5530 Purnode · BE
Construction dossier · ON4CRD-DL-R1 · www.on4crd.be
Dummy load — a 50 Ω resistive termination
A prototype to build and qualify at the club. The variant power levels are design targets, not measured performance. Until thermal and RF qualification is complete, limit initial tests to 1 W for 30 seconds, then allow the load to cool. No measurement curves or certification are claimed.
Disclaimer
These dossiers are supplied as is for educational and experimental purposes. Calculations, simulations and file checks are neither measured performance nor certification or qualification of the assembled device.
The person building or using the device must check the schematics, components, connections and protective measures, follow manufacturer instructions and applicable regulations, and have the completed device validated before use. Depending on the device, electrical voltages, radiofrequency energy and heat can cause electric shock, burns or fire. Tests must be conducted by a competent person, starting at low power with suitable protective measures.
To the extent permitted by law, ON4CRD and the contributors do not guarantee fitness for a particular purpose or results, and disclaim liability for damage arising from construction, modification or use. This notice does not limit any mandatory rights or any liability that the law does not allow to be excluded.
Three variants using the same board
DL-5 · 5 W
20 × 1000 Ω · 1 %
MRS25000C1001FCT00
- Rated power per resistor
- 0.6 W
- Sum of rated powers
- 12 W
- Target power after qualification
- 5 W
DL-15 · 15 W
20 × 1000 Ω · 1 %
PR02000201001FA100
- Rated power per resistor
- 2.0 W
- Sum of rated powers
- 40 W
- Target power after qualification
- 15 W
DL-25 · 25 W
20 × 1000 Ω · 1 %
PR03000201001FAC00
- Rated power per resistor
- 3.0 W
- Sum of rated powers
- 60 W
- Target power after qualification
- 25 W
All twenty resistors must have the same resistance and part number within a variant. Use the documented part and apply its temperature derating. Adding the individual power ratings never establishes the assembled load’s permissible power by itself: the enclosure, ventilation and ambient temperature may require a lower limit.
Electrical and thermal calculations
Twenty identical resistors in parallel give the targeted value. For individually measured resistors, use the inverse of the sum of the conductances. A missing branch increases the total resistance: identify the cause before any RF test.
R = 1 / Σ(1 / Rᵢ) = 1000 / 20 = 50 Ω
At total power P, each identical resistor dissipates P / 20. The voltages and currents in the table are RMS values calculated for an ideal load; the peak voltage is the RMS voltage multiplied by the square root of two. Use a suitable wattmeter to check the actual applied power.
Pᵢ = P / 20 · URMS = √(P × 50) · IRMS = √(P / 50) · Upeak = √2 × URMS
| Variant | Dissipation per resistor at target power | RMS voltage | Total RMS current |
|---|---|---|---|
| DL-5 | 0.25 W | 15.81 V | 0.316 A |
| DL-15 | 0.75 W | 27.39 V | 0.548 A |
| DL-25 | 1.25 W | 35.36 V | 0.707 A |
With 1 % components, the theoretical cold resistance lies between 49,5 Ω and 50,5 Ω. These bounds do not include multimeter uncertainty, solder joints or heating. Measure test-lead resistance and assess the reading against the instrument’s uncertainty.
Power becomes heat. Apply the manufacturer's derating curve to the local ambient temperature around the components and maintain a margin. Also measure the temperature of the hottest resistor body with an insulated thermocouple. Do not substitute this surface temperature for the ambient temperature specified in the manual. The thermal equilibrium test must validate the board in its final enclosure; a still-rising temperature does not validate any continuous operation.
A multimeter measures DC resistance; RF impedance also depends on parasitic inductance and capacitance. A sweep from 1 MHz to 30 MHz is a qualification target. Accept only frequencies where the measured VSWR is no greater than 1,2. A good DC value guarantees neither the whole HF range nor operation at VHF or UHF.
Pallowed ≤ 20 × Prated × k(Tambient, local)
Bill of materials
The board and connectors are shared by the three variants; only the twenty resistors’ part number changes. The CSV bills of materials provide a workshop checklist. Check the dimensions, tolerance, construction and derating of the actual ordered part before buying it or drilling the enclosure.
| Reference | Quantity | Component | Specification / choice |
|---|---|---|---|
| R1–R20 | 20 | Identical axial resistors | 1000 Ω, tolerance 1 %: MRS25 for DL-5, copper-lead PR02 for DL-15 and copper-lead PR03 for DL-25. Exclude lower-power FeCu-lead versions. These are spirally trimmed metal-film resistors: measure their RF behaviour rather than assuming zero inductance. |
| PCB1 | 1 | Printed circuit board | FR-4, two layers, 90 × 100 mm, 1,6 mm thick, 35 µm copper. Axial lead pitch 25,4 mm; forty plated resistor holes, two coaxial connection holes and four M3 mounting holes. See the fabrication files for hole diameters. |
| J1 | 1 | Chassis coaxial connector | Chassis-mounted female BNC connector, 50 Ω, with its body electrically bonded to the enclosure. Check the chosen connector’s power rating and mechanical strength. The board has cable pads rather than a specific BNC footprint. |
| W1 | 1 | Short coaxial link | 50 Ω coaxial cable, for example RG-316, kept as short as possible; centre conductor to RF, braid to GND. Check cable losses, power rating and temperature limits in its datasheet. |
| BOX1 | 1 | Vented metal enclosure | Sufficient volume to allow air circulation around the resistors, with protected openings. No conductive part should touch the RF pads; do not rely on a closed enclosure to dissipate the intended power. |
| H1–H4 | 4 | Spacers and screws | Four insulated mounts suitable for the M3 holes, with clearance beneath the solder joints. Provide a separate short connection between the coaxial ground and the enclosure. |
Electrical diagram
Printed circuit board and layout
The 90 × 100 mm board has twenty resistors in two columns of ten, with a 25,4 mm axial lead pitch and 8 mm vertical spacing. Mount the resistor bodies 5 mm above the board. Check the layout against the actual components, verify enclosure clearances and inspect every layer in a Gerber viewer before ordering. This layout does not establish RF impedance performance.
