VHF/UHF weekend radio station

jure_m · Joined: 14 Jan 2005 Posts: 68 Location: Ljubljana

Hi all,

not long ago I have seen DRA818V module, which is a complete FM HAM radio station that needs 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 a first version of Bascom-AVR program and after some HW problems the radio station was nicely working by the Sunday evening.

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

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.

I will post a Bascom-AVR program when I do translation of the comments. From a simple program which proved the concept it grew a bit.

Best regards
Jure

Paulvk · Joined: 28 Jul 2006 Posts: 1257 Location: SYDNEY

Hello jure_m

Very nice indeed

Regards Paul

albertsm · Joined: 09 Apr 2004 Posts: 5922 Location: Holland

nice project Jure. Seems like a great module.

jure_m · Joined: 14 Jan 2005 Posts: 68 Location: Ljubljana

Hi,

I just want to add few photos of the radio. I'd love to have nicer buttons, but also as such it looks quite nice.

Best regards
Jure

jure_m · Joined: 14 Jan 2005 Posts: 68 Location: Ljubljana

Hi all,

here is the follow up of this project. Schematics & Bascom-AVR program are attached.

On the schematics I need to add some explanations.IC5 is basically not needed if the board is about to be powered from 12V. IC5 was added in case that the board was powered directly from LiPo cell (nice feature for Portable work where we need every Watthour from the battery). Fully powered LiPo can have 4.5V, while it's normal voltage is below 4V, which may cause that LCD might not have proper contrast, hence we need IC5 to add that much negative voltage so that LCD displays in order. If you omit IC5 then the middle contact of J2 should be connected directly to GND.

On the board you will find also microphone preamplifier. This was added after during tests electret mike did not perform well enough. You may want to adjust amplification of the preamp around Q2 and change R10 - smaller R10 means smaller amplification. On this schematics a dynamic microphone was used.

Perhaps you'd want firstly to try your electret mike without Q2. In this case you do not need to use R10, C23 (and Q2) and connect electret mike to junction R1/C3.

Jumper J1 was meant to achieve higher amplification of the LM386. During testing I have seen that LM386 has enough amplification with J1 open, but you may want to try that yourself.

SP2 is active buzzer, which sounds when we confirm settings done with encoder.

The Bascom program cannot be described in few lines, but it's also rather well commented so there should be no problem when you want to modify it. This version of the programme is for 134 to 174 MHz band, while I am already preparing 400 to 470 MHz version.

Best regards
Jure

Paulvk · Joined: 28 Jul 2006 Posts: 1257 Location: SYDNEY

This would be a great project to submit to the ARRLs QST magazine
The march edition featured a talking frequency counter written in Bascom.

Regards Paul

albertsm · Joined: 09 Apr 2004 Posts: 5922 Location: Holland

thanks for sharing Jure. And for the instructions.
The code is indeed well documented and understandable.

jure_m · Joined: 14 Jan 2005 Posts: 68 Location: Ljubljana

jure_m · Joined: 14 Jan 2005 Posts: 68 Location: Ljubljana

There is another nice feature about these modules. When I was writing SW for the 70 cm version I noticed that I receive some signals. It has turned out that 2m module does receive also 70 cm signals. I did not measure how attenuated 70 cm signals were, but reception from a repeater that is 18 km away was very good. Unfortunately TX does not perform that well.

I have a plan to make a 2m RTX which can also receive 70 cm, which can be handy.

Best regards
Jure

jure_m · Joined: 14 Jan 2005 Posts: 68 Location: Ljubljana

Hi,

I have agreed with HAM operators from Slovenia to bring my VHF radio to HAMRADIO fair that will take place in Friedrichshafen this June. The VHF radio will be displayed & running at the Slovenian booth of the S5 radio amateur association ZRS. The booth No. may change, that was the booth No. from 2014.

In the mean time I have updated SW so that I use Nokia5510 LCD which can show much more info on LCD than 2x16 LCD module, see attached photo.

Best regards
Jure

albertsm · Joined: 09 Apr 2004 Posts: 5922 Location: Holland

That looks much better Jure.
I like these small graph lcd's Smile

jure_m · Joined: 14 Jan 2005 Posts: 68 Location: Ljubljana

albertsm · Joined: 09 Apr 2004 Posts: 5922 Location: Holland

end result looks great. thanks for showing the finished project.

aphawk · Joined: 23 Jan 2010 Posts: 168 Location: Brazil

Wow !!!!

Very nice !!!! This will be a product, a kit, or will sell the PCB ?

I have some Baofeng radios here, but one radio that I can program all the functions is like a dream !!!

Paulo

jure_m · Joined: 14 Jan 2005 Posts: 68 Location: Ljubljana