W4WVP

Volunteer Job Information

Title: Ham Radio
Location: MCM Course
Date: Sunday, October 31, 2010
04:00 AM - 03:00 PM
Coordinator: Bruce Freund
Description: Ham Operators provide voice and data communication in support of the Marine Corps Marathon and direct support of MCM medical operations.

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http://www.doitsports.com/volunteer2/user-volunteer-signup.tcl?job_id=47102508&event_id=2061&job_desp=Ham+Radio&volunteer_date=2010%2d10%2d31&start_time=04%3a00+AM&end_time=03%3a00+PM

Building an HF Stealth Antenna within a Tight Budget
Ken Heitner WB4AKK

Arlington Amateur Radio Club
Operating Mobile HF is Potentially Fun & Useful
The key problem with HF mobile is the antenna.
Various HF whips over the years have come and gone
Most HF mobiles today use the screwdriver antenna. You can build your own??
Maybe the approach used in the Stealth HF antenna is the way to go

An Example of a Stealth HF Mobile Antenna
Another View of Stealth AntennaSee the Radiating Element

Can We Afford This ? – NoCan We Build This ? - Maybe
This is a commercial product, and that means expensive
But if the concept is valid, maybe we can build a simpler and cheaper version
So let us examine how it works

Operating Concepts - 1
The basic antenna concept is a magnetic loop antenna
The 50 ohm coax feeds the antenna via a small loop.
The main loop is tuned to resonance by the high voltage capacitor

Operating Concepts - 2
The Stealth antenna is build on a modified loop concept.
The coax feeds on side of the antenna, in what might remind you of a gamma match
The loop is also tuned by a HV capacitor

Operating Concept - 3
Yet another feedpoint concept is the omega match
This concept is offered in the loop matchboxes made by MFJ
This may be easier to tune for a perfect match

Operating Concept - 4
This approach might be good for those whose radio already has a built in antenna tuner
It just steps up the low antenna impedance with a wide band transformer

General Project Approach
Simplify the antenna geometry so it is easier to build
Build the basic antenna framework first
Consider alternative feedpoint approaches for trial and error testing
Who knows – Maybe one of us will come up with even a better way to do this

Simplified Antenna GeometryPlan View
Simplified Antenna Geometry Elevation View

Simplified Antenna Geometry
Makes the antenna buildable from commonly available copper and PVC pipe
Once the basic antenna is built, then we can try different feedpoint concepts and see what we like. Each antenna can be customized for your vehicle roof size

Discussion Time !
Let me hear who would be interested in trying this project out.
Let us leave the details for a separate meeting of those specifically interested.
No rush….We can do this at our own pace
Might be fun for the next VA QSO Party

A member of REACT visited with me during the Arlington County Fair. He mentioned that many members of REACT have amateur radio licenses. He also noted that REACT has repeaters that use the GMRS frequency allocations. GMRS channels are provided for UHF repeaters. REACT has repeaters set up in Washington, DC area. These require GMRS radios with appropriate setups to operate.