Manufacturing files and documents
Download files belonging to the same revision. The Gerber archive contains the layers and drill data needed for the fabricator’s review; the source regenerates the files. Read the manufacturing instructions and inspect the fabricator’s preview before ordering. The CSV files are bills of materials, not sales quotations.
The complete archive includes the educational board’s Gerber files, diagrams, bills of materials, instructions and sources for every variant. The high-power models use a complete commercial RF load; they do not use the printed circuit board of the low-power variants.
- Gerber and drill archive (ZIP)
- Circuit source and generator (Node.js)
- Manufacturing instructions (FR · TXT)
- Electrical schematic (SVG) (SVG)
- Component layout (SVG) (SVG)
- Printed circuit board and layout (SVG · Ø)
- File inventory and checks (JSON)
- High-power bench diagram and bill of materials (SVG)
- Circuit source and generator (Node.js · DL-100 → DL-3000)
- Complete dossier for all variants (ZIP) (ZIP)
- File inventory and checks (JSON · DOSSIER)
- File inventory and checks (JSON · DL-100 → DL-3000)
- Manufacturing instructions (FR · TXT · DOSSIER)
- Circuit source and generator (Node.js · DOSSIER)
- Bill of materials CSV · DL-5
- Bill of materials CSV · DL-15
- Bill of materials CSV · DL-25
- Bill of materials CSV · DL-100 → DL-3000
Step-by-step assembly · DL-5 / DL-15 / DL-25
- Prepare a multimeter, soldering station, cutters, coaxial cable and temperature measurement equipment. Choose the variant and identify twenty resistors with the same part number. Measure and record each resistance; reject incorrect values and damaged parts.
- Inspect the bare board for bridges between RF and GND, continuity within each net and clean holes. Check component fit before soldering. Form the leads without stressing the bodies and mount the resistors 5 mm above the board for airflow, retaining the specified electrical clearances.
- Solder the twenty resistors, one branch between RF and GND each time. Cut the excess, inspect both sides, and remove conductive residues. No wire, screw, or solder bridge should short-circuit the resistor bank.
- Fit the chassis connector and secure the board to its spacers. Keep the coaxial cable short: centre conductor to RF, braid to GND. Bond the connector body to the enclosure through clean, reliable metal contact. Check that no RF pad or solder joint touches a wall or screw.
- Complete the mechanical inspection, cleaning, and continuity measurements before closing. Photograph both sides and the wiring. Affix a temporary label with the variant, revision, and first test limit; the final limit will depend on RF measurements and the thermal measurements of the complete assembly.
Commissioning and qualification · DL-5 / DL-15 / DL-25
- With the RF source disconnected, measure cold resistance through the connector. Check test-lead resistance, consistency with the component tolerance and continuity between shield and enclosure. A near-zero reading, open circuit or unexplained value requires repair before proceeding.
- Calibrate the network analyser at the connector reference plane using suitable standards. Sweep the intended band and retain the VSWR trace together with cable details, date and calibration. Define the usable band from the results. Completely disconnect the analyser and multimeter before connecting an RF source.
- With a wattmeter and a source whose low power is verifiable, start at 1 W for a maximum of 30 seconds. Stop, then allow to return to room temperature. Check the cold resistance and the condition of the assembly again. If the source does not allow this adjustment and its verification, do not perform this test.
- Continue in supervised power steps only after the initial checks pass. At each step, record power, duration, local ambient temperature and the hottest component temperature. Follow the datasheet and its derating curve with a margin; stop if readings drift, an unusual smell appears or temperatures are abnormal. A short test does not establish a continuous power rating.
- Qualify the selected power in the final enclosure until thermal equilibrium is reached, without exceeding documented component and material limits. Recheck VSWR at low power, then cold resistance. If the target cannot be met, adopt a lower measured limit. Label the load with its maximum power, permitted duration, ventilation, ambient temperature and verified frequency range.
Variants from 100 to 3 000 W — benches with complete RF loads
Above the educational circuit’s power range, the project becomes a test bench built around a complete RF termination specified by its manufacturer. The proposed units include both the resistive element and its coaxial structure: the small board’s Gerber files cannot replace them. The powers below are bench targets; also observe the ratings of the load, cables and connectors.
| Variant | Complete RF load | RMS voltage | Total RMS current | Cooling |
|---|---|---|---|---|
| DL-100 100 W | Bird 8135 150 W | 70.7 V | 1.41 A | Convection, as specified in the manual |
| DL-250 250 W | Bird 8141 250 W | 111.8 V | 2.24 A | Convection, as specified in the manual |
| DL-500 500 W | Bird 8201 500 W | 158.1 V | 3.16 A | Convection, as specified in the manual |
| DL-1000 1000 W | Bird 8251 1000 W | 223.6 V | 4.47 A | Convection, as specified in the manual |
| DL-1500 1500 W | Bird 8860 1500 W | 273.9 V | 5.48 A | Convection, as specified in the manual |
| DL-3000 3000 W | Bird 8720 5000 W | 387.3 V | 7.75 A | Water, flow as specified in the manual |
The signal path is transmitter → directional wattmeter → suitably rated coaxial line → 50 Ω load. Mount the unit as instructed, preserve clearances and orientation, earth the chassis as required by the equipment, and guard accessible parts. For DL-3000, use a complete 5 kW Bird 8720, limited here to 3 000 W, with an EIA 1-5/8 flange and an equally rated line. Never connect several 50 Ω loads directly in parallel.
