Below you can find the NEC 4 calculations of the MACO FLAT 6. (M106C)
The sizes are from the manual which can be found here:
http://www.servicedocs.com/ARTIKELEN/7200252850001.pdf
The dimensions used are those described for 27.005 MHz.
Below a confirmation of the input in Eznec:
The azimuth plot 11 dBI gain, but a very bad front to back.
The elevation plot could be improved as well.
By removing the 2nd director the gain drops with 0,8 dB but the front to back improves with over 10 dB.
Overall conclusion :
Maco antennas generally are “good”.
Im not sure if MACO is aware of the situation, so we mailed them “our” findings.
At this moment the best advice migth be not to use the maco provided dimensions:
We advise to change the antenna into:
http://cb-antennas.com/?page_id=231
All you need to do is change the dimensions.
Element diameters etc are equal.
And best of all..that antenna can be direct fed using a split driven element.