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Station description

WRTC-2010 is for the first time Field Day style competition.

All competitors will be located in the same geographical area within 40 x 30 km where height differences are not greater than 40 meters. All competitor locations will be separated at least 500 m from each other.

    When you get to your location you will find ready to go (installed):
  1. * 20/15/10 m tri-bander with one feed line and PL-259 male connector on 12 m tower with antenna rotator and control unit
  2. * 40 m Inverted V dipole with feed line and PL-259 male connector
  3. * 80 m Inverted V dipole with feed line and PL-259 male connector
  4. * 2 x 100 watts peak power monitors
    Peak power monitors act on forward power only, which is greater than transmitted power when SWR > 1. In order to transmit 100 W to a mismatched antenna, an external tuner is needed to bring the SWR down, thus avoiding premature triggering of the power monitor.
    Description of regulations on power monitoring (PDF, 0.5 Mb).
  5. * 2 PL259-PL259 jumpers for 100 watts peak power monitors
  6. * Tent
  7. * 2 kw Power Generator with 30 m power cable going to the tent
    No own backup power generators are allowed. No own Uninterruptable Power Supplies, 12 V accumulator batteries or similar power sources are allowed for power backup. Exception: built-in batteries in portable computers, audio recorder, other peripherals, CMOS memory backup batteries are allowed.
  8. * 50 Liters of gazoline for generator
  9. 1 grounding rod driven nearby and connected to generator, and 1 grounding rod with a piece of wire driven nearby tent
  10. 3 x 5 EU (Schuko) outlets
  11. 2 lamps
  12. * Electrical Fan
  13. * 3 plastic tables
  14. * 3 plastic chairs
  15. WC cabin with hand wash facilities
  16. 30 liters of drinking water
  17. Competitors are not allowed to substitute equipment in items marked with asterisk (*) by any other equipment unless permision is given by Judging committee.

    Since this is a field day style operation each team will have a generator which has to be filled with gasoline. To avoid team members spending their time for re-filling generator we will have specially dedicated person at every location to help keeping it up and running during the contest period, so teams will concentrate on the contest battle.

    Typical SWR vs. frequency curves for HF-37 tri-band antenna

    Measured at the end of 50 Ohm coaxial feeding line
    by use of AA-200 antenna analyser.
    20 meters band
    14 MHz band

    15 meters band
    21 MHz band

    10 meters band
    28 MHz band

    Use of 80 m and 40 m Inverted Vee dipole antennas

    1. 80 m Inverted Vee dipole antenna

    The 80 m Vee feed point is at 37 feet, antenna is fed through 1:1 balun.

    End insulators are at 5-7 feet above the ground level depending on a tension in guy wires. Insulators' positions will be pre-adjusted to get resonance at 3750 kHz while the rest of wire is rolled (see fig. 1). The rolls of wire are located at the lower end' insulator.

    Unrolling this extra piece of wire along the guy rope will lower the resonance to 3525 kHz or to another frequency of your choice between 3525 and 3750 kHz. This "roll matching" is simple, once pruned needs no more adjustments. Walking to the field, unrolling the wire, fixing it with the tape to the guy rope takes less then 5 minutes.

    The 1:1.5 SWR bandwidth is about 90 kHz.

    Comments: The WRTC-2010 Organizing committee had tested different ways of broadbanding the Vees in a fact. The solution we chosen was found the most simple and repeatable in different circumstances. This classic solution was chosen in face of complexity of other designs and some field-style operation limitations. Of course, one can tune antenna length to the middle of 80 m band (e.g. to 3650 kHz) and make antenna more broadband using some technique (e.g. using known coax stub technique but you are allowed to do it at antenna connector only).

    The roll to tune antenna
    Fig. 1 - The roll of wire at lower end insulator serves for antenna tuning.

    SWR of 80 m Inverted Vee dipole antenna on 3525 kHz
    Fig. 2 - SWR of 80 m Inverted Vee dipole antenna when tuned to 3525 kHz.

    Input impedance of antenna
    Fig. 3 - Input impedance of antenna in fig. 2.

    Input impedance of antenna on 3775 kHz
    Fig. 4 - SWR of 80 m Inverted Vee dipole antenna when tuned to 3775 kHz (a bit too high in fact).

    Input impedance of antenna
    Fig. 5 – Input impedance of antenna in fig. 4.

    2. 40 m Inverted Vee dipole antenna

    The 40 m Vee feed point is at 33 feet, end insulators are at 9-10 feet, and it is easy (and will be done by volunteers) to prune it to SWR=1.15 at 7075 kHz.

    The 1:1.5 SWR bandwidth is about 180 kHz.

    You can readjust the antenna's resonance to the frequency you prefer in a few minutes.

Supported by:

Moscow region government
Moscow region government
Samsung Electronics
Ural Contest Group
Northern California DX Foundation
The YASME Foundation
©2009-2010 WRTC