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Re: [wsjtgroup] Digest Number 721

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  • almacottage
    jerry . on 2m most types of coax are lossy unless you have very short run of large diameter coax . what you need is the lowest loss coax you can afford to put
    Message 1 of 1 , Jul 31, 2005
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      jerry .

      on 2m most types of coax are lossy unless you have very short run of large
      diameter coax .

      what you need is the lowest loss coax you can afford to put up, in fact youd
      be more wise to spend youre money on coax than another aerial .

      look on ebay , you might see some heliax that is the right length , you need
      to look for LDF450-A or LDF550-A .

      the 550 is like a broom handle for thickness and the 450 is about as thick
      as youre finger , both are the most commonly used coax on 2m within EME and
      DXING circles .


      also there is LMR -600 which is easily obtained in usa and probably youre
      best bet .


      there is a coax sold in europe called ECOFLEX 15 and this is pliable and
      good on 2m for average runs .

      you need to buy coax that you can also obtain plugs for , some coax is hard
      to get them for.

      if you are absolutely unable to buy the larger coax then look into using
      LMR400 or belden 9913 as these are both similar to rg8 but lower in losses
      .

      i have a 50m run of LDF550-A & FSJ450 heliax & 9913 on my 2m array and i
      lose around 2db in coax loss , with the 550w that my amplifier puts out in
      the shack i get 340w out of end of coax run .

      if i were to put 5w into it i would see less than 3w out of other end , its
      amazing at what can be lost or gained through choice of coax ..

      per 10m [32feet] of coax , approx losses are :::

      rg58 = 1.9db

      rg8u = 0.83db

      belden 9913 = 0.45db

      ldf450 = 0.25db similar also LMR400

      ldf550 = 0.14db similar also LMR600

      if you had 3db in coax loss thats half youre power gone in the coax
      before it reaches the aerial and half the signal received before it reaches
      tcvr , also its almost 1 s point in received signal lost .

      to get 3db RX/TX gain increase on yagi aerials youd need to add a second
      aerial stacked in phase or double the boomlength .

      3db extra gain in transmit and receive is a lot to have and can make
      difference between hearing and being heard .

      by getting coax loss down to absolute minimum youll get maximum benefit out
      of aerial used and power used ..

      if you do have to run long length of smaller coax then fit a masthead pre
      amp and sequencer , ie SP2000 and DCW-15B and make sure youre rf output from
      tcvr is enough to overcome coax loss by time it reaches aerial .

      QRP isnt allways trully QRP , sometimes its much less than you think .

      what you need is QRP and maximum efficiency in order to benefit .

      a directional aerial is of course more beneficial but something like a
      crossed yagi is ideal for all types of 2m working , if you put a remote
      operated 2 way antenna switch at the masthead you can use one run of main
      coax and alter polarisation from within shack to suit what polarisation you
      are trying to work .

      you need to have a fibreglass stub mast thru the plane of yagi elements if
      you dont run a crossed yagi offset from the mast .

      i did find that a quad with the elements at 45 degs angle to the mast worked
      well on both horizontal and vertical polarisation , if you are only able to
      put up a loop or similar then a 2 element quad with the wire at 45degs would
      work very well for you and can be mounted with aluminium stub mast passing
      thru middle of it.

      hope this is of use .
      73 ian m0bcg

      ----- Original Message -----
      From: <wsjtgroup@yahoogroups.com>
      To: <wsjtgroup@yahoogroups.com>
      Sent: Sunday, July 31, 2005 8:57 AM
      Subject: [wsjtgroup] Digest Number 721


