Monday, January 26, 2009

Winter Portable Operation

This post is related to a winter weekend trip to Silent Lake where my wife and shared some quiet time and I was also able to operate portable.

Silent lake Provincial Park is one of a few provincial parks in Ontario which have winter camping facilities. It is located in central Ontario and is a 3.5hr drive west from Ottawa. We arrived at the park office at about 9:30AM where we were greeted by the Park Warden and were taken to our Yurt by skidoo and trailer. The temperature was -25C when we arrived, and although it warmed up a bit during the day it remained very cold.

The Yurt we stayed in was a simple and basic structure, as expected, equipped with plenty of firewood, a good axe, and a wood stove for heating. Two bunks provide room to sleep 6.

I setup the buddipole vertical in a new configuration, I replaced the standard stainless steel whip with a long whip.

The vertical was built as
  • Long Whip (fully extended)
  • Red Coil (tapped 13 from the bottom)
  • Dipole Arm
  • Wersatee
  • 1 28.5ft Counterpoise
  • TRSB set to 2:1 (for a 25ohm antenna)
  • Feedpoint about 2m from the ground
I simulated this configuration with 4NEC2 and predicted it should resonate at 7.1MHz.

The radiation pattern was also predicted as below.

The file for this 4NEC2 is archived in the Yahoo Buddipole group in the folder
(See file : AC_Vbud_40M_07_V01)

This tuned up at 1:1 SWR on my IC7000 just as predicted.

Since the Yurt has no electricity, my operating station was powered by 4 50AH Gell-cells and a N8XJK battery booster. The laptop was also powered off of the same cells. I operated for 5hrs and the 4 cells were depleted to 70% capacity.

Most of my operating was in the evening and by candle light. The small wood stove needed attention once and a while.

From 20:45UTC to 3:00UTC I was able to complete 15 PSK31 QSOs and I want to thank everyone who I was able to contact. You can see my log below.

Google Earth export shows just how far 50W and a Buddipole can throw a signal. I was very pleased by the following QSO's in particular.

EA8CFV 559 599 Padron Eligio 281 5,469.59 IL18tl Spain

P40PZ 599 579 Peter 91 3,675.83 FK42xo Aruba

W6TJK 559 599 Thomas J Kenville 291 3,931.85 CM87xb United States of America

XE1YK 599 599 CARLOS EDUARDO LEVY VAZQUEZ 50 3,610.25 EK09jh Mexico

K3ML 559 589 MILFORD C GOSSARD 291 2,348.95 EL94gq United States of America

K4WNY 559 599 RONALD S TURNER 291 1,626.32 EM55ak United States of America

VA3SQ 599 599 John D Sibbett 1 378.47 FN02jx Canada

Special note and thanks to Peter P40PZ in Aruba, as this QSO was my first to DXCC country 91.




Mark's post from an earlier trip

Saturday, January 10, 2009


I have been experimenting with using a Buddipole for portable operations. Details on the Buddipole can be found at this link.

One configuration that is interesting is the 40m vertical as described in the Buddipole document at this link. I have used this and it tunes up very nicely, but I was also interested in seeing if I could model this configuration and possible find another more efficient configuration using other components.

I loaded a copy of 4NEC2 and generated a few simple antennas, dipole, Inverted Vee, and a vertical.

Model 1: Basic 40m Vertical w/ 1 counterpoise

Setup is Versatee + Dipole Arm + Red Coil + Short Whip and 1 counterpoise. I use the TRSB at 1:1 setting.

Key parameters: With the help of Dave KI6AWR, I am using a 28.2uH for the red coil.

This prediction of this antenna can be made to resonate at 7.07MHz but the SWR of 3.4 is worse than I had observed in reality.

This configuration has the following predicted values

Resonant frequency: 7.07MHz
SWR: 3.45

Model 2: Extended 40m Vertical w/ 1 counterpoise

Setup is Versatee +Red Coil + Dipole Arm 1 + Dipole Arm 2 + Long Whip and 1 counterpoise.

In this configuration there the vertical is 1.4m longer due to the second dipole arm and the longer length of the long whip. Also the red coil has been placed at the bottom of the vertical. The counterpoise is unchanged, and the loading coil is tapped at 49% of its full value. (this returns the antenna to resonance at 7.07MHz.

There is expected to be 1.4dB more gain at the same takeoff angle of 50degrees.

It should be possible to use a long whip and both dipole arms to extend the vertical. A bit more gain is expected and the red coil is expected to be at to 49% (20 of 41 turns) to compensate for the longer antenna. The counterpoise length does not need to be adjusted.

End Notes:

a) I am unsure why the predicted SWRs are so high. I was expecting better than 2:1.