At 3 000 W into 50 Ω: 387,3 V RMS, 547,7 V peak and 7,75 A RMS; the heat to remove is 3 kW. For water warming by 10 °C, the ideal energy balance gives about 4,3 L/min. This calculation does not replace the required flow: the 8720 manual specifies from 3,8 L/min at 5 °C to 15,2 L/min at 80 °C. Use the specified flow for the actual inlet temperature, check water pressure and quality, purge the system and provide drainage or a heat exchanger capable of removing 3 kW.
Q = P / (ρ × c × ΔT) = 3000 × 60 / (1 × 4180 × 10) ≈ 4.3 L/min
The DL-3000 bench requires a complete Bird 8720 load, a compatible EIA 1-5/8 coupling kit, coaxial line and directional wattmeter rated for at least 3 kW in the chosen band, water fittings of size 1/4 as specified in the manual, two hoses, flow measurement, two temperature probes, an isolated 24 V control supply, a manually reset protective relay, flow and overtemperature contacts, and a guarded chassis. For a closed cooling loop, add a pump sized for the pressure losses and a heat exchanger; a reservoir alone cannot support continuous operation.
Have a competent person inspect the bench and its protection circuit before transmitting. Hardware amplifier enable must depend on adequate water flow, acceptable temperatures, a closed cover and manual reset; a broken wire or loss of power must remove enable. Test each fault without RF power and check its shutdown time against the amplifier documentation. Calibrate at low power, then increase in steps while recording forward and reflected power, temperatures and flow. No high-power test results are supplied here. Turn off RF before any work or disconnection; the analyser must never remain connected during transmission.
Dossiers for each variant
DL-5 · 5 W · Printed circuit board assembly
Vishay MRS25 · MRS25000C1001FCT00 · ON4CRD-DL-R1
- Target power after qualification
- 5 W
- RMS voltage
- 15.81 V
- Peak voltage
- 22.36 V
- Total RMS current
- 0.316 A
- Heat to remove
- 5 W
- Dissipation per resistor at target power
- 0.25 W
The electrical values assume an ideal 50 Ω load and a sinusoidal waveform. Nominal power margin does not establish the bench’s cooling capacity or RF performance.
Bill of materials · DL-5
| Reference | Quantity | Component | Specification / choice |
|---|---|---|---|
| R1–R20 | 20 | Identical axial resistors | MRS25000C1001FCT00 · 1000 Ω · 1 % · 0.6 W |
| PCB1 | 1 | Printed circuit board | FR-4, two layers, 90 × 100 mm, 1,6 mm thick, 35 µm copper. Axial lead pitch 25,4 mm; forty plated resistor holes, two coaxial connection holes and four M3 mounting holes. See the fabrication files for hole diameters. |
| J1 | 1 | Chassis coaxial connector | Chassis-mounted female BNC connector, 50 Ω, with its body electrically bonded to the enclosure. Check the chosen connector’s power rating and mechanical strength. The board has cable pads rather than a specific BNC footprint. |
| W1 | 1 | Short coaxial link | 50 Ω coaxial cable, for example RG-316, kept as short as possible; centre conductor to RF, braid to GND. Check cable losses, power rating and temperature limits in its datasheet. |
| BOX1 | 1 | Vented metal enclosure | Sufficient volume to allow air circulation around the resistors, with protected openings. No conductive part should touch the RF pads; do not rely on a closed enclosure to dissipate the intended power. |
| H1–H4 | 4 | Spacers and screws | Four insulated mounts suitable for the M3 holes, with clearance beneath the solder joints. Provide a separate short connection between the coaxial ground and the enclosure. |
Step-by-step assembly
Inspect the bare board for bridges between RF and GND, continuity within each net and clean holes. Check component fit before soldering. Form the leads without stressing the bodies and mount the resistors 5 mm above the board for airflow, retaining the specified electrical clearances. Fit the chassis connector and secure the board to its spacers. Keep the coaxial cable short: centre conductor to RF, braid to GND. Bond the connector body to the enclosure through clean, reliable metal contact. Check that no RF pad or solder joint touches a wall or screw.
Air cooling of the resistor bank. Keep the resistors raised above the board and qualify the actual enclosure and ventilation. The permissible power may be lower than the design target.
Commissioning and qualification
With a wattmeter and a source whose low power is verifiable, start at 1 W for a maximum of 30 seconds. Stop, then allow to return to room temperature. Check the cold resistance and the condition of the assembly again. If the source does not allow this adjustment and its verification, do not perform this test. Qualify the selected power in the final enclosure until thermal equilibrium is reached, without exceeding documented component and material limits. Recheck VSWR at low power, then cold resistance. If the target cannot be met, adopt a lower measured limit. Label the load with its maximum power, permitted duration, ventilation, ambient temperature and verified frequency range.
Assembly qualification : To be measured on the completed assembly
Documents for this variant
DL-15 · 15 W · Printed circuit board assembly
Vishay PR02 Cu-lead 0.78 mm · PR02000201001FA100 · ON4CRD-DL-R1
- Target power after qualification
- 15 W
- RMS voltage
- 27.39 V
- Peak voltage
- 38.73 V
- Total RMS current
- 0.548 A
- Heat to remove
- 15 W
- Dissipation per resistor at target power
- 0.75 W
The electrical values assume an ideal 50 Ω load and a sinusoidal waveform. Nominal power margin does not establish the bench’s cooling capacity or RF performance.
