[amsat-bb] Re: Arrow and ELK Comparative Antenna Tests
Patrick STODDARD (WD9EWK/VA7EWK)
amsat-bb at wd9ewk.net
Mon Apr 25 09:58:35 PDT 2011
> Thanks John and Patrick. Interesting results and a very nice study.
John and I talked about doing this a few weeks ago while at a hamfest. John
called me Saturday morning, and asked if I was free in the afternoon. I went
over to his house in the early afternoon, and we turned his front yard into a
testing field for antennas for an hour or so. :-)
> Question---what was your testing method? I can't glean that from the information below.
On the west end of his front yard, John set up an IFR-1200 station monitor
with a long 2m/70cm duckie as the transmitter. The antenna was either a
Diamond RH77CA or the MFJ equivalent. I may be able to figure it out from
the photos I took, or John can jump in and answer that. On the east end of
the front yard, he had his Icom IC-910H satellite transceiver as the receiver
along with an RLC Electronics switch attenuator:
between the antenna and the transceiver. John set the station monitor so
it would transmit a signal that could be attenuated for an S-9 reading on the
IC-910H. We used a large cardboard box to hold the antennas, pointing
them toward the station monitor across the yard, and switching levels of
attenuation with each antenna to have an S-9 reading on each band.
The PortaFox antenna John mentioned is a log periodic designed and
made by Michael Brennan KA6PGN, based on the Elk Antennas log
periodics. He had these antennas on display, along with lots of military
radios, at the Palm Springs (California) hamfest in late January. He also
visited the Yuma (Arizona) hamfest in February, where he sold me the
antenna with elements to make it work either as a monoband 2m antenna
or as a 2m/70cm antenna. The elements are just like those Elk Antennas
uses with their antennas, thicker than those on an Arrow Yagi.
My PortaFox has a length of coax from the feedpoint at the front of the
antenna inside the double boom to a BNC connector at the rear. This is
similar to how I run coax from my Elk through the PVC handle toward the
rear of the antenna, but Michael has done in in a more elegant manner
with the PortaFox. Other PortaFox antennas Michael had came with a long
length of coax from the feedpoint, and you could put your preferred coax
connector on the other end.
I have lots of pictures from this antenna test at home, and will post them
somewhere tonight once I scale them down a bit for the web. The photos
are 12-megapixel photos from my mobile phone's camera.
As for KK0SD's comment, yes - I remember WA5VJB's article in CQ VHF
where he mentioned insulating the elements on an Arrow Yagi from the
boom. He also mentioned he had some ideas to increase the gain from
an Arrow Yagi, but (as far as I know) this follow-up article has never been
More information about the AMSAT-BB