Fantastic Proven Results From A Cushcraft R7000
My antenna farm, if you can call it that, now sports a Cushcraft R7000 vertical antenna. I have the original version of the antenna which was manufactured in the 1990’s until a modified design was produced.
At around the same time, MFJ acquired the Cushcraft company and continues to manufacture and sell antennas under the Cushcraft brand.
The Cushcraft R7000 is a seven band antenna covering 10m, 12m, 15m, 17m, 20m, 30m and 40m. It’s clever design allows it to use only three traps. The three traps are for CT1 (10/12m), CT2 (15/17m) and CT3 (20/30m). The 40m segment is tuned by adjusting the length of the top section.
Although very reliable, the traps on the Cushcraft R7000 can be prone to problems. The main problem being corrosion occurring between the aluminium trap housing and the connection point of the internal coil. Once corrosion occurs, the result can manifest itself as fluctuating SWR when the antenna moves in the wind.
A secondary problem with the traps on the Cushcraft R7000 is that after strong winds it may be discovered that the SWR and resonance of certain bands of the antenna have changed. The cause of this is simply down to the weight of the traps coupled with vibrations caused by strong winds which allow the traps to move down the main mast sections.
No matter how much the clamps securing the traps are tightened, it appears the only method that can be used to prevent this happening is to drill a small hole and fit either a small self tapping screw or some kind of metal pin to lock the trap securely in place.
An advantage of this antenna is that it doesn’t need any extra radials, in fact Cushcraft specifically instructs the user not to add any radials. Coupled with this, to work effectively it only needs to be mounted at a height of between about 10-20 feet.
Mine is mounted on a 9 foot pole as that’s what I had available at the time of installation. Even at this low height, I can hear stations on this antenna that I can’t hear on my doublet!