NJDTechnologies

Radio: it's not just a hobby, it's a way of life

Current Operating Frequency and Mode

OFF AIR

SCHEDULED ACTIVITY: CQ 474.5 kHz CW by 0020z through sunset

Another Pedestrian Mobile outing with KF5RYI

– Posted in: QRP

On Saturday, June 20, 2015, I posted the following on the QRP-L reflector:

“I was fortunate to have a nice pedestrian mobile outing this morning with Steve, KF5RYI, on the Joe Pool Lake dam just outside of Dallas. 20-meters was slow to open or we were early to start but first station worked was JH0NEC in the AA contest. He popped up on .060 and after a few attempts he got my call right… He was followed by WB9EAO, KG4LLQ, K4KRW and finally KC8CJG. I would have also had VE3CGC who was asking for the /PM on .060 but we had an encounter with the Army Corp of Engineers wondering what we were doing so someone sniped that Q. Best RBN report was from VK4CT at 9db S/N. The dam is very much in the clear and relatively high up compared to much of the surrounding terrain. This area is the highest point in North Central Texas. I Had a few questions about my setup. You can see pics of a January outing with Steve at http://njdtechnologies.net/hf-pedestrian-mobile-at-cedar-hill-state-park/ . The antenna has changed a bit in that I have removed the feedpoint transformer and replaced it with a airdux coil/tap about half way up the pole and short trailing wire. Resonance on 20m is easy and the ATU in the KX3 cleans up variations in R very easily. Power today was 5W. I’m sure Steve has his own stories to tell but we may make this a regular thing if locals would like to join us… plenty of room to spread out up and down the 4 mile dam.”

We had a great time and I received several questions about the recent antenna mods made since posting pictures  previously from our January outing.  The original antenna, a helically wound fishing pole about 12 feet long with a few sections removed, using about 33 feet of wire haphazardly wound to fit the space available used a 9:1 feed point transformer to get the impedance closer to a reasonable match for the KX3 internal tuner.   Being nearly a half-wave on 20m, I neglected any additional counterpoise other than the 3-5 foot coax between the KX3 and antenna feed point.  It worked well and was convenient but the haphazard design could be better.

As a very happy user of quarter-waver verticals I decided to modify the original system to add a coil about half-way up the pole and use a drag wire for ground return.  The system is mechanically stable and matches easily and if Reverse Beacon Network spots are any indication, this system will be a nice performer on 20-meters.  See pictures below:

kb5njd_pm with new antenna20-meter RBN search for KB5NJD/PM.  Note the spot from VK4CT.  How can I argue with that?

S2090001Air-dux coil with tap point.  Note that bypassing the coil completely yielded good performance on 12 and 15 meters

S2090003Weighted base, feed point and breakaway radials.  I will probably keep only one radial in the long term

None of this is rocket science but since I received questions I wanted to further document the system changes.

I am really looking forward to more foot portable outings in spite of the funny looks and questions that I get.  I can only hope that I don’t end up in Gitmo because someone gets the wrong impression of what I am doing or doesn’t believe that I am actually talking to people around the world as a “one man band” and doing so with my hands.

If you are in the North Texas area and are interested in going on a walkabout, send me a message in the contact section.

Oh and next time I will try to remember to bring the Go Pro camera to document the blessed event.