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(Possibly) a stupid question on a RF failsafe....

Discussion in 'General Ham Radio Discussion' started by iiiquaziii, Aug 6, 2017.

  1. Paul-W5lz

    Paul-W5lz
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    I think that since you are aware that your cable isn't the best in the world you probably should just go ahead and use it. It doesn't have to be the best in the world to work. Would better shielding be better? Probably, but until there's some particular problem, why waste a lot of worry on it (especially if you can't change it right now)? I've used some really crumby coax before, it was just all I had at the time. No particular problems with it, some -potential- problems but until they happen, save the worry for something else.
    The biggy about that 2 conductor wiring is the safety part. It really can cause some shocking problems. This old house has every kind of electrical wiring there ever was. I've corrected some of it and live with the rest. It'd be smart to re-do it. Do what you can, when you can, and don't stick things in those electrical outlets that don't belong there.
    Baluns on HF antennas are nice, but certainly not a necessity at all. Wanna use them? Do so. Keep in mind that they ARE frequency/band specific, and bigger is better to some weird extent. (Can you tell I'm not a big fan of baluns?)
    Have fun while you're doing all that stuff.
    Paul


     

  2. Robb

    Robb
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    If it is as clean as you say; then run with it until it proves to have a fault of some kind. The only difference between RG-58 and RG-8 is that the RG-58 is good up to 400 watts and the RG-8 is good to 1,000 watts more/less - depending on the brand. Belden is good schtuff.
     
  3. Captain Kilowatt

    Captain Kilowatt
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    One thing you can do is connect a dummy load to the far end of the cable and a watt meter at the radio end and note the power out. Next move the meter to the far end near the dummy load and note the power again. If there are excessive losses then it indicates the cable may not be as good as you think it is however the cable will NOT simply fail and ruin your radio. It simply means you have more losses. Sometimes the inner insulation may be discoloured and the copper still bright and shiny. The discolourisation is due to water having infiltrated the cable. In any event use it. The worse that can happen is your signal will be down from what it is capable of but the difference in dB will be hardly noticed if at all depending on the amount of actual loss.
     
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  4. bob85

    bob85
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    iiiquaziii
    use the rg58 if that's all you have, it will get the job done until you can afford something better,

    i once ran a long run of rg58 as a temporary (few days) setup because that's all i had sat doing nothing at the time & wanted to get back on air,

    the temporary setup turned into several years even though i had much better new stuff within days & left it sat on a reel in the garage,
    when i first measured the loss on the new rg58 100w in the shack gave me 42w at the antenna on 27mhz,
    it never stopped me making contacts all over the globe,

    Robb
    what power coax can handle depends on what is connected to the far end, manufactures specs are conservative providing vswr is very low,

    i can tell you from plenty of personal experience that even cheap rg58 not belden quality can handle 600w+ fm IF vswr is very low, gets pretty warm on long overs but it can work reliably for years,

    it goes tits up @ lower power than the coax is rated for when vswr is not very low as seen in sirio gainmasters that use rg58 size coax above the stub & the mk1 stub matched vortex Q64,

    i have known rg8x feeding a sirio 827 be destroyed, fried like chicken by a local using his ACOM-1000 on FM when the 827 developed the open circuit fault arcing & burning the top of the coil off,
    the amps protection circuit saved the ACOM,


    seen the same thing with another local but less dramatic using rg58 feeding another sirio827 that went oc & damaged the coax & smaller base amp.
     
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  5. nomadradio

    nomadradio
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    If you have a dummy load it's no big trick to measure coax loss.

    Put the wattmeter between the radio and the coax and note the power reading.

    Now move the meter to the other end of the coax, at the dummy-load end.

    The difference between the power readings will tell you how much this piece of coax will lose when feeding your antenna.

    73
     
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  6. KD2GOE

    KD2GOE
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    As a Note i had to cut off 10' off that RG58 coax he is using before i got to good copper..
    I never toll him "Belden" was bad cable just that That cable is so so i would not trust on a $600+ radio.

    And Quaz you still need to fix your pl-259 connector with the cable falling out..


    i have never seen any balun that was marketed as frequency/band specific can you explain???
     
  7. Paul-W5lz

    Paul-W5lz
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    Pick a balun, ask the manufacturer the frequency limit of that balun. It deals with how and from what they are made from.
     
  8. KD2GOE

    KD2GOE
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    .

    All say 160 m to 10 m with my MFJ analyzer and 50 ohm dumby load on my 1to1 balun i get 1:1 from 1.8mhz to 30mhz 50mhz get up to 2:0
    On my 4:1 i get near the same readins
     
  9. iiiquaziii

    iiiquaziii
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    Yeah this project is planned for one of my next big things. I've re-wired most of the house at this point. The radio room is the last room standing with old 2 wire outlets. I have had some issues in other rooms, and just decided to re-wire them as I had a several hundred foot coil of romex....havent got to the pc/radio room yet though.

    I do have a 8 ft copper grounding rod I just installed outside the radio room, that I grounded the radio stuff to a couple weeks ago. I really do need to get around do doing the outlets. I have the radio/computer room on the worst wiring in the house.....
     
  10. Paul-W5lz

    Paul-W5lz
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    Without getting into it, read the NEC about grounding, both safety grounding and RF grounding. I gets very 'involved' very quickly. A single ground rod 8 feet long or 80 feet long is almost useless for RF.

    NEC = National Electrical Code
     
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  11. Captain Kilowatt

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    Most baluns are broadband however those commonly called a choke-balun are not. They are a coil of feedline at the feedpoint and choke off RF from the feedline. Although they are properly called simply a choke they are usually called a choke-balun because they are used between a balanced antenna and an unbalanced feedline to keep RF off the feedline. Air core chokes like this tend to be somewhat frequency sensitive for maximum effectiveness which depends on the proper diameter of the coil and proper number of turns.
     
  12. KD2GOE

    KD2GOE
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    Yeah he was never intending to go with a coil of feedline or "dirty balun" he was looking in to a MFJ-918... i suggested he get one on his 40/20m antenna then a guy at his work is a Ham and he all so told him to run one...
    what was all so confusing is he posted "Pick a balun, ask the manufacturer the frequency limit of that balun" witch is leading me to think he is not talking about a coil of wire.
     
    #42 KD2GOE, Aug 10, 2017
    Last edited: Aug 10, 2017
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  13. Paul-W5lz

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    Big difference between a choke and a balun, they are not the same at all.
    Baluns are not all made the same. Different torroid materials, size of wire, etc. So, they are frequency dependent. Broadbanded, yes, but seldom very useful if they aren't at least 'close'.
    What I've found out over a lot of years is that a balun has made little difference for me on HF. The biggest thing was a slight change in the resulting radiation pattern, which in most cases makes no significant difference at all. I've also been in the position where a balun 'popped' while in use. That can cause all kinds of problems. I've usually had the extra coax to wind a choke and that'd take care of the RF/CMC thingy.
    What it amounts to is if it makes you feel better to use a balun, then use one.
     
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  14. Captain Kilowatt

    Captain Kilowatt
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    I have used the choke method on a balanced feed tribander and air core baluns only but never a ferrite core. Also used 4:1 halfwave coaxial baluns on VHF but again.......never a ferrite or iron powder core.
     
  15. KD2GOE

    KD2GOE
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    I have a W2AU on my fan dipole..

    And made the same ones he made in the video's

    Part 1


    part 2


    Part 3
     

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