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> Six meter flexible antenna for portable operation 50MHZ
Six meter flexible antenna for portable operation 50MHZ
Six Meter (50Mhz) Portable Coax Antenna
This is a small antenna for 6 meters, after using it you can roll-it up with the feeder attached (not supplied) and pack it away.
It is based on the 'Townsman' design by B.J.P Howlett G3JAM (Wireless World February 1980) but instead of using aluminium strips it uses a length of coax as the radiating element. It is 3.5 mtrs in length and is terminated with a 50ohm BNC socket at the base.
It operates as a half wave dipole for optimal matching to 50 ohms there is a impedance transformer mounted in the base.
This antenna is as good as a 'slim jim' or 'J' antenna. It out performs the 'rubber duck' antennas fitted to most hand helds so it is ideal for use in hotel rooms or other accommodation when away from the home station, just attach the end to the ceiling with a pin and let it hang down. For outdoor use just throw a string over a tree branch and pull the antenna up, you can even elevate it with a kite !!. Rolled up it takes no space at all, ideal for holidays.
It can also be mounted in a glass fiber rod ( not carbon) for a more permanent installation.
The antenna has been air tested and the VSWR checked. The basic antenna is water proof but if you are going to use it outdoors for long periods the feeder connection should be taped up with self amalgamating tape.
The maximun input power is 25 watts, but it can handle 50 watts for short periods.
A number of tests have been performed on this type of antenna and by coiling the feeder to form a choke just below the connection to the antenna the overall performance can be improved. This is a quote from G3SMW regarding the 2m/70cm version of this antenna.
" We have added an RG58 "tail", part of which is coiled to form a choke. This choke is to reduce currents on the outside of the feeder that could tilt the main lobes of the vertical radiation patterns (VRP) up or down. It also avoids possible matching problems at the transceiver. This air-cored choke construction, winding the coax tail inside a 20mm PVC tube (wound with 6 turns of the PVC cable jacket touching), is satisfactory and reliable. We checked VRP's on a large flat open area (Playing Field). Whilst the 70cm VRP is not quite optimum, it does have one of its maxima in the horizontal plane and this is within about a decibel of the others. After initially trimming the top, the VSWR was below 1.5 at the centre of both bands, and below 2 at the band edges. The antenna performance is considered quite acceptable for its purpose on both bands. "
Comment receved from previous sales
just to say that the antenna works really good, just worked 6 stations on e's on 50mhz, first contacts on 6 for 21 years. Thank you and good luck.
