Topics For Technicians!
Build a 1/4 Wave HF Multiband Vertical for 40 - 10 Meters
This multiband vertical idea is based on many other home brew multiband verticles floating around the internet but it is another simple way to build a multiband ground mounted verticle that is very inexpensive and should cover 40 through 10 meters using PVC tubing as a support. When properly built, it should act as a 1/4 wave ground mounted "ground plane" type antenna on most of the disign bands.
It consists of 3 sections of thickwall PVC connected together and may be self supporting, but guying is recommended due to its 33 feet + overall height!
1 ea 12 foot bottom section, and 2 each 8 foot length sections connected together using your own construction techniques, but bolting the sections together would be a good strong method of connecting them together and preventing them from slipping. The top most section is a 102 inch steel CB type whip that is used for adjusting the 40 meter section.
Each of the 5 "supporting arms", as seen in the drawing below, is attached to the main PVC vertical portion using simple PVC "T's" or your own method. They are used as the support points on the main "mast" for attaching the ends of each 1/4 wave vertical radiator. Sky hooks won't work! Try to keep the vertical radiators as far apart from each other in your building progress as possible..this will help with the tuning process.
The exact lengths of the radiators are not mentioned here due to variations on your construction and the properties of the ground under your vertical but using the standard 1/4 wave vertical forumula of 234 / your frequency for each band = feet should get you started. You should always cut long and trim/tune each individual section as needed for lowest swr.
Please note that the 40 meter vertical radiator is made up of wire from the base to the top most part of the upper PVC section. From there you use a stainless steel "CB" type 102 inch whip for the top extention and tune it as needed for the 40 meter band...this gives you the length needed for adjusting to a 1/4 wave length vertical when you include the bottom section of about 28 feet of wire. You will have about 3 feet more whip than you need for the whip but use this extra to tune the final length for lowest swr.
NOTE..There is no need to CUT the whip which may be difficult (most are made from stainless steal)...just simply use adjustable hose clamps (or your own method) to attach the whip to the main 40 meter bare wire that is going down to the base of the vertical PVC tubing. Then adjust and tighten the metal hose clamps as needed by sliding the whip up or down for best tuning. When done, try to seal the connection points between the whip and the wire to help eliminate dissimilar metals oxidation.
The various "vertical wires" may interact with other bands so some adjustments of the antenna lengths may be needed. The use of an antenna analyzer would be a good idea if you have one, but if not, then use your trusty swr meter. You might also eliminate the 15 meter vertical section and use the 40 meter section as a third multiple on 15 meters. The swr on 15 meters, using the 40 meter section for 15, may not be extremly low, but might be useable..your choice.
If you don't want to "fool" with adjusting each individual 1/4 wave verticle, then the use of a good antenna tuner in the shack should peak and tweak each band as long as the lengths of the vertical elements are close to 1/4 wave length or a bit longer.
The antenna is fed at the bottom as with any other vertical construction with 50 ohm coaxial cable and all vertical 1/4 wave vertical elements are connected together at the base of the PVC tubing and they are connected to the center conductor of the coax.
The radials should be at least 1/4 wave long for each band and as many as you can put down under the antenna for best performance and low swr.
This may not be a "plug and play" antenna so some fun will be had getting it on the air..but hey, isn't that what antenna building is all about.
See the KL7JR radial ring project for some ideas for the radial system.
This idea can be modifed as needed for best performance or for the bands that you desire. You should also see the link below for some other ideas that may help you enjoy getting this type of antenna on the air! Have fun!
Additional similar antenna project for more ideas!