[ScanIndiana] Re: cable question

[David L Norris]

Some Performance Info:

Coax (good stuff):
  LMR400: $1.00/ft,  3.9 db loss per 100ft @ 900 MHz
  9913:   $1.00/ft,  4.2 db loss per 100ft @ 900 MHz
  RG-6:   $0.05/ft,  5.6 db loss per 100ft @ 900 MHz

Using 75ohm coax with a 50 ohm antenna and radio will result in 0.68 db
loss (125 ohms impedance or about 2:1 SWR).

Junk Coax (for comparison with good coax):
 RG-8X:   $0.40/ft, 12.8 db loss per 100ft @ 900 MHz
 RG-58:   $0.30/ft, 20.0 db loss per 100ft @ 900 MHz


Connectors (with Radio Shack bloated prices):
     N:     $5    ,  0.1 db loss @ 900 MHz
 PL259:     $5    ,  0.5 db, variable above 300 MHz
   BNC:     $5    ,  0.1 db loss @ 900 MHz


Adapters (Remember: radio has BNC, discone has SO239):
  N-to-PL259: $5  ,  0.6 db loss, variable above 300 MHz
  BNC to N:   $5  ,  0.2 db loss @ 900 MHz




Some price versus performance:

Case 1 (RG-6 from hardware store; connectors from RadShack):
  100 feet of RG-6 + BNC at radio + PL259 at antenna + mismatch
        5.6 db     +    0.1 db    +    0.5 db        + .068 db = 6.88 db
        $20        +      $5      +     $5                     = $30

Case 2 (LMR400 with N connectors adapted to antenna and radio):
  100 feet LMR400  + N on BNC-to-N at radio + N on N-to-PL259 at antenna
        3.9 db     +       0.3 db           +    0.7 db        = 4.9 db
        $100       +      $5 + $5           +    $5 + $5       = $120



So, you can squeeze out maybe another 2 db for an added $90 or so; $50
more if you get lucky and find LMR400 or 9913 cheap.  If you need less
than 100 feet then RG-6 cable loss of course drops dramatically.  If
you're listening to mostly 0-500 MHz then your connector loss and RG-6
loss is very minimal.


BTW, anyone wanting to _build_ a discone on the cheap might look here:
  http://www.qsl.net/n8oou/discone.htm

-- 
 David Norris
  http://www.webaugur.com/dave/
  ICQ - 412039