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Old 02-27-2013, 09:35 AM   #1
dickreid1
Junior Member
 
Join Date: Jan 2013
Posts: 1
Default Experimental loading of RV ladder

I read a forum thead where someone was wondering about using his
RV's ladder as an antenna. It bugged me that there was no conclusion to the discussion so I finally had to try it myself.

My ladder floats electrically by being attached to a fiberglass roof then bending downward being attached at two points to the fiberglass back wall. The lower ladder section is hinged and not electrically connected to the upper section having three rungs at 14" spacing. The upper section is 53". The lower section is 39" having two rungs at 14" spacing Total 7.67 ft - not including the 22" horizontal top section that connects to the roof. Ladder width is 12'. The RV chassis is 23" from ground. The antenna analyzer used is the YouKit FG-01 to 12 ft. RG-58/U coax.

With coax shielding attached to chassis I found:
a. The upper ladder section loads from the bottom at 9.4 MHz, SWR 1:1.5
With the upper and lower ladder sections connected the ladder loads:
b. From the bottom at 7.3 MHz, SWR 1:1.9
c. From the 5th rung 18" up:7.5 MHz, SWR 1:2.0
d. From the 4th rung 32" up: 7.8 MHz, SWR 1:1.5
e. From the 3th rung 46" up: 8.5 MHZ, SWR 1:1.6

Idly I speculate about 1/16 wavelength with a width factor of around 0.91-0.92.

Treating the ladder sections as a dipole loaded off-center with the coax shield connected to the lower (short) ladder section:
f. The ladder loads from the rungs 14" apart, 22.4MHz, SWR 1:1.1, Z=55
g. The ladder loads at hinges 2" apart, 22.5-23.0 MHz, SWR 1:1.0, Z=49

And for the heck of it, I connected the luggage rack at the top and got:
The ladder/rack dipole loads at 18.5 MHz, with SWR 1:1.0 with range of 17.5 to 19.5 under SWR 2.0.
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