View Full Version : Experimental loading of RV ladder

02-27-2013, 09:35 AM
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.

02-27-2013, 09:45 AM
I had a Toyota MH that used the luggage rack as a TV antenna it used a short stub as match and the rest for the antenna. I can say the swr was all over the place but it was resonate in many different freqs.

02-28-2013, 04:48 PM
Welcome to the ORR.net forum, Dick. As first posts go, that one was a dandy! Keep it up!


03-01-2013, 10:19 AM
Several years ago, Collins Radio manufactured a hf antenna designed for intercontinental aircraft .

This antenna was 13'5" long and stood off the belly of the aircraft 8.5" and was fed by a tuner also made by Collins as was the Transceiver.

System worked pretty well for the most part , and I don't see any good reason something like this would not work on top of a motor home , would be interesting to try.

Also many years ago, I made a "luggage rack" loop type antenna on top of a friend's "cab-over" camper which loaded 40 - 6 quite well ( have the dimensions here somewhere ).

03-02-2013, 11:50 AM
Google magnetic loop antennas.. There is one on the market (Did not get the price) that looks like a giant hand basket, They show it cargo strapped to the roof of a jeep.

There is another one that was featured in the LAST episode of Amateurlogic.TV I think "omin-tech" or something like that Looks like a flying wing, can be used with a sheet steel ground (RV roof covered with metal) but I googled it and found out the price tag, They are PLANNING a lower cost ham radio line, but if you go to the web site and check out the professional model.. Have clean undies handy, you may need 'em.