My Review Page
1. Cushcraft 8040V Vertical
The antenna arrived in a 7ft long cardboard box, and I opened this on the grass outside to check the contents. There seems to be no such thing as a "simple vertical" these days, because looking at the contents check list, there are some 42 parts to check off, including some with multiples, such as 45 8-32 Hex nuts and bolts.
However, the proper thing to do is to check the list to make sure nothing is missing, before assembling the antenna. Prior to that, I had laid out the components on the grass and they can be seen in Fig 1. Assembly is relatively straightforward, so long as you follow the instructions. The first important thing to do is to run through the check list of components and identify each one. Make sure that everything is there before starting assembly. After that, it is just a matter of reading and ticking each step as you work your way through the book. The booklet is 12 pages in length and has quite a good selection of pictures to help as well. On the front cover, there is a picture of the completed antenna so that you can check the finished product looks the same!
Particular attention should be paid to the loading coil assembly, as it is quite easy to start mounting the coils in the wrong holes, so follow the diagram very carefully and it will save time. Some of the holes that have to be aligned do not align very well, but I am being hypercritical here and it was easy enough to overcome that problem. I took around 3 hours to assemble the complete antenna. When installing the radial rods, it is a good idea to employ something like a saw bench to clamp the antenna main mast so that the top remains well off the ground. The radial rods are stainless rod stock but would bend quite easily I would suspect.
The loading coils are well made and waterproofed, and a very neat way of mounting them is used to good effect. Likewise, the radial rods are mounted in a novel mounting clamp, and are very rigid after assembly. It would also be an easy matter to replace any if needed. Experimentation with the radial rods is a good idea too, depending on your operating preferences. For example, the 80 meter rods may be clamped at maximum extension from the radial ring to give a better coverage of the low end of the 80 meter band.
The completed antenna is only around 25ft tall, but it does become top heavy and it is advisable to thoroughly read the book a couple of times, as I have already suggested, before starting. There is some very good advice in there and it seems that most problems have been thought of and catered for with good advice.
Mounting the Antenna.
As this was to be a temporary installation, I decided that knocking a 3 ft piece of 2 inch dural tube into the ground and clamping the antenna to the side of it would be sufficient. The main top part of the antenna is offered to the bottom section, which is already mounted as just described, and then clamped. However, the bottom piece is about 4ft off the ground, so I had to stand on a saw bench and lift the antenna above the bottom section before lowering it and then clamping it. This is more difficult than it looks. The antenna tends to whip around and I only just managed to do it on my own. I should have taken the advice given in the booklet about using the "buddy" system. In other words, get some help.
If the installation is to be a permanent one, then the mounting post must be concreted into the ground. I found that even with two feet into the ground, the antenna pulled it over and I had to resort to a single guy to hold it in a vertical plane. Substantial mounting clamps should also be used.
Ground radials.
A 400ft reel of 18SWG enameled copper wire is provided for the ground radials. The suggested configuration in the booklet is for four 65ft and four 35ft radials. When laid out in a spoke pattern in a straight line from the base of the antenna, this predicates a garden roughly 130ft by about 80ft of free space. Most modern places these days are not that large including the house and front garden! However, I cut them and installed them as suggested. With ground radials, the usual aim is for as many as possible. However, this tends to reduce the feed impedance below 50 ohms. A compromise can be reached however with the aid of an antenna analyser. The radials should be buried preferably, or you will have problems when cutting the grass. Even though I was careful to move all the radials prior to cutting my grass, I then got one caught around my strimmer. Just remember, it takes a lot longer to untangle it than it does to get it caught in the first place, so cut a slot with the spade any bury them out of the way.
Feeder.
Good quality coax, such as RG213U, or similar should be used. Connection is at the base with a couple of solder tag connections. Make sure that the connections are secure, tight and waterproofed. Self amalgamating tape should be used on the end of the coax, and perhaps painted with a coax seal. I have not used this myself but have read of good results from using this. The coax can be buried, but for this review it was left on the surface, just like the radials. I also made a common-mode choke balun at the feed by winding about 10ft of the coax into a coil and taping it together. This has the effect of isolating the antenna from the rest of the feed line.
Results.
I used an MFJ 259 antenna analyser to test the antenna. I had not been too fussy about where the top resonators were fixed so I decided to test it before tuning. I was quite surprised. It was resonant on 3.540 with a 1.1 to 1.0 SWR and a feed impedance of 50 Ohms. I then tried 7MHz and it was resonant at 7.011 with 1.1 to 1.0 SWR and a 50 Ohm feed impedance. On 80 meters the band width was roughly 80kHz and on forty about twice as much before the SWR exceeded 2.0 to 1.0. This was a test back in the shack, so I then decided to test again at the bottom of the antenna. To my surprise it did not change very much at all.
As most modern amateurs will probably be interested in SSB operation rather than CW, I decided to tune it for the top end. Dave, G3MPN, came over to give a hand. We lowered the antenna and shortened the top. In fact we almost lost it, as we left it with about an inch poking out. On re-assembly, the resonant frequency had changed to 3.740 and the bandwidth had increased slightly. Forty meters was not affected at all.
I then altered the ground radials in such a way that they extended from the base of the antenna in a spiral fashion. This would allow somebody with a smaller garden to install this antenna. I found that the effect on the performance had not changed much at all. It does mention in the booklet that the radials can be bent around objects and I found this did not affect the performance very much at all.
There is an old adage in amateur radio that says a vertical antenna radiates an equally weak signal in all directions. However, if one is unable to put up towers or poles taller than 40ft, this antenna definitely offers an ideal opportunity to operate on 80 and 40 meters where a suitable full size alternative could not be employed. I did more listening than actual transmitting as it enabled me to get a more comprehensive overall performance idea of the antenna. I was slightly unfair here, in that I was comparing it to inverted V dipoles at 90 ft. It is true that the Cushcraft was on average two S-units down on most signals, but then it is a compromise type of antenna and only 24ft above ground. The only signals where it was equal in performance to my V's was on very local stations, within a few miles. There the two were just about the same.
Propagation is not good at present, plus we are in the summer doldrums anyway, so I did not get a chance to hear any real DX. However, a vertical works well by virtue of it's low angle of radiation, so it will obviously be of value to those with limited space. There is also the added advantage that this antenna offers a solution to the problem of 40 and 80 meter operation in a small space. Once disassembled, it can be packed into quite a small box, so would be ideal for portable use. It is rated at 1.5kW so will handle the full legal limit with no problems. It is priced at £200.