Bill of materials · DL-15
| Reference | Quantity | Component | Specification / choice |
|---|---|---|---|
| R1–R20 | 20 | Identical axial resistors | PR02000201001FA100 · 1000 Ω · 1 % · 2.0 W |
| PCB1 | 1 | Printed circuit board | FR-4, two layers, 90 × 100 mm, 1,6 mm thick, 35 µm copper. Axial lead pitch 25,4 mm; forty plated resistor holes, two coaxial connection holes and four M3 mounting holes. See the fabrication files for hole diameters. |
| J1 | 1 | Chassis coaxial connector | Chassis-mounted female BNC connector, 50 Ω, with its body electrically bonded to the enclosure. Check the chosen connector’s power rating and mechanical strength. The board has cable pads rather than a specific BNC footprint. |
| W1 | 1 | Short coaxial link | 50 Ω coaxial cable, for example RG-316, kept as short as possible; centre conductor to RF, braid to GND. Check cable losses, power rating and temperature limits in its datasheet. |
| BOX1 | 1 | Vented metal enclosure | Sufficient volume to allow air circulation around the resistors, with protected openings. No conductive part should touch the RF pads; do not rely on a closed enclosure to dissipate the intended power. |
| H1–H4 | 4 | Spacers and screws | Four insulated mounts suitable for the M3 holes, with clearance beneath the solder joints. Provide a separate short connection between the coaxial ground and the enclosure. |
Step-by-step assembly
Inspect the bare board for bridges between RF and GND, continuity within each net and clean holes. Check component fit before soldering. Form the leads without stressing the bodies and mount the resistors 5 mm above the board for airflow, retaining the specified electrical clearances. Fit the chassis connector and secure the board to its spacers. Keep the coaxial cable short: centre conductor to RF, braid to GND. Bond the connector body to the enclosure through clean, reliable metal contact. Check that no RF pad or solder joint touches a wall or screw.
Air cooling of the resistor bank. Keep the resistors raised above the board and qualify the actual enclosure and ventilation. The permissible power may be lower than the design target.
Commissioning and qualification
With a wattmeter and a source whose low power is verifiable, start at 1 W for a maximum of 30 seconds. Stop, then allow to return to room temperature. Check the cold resistance and the condition of the assembly again. If the source does not allow this adjustment and its verification, do not perform this test. Qualify the selected power in the final enclosure until thermal equilibrium is reached, without exceeding documented component and material limits. Recheck VSWR at low power, then cold resistance. If the target cannot be met, adopt a lower measured limit. Label the load with its maximum power, permitted duration, ventilation, ambient temperature and verified frequency range.
Assembly qualification : To be measured on the completed assembly
Documents for this variant
DL-25 · 25 W · Printed circuit board assembly
Vishay PR03 Cu-lead 0.78 mm · PR03000201001FAC00 · ON4CRD-DL-R1
- Target power after qualification
- 25 W
- RMS voltage
- 35.36 V
- Peak voltage
- 50.00 V
- Total RMS current
- 0.707 A
- Heat to remove
- 25 W
- Dissipation per resistor at target power
- 1.25 W
The electrical values assume an ideal 50 Ω load and a sinusoidal waveform. Nominal power margin does not establish the bench’s cooling capacity or RF performance.
Bill of materials · DL-25
| Reference | Quantity | Component | Specification / choice |
|---|---|---|---|
| R1–R20 | 20 | Identical axial resistors | PR03000201001FAC00 · 1000 Ω · 1 % · 3.0 W |
| PCB1 | 1 | Printed circuit board | FR-4, two layers, 90 × 100 mm, 1,6 mm thick, 35 µm copper. Axial lead pitch 25,4 mm; forty plated resistor holes, two coaxial connection holes and four M3 mounting holes. See the fabrication files for hole diameters. |
| J1 | 1 | Chassis coaxial connector | Chassis-mounted female BNC connector, 50 Ω, with its body electrically bonded to the enclosure. Check the chosen connector’s power rating and mechanical strength. The board has cable pads rather than a specific BNC footprint. |
| W1 | 1 | Short coaxial link | 50 Ω coaxial cable, for example RG-316, kept as short as possible; centre conductor to RF, braid to GND. Check cable losses, power rating and temperature limits in its datasheet. |
| BOX1 | 1 | Vented metal enclosure | Sufficient volume to allow air circulation around the resistors, with protected openings. No conductive part should touch the RF pads; do not rely on a closed enclosure to dissipate the intended power. |
| H1–H4 | 4 | Spacers and screws | Four insulated mounts suitable for the M3 holes, with clearance beneath the solder joints. Provide a separate short connection between the coaxial ground and the enclosure. |
Step-by-step assembly
Inspect the bare board for bridges between RF and GND, continuity within each net and clean holes. Check component fit before soldering. Form the leads without stressing the bodies and mount the resistors 5 mm above the board for airflow, retaining the specified electrical clearances. Fit the chassis connector and secure the board to its spacers. Keep the coaxial cable short: centre conductor to RF, braid to GND. Bond the connector body to the enclosure through clean, reliable metal contact. Check that no RF pad or solder joint touches a wall or screw.
Air cooling of the resistor bank. Keep the resistors raised above the board and qualify the actual enclosure and ventilation. The permissible power may be lower than the design target.
Commissioning and qualification
With a wattmeter and a source whose low power is verifiable, start at 1 W for a maximum of 30 seconds. Stop, then allow to return to room temperature. Check the cold resistance and the condition of the assembly again. If the source does not allow this adjustment and its verification, do not perform this test. Qualify the selected power in the final enclosure until thermal equilibrium is reached, without exceeding documented component and material limits. Recheck VSWR at low power, then cold resistance. If the target cannot be met, adopt a lower measured limit. Label the load with its maximum power, permitted duration, ventilation, ambient temperature and verified frequency range.
Assembly qualification : To be measured on the completed assembly
Documents for this variant
DL-100 · 100 W · Integration of a complete RF load
Bird 8135 · ON4CRD-DL-HP-R1
- Target power after qualification
- 100 W
- RMS voltage
- 70.71 V
- Peak voltage
- 100.00 V
- Total RMS current
- 1.414 A
- Heat to remove
- 100 W
- Module power rating
- 150 W
The electrical values assume an ideal 50 Ω load and a sinusoidal waveform. Nominal power margin does not establish the bench’s cooling capacity or RF performance.
