antennas

a small matching unit to use the watson w2000 triband antenna on 70mhz

Submitted by gerry on Tue, 05/17/2016 - 15:34

I recently upgraded my shack to an ICOM IC7300, which in the EU specification includes the 4 meter / 70MHz band. I do not have a vertical for 4m, or space for one right now, but had read about others using a small matching unit to provide the necessary match using the Diamond V2000, or Watson W2000, as my version is badged.

Plotting Antenna Response using a Wobbulator and Return Loss Bridge

Submitted by gerry on Fri, 05/13/2016 - 15:21

At the Mayo Amateur Radio Rally a couple of years ago, a NI ham, Tom Herbison, MI0IOU was selling an interesting kit for the Raspberry Pi. It combined an Analogue Devices Clock Generator (AD9850) and an RF power meter (AD8307) to give a programmable sweep generator & detector... commonly known as a Wobbulator. I bought one and had anenjoyable afternoon not long afterward building it. It was a relatively easy build, and I got some use out of it tuning some Band Pass Filters I had built for use on multi-station portable ops.

Homebrewing an Off-centre Fed Dipole

Submitted by gerry on Wed, 03/04/2015 - 13:44

During HF field day 2010, I had occasion to get some experience with the off-centre fed dipole, in this case, a commercially made unit from Buckmaster.
Prior to this, I had heard that OCF dipoles ‘are a compromise’, ‘are noisy’, ‘are deaf’, ‘have wildly varying radiation patterns’ and many other negative comments. During field-day, our experiences definitely gave me cause to doubt the nay-sayers.

20m Moxon for Portable Use

Submitted by gerry on Mon, 03/16/2009 - 10:14

We (the Galway VHF Group) have a good many portable operations coming up this year, so, to supplement our portable HF antenna collection, I thought a 20m Moxon might be a nice project.
The only real expense was the 4 fibreglass fishing poles, but they ended up very cheap, even when you factor in postage from the UK.
The design was going to be based around a spreader made from a rectangle of 12mm ply, with 25mm dowel bolted on at the relevant angles.