Contest Techniques - Have We Found Them All ?

  • Print
Details
Category: WRTC 2006

Fortunately, the WRTC 2006 organizing committee was not conservative, and modified the WRTC rules, as used during the previous events. The new, less restrictive rules allowed technical innovations, which under the old rules would not have been allowed. The result was, that not only a team's experience and tactical cleverness was highlighted, but also their ability to use technical knowledge to come up with a good technology concept as part of the contest stategy. This broadened the scope of the WRTC contest and made Brazil more interesting.
Unfortunately, however, the rule changes were officially announced just four months before the WRTC event, which left us with only a short period for developing and producing the large amount of hardware required for the implementation of our ideas.

The door for real innovation was now open

The new rules allowed for two operators, two receivers but only for one transmitter, one PA and one antenna for any given band. What the rules did allow was almost unlimited station automation.

The simple question was: How to utilize two Ops and maximize the efficient use of 24 hours?

pt5l-odozgo-malaI have the great luck to have Sinisa, YT1NT, as a good friend. He is a genius when it comes to development. He is an excellent engineer with brilliant ideas as well as being very systematic. After it became clear that I would be one of the team leaders, we had many discussions
dealing with strategy and technology, so that we could hopefully find a winning concept, which could be realized within four months. I invited him to be in charge of technical support as part of our team. We decide that Sinisa would design most of the components, assemble the MCU and write software. I would build the filters, SDB, audio distribution and switching boxes.



STRATEGY STATEMENT
The first step was to determine our basic requirement:

  • First and foremost, both operators must be as autonomous as possible while sharing TX, PA and antennas.
  • This meant abandoning the traditional approach, where the secondary operator supports the primary operator mainly by:
    - Searching and pouncing for multipliers
    - Tuning VFO B to a desired frequency
    - Filling the band map
    - Preparing the station for the main op, allowing him to work
      multipliers very quickly.

We decided to make the second op a more equal operator, allowing the primary op to follow his own running strategy with minimal interruption by the secondary, who should, for example, work the S&P multipliers on his own.

To realize that, we needed to have very complex station automation and new hardware had to be design and produced, creating new very unique station design, never seen before.

Based on the above, we could then ascertain what we would need and which tasks had to be solved:

Filters-in-Brazil-mala









PP5QY, YT1NT and YT6A
 Design and build a triplexer filter along with other filters, capable of allowing both operators to simultaneously use a log periodic antenna for the 20m, 15m and 10m bands. This would allow the secondary operator to use the best antenna for searching and pouncing.
Use of a nonresonant antenna could mean a 20dB less signal for S&P.
This was something we had to avoid. Also the filter system would reduce the level of interference between the two operating positions.













R4C-mala Digitize an old analog R4C, so that it could be integrated in our digital system. We decide to use the R4C because of its general receiver performance, its superior rejection of out of band signals and various modifications, which we had already added to it.

Crystal--mala Employ new multiple crystal front end filters` board for 40M. As most demanding band, 40M is also the most narrow one. Having no idea how it looks like from South Brazil, we decided to built it. More details in text below.
kontroler--mala Develop MCU - Microprocessor based Control Unit to manage the complete system

An easy task with only about two months left?  Hi Hi

STATION AUTOMATION INCLUDE
In greater detail, the automation of the station included:

  • The MCU, a fully automatic controller for the station hardware, including both radios and all peripheral devices.
  • An interface for the otherwise analog Drake R4C. Bringing the R4C into the digital age allows the storage and transfer of operating parameters between the Drake and the FT1000 via the MCU.
  • High power triplexer filter system for the high bands.
  • High power band pass filters, also to allow the simultaneous use of two radios with a minimum of interference. These filters were placed at the output of the PA, meaning they had to be able to handle 1500W with low loss, while providing typically about 70dB attenuation on neighboring bands. These filters were partially also used in the reception path.

