Hi all, 

not long ago I have seen DRA818V module, which is a complete FM HAM radio station that requires microphone, AF amplifier and a MCU. So I have ordered a couple of them and by the time I got modules, I have designed a PCB. And it turned out that this was really a weekend project, PCB was soldered in no time, in the rest of the weekend I wrote first version of Bascom-AVR program and after some HW problems the radio station was nicely working by the Sunday evening. Read more if interested.



DRA818 module comes in two versions: DRA818V, that covers freq. from 134 to 174 MHz and DRA818U that covers freq. from 400 to 470 MHz. The best with these modules is their price: 13 US$. 

At the present time I am finishing enclosure for this weekend project, also SW would need some routines that would make RTX "user friendly". 

At the present I have programmed it to have: 

1. simplex channels with 12.5 kHz step 
2. repeater channels with 12.5 kHz step (subtones included) 
3. Echolink repeaters (covering local Echolinks) (subtones included) 
4. free freq. set with steps 12.5 kHz, 100 kHz and 1 MHz 
5. set squelch level, volume and microphone level 

The board is doublesided, because we do make doublesided PCBs on a panel - see the link here. I did use largest SMD components not to be too hard for soldering.

On the components side there are some components, beside ATMega168, BNC connector, LCD and of course DRA818. The board is universal for both modules: VHF or UHF version. The only differences are in the MCU program and outpuit filters.



 And the look to the LCD menus:


The Bascom-AVR program does a lot of things, but basically it does send data to the module via UART. Here is how it looks a freq. and other setup:

Print "AT+DMOSETGROUP=" ; 0 ; "," ; Ftx1_free ; "," ; Ftx1_free ; "," ; Tx_ctcss ; "," ; Squ ; "," ; Rx_ctcss ' simplex
Print "AT+DMOSETVOLUME=" ; Volume
Print "AT+DMOSETMIC=" ; Mod_level ; "," ; 0

All the rest of the program is about setting frequency in the selected mode, i.e. simplex, repeater, Echolink mode and free frequency mode. 

Modules offer much more, like programmable filters, subtones on RX/TX, DTMF, scrambling, sending SMS, like on phones, VOX... 

So a lot of things still to be programmed/played with. 



Images above show finished VHF radio station that covers frequency from 134 to 174 MHz with 0,5 and 1W output power. To play with this nice module you'd require radioamateurs licence.

Best regards 

Jurij, my HAM callsign is S52CQ


PS: see next parts of this project on this link.