- Operating orientation
- Horizontal, as specified in the manual
- Permissible ambient temperature
- -40 … 45 °C
- Clearance for airflow
- ≥ 152.4 mm
- RF connection
- QC N (f)
- Nominal module power margin
- 50 W
Bill of materials · DL-100
| Reference | Quantity | Component | Specification / choice |
|---|---|---|---|
| LOAD1 | 1 | Complete RF load | Bird 8135 · 50 Ω · 150 W |
| LINE1 | 1 | Short coaxial link | 50 Ω · ≥ 100 W · 1–30 MHz |
| LINE2 | 1 | Short coaxial link | 50 Ω · ≥ 100 W · 1–30 MHz |
| WM1 | 1 | Directional wattmeter | 50 Ω · ≥ 100 W · 1–30 MHz |
| FRAME1 | 1 | Spacers and screws | ≥ 152.4 mm · Clearance for airflow |
| FIX1 | 1 | Spacers and screws | Manufacturer’s manual |
| PE1 | 1 | Wiring and protective devices | PE · Manufacturer’s manual |
| PS1 | 1 | Isolated control power supply | 24 V DC |
| K1 | 1 | Protective relay | Manufacturer’s manual |
| S1 | 1 | Cover safety contact | Manufacturer’s manual |
| S2 | 1 | Maintained stop control | Manufacturer’s manual |
| S3 | 1 | Manual reset | Manufacturer’s manual |
| IF1 | 1 | Amplifier enable interface | Manufacturer’s manual |
| WIRE1 | 1 | Wiring and protective devices | Manufacturer’s manual |
| LABEL1 | 1 | Limit label and inspection record | Manufacturer’s manual |
| TA1 | 1 | Temperature measurement and monitoring | Manufacturer’s manual |
| TS1 | 1 | Temperature measurement and monitoring | Manufacturer’s manual |
Step-by-step assembly
Mount the complete load on a rigid support as specified in its manual. Observe the required orientation, clearances and venting arrangement. Connect the 50 Ω line and a suitably rated wattmeter, then check the mechanical connections and chassis before transmitting.
Oil-cooled load checks
Oil cooling with natural convection. Use the complete load with its specified fluid; maintain the clearances, orientation and vent arrangement stated in the exact model’s manual. Observe the manufacturer’s ambient temperature and duty limits.
Commissioning and qualification
Check DC resistance against the model’s tolerance and measure VSWR at the connector reference plane at low power. Disconnect the analyser, then increase power in steps without exceeding the ratings of the load, cable or connectors. Record forward and reflected power, duration and temperatures until thermal equilibrium; keep the results and operating conditions.
Have a competent person inspect the bench and its protection circuit before transmitting. Hardware amplifier enable must depend on adequate water flow, acceptable temperatures, a closed cover and manual reset; a broken wire or loss of power must remove enable. Test each fault without RF power and check its shutdown time against the amplifier documentation. Calibrate at low power, then increase in steps while recording forward and reflected power, temperatures and flow. No high-power test results are supplied here. Turn off RF before any work or disconnection; the analyser must never remain connected during transmission.
Assembly qualification : To be measured on the completed assembly
Documents for this variant
DL-250 · 250 W · Integration of a complete RF load
Bird 8141 · ON4CRD-DL-HP-R1
- Target power after qualification
- 250 W
- RMS voltage
- 111.80 V
- Peak voltage
- 158.11 V
- Total RMS current
- 2.236 A
- Heat to remove
- 250 W
- Module power rating
- 250 W
The electrical values assume an ideal 50 Ω load and a sinusoidal waveform. Nominal power margin does not establish the bench’s cooling capacity or RF performance.
- Operating orientation
- Horizontal, as specified in the manual
- Permissible ambient temperature
- -40 … 45 °C
- Clearance for airflow
- ≥ 152.4 mm
- RF connection
- QC N (f)
- Nominal module power margin
- 0 W
Bill of materials · DL-250
| Reference | Quantity | Component | Specification / choice |
|---|---|---|---|
| LOAD1 | 1 | Complete RF load | Bird 8141 · 50 Ω · 250 W |
| LINE1 | 1 | Short coaxial link | 50 Ω · ≥ 250 W · 1–30 MHz |
| LINE2 | 1 | Short coaxial link | 50 Ω · ≥ 250 W · 1–30 MHz |
| WM1 | 1 | Directional wattmeter | 50 Ω · ≥ 250 W · 1–30 MHz |
| FRAME1 | 1 | Spacers and screws | ≥ 152.4 mm · Clearance for airflow |
| FIX1 | 1 | Spacers and screws | Manufacturer’s manual |
| PE1 | 1 | Wiring and protective devices | PE · Manufacturer’s manual |
| PS1 | 1 | Isolated control power supply | 24 V DC |
| K1 | 1 | Protective relay | Manufacturer’s manual |
| S1 | 1 | Cover safety contact | Manufacturer’s manual |
| S2 | 1 | Maintained stop control | Manufacturer’s manual |
| S3 | 1 | Manual reset | Manufacturer’s manual |
| IF1 | 1 | Amplifier enable interface | Manufacturer’s manual |
| WIRE1 | 1 | Wiring and protective devices | Manufacturer’s manual |
| LABEL1 | 1 | Limit label and inspection record | Manufacturer’s manual |
| TA1 | 1 | Temperature measurement and monitoring | Manufacturer’s manual |
| TS1 | 1 | Temperature measurement and monitoring | Manufacturer’s manual |
Step-by-step assembly
Mount the complete load on a rigid support as specified in its manual. Observe the required orientation, clearances and venting arrangement. Connect the 50 Ω line and a suitably rated wattmeter, then check the mechanical connections and chassis before transmitting.
Oil-cooled load checks
Oil cooling with natural convection. Use the complete load with its specified fluid; maintain the clearances, orientation and vent arrangement stated in the exact model’s manual. Observe the manufacturer’s ambient temperature and duty limits.
Commissioning and qualification
Check DC resistance against the model’s tolerance and measure VSWR at the connector reference plane at low power. Disconnect the analyser, then increase power in steps without exceeding the ratings of the load, cable or connectors. Record forward and reflected power, duration and temperatures until thermal equilibrium; keep the results and operating conditions.
