Zack,
The Cushcraft mounting style that I referred to makes use of a small
aluminum saddle plus a cylindrical "half-washer" (both with through
holes) to secure the solid rod elements to the boom using stainless
steel bolts, lockwashers and nuts. The elements are not insulated from
the boom, unlike the original G0KSC design that used insulated tubular
elements. I'm sure the element lengths were corrected since G0KSC
reportedly came to MFJ to model his antennas in this different
configuration and oversee the redesign. Cushcraft/MFJ touts this point
on their webpage. However, some of the photos on the MFJ webpage for my
antenna (LFA-2M9EL) are incorrect.
73, Walt, AJ6T
On 1/29/2019 7:28 AM, Zack Widup wrote:
Well, you got me curious, Walt. I'm not sure what Cushcraft mounting style
is, but are they not insulated from the boom? And the original G0KSC design
used insulated elements? The lengths of elements will change (increase)
when going from insulated to non-insulated elements. I have designed (or
tweaked other designs) and built all the VHF+ Yagis I use and I am really
familiar with element boom correction factors. I just wonder if the element
lengths were corrected.
73, Zack W9SZ
On Mon, Jan 28, 2019 at 10:52 PM Walter Miller, AJ6T <aj6t@comcast.net>
wrote:
Byron,
I have also been intrigued by the LFA Yagi design. I recently ordered a
Cushcraft/MFJ model LFA-2M9EL and I had hoped to get it operational by
the January VHF contest. However, due to construction and tuning
problems the antenna is still sitting on the rear deck. The first
problem I ran into was discovering that no hole had been drilled in the
boom for the first director. Hmmmm....MFJ quality assurance strikes
again. I had to drill a hole with my hand drill at the specified
location. As you noted, the solid rod elements are mounted "Cushcraft
style" to the boom. This is unlike the original G0KSC Innovantennas
design that has insulated elements. I was surprised to discover that
the antenna does not have a connector for the coax feed. You have to
make a three-turn coaxial choke balun and connect the flying leads to
the screw posts on the loop. Don't forget to waterproof those exposed
leads to prevent water from wicking into the coax. After all that I was
unable to find a smooth resonant point when adjusting the loop size with
the antenna pointed skyward. Now I'm considering making or purchasing a
ferrite bead balun to replace the three-turn coaxial choke recommended
in the Cushcraft/MFJ manual. I was surprised to discover on the G0KSC
website that Innovantennas now offers a bead balun to feed their version
of this antenna. I'll come back to attempt to resonate my LFA-2M9EL
when I have time, but for now to say that I am disappointed would be an
understatement. Of course none of this relates to the performance of
this antenna once it is tuned up and put on the air.
73, Walt, AJ6T
On 1/24/2019 5:50 PM, Byron Tatum wrote:
Hello- Has anyone used any of the MFJ versions of the 144 or 222 Mhz
G0KSC loop fed yagis and would be in a position to provide evaluations of
them? I have studied the Innov versions a lot and am very interested in
them. I have studied how well they rank in the VE7BQH yagi tables, however
I guess the MFJ versions are too new to be included in the tables. I
understand that Justin went to MFJ and modeled the LFA's for them using
existing MFJ elements and booms (such as on the 13B2 and 17B2) so that new
tooling would not be required. I like the 1/4" OD element rods on the Innov
antennas. I am a little disappointed in MFJ keeping the 3/16" OD elements
but am trying to keep an open mind on this. Thanks, Byron W5FH
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