HF antenna on a 35 foot fifth wheel.

[kt4et]

This is Bruce KT4ET.
I am having a problem with the new antenna set up. The rig is a Kenwood TS-570S. I bought a 31 foot fiberglass telescoping pole and mount that is on the rear ladder. I bought the MFJ- 933BRT auto tuner. Ground is 12 gauge stranded wire from the frame to the ground wind nut on the tuner. The antenna is a 33 foot piece of wire.........3 pieces of small gauge insulated wire twisted in a drill then cut for 33 feet. It is light enough to not damage the pole.

The big problem is it will be fine with low SWR then the next few minutes later it is well off. The wire is spiral wound not a straight line but it should not make any difference. I spent the work and money to use the rig from 80 meters to 10 with no trouble but it has not been the case.

Any suggestions?

Thanks and 73,

Bruce

 

[joelmyer]

Been there, done that.  ICOMAH-4

33' is a quarter wave (wonderful) at 40 meters & a half wave (were difficult to match) at 80.  Trying to match a halfwave could be your problem.

Two suggestions:  Use a "random" length antena, random meaning carefully selected to avoid multiples of a half wave length.  Here's some notes from the AH-4 Yahoo Group:

------------------------------------------------------------------------------
Here are the ideal lengths for your radiating wire.

27' (23-32)
40' (35-44)
58' (52-64)
76' (70-81)
95' (92-98)
109' (105-113)
145' (140-148)

As you mentioned the counterpoise needs to be larger than the
radiating wire
by 5 % .

The counterpoise alone is sufficient for your ground.
-------------------------------------------------------------------------------------------

With the vertical on the ladder, most of your energy is radiated into the rv.  Throwing your random length wire up into a tree is probably a little better than on the pole.

Enen better is a doublet, I built a 100' doublet with the Wireman's "invisible" wire and 25 ft of tv twin lead.  Your 31' poled will holu this up at the bottom of the top section. Then put the tuner at the base of pole.

Joel

 

[joelmyer]

Added:  Your post was ringing bells so I looked you up on QRZ.  I think we've already had this discussion somewhere else. But the random lengths may help.

Joel