      > There are 2 messages in this issue.
      >
      > Topics in this digest:
      >
      > 1. Re: Antenna Question
      > From: Ken Roberson <kwroberson@...>
      > 2. RE: Antenna Question
      > From: "Rick Graham" <rick.graham3@...>
      >
      >
      > ________________________________________________________________________
      > ________________________________________________________________________
      >
      > Message: 1
      > Date: Sat, 30 Jul 2005 08:57:57 -0700 (PDT)
      > From: Ken Roberson <kwroberson@...>
      > Subject: Re: Antenna Question
      >
      > Jerry,
      >
      > Sounds good to me , the new cable will also help , and the LMR 400
      > is great , I am using LMR 600 on my 17 ele 2 meter beam.
      > The LMR 600 is a lot harder to work with , But has very low loss.
      > Not 100 percent sure abt gain on Par OA-50 , But The Moxin
      > Works and if U can rotate it even better , Thats
      > all I know .
      > Good luck , We can try agn after u get up and running.
      >
      > 73 Ken K5DNL
      >
      >
      > jfelts13 <nr5a@...> wrote:
      > My flying buddy is coming over in the morning he is going to change
      > the junk mask my 2m beam is on now to a little bit better one, and
      > put my old rotor on it. Rotor seems to be working ok now. I'll be
      > going from about 12foot up beamed east to around 18ft. Hey thats 6ft
      > higher plus a rotor. Oh yes I'm getting rid of the RG-58 thats on it
      > now and going a little bit better RG-8U.
      >
      > When the tower gets put up in a couple of months I'll be running LMR-
      > 400 to it.
      >
      > Now the question, has to do with 5 watts Not enough I know. I
      > currently run a Par OA-50 its eactly 18ft up. Would a Moxin at 13-14
      > feet that can be turned be better??? I have this hang up about giving
      > up what height I have.
      >
      > Just want opions guys. More power I know, but I have the QRP disease
      > for 38years, its just wrong to run more than 5 watts. You don't know
      > how much I cringe when I run 75 watts on 2. (And I have a 160 watt
      > amp coming) its just completely out of control.
      >
      > Jerry - NR5A - South Dakota
      >
      >
      >
      >
      >
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      > Message: 2
      > Date: Sat, 30 Jul 2005 20:33:38 -0400
      > From: "Rick Graham" <rick.graham3@...>
      > Subject: RE: Antenna Question
      >
      > For good QRP work - its all about the metal! The more you have up (tuned)
      > the better your 5watts will work. I'm still amazed at how well my lil 817
      > works in the car for HF work. And for moderate DX pileups, a little
      > patience
      > and perseverance will net me the DX.
      >
      > Good luck with VHF/UHFQrp.
      >
      > 73 DE AI3W, Rick
      >
      > _____
      >
      > From: wsjtgroup@yahoogroups.com [mailto:wsjtgroup@yahoogroups.com] On
      > Behalf
      > Of jfelts13
      > Sent: Friday, July 29, 2005 9:28 PM
      > To: wsjtgroup@yahoogroups.com
      > Subject: [wsjtgroup] Antenna Question
      >
      >
      > My flying buddy is coming over in the morning he is going to change
      > the junk mask my 2m beam is on now to a little bit better one, and
      > put my old rotor on it. Rotor seems to be working ok now. I'll be
      > going from about 12foot up beamed east to around 18ft. Hey thats 6ft
      > higher plus a rotor. Oh yes I'm getting rid of the RG-58 thats on it
      > now and going a little bit better RG-8U.
      >
      > When the tower gets put up in a couple of months I'll be running LMR-
      > 400 to it.
      >
      > Now the question, has to do with 5 watts Not enough I know. I
      > currently run a Par OA-50 its eactly 18ft up. Would a Moxin at 13-14
      > feet that can be turned be better??? I have this hang up about giving
      > up what height I have.
      >
      > Just want opions guys. More power I know, but I have the QRP disease
      > for 38years, its just wrong to run more than 5 watts. You don't know
      > how much I cringe when I run 75 watts on 2. (And I have a 160 watt
      > amp coming) its just completely out of control.
      >
      > Jerry - NR5A - South Dakota
      >
      >
      >
      >
      >
      > To unsubscribe, send an email to:
      > wsjtgroup-unsubscribe@yahoogroups.com
      >
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