Filter-28-mala

Switcher-otvoren-mala

Antenna switching boxes

Switching boxes controlled by the MCU. To switch the antennas and filters seven boxes were used, all designed for 1.5kW.

 

WRTC-board-mala Signal Distribution board
The Signal Distribution Board (SDB) - a very important piece of hardware. Imagine being a long way from home with 9 antenna filters, 7 switching boxes, 40M front end, and a copious number of cables for circa 50 interconnections. In other words, a real mess. And in southern Brazil we had to set up in a  room for errors. The SDB provided male and female connectors and a
"pinning scheme" so that it was not possible to use the wrong wire in the wrong place, and at the same time allowed most control cables to be identical.
BPF-7011-10-kHz-mala

Selected frequency range front end filters

The 40M front end unit. This used a bank of 800Hz -3dB narrow bandwidth crystal filters in steps of one kHz. The filters ranged from 7011 to 7025 kHz, i.e. 7011, 7012, 7013, etc. This unit was used directly in front of the receivers and eliminated large, close in signal problems on the 40m band. This meant a real improvement in signal to noise ratios, because the RX only "sees" a tiny part of the entire band. The appropriate filters were switched in and out by the MCU based on the receiver frequency. While this was a real expense, there is no better solution for the 40m zoo.


Microprocessor Central Unit
The MCU provided:

  • Communication with and control of the FT1000 using the CAT port of the radio.
  • PTT and keying signals for the FT1000.
  • Communication with the Drake R4C.
  • Switching signals for the 7 switching boxes.
  • Communication with both PCs, e.g. band and mode information.
  • Switching signals for the crystal filter front end, when operating on 40m.
  • Buffering operating parameters for each band, e.g. the attenuator setting.
  • Sensing which band the PA is tuned to.
  • Providing logic for the use and keying of the PA based on its present tuning and the band information from the radios.

    Optpkapler-malaThe ACOM 1010 is not a linear with automatic tuning, so it was often better to "go barefoot" for a few seconds, and not waste time retuning the amp. To sense which band the ACOM was tuned to, we designed a PCB with optocouplers which we taped on the front of the PA

 

  • Lastly, the MCU provides two CW keyers and foot switches with the necessary logic to recognize which operator is operating his key and then switch the transmitter frequency, all filters, antennas, etc. and, if possible, key the PA for transmission. This also worked with the foot switches when operating SSB.

The system switches the transmitter frequency, mode, antenna, filter, etc. with a latency of about 10mS. After transmission the FT1000 returns to running RX frequency.

What does all of this mean:

  • The OPs are almost totally independent.
  • The running OP never encroaches on the S&P OP, because the S&P OP is always listening with R4C.
  • The S&P OP causes a minimal interruption of about one second when he needs the transmitter, i.e. for "PT5L" call sign or "RST ...". - this almost doubles the on air time of the station.

USE FOR THE AVERAGE CONTESTER

What's new for General Contesting?

Some of parts of the above concept can be used for general contesting.

Firstly, efficient usage of interlaced multi bands yagis for two simultaneous tasks. Many of contesters are limited in space and can't put more than one, or two towers. Triplexers can be used in SO2R configuration, using single tribanders, or multiband stacks by both radios in the same time.

Secondly, high isolation, high power, low insertion loss filters are a hallmark of the "professionalism" of any contest station. Filters with high performance characteristics, for high power, mounted after linear amplifier, directly in the antenna line are a most efficient way to prevent interference between radios and to cut harmonics. As you are switching antennas anyhow, with this concept you do not have any additional switching and no band decoders needed.

Thirdly, seamless, selected frequency range front end filters. As mentioned above, front end crystal filters can greatly improve the performance of your receiver by eliminating problems with intermodulation generated by strong signals near the receiving frequency. (Note by 4N6FZ: This is especially important in Europe.)

Lastly, station automation to create space for higher scores by increasing operator efficiency.