After enjoying a number of VHF UHF / Microwave field days in recent months, I decided it was about time I wrote a few words about the experience in the off chance that it may act as a catalyst for one or two of you to “give field days a go”!
This article is not intended to give a definitive solution to the topic of field days but rather to provide an exposé’ on how I went about assembling a field day station that has given me many hours of enjoyment.
Much of the detail relating to specific pieces of equipment that I have used in the field day station can be found elsewhere on this Blog!
To begin this exposé’ I think it is important to identify what was and has been the motivating force that has driven me to build my field day station. Put simply, I wanted a station that:
(a) covered a variety of bands within the class of field day eg.,(VHF UHF / Microwave),
(b) had antennae that provided adequate gain without being critical to point,
(c) was simple to transport,
(d) assembled easily (one man),
(e) was reliable and had dedicated equipment,
(f) provided a self contained power system (batteries, solar panels and generator)
(g) had an operating position that protected the operator from the elements,
(h) was a pleasure to operate in a variety of locations.
With these factors guiding my every step, I began what has been quite a challenging project!
The first step was to decide what range of frequencies I was going to provide for my portable field day station. From my observations of over fifty years of amateur radio, the field day activity in Australia is clustered into two areas of the spectrum – above and below 50 MHz. This article will only focus on 50 MHz and above with the highest frequency being 10 GHz.
The next step was to consider what type of antennae would be practical for each of the bands and making sure that the correct polarisation was available for the respective modes to be used throughout the chosen spectrum.
In Australia most of the SSB contacts on the various bands 50 MHz and above, use horizontal polarisation while FM contacts use vertical polarisation, so it was very important that if maximum contacts were to be enjoyed, attention to the polarisation issue was important.
Mounting the 6 m Halo.
The antennae that I chose provide maximum flexibility without requiring me to be constantly adjusting the azimuth just to make contact. I also chose to use a YAESU variable speed, computer controlled rotator, that provides (all weather) azimuth adjustment from the operating position.
The antennae that I have used are;
(a) 6 m Halo or 3 ele Yagi (horizontally polarized)
(b) 2 m Halo or 8 ele Yagi (horizontally polarized)
(c) 70 cm 13 ele Yagi (horizontally polarized)
(d) 23 cm 19 ele Yagi (horizontally polarized)
(e) 13 cm 600 x 400 mm Grid Pack ( horizontally polarized)
(f) 9 cm 900 mm off-set Dish (horizontally polarized)
(g) 6 cm 600 mm off-set Dish (horizontally polarized)
(h) 3 cm 300 mm prime-focus Dish (horizontally polarized)
(i) 2 m, 70 cm, 23 cm Tri-band Vertical (Diamond X-5000N)
(j). Active GPSDO Antenna (powered via coax feed)
Having operated in field days for more years than I wish to remember, the most critical part of the station has always been the mast which was and has been either too heavy for one man to erect or too light which invariably bent in the middle when attempting to raise it into position! With this in mind, I was determined to find a better way.
After considerable thought and research I was sure what I did not want. I didn’t want a mast that;
(a) attached to my car in any way,
(b) required pegs driven into the ground or what ever surface I happened to be parked on,
(c) needed more than one person to erect,
(d) relied on the “armstrong” method of antenna rotation,
(e) used my car to transport a variety of lengths of pipe and antennae,
(f) didn’t allow all of the antennae outlined above to be mounted on the same mast.
With all these thoughts and criteria buzzing around in my head, the gem of an idea began to develop! It soon became obvious – the best solution for my needs would be a “box-trailer” mounted system.
With the decision made, the system began with a 50mm steel angle-iron frame that could be slipped into the base of a 1800×1200 box-trailer and bolted to the base (this meant that it could be removed when not required for field days). Cross braces were then added to the base frame to allow a central ” gin-pole” to be positioned which had an internal pulley added to the top and tripod support braces to ensure stability. A winch was added to facilitate the raising of the mast using the gin-pole. The mounting for the mast rotator was accomplished by attaching a hinged mast stub at the base of the gin-pole. A piece of 50 mm angle was bolted to the gin-pole near the top which would assist with anchoring the mast bearing when the mast was in a vertical position.
The last requirement was the mast itself. It needed strength, but could not be too heavy; it must be capable of collapsing to form manageable “one man” lengths and be at least six meters in length when assembled. The final solution was a 50 mm scaffolding tube that was cut in half and sleeved. The sections were pushed together and bolted when assembled. Cross arms were added to the bottom section for mounting the Microwave Antennae and Transverters. A small offset sub-mast was added to the top section to mount the GPSDO antenna.
After manufacturing all of the components and assembling the system, one final problem presented itself. How was I going to carry all of the antennae and mast sections safely?
The accompany photographs show how a series of mounting brackets have been added to the assembly to facilitate the transporting of all of the antennae. Labels have been added to ensure that all of the components are returned to their respective locations. Yes I could have just bundled all of the antennae and lay them in the trailer but by having a specific location for each component, nothing is forgotten and most importantly, nothing gets damaged!
The operating position in a field day station has always been an issue for me as it seems to be the forgotten ingredient in what can be a well planed expedition into the field. I know I have been guilty of thinking I will just take a small table and that is all I will need. While I have managed to do this on a number of occasions, I have had some monumental failures with tables collapsing resulting in damaged equipment etc. Having gone to the trouble of working out a suitable antennae system, I decided it was time to have an operating position that was easy to setup, functional and sturdy.
During my frequent visits to the hardware store, while constructing the antenna system, I became aware that the “Stanley Tool Company” was selling a “Fat Max” toolbox with wheels, that has three major storage areas that could adequately store all the cables and minor components for the portable operation and also act as a console for mounting the transceivers. In addition, the lid of the toolbox could be used as a operating desk with the addition of a three-ply insert and a support strut. The accompanying photographs show the toolbox in operation.
With the system components completed, the next area to be addressed was the power system. When operating portable, I usually rely heavily on battery power that is separate from the vehicle battery. In the past I have tried to use the vehicle battery as part of the power source with disastrous results ( modern vehicles and flat batteries don’t mix)!
I therefore decided to use 2 x 150 ah AGM batteries supported by 160 watt Solar Panels for daytime operation. This decision has proven to be most satisfactory with an average of 12 amps per hour being fed back to the batteries under good sunlight conditions. During the evening however, battery charging is achieved by using a Honda EU20i, 2 Kva generator that feeds a CTEK 25000 series Smart Charger that is very effective at keeping the batteries fully charged. The Honda Generator is extremely quiet acoustically and electrically. These factors, coupled with good fuel efficiency, have proven to be an excellent addition to the Field Day Station.
Weather conditions are a critical factor in the field especially when considering operator comfort and over the years I have tried a variety of shelters / tents etc., however I have never been totally happy with the amount of equipment / effort that was required to setup a suitable shelter. What I really required was a shelter that was attached to my vehicle, that I could assemble by myself and provided all weather protection. The Supa-Peg RV Awning that is manufactured in South East Queensland, matched all of my requirements and has proved to be an excellent all weather shelter that can be setup in a matter of minutes.
No field day operation would be complete without some method of storing a cold drink, milk and food. This has been achieved by using a WAECO 35 L – 12 volt fridge/freezer that has done the job very well indeed.
Well I hope this article may have provided some ideas for one or two of you who are thinking of going into the field. This project has certainly made “Field Days” fun for me.