Results 1 to 6 of 6

Thread: Is cnt-40 cable ok for uhf

  1. #1
    radiogeek97 No Longer Registered

    Default Is cnt-40 cable ok for uhf

    folks

    we had a vendor install sme feedline for a microwave link and for a 40W uhf 460MGHZ control staion. I was expecting lmr-600 but what got installed was cnt-400. The cable run is about 150feet. We will be runnng a control station from this cable which will see moderate daily use. I dont know what type of antenna got installed but I will post that when i find out. I guess my question is what if any better cable should have we put in , or is this sufficient, should we put in a higher gain antenna to compensnsate for the cable? The control station really only has to "hit" a few local repeaters and on occasion we may use direct if there is an infracture failure. What are your thoughts

    thanks in avance


  2. #2
    chpalmer No Longer Registered

    Default

    http://www.timesmicrowave.com/cgi-bin/calculate.pl

    I get about 39% efficiency on the Times calculator. If you are using it to get to your repeater then it is probably usable. As long as it works I suppose.

    My shop would never use any less than 1/2" on a run like that. In fact Id push for 7/8" as Id be trying to think about possible interference your system is trying to compete with. But Ive become very cynical lately due to bad frequency coordination by competitors.

  3. #3
    radiogeek97 No Longer Registered

    Default

    I will have to look back thru the quote but i think it is one of thise things where the quote from motorola just said "install xxx" antenna cable here. It is one of those things that fell thru the cracks as far as being nailed down specifically this or that type of cable. The specs I found on this cable seem to have it as more appropriate for microwave frequencies than for the uhf band.

  4. #4
    Join Date
    Jan 22, 2013
    Location
    Florida, U.S of A.
    Posts
    251
    Thanks
    304
    Thanked 305 Times in 114 Posts
    Country: United States

    Default

    My info shows 1.9 dB loss per 100 ft @ 450 Mhz. That would be 2.85 @ 150 feet. Only about a half dB better per 100 feet than LDF 4-50. Your 40 watts at the end of the coax will equal slightly more than 20 watts. A unity gain omni is no gain. A 3 dB omni will give you slightly more than 40 watts ERP. A 3 element yagi will give about 6 dB gain (ok, depends on who makes it and dBi or dBd...) and your ERP goes to about 80 watts. What is your control station licensed for? You need omni coverage or just pointing at 1 repeater? If you really think you need to operate direct as a backup, you probably should look at 7/8" coax and a 6 dB omni. Again, if you are licensed as FX0 or FX1 control, max ERP shouldn't be more than 20-25 watts ERP and you will exceed that with anything more than a unity gain omni.

    As far as microwave, it depends on frequency and length of the run. A lot of MW links down-convert the primary frequency if the radio is tower mounted so LDF -4 or CNT 400 is acceptable in a lot of cases.

    For the use you stated for UHF, I really don't see any problem with CNT400. I personally have never used it though, maybe others have a comment good or bad. Based on the manufacturers spec, should be fine. Now, if you PAID for LDF4-50 and got CNT400, I'd raise hell because LDF lists at $3.20/foot and CNT400 lists at .95 cents/foot.

    Dave
    Last edited by mss-dave; Apr 07, 2013 at 04:59 AM. Reason: Smacking head on desk....

  5. #5
    radiogeek97 No Longer Registered

    Default

    dave
    thanks for the info, i think an omni is what motorola specked out but I will confirm that when i see it i think the 20w should suffice we are in a metro area and I can look strait across and see all the antena farms that the various PS repeateers are located. I will look into the issue of wha was or was not quoted. i fear that it was just "open ended" soo we get what we got, but I willl confirm

    thanks again !!

  6. #6
    Join Date
    Jan 22, 2013
    Location
    Florida, U.S of A.
    Posts
    251
    Thanks
    304
    Thanked 305 Times in 114 Posts
    Country: United States

    Default

    Welcome!

    I need to correct info again..... LDF4-50 would be 1 /2 dB better per 100 feet than CNT 400. Had it the other way around. I've seen Motorola spec 1/4" Superflex for control stations. Sure not the best in the world for long runs or being outside though.
    Last edited by mss-dave; Apr 07, 2013 at 10:56 PM.