Repairing and Optimizing the CushCraft R-7000

For several years; I was a severly ANTI-VERTICAL operator,believing that there was NO WAY a vertical actually works any better than a DUMMY LOAD in radio operations. Several hundred DX contacts later, I am now a believer in the value of the vertical for DX and in stealth radio operations.

I have utilized Cushcraft R7000 vertical at my location for about 10 years now; purchased used from a hamfest in Midland, TX. As purchased, this antenna gave me quite a few problems: intermittent SWR, frequent adjustments to correct bad swr,and an intermittent dead short situation on the 15m band.

The R7000 is mounted approximately 15ft above ground, on a short push up mast. Through trial and error, I discovered that this antenna seems to perform most optimally when not located directly on the ground.

I located the R7000 in the center of 6 large Oak trees in my backyard. This location afforded the best stealth operation; largely invisible from the adjacent neighbors. This is imporant since I operate in an Antenna restricted neighborhood; No antennas of any kind are permitted by the HOA. I did have to do a bit of tree trimming to clear an area of about an 8 foot radius around the antenna (from the crossed counterpoises to the top of the antenna). Before I cleared the tree limbs I was getting a very marginal 1.9 SWR that would jump to 2.0 or higher if it rained or the limbs were actually touching the radiating element. Now that the limbs are cleared I operate without any kind of tuner and the SWR stays below 1.5 on all bands 10m thru 40m. Close proximity of tree limbs and branches close to the top of the antenna affects SWR on the 30 and 40 meter bands.

Dead Shorts on 15M band:

This problem was traced to poor trap construction and factory quality control. Each antenna trap has two elements (10/12, 15/17, and 20/30). At the base of the 15/17 trap is an aluminum collar that is only riveted to the trap. I found that this collar was very loose and it needed tightened or replaced. I drilled out the rivet that bonded the collar to the rest of the trap and replaced with a stainless steel bolt, star washer, lock nut, and nut. I brushed the aluminum collar where it makes contact with the trap base and tightened the bolt assembly.

Varying SWR in different weather:

This was caused by the screws attaching the trap coil wires to the trap contact points. These screws loosen over time and form poor electrical contact with the trap body. I removed all of the original hexhead screws and increased to the next larger guage. This allowed the screws to be tightened much better. In addition, I placed aluminum star washers under the screw head next to the body and used aluminum lock washers under each screw head.

Antenna element adustments won't hold:

The last mod performed to this vertical cures the antenna from adjusting its own length! This antenna moves around quite a bit in the wind; even when guyed at a point half way it's vertical length. As a result, the telescopic sections of the antenna settle somewhat over time, sliding into the larger sections. This problem was cured by resetting the elements to the proper lengths, drilling a pilot hole thru all the sections of the antenna and installing aluminum cotter pins in the holes to completely stop the pipes from collapsing. The pipe clamps are still used as the main system to clamp the pipes to the correct length;but there is now absolutely no change in length possible. No more adjusting of the antenna after every cold snap.

Ants nesting in R7000 balun box:

After operating for a while I noticed that I my swr was deteriorating again. As I disassembled the antenna I noted that there was a trail of ants going into and out of the balun box assembly. I removed the assembly from the antenna, took the cover off, and was greated by a huge nest of ants and their eggs and larva. It was easy to clean everything out; but a close inspection of the balun box showed that it was going to be real easy for the ants to restore their nest as soon as they wanted too!. To cure this situation; I used silicon seal to completly seal the large opening around the antenna jack. Then I used a very fine drill bit to create a pattern of holes in the bottom of the box that would be too small for the ants to use as a portal into the box. No more Ant problems!

After all of the repair and optimization processes above were completed; the R7000 now tunes up great across the entire CW portions of all of the bands'10m through 40m and has needed little maintenance or adjustments over the past 10 or so years. Best of all, this antenna has really allowed me to work a lot of DX and contesting activities from my location.

GL and 73.......Dave, N5IW

Other links with great info on R7 and R7000 antennas:

-Repairing R7 Matching Box

-Cushcraft R5 1/2 wave vertical repair

-CUSHCRAFT R7000 Problem and Repair