InnovAntennas LogPer shortwave antennas

Technical description

The BOLPA (Band Optimised Log Periodic Array) is a log periodic dipole array (LPDA). Rather than sizing and distributing all elements to provide uniform performance everywhere, the BOLPA has been optimized to provide the highest performance within the amateur radio bands, resulting in exceptional performance across the entire covered band. With a direct 50-ohm feed point, the overall front-to-back ratio and antenna gain is significantly improved compared to conventional 200-ohm LPDAs.

Designer Justin Johnson G0KSC describes the BOLPA design in more detail in the "ARRL Antenna Book".

Application description

BOLPA-10

The "Band Optimised Log.Per Antenna" (BOLPA-10) is a dipole array with 10 elements for the frequency range from 14 to 30 MHz. Through careful calculations and practical optimizations, the spacing and lengths of the elements have been chosen to favor the amateur radio bands. Hence the name "Band Optimised LPDA". This results in a uniform gain of about 7 dBi over the entire frequency range, with an SWR of usually better than 1.5:1. It can be operated with up to 5000 watts transmit power.

The length of 7.7m is relatively short for an antenna of this type. 

BOLPA-4

The BOLPA-4 is brand new and offers the advantages of the BOLPA for those who have less space. The BOLPA-4 has a boom length of 5.5m and only 4 elements, but fully covers the 15m band and the 24.8 - 30MHz range. Like all BOLPAs, the BOLPA-4 has a direct impedance of 50 ohms at the feed point and is a super heavy duty antenna that will survive wind speeds in excess of 160km/h.

BOLPA-3

The BOLPA-4 is manufactured on a much smaller boom and is therefore for lightweight masts. The BOLPA-3 has a 3.5 m boom and covers 24.8 MHz to 30 MHz without gaps. So it is an excellent choice for those who want something for the upper HF bands for the current solar peak.

BOLPA-2

The BOLPA-2 is a very compact version of this antenna with only a 2.4m boom and 2 elements. The BOLPA-2 covers the 11m and 10m band. Even on 12m the antenna can still be operated with a tuner and still has around 4.5dBi on this band. If the space on the mast is limited, but 10m is a must, the BOLPA-2 is the right choice.

DELPA-13

The DELPA-13 is a dipole array with 13 elements for the frequency range from 10 to 54 MHz. 

The boom length of 11.5m is optimal for an antenna of this type. It provides a uniform gain of about 6 dBi from 10-54 MHz, with an SWR of mostly better than 1.5:1.