2008 KØS, Strange Antenna ChallengeSM

Hosted by Erik E. Weaver nØew and Dwayne T. Walker wb5plj,

Event Dates: May 24-26, 2008


UPDATED: May 9th, 2009

 


Vertical is up

Yay! It's up!

 


      ...If it is metal...

                     ...If you can tune it...

                                    ...If you can load enough power into it...

...You too can make contacts!


2008 Recap

This year Dwayne and I remained inside the 20-meter band the entire time we operated. We used an aluminum multi-task ladder as the primary radiator, which is one of those ladders that can be bent into a variety of configurations. It is approximately 15-feet long when fully extended. It seems to work quite well as an antenna! We found it to be very wide-banded as well, which given it's girth is to be expected. Once tuned on 20-meters we were able to graze anywhere within the General Class of the 20-meter band without needing to retune the transmatch.

    ( We did not attempt to stray beyond the General Class band limits because we prefer to remain within the General Class segment of any band we may utilize so as to maximize the number of stations that have the opportunity to work us. )

    Configurations used:

    Saturday and Sunday we used the ladder rigged straight up in the air as a vertical antenna. It sat on a 16-foot trailer which served as the ground plane. On Monday we moved the ladder into the side yard, and set it up in an A-Frame configuration for the primary radiator, separated from the ground plane by 2x4 lumber. It's ground plane was a closed aluminum step ladder, which in turn sat upon the seats of two metal folding chairs used as saw horses. We figured if the metal-to-metal contact between the step ladder and chairs was conductive enough to matter, fine, and if not, also fine. Provided we were able to tune it up and make contacts with relative ease we don't really care.

Basic Connections

We connected to the Strange Antenna with a short length of wire using hose clamps to press the tips of the wire against the metal. The opposite end of the wires lead to a home-made 1:1 current balun. This is used to help insure the RF is kept off the outside of the coax shielding. We do not wish the transmission line to become a radiating element of the antenna system. The coax used was 78-ft, 4.5-inches, of LMR-400 (measured from the base of the PL-259's tip, to the base of the opposite PL-259's tip). The coax was then connected to a MFJ-969 "Deluxe Versa Tuner II" transmatch. This model uses a roller inductor going to ground with two air-variable capacitors completing a "T" configuration.

AIM-4170 Antenna Analyzer

This was the first year we used the AIM-4170 Antenna Analyzer to record the complex impedance of the antennas we employed. This is reported to have an accuracy of +/- 3% which is much more accurate than the MFJ antenna analyzers which are reported to be approximately +/- 10% at HF and on the order of 20% for 2-meters and 30% at 440 MHz.

    One of its nicest features was the ability to sweep a user-defined range of frequencies at the touch of a button. Sweetness itself I assure you! A comma separated file is also generated at the same time, so once saved under a unique filename, we are able to refer back to this sweep at a future date. Very nice! The only trouble we experienced was getting the device to recognize which com port was needed. That was very clunky and was the most time consuming part of using this device. Still, a great time-saver compared to using the MFJ-269 as we had in the past. And as already mentioned, about 3-times as accurate.

    In the following scans taken with the AIM-4170 Antenna Analyzer:

    The various screen shots shown below were generated by capturing a "screen print" in Paint, importing that JPEG into Adobe Photoshop, and then cropping and reducing the filesize.

 


Vertical Ladder over Trailer

    We used this Strange Antenna both Saturday and Sunday. It seemed to work quite well on 20-meters.

Vertical Ladder with Trailer

Vertical Aluminum Multitask Ladder with 16-Foot Trailer as Ground Plane
K0S Strange Antenna Challenge Special Event
May 24 & May 25, 2008
Springfield, MO

  Analyzer Scan

AIM-4170 Antenna Analyzer Scan 2.0 MHz - 30.0 MHz
Vertical Ladder over Trailer Ground Plane

 

 

A-Frame Ladder

    We only used the A-Frame antenna for about an hour on Monday. It seemed like it was getting out about as well as the other one, but on Monday it just didn't seem people were interested in talking very much. We had difficulty in engaging in QSO's because it seemed like everyone kept saying "73" before we filled in the log. So we gave up. It was too much like pulling teeth! Besides, it was getting about time to start tearing down the antennas and station anyway. If we missed you, hope to work you next year!

A-Frame Vertical Ladder over Step Ladder Ground Plane

Aluminum Multitask Ladder in A-Frame over Step Ladder/Metal Folding Chairs as Ground Plane
K0S Strange Antenna Challenge Special Event
May 26, 2008
Springfield, MO

  Analyzer Scan

AIM-4170 Antenna Analyzer Scan 2.0 MHz - 30.0 MHz
A-Frame Ladder over Step Ladder Ground Plane

 

 

For comparison purposes, below is the AIM-4170 Antenna Analyzer Scan of the Commercial Buddipole


The Buddipole was only used as a reference antenna during the special event, and never to contact any of those we worked as the special event station K0S.
This is a commercial antenna designed primarily for portable operations by Budd W3FF. More information may be found at their web site: www.buddipole.com
Please note, no effort was made to optimize the Buddipole. We simply transformed the complex impedance with my LDG Z-11 Pro automatic antenna tuner.

Analyzer Scan

AIM-4170 Antenna Analyzer Scan 2.0 MHz - 32.0 MHz
Buddipole Dipole on 16-Foot Mast

 

  Buddipole

Buddipole Dipole on 16-Foot Mast
Each side of the dipole: two 22" arms; "red" coil (no taps); "black" whip fully extended;
One 22" arm extended above dipole serving as a truss support;

 

  Buddipole

These are the sand bags, which worked very, very well.
We found "pea gravel" actually worked better than sand. Each bags weighs between 10 and 15 pounds.
It would take an extremely strong wind to blow this over!

 

  2008 Log

2008 K0S LOG 1 of 5 -- Ladder Vertical

 

  2008 Log

2008 K0S LOG 2 of 5 -- Ladder Vertical

 

  2008 Log

2008 K0S LOG 3 of 5 -- Ladder Vertical

 

  2008 Log

2008 K0S LOG 4 of 5 -- Ladder Vertical

 

  2008 Log

2008 K0S LOG 5 of 5 -- A-Frame Ladder

 

 

 

  n0ew reflected in screen

Erik NØEW reflected in computer screen

 

  n0ew

Erik NØEW

 

  wb5plj

Dwayne WB5PLJ

 

 


Run Your Own K0S Satellite Station!

Running your own "Strange Antenna Satellite Station" is tons of fun!

    There are many benefits to participating in, and promoting, The Strange Antenna Challenge. It provides a unique "hook" to help secure media attention, it provides learning opportunities to share you rknowledge of antennas systems and impedance matching techniques limited only by your imagination, is a wonderfully intreiging means of engaging the public, and demonstrates the extreme flexibility of the amateur radio service.

    Unfortunately, not everyone that participates as a Satellite Station sends us pictures and tells us about the fun they are having, but the following fine folks have! Please, take a few minutes and see what fun some of your fellow hams had this year. And why not consider using this special event to promote your ham radio club next year?

    Have we mentioned how much fun this is?


    73 ~ Erik n0ew



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73 de Erik, nØew
© 2002 - 2009 Erik E. Weaver, n0ew
 
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