This morning I helped out Jim, N1WWE, check out his Cushcraft R7000 vertical prior to final installation. This is a 40 -10 antenna that mounts on a mast. The directions (TNX de K1DM) says if not mounted on a tower or structure, a 10 foot mast on the ground will do. Well, prior to permanent installation on a mast in his back yard, I checked all the dimensions and propped it up against his deck to check the SWR on each band with my MFJ analyzer. Some of the dimensions were “off” from those given in the instrctions by about an inch…but the top section was over a foot longer than indicated in the instructions. After making the lengths correct, what were the results?
Horrible! It was pretty flat at about 2:1 across 10 meters…just as the directions say. 12 meters the best point was about 2.6:1. But there was no resonant point anywhere near 17 meters….15 and 20 meters were not much better…and 40 meters was resonant (that is around 2: 1 at best) below the band. I didn’t even attempt to tweak the antenna adjustments since there was really no place to even start on 17, 15, and 20 meters.
This seemed to coincide with the reviews on eHam that for the most part concluded that this antenna is CRAP!!. Some indicated that when you tweak it on one band, it then srews up the other bands. Based on the comments, s-canning this antenna seemed to be the preferred route. Could this antenna be really that bad? Or could it really make that much of a difference by getting it up in the air and off the ground?
Jim seemed to remember that when originally set up some time ago at a previous location, that Cushcratf had sent him some addendum of instructions as there was a change made in its configuration….maybe the directions I have are for a different earlier (or later) version?
Jim’s previous antenna at this location (before Sandy) was a coax fed 135 foot dipole that with a tuner he used successfully on all bands. It goes from the peak of the house (about 40 feet) to a flagpole. It seems that we will re-do this antenna with new wire and coax …and leave the R7000 on the garage floor.
Anyone have any thoughts or experience with the R7000 that would explain the results we got?
— John, W1XX