Have a competent person inspect the bench and its protection circuit before transmitting. Hardware amplifier enable must depend on adequate water flow, acceptable temperatures, a closed cover and manual reset; a broken wire or loss of power must remove enable. Test each fault without RF power and check its shutdown time against the amplifier documentation. Calibrate at low power, then increase in steps while recording forward and reflected power, temperatures and flow. No high-power test results are supplied here. Turn off RF before any work or disconnection; the analyser must never remain connected during transmission.
Assembly qualification : To be measured on the completed assembly
Documents for this variant
DL-500 · 500 W · Integration of a complete RF load
Bird 8201 · ON4CRD-DL-HP-R1
- Target power after qualification
- 500 W
- RMS voltage
- 158.11 V
- Peak voltage
- 223.61 V
- Total RMS current
- 3.162 A
- Heat to remove
- 500 W
- Module power rating
- 500 W
The electrical values assume an ideal 50 Ω load and a sinusoidal waveform. Nominal power margin does not establish the bench’s cooling capacity or RF performance.
- Operating orientation
- Horizontal, as specified in the manual
- Permissible ambient temperature
- -40 … 45 °C
- Clearance for airflow
- ≥ 152.4 mm
- RF connection
- QC N (f)
- Nominal module power margin
- 0 W
Bill of materials · DL-500
| Reference | Quantity | Component | Specification / choice |
|---|---|---|---|
| LOAD1 | 1 | Complete RF load | Bird 8201 · 50 Ω · 500 W |
| LINE1 | 1 | Short coaxial link | 50 Ω · ≥ 500 W · 1–30 MHz |
| LINE2 | 1 | Short coaxial link | 50 Ω · ≥ 500 W · 1–30 MHz |
| WM1 | 1 | Directional wattmeter | 50 Ω · ≥ 500 W · 1–30 MHz |
| FRAME1 | 1 | Spacers and screws | ≥ 152.4 mm · Clearance for airflow |
| FIX1 | 1 | Spacers and screws | Manufacturer’s manual |
| PE1 | 1 | Wiring and protective devices | PE · Manufacturer’s manual |
| PS1 | 1 | Isolated control power supply | 24 V DC |
| K1 | 1 | Protective relay | Manufacturer’s manual |
| S1 | 1 | Cover safety contact | Manufacturer’s manual |
| S2 | 1 | Maintained stop control | Manufacturer’s manual |
| S3 | 1 | Manual reset | Manufacturer’s manual |
| IF1 | 1 | Amplifier enable interface | Manufacturer’s manual |
| WIRE1 | 1 | Wiring and protective devices | Manufacturer’s manual |
| LABEL1 | 1 | Limit label and inspection record | Manufacturer’s manual |
| TA1 | 1 | Temperature measurement and monitoring | Manufacturer’s manual |
| TS1 | 1 | Temperature measurement and monitoring | Manufacturer’s manual |
Step-by-step assembly
Mount the complete load on a rigid support as specified in its manual. Observe the required orientation, clearances and venting arrangement. Connect the 50 Ω line and a suitably rated wattmeter, then check the mechanical connections and chassis before transmitting.
Oil-cooled load checks
Oil cooling with natural convection. Use the complete load with its specified fluid; maintain the clearances, orientation and vent arrangement stated in the exact model’s manual. Observe the manufacturer’s ambient temperature and duty limits.
Commissioning and qualification
Check DC resistance against the model’s tolerance and measure VSWR at the connector reference plane at low power. Disconnect the analyser, then increase power in steps without exceeding the ratings of the load, cable or connectors. Record forward and reflected power, duration and temperatures until thermal equilibrium; keep the results and operating conditions.
Have a competent person inspect the bench and its protection circuit before transmitting. Hardware amplifier enable must depend on adequate water flow, acceptable temperatures, a closed cover and manual reset; a broken wire or loss of power must remove enable. Test each fault without RF power and check its shutdown time against the amplifier documentation. Calibrate at low power, then increase in steps while recording forward and reflected power, temperatures and flow. No high-power test results are supplied here. Turn off RF before any work or disconnection; the analyser must never remain connected during transmission.
Assembly qualification : To be measured on the completed assembly
Documents for this variant
DL-1000 · 1000 W · Integration of a complete RF load
Bird 8251 · ON4CRD-DL-HP-R1
- Target power after qualification
- 1000 W
- RMS voltage
- 223.61 V
- Peak voltage
- 316.23 V
- Total RMS current
- 4.472 A
- Heat to remove
- 1000 W
- Module power rating
- 1000 W
The electrical values assume an ideal 50 Ω load and a sinusoidal waveform. Nominal power margin does not establish the bench’s cooling capacity or RF performance.
- Operating orientation
- Horizontal, as specified in the manual
- Permissible ambient temperature
- -40 … 45 °C
- Clearance for airflow
- ≥ 152.4 mm
- RF connection
- QC LC (f)
- Nominal module power margin
- 0 W
Bill of materials · DL-1000
| Reference | Quantity | Component | Specification / choice |
|---|---|---|---|
| LOAD1 | 1 | Complete RF load | Bird 8251 · 50 Ω · 1000 W |
| LINE1 | 1 | Short coaxial link | 50 Ω · ≥ 1000 W · 1–30 MHz |
| LINE2 | 1 | Short coaxial link | 50 Ω · ≥ 1000 W · 1–30 MHz |
| WM1 | 1 | Directional wattmeter | 50 Ω · ≥ 1000 W · 1–30 MHz |
| FRAME1 | 1 | Spacers and screws | ≥ 152.4 mm · Clearance for airflow |
| FIX1 | 1 | Spacers and screws | Manufacturer’s manual |
| PE1 | 1 | Wiring and protective devices | PE · Manufacturer’s manual |
| PS1 | 1 | Isolated control power supply | 24 V DC |
| K1 | 1 | Protective relay | Manufacturer’s manual |
| S1 | 1 | Cover safety contact | Manufacturer’s manual |
| S2 | 1 | Maintained stop control | Manufacturer’s manual |
| S3 | 1 | Manual reset | Manufacturer’s manual |
| IF1 | 1 | Amplifier enable interface | Manufacturer’s manual |
| WIRE1 | 1 | Wiring and protective devices | Manufacturer’s manual |
| LABEL1 | 1 | Limit label and inspection record | Manufacturer’s manual |
| TA1 | 1 | Temperature measurement and monitoring | Manufacturer’s manual |
| TS1 | 1 | Temperature measurement and monitoring | Manufacturer’s manual |
| PLUG1 | 1 | Specified vent plug | Manufacturer’s manual |
| INT1 | 1 | Load thermal-switch contact | Manufacturer’s manual |
Step-by-step assembly
Mount the complete load on a rigid support as specified in its manual. Observe the required orientation, clearances and venting arrangement. Connect the 50 Ω line and a suitably rated wattmeter, then check the mechanical connections and chassis before transmitting.
