussion in 'VHF/UHF - 50Mhz and Beyond' started by N8SAN, Mar 7, 2019.

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  1. N8SAN

    N8SAN Ham Member QRZ Page

    Hey everyone! Hope you're all doing well.
    I have a Comet GP-3 that I STILL need to get on my mast above the Mosley.
    If I were to get a short piece of LMR-400UF to go from the Comet for the rotor loop then run "regular" coax to the shack, how detrimental would that be to signal loss?
    It's about a 75' total run from the Comet to the radio.
    I was thinking 10' UF from the Comet, union, then non UF LMR400 to the radio.

    Go for it?? Meh, probably ok? OH DEAR GOD NO!?? :D

  2. AA5CT

    AA5CT Ham Member QRZ Page

    SURELY there must be an on-line calculator for this sort of thing! :)

    Drop-down boxes for cable type, length of jumpers of a different cable type, etc.
    K3XR likes this.
  3. K7JEM

    K7JEM Ham Member QRZ Page

    The difference in attenuation of 10' of UF or regular LMR400 is minimal. I would use type N connectors and a barrel connector, although plain old PL259 would also be OK, just a slight bit more loss. IOW, don't worry much about it, just get it done.
  4. KE0NSK

    KE0NSK Ham Member QRZ Page

    For a gp3 that is plenty, and if anyone tells you different, they are wasting your money.
  5. N8SAN

    N8SAN Ham Member QRZ Page

    Perfect. That's what I was thinking, but just wanted to be sure how detrimental a barrel union would be. Doesn't sound like much!
    Thank you!
  6. WA9SVD

    WA9SVD Ham Member QRZ Page

    The "loss" in a good quality barrel connector is immeasurable even at 2 Meters. Poor quality junk barrels, may have high loss. Use Amphenol or equivalent quality connectors, and don't worry about it.
  7. KM3F

    KM3F Ham Member QRZ Page

    Barrel loss becomes a larger factor when the length gets longer than about 3 inches.
    Don't use UHF barrel connectors with only 4 locking notches on each end.
    They tend not to be any good above 10 meters as tested into a flat dummy load with an Analyzer.
    That's how I found out trying to use them as window feed-throughs on 6 meters up and seeing the SWR go off and get lost after carefully testing each section of the installation up to that point.
    Good luck..
  8. KC4YLV

    KC4YLV Ham Member QRZ Page

    if you're going to do this, use lmr 240 ultraflex. You'll never notice the difference with that short of a run, and it's wayyyy more flexy than the 400UF stuff.

    i use 240UF for both rotator loops on my satellite/weak signal mast, and for patch cables inside the shack from patch panel to radios.
  9. N8EKT

    N8EKT Ham Member QRZ Page

    Despite all the ham radio wives tales, you will never see the difference since loss is so miniscule at vhf frequencies

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