These consist of two Pro-HF mobile whips for the band of choice, a short stub mast fitted with a dipole centre and a fixing bracket.
Loosen the grub screws at the top of the loading coils and slide the whips in to the point where the black ring is marked on them and tighten the grub screws with the supplied alan key. Screw the two completed whips into either side of the dipole centre. A 13mm spanner may be necessary to ensure they are tight. Also attach your coaxial cable (50ohm) to the SO239 socket.
Using either an antenna analyser, or your transceiver with a SWR meter, adjust the whips to tune on your favourite spot. The bandwidth may be rather narrow so choose for your favourite mode – the CW portion will be near the black mark the DATA portion a little higher up the band and the phone portion even higher. Remember that the shorter the antenna, the higher the resonant point. As it is a balanced dipole antenna remember to adjust each side equally. Use of an external ATU can extend the tuneable
range / bandwidth of the antenna.
Once you have your match, fit the stub boom and antenna to your mast using the supplied clamp and raise it up to operating position. This is also suitable for loft mounting.
The 40m (7MHz) version will also be resonant on 15m (21MHz) (third harmonic).
Sigma AM-PRO 40 Meter HF Antenna
Specifications
● Power handling 250 watts
● Length 5 Meters / 16 feet 4 inches (Approx)
● Impedance 50 Ohms
● Frequency 7.1 MHz
● SWR 1.5:1
● Whip 17.7 ph stainless
● Fitting 3/8 UNF
● Made in Great Britain