FCC PART 15 SUBPART C TEST REPORT

Document Information

Report No.: CTA23110804401

Page: 2 of 38

Equipment under Test: FLOW 100-Key Dual Mode Low Profile Mechanical Keyboard

Model /Type: OE919

Listed Models: N/A

Applicant: SHENZHEN LOFREE CULTURE CO., LTD

Manufacturer: SHENZHEN LOFREE CULTURE CO., LTD

Test Result: PASS

The test report merely corresponds to the test sample. It is not permitted to copy extracts of these test result without the written permission of the test laboratory.

Contents

This document outlines the test standards, summary of the product, test environment, detailed test conditions and results, test setup photos, and photos of the equipment under test.

• 1 TEST STANDARDS
• 2 SUMMARY
  • 2.1 General Remarks
  • 2.2 Product Description
  • 2.3 Equipment Under Test
  • 2.4 Short description of the Equipment under Test (EUT)
  • 2.5 EUT operation mode
  • 2.6 Block Diagram of Test Setup
  • 2.7 Related Submittal(s) / Grant (s)
  • 2.8 Modifications
• 3 TEST ENVIRONMENT
  • 3.1 Address of the test laboratory
  • 3.2 Test Facility
  • 3.3 Environmental conditions
  • 3.4 Summary of measurement results
  • 3.5 Statement of the measurement uncertainty
  • 3.6 Equipments Used during the Test
• 4 TEST CONDITIONS AND RESULTS
  • 4.1 AC Power Conducted Emission
  • 4.2 Radiated Emissions and Band Edge
  • 4.3 Maximum Peak Output Power
  • 4.4 Power Spectral Density
  • 4.5 6dB Bandwidth
  • 4.6 Out-of-band Emissions
  • 4.7 Antenna Requirement
• 5 TEST SETUP PHOTOS OF THE EUT
• 6 PHOTOS OF THE EUT

1 TEST STANDARDS

The tests were performed according to the following standards:

• FCC Rules Part 15.247: Frequency Hopping, Direct Spread Spectrum and Hybrid Systems that are in operation within the bands of 902-928 MHz, 2400-2483.5 MHz, and 5725-5850 MHz.
• ANSI C63.10-2013: American National Standard for Testing Unlicensed Wireless Devices
• KDB558074 D01 V03r05: Guidance for Performing Compliance Measurements on Digital Transmission Systems (DTS) Operating Under §15.247

2 SUMMARY

2.1 General Remarks

Date of receipt of test sample: Nov. 08, 2023

Testing commenced on: Nov. 08, 2023

Testing concluded on: Nov. 17, 2023

2.2 Product Description

Product Description: FLOW 100-Key Dual Mode Low Profile Mechanical Keyboard

Model/Type reference: OE919

Power supply: DC 3.7V From battery and DC 5.0V From external circuit

PC information (Auxiliary test supplied by testing Lab): Model: E470C, Trade Mark: thinkpad

Hardware version: C36SM#01

Software version: C36SM_HLT_A13M_OVERSEA_V1.0

Testing sample ID: CTA231108044-1# (Engineer sample), CTA231108044-2# (Normal sample)

Bluetooth BLE Supported type: Bluetooth low Energy

Modulation: GFSK

Operation frequency: 2402MHz to 2480MHz

Channel number: 40

Channel separation: 2 MHz

Antenna type: PCB antenna

Antenna gain: 2.53 dBi

2.3 Equipment Under Test - Power supply system utilised

Power supply voltage:

• 230V / 50 Hz
• 120V / 60Hz
• 12 V DC
• 24 V DC
• Other (specified in blank below)

Actual utilized: DC3.7V From battery and DC 5.0V From external circuit

2.4 Short description of the Equipment under Test (EUT)

This is a FLOW 100-Key Dual Mode Low Profile Mechanical Keyboard. For more details, refer to the user's manual of the EUT.

2.5 EUT operation mode

The Applicant provides communication tools software (Engineer mode) to control the EUT for staying in continuous transmitting (Duty Cycle more than 98%) and receiving mode for testing. There are 40 channels provided to the EUT and Channel 00/19/39 were selected to test.

