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Get Ready for the ARRL Homebrew Challenge III

10/06/2010

The ARRL has sponsored two Homebrew Challenges in the past, designed to test our members’ design and construction skills by making useful amateur gear at low cost -- and sharing their results with our members. Our first ARRL Homebrew Challenge, announced in QST for August 2006, required the construction of a 40 meter, 5 W voice and CW transceiver built for less than $50 of new parts. The Second Homebrew Challenge, announced in February 2009, resulted in a number of creative designs of low cost 50 W linear amplifiers to follow the transceiver -- two for about $30, as well as a multiband amplifier with many features for somewhat more.

This time, we announce a challenge to build a transceiver in celebration of the (slow) return of sunspots. This challenge will be in two parts and readers can enter into either or both:

  • A single band 25 W SSB and CW transceiver for 10 or 6 meters (Option 1), with a prize of $200.
  • A 25 W SSB and CW transceiver that can be switched between 10 and 6 meters, using one or two switches, (Option 2), with a prize of $300.

Instead of challenging entrants to make the transceiver at the lowest cost, this time we will challenge builders to provide the highest quality, best performance and most features within the cost target of $150 for Option 1 and $200 for Option 2.

In addition to the cash prize, the winners of these challenges will have articles describing their designs in QST and will receive our usual page rate for the published articles. Additional entrants who meet the minimum requirements -- and have interesting design features -- may also be considered for QST or ARRL Web articles.

Entrants for either option must be received at ARRL Headquarters no later than November 1, 2011. To be considered, each entrant must submit a working transceiver that is suitable for testing in the ARRL Lab and for on-the-air judging by the ARRL staff judges. Documentation required includes a priced parts list indicating the source and purchase price of each part, an article draft including a design description, construction hints, alignment instruction, block and schematic diagrams. Photographs may be provided, but final magazine photos will be taken by ARRL staff.

For this challenge, some specific requirements are provided as follows:

  • Frequency coverage
    o   10 meters -- 28.0-28.6 MHz or greater.
    o   6 meters -- 50.0-50.25 MHz or greater.
  •  Frequency readout (mechanical or electronic) resolution: less than 1 kHz.
  • Receiver noise figure
    o   10 meters -- less than 8 dB.
    o   6 meters -- less than 5 dB.
  • Receiver selectivity maximum: 3 kHz at 6 dB.
  • Receiver audio output: minimum: 0.5 W minimum with less than 10 percent distortion.
  • Transmitter must meet all FCC requirements. Note that for HF, spurious signals need to be down 43 dB below the carrier, while they must be down 60 dB on 6 meters.
  • TR switching:
    o   CW -- semi or full break-in operation
    o   Voice -- VOX or push-to-talk
  • Mic sensitivity: Adjustable, with full 25 W output from standard low impedance dynamic mic or equivalent.
  • Output of 25 W into 50 W load with up to 2:1 SWR for at least 30 seconds. No damage driving open or short at antenna jack for 30 seconds.
  • Power required: Either 120 V ac, 60 Hz mains or a nominal 13.8 V dc supply.

Evaluation Criteria

Transceivers that meet all the cost and specific performance requirements will be evaluated by ARRL staff members based on the following criteria:

  • Elegance and originality of design, craftsmanship (10 percent).
  • Receiver laboratory performance (25 percent).
    o   Dynamic performance; (blocking gain compression and two-tone, third-order IMD)
    o   Image and spurious rejection
    o   Sensitivity and selectivity
  • Transmit lab performance (25 percent).
    o   Audio response and distortion
    o   Keying waveform
    o   Keying sidebands
  • Operating convenience (25 percent).
    o   Intuitiveness of controls and functions
    o   Ease of tuning CW and SSB signals
    o   Frequency accuracy and calibration
    o   AGC action smoothness
    o   Mechanical and thermal stability
  • Ease of duplication, adjustment and calibration (15 percent).

The evaluation will be conducted by vote of the judges and will be final.

General Requirements

  • The cost target of $150 for Option 1 and $200 for Option 2 must include the retail cost of all parts required to assemble the transceiver. The following definitions of cost elements are intended to assist builders in understanding what needs to be included.
  • Parts must be readily available either from local retailers or by mail order. No “flea market specials” allowed.
  • Any test equipment other than a multimeter, RF power meter and communications receiver must either be constructed as part of the project or purchased as part of the budget. A personal computer and standard office software may be used in the design process, as well as any specialized freeware. Software requiring the purchase of a special license must have the license cost included as part of the total cost.
  • The full cost of parts purchased must be included in the above targets. This means that parts should be purchased for single unit price, unless multiple parts of the same type are used. For example, if seven 0.01 µF capacitors are used and it makes sense to purchase 10, the total price for 10 can be apportioned over the seven, if that is less than the single unit cost. If any “free sample” parts are used, they must be priced at their regular retail cost.
  • To equalize purchase options, parts cost need not include shipping, handling or sales tax.
  • Cost of usual construction consumables such as wire, solder, tape, PC etchant and similar items need not be included. If a PC board is used, the cost of the raw board must be included, as well as any costs incurred in board layout (for example, software based board provider charges).
  • Each entrant must submit a sample of the station with documentation indicating the source and price of each part used in the construction. A draft QST article will also be provided including a discussion of the design with schematic diagram and description of the construction, test and alignment steps. All portions of the entry must be received at ARRL Headquarters before November 1, 2011.
  • The station will first be evaluated by the ARRL Laboratory in a manner similar to a QST Product Review of HF transceivers. Entries determined by the Lab to be acceptable on the basis of FCC spectral purity requirements will be evaluated by the QST Technical Editorial Staff based on the listed requirements.


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