I eluded to the fact that asking about antenna comparisons has a large
component of personal bias (I bought it and use it so it must be good) and
little reproducible comparison statistics (even the K7LXC & N0AX report
acknowledges the technical difficulties comparing antennas).
[personal bias] Prior to my tower crash in 2003 I had a Mosley PRO-67B up 90
feet. It covered 40 ~ 10 meters, excluding 30 meters. With 2 elements on 40m
up that high it worked well. Although not designed for 30m I even made
contacts on that band. I used the internal antenna tuner in the rig.
My original intention was to install another antenna that covered 40 ~ 10
meters on a single boom. I was looking at the Force 12 and the bigger Mosley
products when an TH-11DX became available in an estate sale. I asked around
the DX club and was surprised that many of the top DXers in my area were
using this antenna. It wasn't peer pressure but more like peer
recommendations that convinced me to buy the TH-11DX. And it didn't hurt my
"ham ego" that this used antenna was priced about 50% off retail.
When I picked it up, the antenna was in "chunks"... it had been disassembled
only to the point it could be bundled together in pieces 12 ~ 15 feet long.
This was a perfect length for strapping to the rooftop carrier on my van. It
took me more than several days to take it apart, clean up the joints,
replace corroded fasteners, and reassemble the beam. I wasn't in a
particular hurry but the thought that purchasing a new antenna and
assembling it would be a better value if you didn't have the time to putz
with a project like this. There were several trips to the hardware store for
small fasteners and stainless hardware.
My replacement tower is 70 feet and this is where the TH-11DX rides. The
antenna is on a 24 foot boom which holds 11 elements. The driven elements
are the standard Hy-Gain log periodic design and the reflectors are full
sized. Only the directors have traps for 10 and 15 meters. The antenna is
heavy, close to 100 pounds if I remember correct. It includes the BN4000
current balun which is rated for 2000 Watts continuous and 4000 Watts peak.
I ran VSWR sweeps with the antenna mounted on a 6 foot pole before I put it
on the tower. I wanted to make sure it was going to resonate in the ham
bands. It looked reasonable (I didn't keep those graphs) so I installed it.
I then ran sweeps by connecting my analyzer to the pigtail at the top of the
You will find the 5 files on my website http://chudek.aberon.net in the AEA
HF ANALYST CHARTS folder. Go into the TH-11DX folder and download the PDF's.
You will also find sweeps for two other TH-11DX's at K0IEA and KF0QR. These
were taken from the shack end of their feedline so there will be some
transmission line bias in these values. In addition, all three antennas are
at different heights; 50, 70, and 90 feet which complicates direct
comparisons even further. Add into the equation these antenna locations have
different terrain and any direct comparison is futile. But I had a new toy
(analyzer) and had fun using it.
ASIDE: Regarding transmission line bias, you can download the 160m inverted
vee chart found in a separate directory. I made two measurements; the first
directly connected to the feedpoint and the second at the end of 1/2
wavelength of RG8x coax. As you know, a 0.5 wavelength transmission line
should present the same feedpoint values to the transmitter end. I overlaid
the two sweeps on one graph so it is easy to see how a feedline can "bias"
the results. In the case of 160m 3:1 bandwidth, it looks like you have an
extra 40 KHz of bandwidth due to this phenomenon.
So what's this long winded message really saying? Pick an antenna for it's
match to your needs and goals. These are usually a combination of cost,
product availability, available space, tower capacity, band coverage
desired, durability, and reputation. Busting through a pile-up also depends
upon operator skills.
Regarding my 40m coverage... do I miss that? Well kind of. But I solved that
issue by side mounting a single element, full sized Telrex 40m dipole at 65
feet. And I also installed a sloping wire dipole. I find it interesting that
95% of the time the Telrex hears better but there have been times when I
could hear a station on the wire that was simply not audible on the
horizontal antenna. Would a 2 element yagi make a difference? I don't know.
So is anyone interested in buying my 3 element 20m Gotham yagi, new in the
73 de Bob - K0RC in MN
----- Original Message -----
From: "Richards" <email@example.com>
To: "Robert Chudek - K0RC" <firstname.lastname@example.org>
Sent: Tuesday, July 29, 2008 1:12 AM
Subject: Re: [TowerTalk] Antenna Selection Assistance
> Excellent analogy, and yet I think it is still a fair question...
> notwithstanding how it open ended it might be. I like red cars!!
> Man.. I looked up the HyGain TH-11DX on rig pix... and it is
> REALLY BIG. No wonder you like it!
> If it was originally "temporary" -- what was the alternative antennas you
> had considered putting up there after wards, but did not, because it
> works so well. In other words, what were the other "Leading Contendas"?
> ///////////////////// K8JHR ////////////////////
> Robert Chudek - K0RC wrote:
>> A HyGain TH-11DX. It was going to be a temporary antenna for me
> but it works so well I'm leaving it up there at 70 feet.
>> But you do realize you're asking us what color car you
> should buy next, right?
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