Operation Frequency Table:

2.6 Block Diagram of Test Setup

Diagram shows the EUT connected to a DC 5.0V power source from PC.

2.7 Related Submittal(s) / Grant (s)

This submittal(s) (test report) is intended for the device filing to comply with Section 15.247 of the FCC Part 15, Subpart C Rules.

2.8 Modifications

No modifications were implemented to meet testing criteria.

3 TEST ENVIRONMENT

3.1 Address of the test laboratory

Shenzhen CTA Testing Technology Co., Ltd. Room 106, Building 1, Yibaolai Industrial Park, Qiaotou Community, Fuhai Street, Bao'an District, Shenzhen, China

3.2 Test Facility

The test facility is recognized, certified, or accredited by the following organizations:

• FCC-Registration No.: 517856 Designation Number: CN1318
• Shenzhen CTA Testing Technology Co., Ltd. has been listed on the US Federal Communications Commission list of test facilities recognized to perform electromagnetic emissions measurements.
• A2LA-Lab Cert. No.: 6534.01
• Shenzhen CTA Testing Technology Co., Ltd. has been listed by American Association for Laboratory Accreditation to perform electromagnetic emission measurement.

The 3m-Semi anechoic test site fulfils CISPR 16-1-4 according to ANSI C63.10 and CISPR 16-1-4:2010.

3.3 Environmental conditions

During the measurement the environmental conditions were within the listed ranges:

Radiated Emission:

AC Main Conducted testing:

Conducted testing:

3.4 Summary of measurement results

Remark:

• 1. The measurement uncertainty is not included in the test result.
• 2. We tested all test mode and recorded worst case in report.

3.5 Statement of the measurement uncertainty

The data and results referenced in this document are true and accurate. The reader is cautioned that there may be errors within the calibration limits of the equipment and facilities. The measurement uncertainty was calculated for all measurements listed in this test report according to TR-100028-01 "Electromagnetic compatibility and Radio spectrum Matters (ERM); Uncertainties in the measurement of mobile radio equipment characteristics; Part 1" and TR-100028-02 "Electromagnetic compatibility and Radio spectrum Matters (ERM); Uncertainties in the measurement of mobile radio equipment characteristics; Part 2" and is documented in the Shenzhen CTA Testing Technology Co., Ltd. quality system according to DIN EN ISO/IEC 17025. Furthermore, component and process variability of devices similar to that tested may result in additional deviation. The manufacturer has the sole responsibility of continued compliance of the device.

Hereafter the best measurement capability for Shenzhen CTA Testing Technology Co., Ltd.:

(1) This uncertainty represents an expanded uncertainty expressed at approximately the 95% confidence level using a coverage factor of k=2.

3.6 Equipments Used during the Test

4 TEST CONDITIONS AND RESULTS

4.1 AC Power Conducted Emission

TEST CONFIGURATION

Diagram shows the Equipment Under Test (EUT) connected to a Line Impedance Stabilization Network (LISN). The LISN is connected to an EMI receiver. A reference ground plane is depicted below the EUT and LISN. A vertical reference plane is also indicated.

TEST PROCEDURE

1. The equipment was set up as per the test configuration to simulate typical actual usage per the user's manual. The EUT is a tabletop system, a wooden table with a height of 0.8 meters is used and is placed on the ground plane as per ANSI C63.10-2013.
2. Support equipment, if needed, was placed as per ANSI C63.10-2013
3. All I/O cables were positioned to simulate typical actual usage as per ANSI C63.10-2013
4. The EUT received DC 12V power from adapter, the adapter received AC120V/60Hz and AC 240V/60Hz power through a Line Impedance Stabilization Network (LISN) which supplied power source and was grounded to the ground plane.
5. All support equipments received AC power from a second LISN, if any.
6. The EUT test program was started. Emissions were measured on each current carrying line of the EUT using a spectrum Analyzer / Receiver connected to the LISN powering the EUT. The LISN has two monitoring points: Line 1 (Hot Side) and Line 2 (Neutral Side). Two scans were taken: one with Line 1 connected to Analyzer / Receiver and Line 2 connected to a 50 ohm load; the second scan had Line 1 connected to a 50 ohm load and Line 2 connected to the Analyzer / Receiver.
7. Analyzer / Receiver scanned from 150 KHz to 30MHz for emissions in each of the test modes.
8. During the above scans, the emissions were maximized by cable manipulation.

