The SA828 uhf  transceiver Module

This is a small complete UHF transceiver on a pc board , it has a sensitivity of around –122 dBm for 12 dB s/n and a maximum RF output of +30 dBm/+27 dBm (1 W on High power and 0.5 W on low power ). the SA828 comes with a 16 ch selectable switch and can be programmed in individual transmit and receive frequencies from 420 to 480 Mhz so simplex and duplex frequencies can be programmed via a separate usb to TTL converter using proprietry software provided by the manufacturer .The antenna is connected via a SMA female connector. On board ptt , vox enable, microphone. vol control , 2 w audio , The SA828 like others in this class is based on the RDA1648 direct conversion transceiver . the module draws on receive about 63 mA squelched

The module was run off a lithium battery at 3.96 volts and programmed to 433.3 Mhz .The transmit output was measured through a Bird 30 dB power attenuator and into the Agilent 4407 Spectrum analyser .

                        photo  high power 

The High power output was measured at 30 - 0.76 = +29.24 dBm and the associated current consumption was 260 mA

I was interested in the level of second harmonic so I looked 866.6 MHz and found the level at 30 –28.5 = +1.5 dBm

I had some of the new minicircuits monolithic ceramic low pass filters which have a very good low pass filtering performance " see my website"  Mini Circuits   Low Pass filters .... SMD    ,        and low insertion loss and soldered this into the antenna output feed line using very short earth connection for maximum filter performance.. At first I only soldered one earth connection to the pc board ground plane but additional soldering obtained another 3 db additional harmonic suppression ( didn’t change the fundamental through loss ..)

I measured the rf output level after the filter and found                      30- 1.8 dB = +28.2 dBm . high power

I bridged pc board  jumpers to enable  the low power connection and measured 30 – 4.3 = +25.7 dBm The second harmonic in high power setting was measured with the low pass filter in place at 866.6 MHz was 30 – 74 = -44 dBm and at low power was 30 – 80 = -50 dBm however I did notice two harmonics one at 300 Khz above the carrier and one 300khz below the carrier at 30 – 70 dBm = -40 dBm .

                photo spuries 

Programming of the module is done via a USB to ttl converter ,you can use a terminal program and input commands via "modem’ directives or you can use the supplied frequency programming software supplied by the company , you cannot save the frequencies in the factory software to a file in a PC or I cant find how you do it but you can down load what you uploaded to previously and clone it to another sa828 .The SA828 has eeprom and remembers program parameters when turned off .

You do not have to have +ve from an external 3.7v source to program the sa828 , merely connect the txd and Rxd as you would between two data systems txd to rxd etc and , the black wire of the usb modem to gnd on the sa828 and the red positive wire of the ttl converter to the positive of the SA828 and the unit will derive programming power from the USB port . just make sure you have the correct active com port selected for the ttl converter .

and run the software from the manufacturers website

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