[Moon-Net] 2M antenna matching Data
Edward R Cole
kl7uw at acsalaska.net
Tue Nov 8 19:30:02 CET 2016
I think you are experiencing normal receiving limitations of using a
small array. I looked up the specs for FO12 and FO13 on VE7BQH
Antenna Chart and get this:
FO12 gain=12.48 dBd, G/T= -3.25
FO13 gain=12.92 dBd, G/T= -2.76
2x array gain =15.48 dBd or 15.92 dBd accordingly.
comparing with my M2 2MXP-20 gain=13.10 dBd, G/T= -2.61H, -253V, 4x
I have about 3 to 4-dB more gain in receive and that makes a lot of
difference in what you can see on JT65. When I was running qrp with
150w I could always copy the single yagi stations better than they
could copy me. I had EIRP=135*150 = 20.2 kW and they might run EIRP
= 32*600 = 19.2 kW; both of us generating about the same signal in
Tx. But I had 3-dB more signal sensitivity due to having more
antenna gain. Of course if they ran 1x with 1000w that helped me
even more 10Log(1000/600) = 2 dB. Now days I run EIRP= 135*1300 = 175.5 KW
G/T is a figure of merit measuring how good your pattern is (how well
does it reject ground noise). This a factor of the design quality,
so higher positive numbers are cleaner patterned antennas. Look over
click on second Tab for 144 antennas.
I am experiencing this same limitation using a single 6m yagi on
eme. The 2x and 4x array stations see my signal long before I see
them. Both stations running QRO.
My yagi gain = 10.85 dBd (13 dBi) and one needs 15 dBi minimum for
doing 6m-eme (easier). I can only see signals in my ground-gain elevation.
You should also try taking advantage of ground-gain (angle depends on
height of antennas); probably good from 4 to 8 degrees
(guessing). My array is at 52-feet above ground so I see gg almost
at MR or down to MS.
Hope this helps explaining your issues (a little).
73, Ed - KL7UW
I benefited from starting eme in 1998 when only CW was used and my
array was minimum capable of eme with 1000w. I made four contacts by
CW before 2003 when I downloaded JT44. All were super big-guns.
At 05:44 AM 11/8/2016, Curt Nixon wrote:
>Thanks for all the comments and directions folks:
>Regarding the data and its presentation, I can only say I copied it
>directly from the dispaly on the software utility. Some of it I
>understand, and some not so much. I am a newb with the Smith chart.
>The software is a data sampling and control utility for the T100. It
>collects sweep samples over a range of frequencies and step sizes and
>loads them to a CSV file. They are then used to plot a smith chart as
>well as an SWR, RL, and R+Jx charts.
>I believe the G is for Gamma which is (I think) the 50 ohm Smith
>normalized values of ZL. I also think the "angle" shown is the angle
>of the vector at the given frequency and as the G point approaches 0+J0
>the angle becomes meaningless due to the minimum sample resolution (25KHz).
>Anyway. I have been using these two antennas for 2+ years and yes they
>are as near identical as my machinist skills (substantial) could build
>them. The T match jumpers are at the ends of the T bars as someone
>They are oriented in the proper phase, and I cut the jumpers to less
>than +- 1/16" from same pc of LMR-400 Brand new. My divider is one of
>the 1/2 WL (1/4 +1/4) from square tube
>THey system has about 28 initials on it but perhaps I am still expecting
>too much from the pair. During the first period of the ARRL weekend
>past, I could not detect a single station, including the mega stations
>which were operating. Even when they worked, stations rarely had a
>hard time detecting me, but I can barely see a trace for them. System
>still shows less than about 1.2:1 SWR.
>So I decided it was time to start at the top and see if something is
>amiss...and it appears that, so far, not the antennas or feed+divider.
>I am next going to check the TR relay(s) and will be working agin for
>the ARRL weekend in 2 weeks. All the leaves are off the trees so that
>may help a little.
>Prior I will do some noise floor tests with the 50 ohm LNA terminated
>and see what it looks like.
>Again, thanks for all the support.
>As an aside, I believe my issues previously noted regarding the big KW
>paging system a mile away on 143.9 has been resolved. It looks like the
>last of the antennas listed on that site have been migrated to DMRS on
>800MHz. So I no longer see any of the intermod junk.
>Moon-Net posting and subscription instructions are at
>No virus found in this message.
>Checked by AVG - www.avg.com
>Version: 2015.0.6201 / Virus Database: 4664/13367 - Release Date: 11/08/16
73, Ed - KL7UW
"Kits made by KL7UW"
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