AC Power Conducted Emission Limit

For intentional device, according to § 15.207(a) AC Power Conducted Emission Limits is as following:

* Decreases with the logarithm of the frequency.

TEST RESULTS

Remark:

• 1. Both modes of BLE 1Mpbs and 2Mpbs were tested at Low, Middle, and High channel; only the worst result of BLE 1Mpbs was reported as below:
• 1. Both 120 VAC, 50/60 Hz and 240 VAC, 50/60 Hz power supply have been tested, only the worst result of 120 VAC, 60 Hz was reported as below:.

Graph Description: The graph displays AC Power Conducted Emission levels (in dBμV) versus Frequency (in Hz). Two limit lines are shown: FCC PART 15 B CLASS B-QP Limit (Quasi-Peak) and FCC PART 15 B CLASS B-AV Limit (Average). The plotted data points represent the measured emissions. The tables below detail the specific measurements and verdict.

Note:1).QP Value (dBμV)= QP Reading (dBμV)+ Factor (dB)
2). Factor (dB)=insertion loss of LISN (dB) + Cable loss (dB)
3). QPMargin (dB) = QP Limit (dBμV) - QP Value (dBμV)
4). AVMargin(dB) = AV Limit (dBμV) - AV Value (dBμV)

Graph Description (Page 12): Similar to the graph on page 11, this plot shows AC Power Conducted Emission levels versus Frequency for the Neutral line. It also displays the QP and AV limit lines, with measured data points plotted. The table below provides specific measurement details and verdicts.

Note:1).QP Value (dBμV)= QP Reading (dBμV)+ Factor (dB)
2). Factor (dB)=insertion loss of LISN (dB) + Cable loss (dB)
3). QPMargin (dB) = QP Limit (dBμV) - QP Value (dBμV)
4). AVMargin(dB) = AV Limit (dBμV) - AV Value (dBμV)

4.2 Radiated Emissions and Band Edge

TEST CONFIGURATION

Frequency range 9 KHz – 30MHz

Diagram shows the EUT placed on a turntable 0.8 meters above a ground plane. A loop antenna is positioned 3 meters away from the EUT, connected via a coaxial cable to a Test Receiver.

Frequency range 30MHz – 1000MHz

Diagram illustrates the EUT on a turntable 0.8 meters above a ground plane. A test antenna is placed at a distance of 3 meters, with its height adjustable from 1 to 4 meters. The setup is connected via a coaxial cable to a Test Receiver.

Frequency range above 1GHz-25GHz

This setup takes place within a Semi-Anechoic Chamber. The EUT is on a turntable 0.8 meters above a ground plane. A test antenna is positioned 3 meters away, with its height adjustable from 1 to 4 meters. The system includes a Measurement Instrument and a Controller in a Control Room, connected via coaxial cables.

TEST PROCEDURE

1. The EUT was placed on a turn table which is 0.8m above ground plane when testing frequency range 9 KHz-1GHz; the EUT was placed on a turn table which is 1.5m above ground plane when testing frequency range 1GHz - 25GHz.
2. Maximum procedure was performed by raising the receiving antenna from 1m to 4m and rotating the turn table from 0° to 360° to acquire the highest emissions from EUT.
3. And also, each emission was to be maximized by changing the polarization of receiving antenna both horizontal and vertical.
4. Repeat above procedures until all frequency measurements have been completed.
5. The EUT minimum operation frequency was 32.768KHz and maximum operation frequency was 2480MHz. So radiated emission test frequency band from 9KHz to 25GHz.
6. The distance between test antenna and EUT as following table states:

Setting test receiver/spectrum as following table states:

