
Shenzhen KYL Communication Equipment Co., Ltd
Tel: +86-755-82943662 sales02@rf-data.com www.rf-data.com
KYL-668H 25W Radio Modem
User Manual
KYL-668H Radio modem is a professional high performance data
transmission radio combining with good DSP technology and wireless
communication technology. This radio supports multiple frequency
band, VHF and UHF. With 25W power output, it has long transmission
distance which reaches about more than 20km in open air.

Shenzhen KYL Communication Equipment Co., Ltd
Tel: +86-755-82943662 sales02@rf-data.com www.rf-data.com
I: Features:
1. High power output: 25W
2. Long transmission distance: More than 20km
3. VHF, UHF band selectable
4. Data transmission, voice transmission both ok
5. Double PLL, double VCO, High reliability
II. Data sheet
● frequency : VHF and UHF frequency band (150MHz, 230MHz,
433MHz, 450MHz ect.), can store about 400 channels
● frequency tolerance:±2.5ppm
● environment temperature:-35 ℃~+75 ℃
● air baud rate:1200bps/2400bps
● ignal Noise Ratio(SNR): ≤-50dB
● Adjacent Channel Selectivity: ≥70dB
● Inter modulation interference: ≥70dB
● Spurious respouse immunity: ≥70dB
● modulate distortion: ≤3%
● residual frequency modulation: ≤-48dB
● frequency deviation: ≤5KHz
● ortho-channel power ratio: ≤-70dB
● RF distance: 20km(25W RF power in the open air)

Shenzhen KYL Communication Equipment Co., Ltd
Tel: +86-755-82943662 sales02@rf-data.com www.rf-data.com
● waiting current: ≤ 1 6 0 m A
● transmitting current: ≤ 6 A ( transmit power 25W )
III. Pin Definition
Connector Pin No. Pin name Description Remarks
Power
connection
1 VCC DC:12V (±10%)
Please use power D.C.
12V, more than 8A
Signal
connection
1 NC
2 RXD(A)
Rxd of RS-232
Rxd of TTL
RS-485 A
RS-232,RS-485,TTL,
only one valid
3 TXD(B)
TxD of RS-232
TxD of TTL
RS-485 B
RS-232,RS-485,TTL,
only one valid
4 NC
5 GND Signal ground
6 PTT
Audio transmitting
enable
Low level is for
transmitting
Microphone input,
modulation sensitivity
10mV
Audio amplifier output
8
ohm
0.5W
Receiving signal
checking
Receiving carrier
signal, high level

Shenzhen KYL Communication Equipment Co., Ltd
Tel: +86-755-82943662 sales02@rf-data.com www.rf-data.com
IV
: Application of KYL-668H
Marine filed, public traffic, interphone system of taxi, industrial
automatic control, electric power schedule, water conservancy
monitor, signal collection and transmission of railway system, oil
extraction and transportation control, measure of oil or water wells,
hydrological monitor, weather information transmission, environment
monitor, container management, goods management in supermarket,
forest protection, intelligent building, wireless beaconing, geological
reconnoiter, mobile location, military training, public security, medical
ward, remote control, detecting, and others automatic control fields.
Notes:
1. About the power supply.
This radio's power output is high to 25W. 12V power D.C., at least 8A
is recommended to use. Please choose power D.C. with good
fluctuation coefficient and anti-interference ability. If you use switch
power supply, please keep the antenna far away from it to avoid
antenna's inference.
Please choose antenna compatible with your radio's frequency bank.
For long distance communication, directional and high gain antenna
would help to reach better effects. And also, please try to mount
antenna at higher level.
Antenna's and its cable's impedance should be accordance with
radio's (50Ω). If not, whole unit's performance will be affected and it
may damage the radio, too.
Choose cable with 50 Ω impedance and low decay material. Make
sure it can be connected with radio and antenna successfully. Please
also consider waterproof and lightning arrester.
If the radio needs to transmit for long time, please pay attention to
transfer heat in time.