Force 12’s C3 vs C3E: Performance trade-offs

By chapter 5 of my recently-mentioned book on antenna modeling I had enough knowledge to modify an existing EZNEC model of my Yagi to include the additional 10m element I added to it shortly after installing the antenna.

Luckily for me the base Force 12 C3 has been modeled and that file is included in the software CD that comes with the ARRL Antenna Handbook. All I had to do was add the new 10m reflector that converts the C3 into a C3E and then compare the before & after to see what my trouble and $99 bought me.

The verdict: on 10m, very little additional forward gain (.75 dB) but a significant amount of front-to-back (5.25 dB) and some (2 dB) front-to-side rejection.

both

10m plots of C3 (two elements) vs. C3E (three elements). Both modeled at antenna height of 42 feet and with peak RF radiation at 12 degrees.

Before &  after plots of 15 and 20 meters showed absolutely no difference caused by the addition of the 10m reflector.

So far, so good.

C3 owners are aware that their antenna has gain and directivity on 12 meters but they may not be aware of the compromise made to this band if/when they upgrade their C3 to a C3E.

With the additional 10m element (a reflector)  the C3E has 1.6 dB less gain, 5 dB less F/B rejection and 3.2 dB less F/S rejection on 12m.

12mC3vsC3E

12 meter plots of C3 (left) and C3E (right). Both modeled at antenna height of 42 feet and with peak RF radiation at 14 degrees.

As someone who uses this Yagi on all bands 10-20m, I think the additional 10m element is a disadvantage overall. I think I’ll remove it and instead add Force 12’s 40m rotatable dipole to the boom.

Who wants to buy a 10m reflector for their C3 – low mileage, RF only applied on Sundays, etc…

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  2 comments for “Force 12’s C3 vs C3E: Performance trade-offs

  1. February 3, 2013 at 1:39 pm

    Hi John

    Do I understand that a Force 12 on 10 or 12m is almost a dipole ?
    I am still working with dipoles and vertical wires.
    However I had prepared to add the 3 original elements again stored under the roof for many years.
    To change 40-20-15-10 dipole to a 4ele trapped beam for 15/10
    1 ele 20&40
    But high winds prevented me this weekend

    • February 3, 2013 at 1:48 pm

      The C3E has 4.5 dB gain on 10m, the C3 a bit less. On 12m, the added element for the 10m band reduces 12m gain to about 1.77 dB – down from 3.2 for the base C3.

      I’ll be posting all the plots here Monday or Tuesday:
      http://www.ae5x.com/blog/dxing/force-12-c3-plots

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