7/8 NOV 09 G6HKS WORKS JAPAN FOR NEW COUNTRY ON 144MHz JR3REX (-21) AND JM1GSH (-25)
WAIT OVER AS RICHARD TRIALS THE NEXTGEN8 - IT FEELS LIKE I'VE GOT THE 9 ELE CQM UP THERE!
G4CQM is now on Twitter, follow my tweets!
You've arrived at the NEW HOME of www.powabeamantennas.co.uk the ultimate YAGI KIT!
Richard Mason G6HKS and Derek Hilleard G4CQM welcome you to PowAbeam Antennas DIY/HOMEBREW yagi kits. We supply all of the parts and State-of-the-Art designs enabling YOU to produce a high performance yagi beam antenna!
Making the antennas is simple BUT you need some basic construction skills and should view this as a learning project with a high performance yagi as the end result.
Amateur Radio VHF yagis are changing for the better, competition between designers and manufacturers has resulted in cleaner polar patterns and higher forward gain. But it's more than just that, accuracy of design and stability are notable developments. PowAbeam NEXTGEN yagis have now replaced our previous antennas. NEXTGEN yagis focus on F/R (Front to Rear power ratio, 90-270 degrees) particularly in the H-Plane, ignored by earlier designers! If you live in an urban environment this can help reduce noise/interference problems. But remember there is NO SUBSTITUTE for getting YOUR yagi up high and in the clear! NEXTGEN yagis have reached a higher level of design accuracy and ALL the NEXTGEN designs have been scrutinized by the master himself, Lionel H. Edwards VE7BQH. G4CQM's NEXTGEN yagis really are top end performers, see Lionel's latest G/T table...
Only PowAbeam Antennas employ a 'Coaxial Dipole' driven element. Advantages include; wide bandwidth, highly efficient, low noise and unrivalled simplicity! It also prevents static electricity charges building up on the inner conductor of your feeder cable, when tested it presents a DC short circuit!
Q. Why is there no matching?
A. All PowAbeam Antennas have been carefully designed using YO7 PRO and AO PRO from K6STI to present a natural 50-Ohms impedance at the feed point!
Q. Isn't this so called 'Coaxial Dipole' just another form of folded dipole?
A. NO! RF currents flow around the entire loop of a folded dipole or LFA loop. There is NO current flow at the centre of the inner conductor inside the coaxial dipole!
Q. Do I need to use a balun?
A. NO! The coaxial dipole is essentially formed from two 1/4 wave shorted end stubs. By connecting the inner conductors together at its centre and creating one complete length of inner conductor, forces the outer conductors of the dipole (the radiating elements) into being equal, i.e. having the current node at the dipoles centre and equal voltage nodes at its tips as with any split dipole fed from a balanced source!
Q. Is this coaxial dipole perfect?
A. NO! When tested on an antenna test range calibrated to traceable national standards a slight squint was observed in the polar pattern. In reality the squint is so small that most operators don't even notice even working EME!
Q. Why use a coaxial dipole then?
A. There are NO MESSY COILS OF COAX, NO EXTERNAL STUBS, NO UNPROTECTED CONNECTIONS, NOTHING TO BURN OUT AND NO TUNING REQUIRED...IT ALSO OFFERS GREATER BANDWIDTH THAN FOLDED DIPOLES OR LOOPS FED PROPERLY WITH BALUNS...It is unrivalled in its simplicity and when used in a 50-Ohms direct feed yagi it produces a highly efficient and low noise solution, ideal for weak signal communication!!
G4CQM's PowAbeam Antennas yagi designs are highly ranked in the famous VE7BQH G/T simulations table, see the latest analysis! LIONEL H. EDWARDS VE7BQH Issue 71 February 6, 2010
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