Field Strength Calculation

The field strength is calculated by adding the Antenna Factor and Cable Factor and subtracting the Amplifier Gain and Duty Cycle Correction Factor(if any) from the measured reading. The basic equation with a sample calculation is as follows:

FS = RA + AF + CL - AG

Where FS = Field Strength, RA = Reading Amplitude, AF = Antenna Factor, CL = Cable Attenuation Factor (Cable Loss), AG = Amplifier Gain

Transd=AF +CL-AG

RADIATION LIMIT

For intentional device, according to § 15.209(a), the general requirement of field strength of radiated emission from intentional radiators at a distance of 3 meters shall not exceed the following table. According to § 15.247(d), in any 100kHz bandwidth outside the frequency band in which the EUT is operating, the radio frequency power that is produced by the intentional radiator shall be at least 20dB below that in the 100kHz bandwidth within the band that contains the highest level of desired power.

The pre-test have done for the EUT in three axes and found the worst emission at position shown in test setup photos.

TEST RESULTS

Remark:

• 1. This test was performed with EUT in X, Y, Z position and the worse case was found when EUT in X position.
• 2. Both modes of BLE 1Mpbs and 2Mpbs were tested at Low, Middle, and High channel and recorded worst mode at BLE 1Mpbs.
• 3. Radiated emission test from 9 KHz to 10th harmonic of fundamental was verified, and no emission found except system noise floor in 9 KHz to 30MHz and not recorded in this report.

For 30MHz-1GHz - Horizontal

Graph Description: The graph shows radiated emission levels (in dBμV/m) versus Frequency (in Hz) for horizontal polarization. The FCC PART 15 B CLASS B-QP Limit line is shown. The plotted data points represent the measured emissions.

Note:1).Level (dBμV/m)= Reading (dBμV)+ Factor (dB/m)
2). Factor(dB/m)=Antenna Factor (dB/m) + Cable loss (dB) - Pre Amplifier gain (dB)
3). Margin(dB) = Limit (dBμV/m) - Level (dBμV/m)

For 30MHz-1GHz - Vertical

Graph Description: The graph shows radiated emission levels (in dBμV/m) versus Frequency (in Hz) for vertical polarization. The FCC PART 15 B CLASS B-QP Limit line is shown. The plotted data points represent the measured emissions.

Note:1).Level (dBμV/m)= Reading (dBμV)+ Factor (dB/m)
2). Factor(dB/m)=Antenna Factor (dB/m) + Cable loss (dB) - Pre Amplifier gain (dB)
3). Margin(dB) = Limit (dBμV/m) - Level (dBμV/m)

For 1GHz to 25GHz

GFSK (above 1GHz)

2402 MHz - Horizontal

2402 MHz - Vertical

2440 MHz - Horizontal

2440 MHz - Vertical

2480 MHz - Horizontal

2480 MHz - Vertical

Results of Band Edges Test (Radiated)

GFSK

2402 MHz - Horizontal

2402 MHz - Vertical

2480 MHz - Horizontal

2480 MHz - Vertical

REMARKS:

• 1. Emission level (dBuV/m) =Raw Value (dBuV)+Correction Factor (dB/m)
• 2. Correction Factor (dB/m) = Antenna Factor (dB/m)+Cable Factor (dB)- Pre-amplifier
• 3. Margin value = Limit value- Emission level.
• 4. -- Mean the PK detector measured value is below average limit.
• 5. The other emission levels were very low against the limit.

4.3 Maximum Peak Output Power

Limit The Maximum Peak Output Power Measurement is 30dBm.

Test Procedure

Remove the antenna from the EUT and then connect a low loss RF cable from the antenna port to the power sensor.

Test Configuration

Diagram shows the EUT connected to a Power Sensor, which is then connected to a Power Meter.

Test Results

Note: 1.The test results including the cable lose.

4.4 Power Spectral Density

Limit For digitally modulated systems, the power spectral density conducted from the intentional radiator to the antenna shall not be greater than 8 dBm in any 3 kHz band during any time interval of continuous transmission.