Oil-cooled load checks
Oil cooling with natural convection. Use the complete load with its specified fluid; maintain the clearances, orientation and vent arrangement stated in the exact model’s manual. Observe the manufacturer’s ambient temperature and duty limits.
Commissioning and qualification
Check DC resistance against the model’s tolerance and measure VSWR at the connector reference plane at low power. Disconnect the analyser, then increase power in steps without exceeding the ratings of the load, cable or connectors. Record forward and reflected power, duration and temperatures until thermal equilibrium; keep the results and operating conditions.
Have a competent person inspect the bench and its protection circuit before transmitting. Hardware amplifier enable must depend on adequate water flow, acceptable temperatures, a closed cover and manual reset; a broken wire or loss of power must remove enable. Test each fault without RF power and check its shutdown time against the amplifier documentation. Calibrate at low power, then increase in steps while recording forward and reflected power, temperatures and flow. No high-power test results are supplied here. Turn off RF before any work or disconnection; the analyser must never remain connected during transmission.
Assembly qualification : To be measured on the completed assembly
Documents for this variant
DL-1500 · 1500 W · Integration of a complete RF load
Bird 8860 · ON4CRD-DL-HP-R1
- Target power after qualification
- 1500 W
- RMS voltage
- 273.86 V
- Peak voltage
- 387.30 V
- Total RMS current
- 5.477 A
- Heat to remove
- 1500 W
- Module power rating
- 1500 W
The electrical values assume an ideal 50 Ω load and a sinusoidal waveform. Nominal power margin does not establish the bench’s cooling capacity or RF performance.
- Operating orientation
- Horizontal, as specified in the manual
- Permissible ambient temperature
- 5 … 40 °C
- Clearance for airflow
- ≥ 305.0 mm
- RF connection
- LC (f)
- Nominal module power margin
- 0 W
Bill of materials · DL-1500
| Reference | Quantity | Component | Specification / choice |
|---|---|---|---|
| LOAD1 | 1 | Complete RF load | Bird 8860 · 50 Ω · 1500 W |
| LINE1 | 1 | Short coaxial link | 50 Ω · ≥ 1500 W · 1–30 MHz |
| LINE2 | 1 | Short coaxial link | 50 Ω · ≥ 1500 W · 1–30 MHz |
| WM1 | 1 | Directional wattmeter | 50 Ω · ≥ 1500 W · 1–30 MHz |
| FRAME1 | 1 | Spacers and screws | ≥ 305.0 mm · Clearance for airflow |
| FIX1 | 1 | Spacers and screws | Manufacturer’s manual |
| PE1 | 1 | Wiring and protective devices | PE · Manufacturer’s manual |
| PS1 | 1 | Isolated control power supply | 24 V DC |
| K1 | 1 | Protective relay | Manufacturer’s manual |
| S1 | 1 | Cover safety contact | Manufacturer’s manual |
| S2 | 1 | Maintained stop control | Manufacturer’s manual |
| S3 | 1 | Manual reset | Manufacturer’s manual |
| IF1 | 1 | Amplifier enable interface | Manufacturer’s manual |
| WIRE1 | 1 | Wiring and protective devices | Manufacturer’s manual |
| LABEL1 | 1 | Limit label and inspection record | Manufacturer’s manual |
| TA1 | 1 | Temperature measurement and monitoring | Manufacturer’s manual |
| TS1 | 1 | Temperature measurement and monitoring | Manufacturer’s manual |
| PLUG1 | 1 | Specified vent plug | Manufacturer’s manual |
| INT1 | 1 | Load thermal-switch contact | Manufacturer’s manual |
Step-by-step assembly
Mount the complete load on a rigid support as specified in its manual. Observe the required orientation, clearances and venting arrangement. Connect the 50 Ω line and a suitably rated wattmeter, then check the mechanical connections and chassis before transmitting.
Oil-cooled load checks
Oil cooling with natural convection. Use the complete load with its specified fluid; maintain the clearances, orientation and vent arrangement stated in the exact model’s manual. Observe the manufacturer’s ambient temperature and duty limits.
Commissioning and qualification
Check DC resistance against the model’s tolerance and measure VSWR at the connector reference plane at low power. Disconnect the analyser, then increase power in steps without exceeding the ratings of the load, cable or connectors. Record forward and reflected power, duration and temperatures until thermal equilibrium; keep the results and operating conditions.
Have a competent person inspect the bench and its protection circuit before transmitting. Hardware amplifier enable must depend on adequate water flow, acceptable temperatures, a closed cover and manual reset; a broken wire or loss of power must remove enable. Test each fault without RF power and check its shutdown time against the amplifier documentation. Calibrate at low power, then increase in steps while recording forward and reflected power, temperatures and flow. No high-power test results are supplied here. Turn off RF before any work or disconnection; the analyser must never remain connected during transmission.
