[Boatanchors] OT: Coax balun. How many turns?

[Phil]

Hi All,

I'm in the preparation phase of re-activating my 10M beacon (last one 
went QRT in 2009).  I've already coordinated the beacon frequency 
(28.290MHz) and I'm just waiting for the IDer kit to arrive (this one).

http://www.hamgadgets.com/ID-O-MATIC-IV

The rig will be a used RadioShack HTX-100, running somewhere between 
10-20 Watts. I anticipate having it on the air within about two weeks.

The antenna will be a Cushcraft AR-10 'Ringo', mounted about 3 feet 
above the mobile home roof.  In reading about it I read some suggestions 
that it might be best to use a coax balun where it's fed with the coax 
to keep RF out of the shack, and the coax from radiating.  Yeah, I  know 
that a 'coax balun' just a few coiled turns coax, tie-wrapped.

The feedline will be a 75 foot run of quality RG-8x.  50 foot might have 
'just' made it IF I stretched things, so I bought a 75 foot run (from 
HRO, AES is no more :(  I thought the minimal loss (at 28MHz) of the 
extra 25 feet would possibly be less than adding on another length with 
a barrel connector.  AND that gives me enough slack for the coax balun.

QUESTIONS:  At 28 MHz how many (and what diameter) turns would you 
suggest?  Also, would it be beneficial to put a second one IN the shack 
before the radio, or might that just radiate RF into the shack?

-- 

73 From "The Beaconeer's Lair"
Specializing in DXing NDBs (Longwave Beacons)
Phil, KO6BB,  http://www.qsl.net/ko6bb/

HF/LF RADIOS:
HOMEBREW: 7 Tube+Rect 1v3 Regenerative RX for LF (built 2015)
Icom:     R-75, Cascaded 250/125Hz CW-Filt, Panadapter. (~2009)
Icom:     IC-7200 Xceiver, DSP IF & filters (~2015).
Kenwood:  TS-450SAT Xceiver, cascaded 250/125Hz Inrad filters.
SDR:      Softrock Ensemble II LF (built from a kit 2015).

ACC:   HOMEBREW  LF-MF Pre-Amp, MFJ-993B HF Auto-Tuner.
        HOMEBREW  4 Port Antenna Multicoupler, Feeds 4 RX's.
AF Filters:  Timewave  DSP-599zx & HOMEBREW  8 Hz Filter.

ANTENNAS: 88 foot Long Ladder-line fed dipole, 35 feet AGL for MW/SW.
           Active Mini-Whip, 36 Feet AGL for LF/MW/SW.
           37 foot "Low Noise Vertical", 11 feet AGL for LF/MW/SW.

Merced, Central California, 37, 18, 37N   120, 30, 6W CM97rh