Test Procedure

1. Use this procedure when the maximum peak conducted output power in the fundamental emission is used to demonstrate compliance.
2. Set the RBW ≥ 3 kHz.
3. Set the VBW ≥ 3× RBW.
4. Set the span to 1.5 times the DTS channel bandwidth.
5. Detector = peak.
6. Sweep time = auto couple.
7. Trace mode = max hold.
8. Allow trace to fully stabilize.
9. Use the peak marker function to determine the maximum power level.
10. If measured value exceeds limit, reduce RBW (no less than 3 kHz) and repeat.
11. The resulting peak PSD level must be 8dBm.

Test Configuration

Diagram shows the EUT connected to a Spectrum Analyzer.

Test Results

Test plot as follows:

Graph Description: The spectrum analyzer plots show the Power Spectral Density for GFSK 1Mbps and GFSK 2Mbps modes across various channels (CH00, CH19, CH39). The X-axis represents Frequency (GHz), and the Y-axis represents Level (dBm). The plots display the measured power spectral density within the specified bandwidth, confirming compliance with the 8 dBm limit.

4.5 6dB Bandwidth

Limit For digital modulation systems, the minimum 6 dB bandwidth shall be at least 500 kHz

Test Procedure

The transmitter output was connected to the spectrum analyzer through an attenuator. The bandwidth of the fundamental frequency was measured by spectrum analyzer with 100 KHz RBW and 300 KHz VBW. The 6dB bandwidth is defined as the total spectrum the power of which is higher than peak power minus 6dB.

Test Configuration

Diagram shows the EUT connected to a Spectrum Analyzer.

Test Results

Test plot as follows:

Graph Description: The spectrum analyzer plots illustrate the 6dB bandwidth measurement for GFSK 1Mbps and GFSK 2Mbps modes across various channels (CH00, CH19, CH39). The X-axis represents Frequency (GHz), and the Y-axis represents Level (dBm). The plots show the measured bandwidth, confirming it exceeds the minimum 500 kHz requirement.

4.6 Out-of-band Emissions

Limit In any 100 kHz bandwidth outside the frequency band in which the spread spectrum or digitally modulated intentional radiator is operating, the radio frequency power that is produced by the intentional radiator shall be at least 20 dB below that in the 100 kHz bandwidth within the band that contains the highest level of the desired power, based on either an RF con-ducted or a radiated measurement, pro-vided the transmitter demonstrates compliance with the peak conducted power limits. If the transmitter com-plies with the conducted power limits based on the use of RMS averaging over a time interval, as permitted under paragraph (b)(3) of this section, the attenuation required under this paragraph shall be 30 dB instead of 20 dB. Attenuation below the general limits specified in §15.209(a) is not required.

Test Procedure

Connect the transmitter output to spectrum analyzer using a low loss RF cable, and set the spectrum analyzer to RBW=100 kHz, VBW= 300 kHz, peak detector , and max hold. Measurements utilizing these setting are made of the in-band reference level, bandedge and out-of-band emissions.

Test Configuration

Diagram shows the EUT connected to a Spectrum Analyzer.

Test Results

Remark: The measurement frequency range is from 30MHz to the 10th harmonic of the fundamental frequency. The lowest, middle and highest channels are tested to verify the spurious emissions and bandage measurement data.

Test plot as follows:

Graph Description: The spectrum analyzer plots display the out-of-band emissions for GFSK 1Mbps and GFSK 2Mbps modes across various frequency ranges (e.g., 2402 MHz, 30MHz-1G, 1G-26.5G). The X-axis represents Frequency, and the Y-axis represents Level (dBm). These plots demonstrate that emissions outside the fundamental band are significantly below the specified limits, adhering to the 20 dB or 30 dB attenuation requirement.

4.7 Antenna Requirement

The EUT is using a PCB antenna. The antenna gain is 2.53 dBi. The antenna is an integral part of the device and cannot be replaced by the user. Therefore, the EUT complies with the antenna requirement of §15.203.

5 TEST SETUP PHOTOS OF THE EUT

Refer to the appendix for test setup photos.

6 PHOTOS OF THE EUT

Refer to the appendix for photos of the EUT.