Assembly qualification : To be measured on the completed assembly
Documents for this variant
DL-3000 · 3000 W · Integration of a complete RF load
Bird 8720 · ON4CRD-DL-HP-R1
- Target power after qualification
- 3000 W
- RMS voltage
- 387.30 V
- Peak voltage
- 547.72 V
- Total RMS current
- 7.746 A
- Heat to remove
- 3000 W
- Module power rating
- 5000 W
The electrical values assume an ideal 50 Ω load and a sinusoidal waveform. Nominal power margin does not establish the bench’s cooling capacity or RF performance.
- Operating orientation
- As specified in the model’s manual
- Permissible ambient temperature
- 5 … 80 °C
- Clearance for airflow
- As specified in the model’s manual
- RF connection
- EIA 1-5/8
- Nominal module power margin
- 2000 W
Bill of materials · DL-3000
| Reference | Quantity | Component | Specification / choice |
|---|---|---|---|
| LOAD1 | 1 | Complete RF load | Bird 8720 · 50 Ω · 5000 W |
| LINE1 | 1 | Short coaxial link | 50 Ω · ≥ 3000 W · 1–30 MHz |
| LINE2 | 1 | Short coaxial link | 50 Ω · ≥ 3000 W · 1–30 MHz |
| WM1 | 1 | Directional wattmeter | 50 Ω · ≥ 3000 W · 1–30 MHz |
| FRAME1 | 1 | Spacers and screws | Manufacturer’s manual |
| FIX1 | 1 | Spacers and screws | Manufacturer’s manual |
| PE1 | 1 | Wiring and protective devices | PE · Manufacturer’s manual |
| PS1 | 1 | Isolated control power supply | 24 V DC |
| K1 | 1 | Protective relay | Manufacturer’s manual |
| S1 | 1 | Cover safety contact | Manufacturer’s manual |
| S2 | 1 | Maintained stop control | Manufacturer’s manual |
| S3 | 1 | Manual reset | Manufacturer’s manual |
| IF1 | 1 | Amplifier enable interface | Manufacturer’s manual |
| WIRE1 | 1 | Wiring and protective devices | Manufacturer’s manual |
| LABEL1 | 1 | Limit label and inspection record | Manufacturer’s manual |
| COUP1 | 1 | Chassis coaxial connector | EIA 1-5/8 |
| FIT1-FIT2 | 2 | Water supply and fittings | 1/4 · Manufacturer’s manual |
| HOSE1-HOSE2 | 2 | Water supply and fittings | Manufacturer’s manual |
| FS1 | 1 | Flow measurement and monitoring | Manufacturer’s manual |
| TS1-TS2 | 2 | Temperature measurement and monitoring | Manufacturer’s manual |
| WATER1 | 1 | Water supply and fittings | Manufacturer’s manual |
| PUMP1 | 1 | Circulation pump (closed loop) | Closed loop only |
| HX1 | 1 | Heat exchanger (closed loop) | ≥ 3000 W · Closed loop only |
| TANK1 | 1 | Reservoir and expansion provision (closed loop) | Closed loop only |
| HYD1 | 1 | Water supply and fittings | Manufacturer’s manual |
| DRAIN1 | 1 | Water supply and fittings | Manufacturer’s manual |
Step-by-step assembly
Mount the complete load on a rigid support as specified in its manual. Observe the required orientation, clearances and venting arrangement. Connect the 50 Ω line and a suitably rated wattmeter, then check the mechanical connections and chassis before transmitting.
Water-cooling checks
At 3 000 W into 50 Ω: 387,3 V RMS, 547,7 V peak and 7,75 A RMS; the heat to remove is 3 kW. For water warming by 10 °C, the ideal energy balance gives about 4,3 L/min. This calculation does not replace the required flow: the 8720 manual specifies from 3,8 L/min at 5 °C to 15,2 L/min at 80 °C. Use the specified flow for the actual inlet temperature, check water pressure and quality, purge the system and provide drainage or a heat exchanger capable of removing 3 kW.
Commissioning and qualification
Check DC resistance against the model’s tolerance and measure VSWR at the connector reference plane at low power. Disconnect the analyser, then increase power in steps without exceeding the ratings of the load, cable or connectors. Record forward and reflected power, duration and temperatures until thermal equilibrium; keep the results and operating conditions.
Have a competent person inspect the bench and its protection circuit before transmitting. Hardware amplifier enable must depend on adequate water flow, acceptable temperatures, a closed cover and manual reset; a broken wire or loss of power must remove enable. Test each fault without RF power and check its shutdown time against the amplifier documentation. Calibrate at low power, then increase in steps while recording forward and reflected power, temperatures and flow. No high-power test results are supplied here. Turn off RF before any work or disconnection; the analyser must never remain connected during transmission.
Assembly qualification : To be measured on the completed assembly
Documents for this variant
Troubleshooting
- Resistance too high: check component values, open branch, and missing solder joints. Count the twenty branches and measure the networks with the source disconnected.
- Resistance too low: look for a bridge between RF and GND, an incorrect value, or contact of the coaxial core with the casing. Disassemble if necessary to isolate the cause.
- Correct DC resistance but high VSWR: first check calibration and cable, then connectors, connection lengths and resistor RF behaviour. Compare against a reference termination; do not add a capacitor by trial and error.
- Excessive or uneven heating: turn off the source, let cool, then check the value and soldering of each branch. Review air circulation and derating; reduce the retained power if necessary. Never touch the resistors to estimate their temperature.
Printable measurement record
Fill in this form with the results actually observed and attach photos, curves, and manuals. Keep a copy with the load. An empty box means a measurement to be carried out, not a validation obtained.
- Variant / revision / resistor references
- Cold resistance / instrument / uncertainty
- Validated band / maximum VSWR / calibration
- Power / duration / temperatures / ventilation
- Selected limit and conditions of use
- Date / operator / observations