First amateur optical contact between OE and OM.

On friday 19th. Jan. 2007 we succed first optical radioamateur contact between Austria and Slovakia. The contact was made between Michael OE3MZC and Rado OM2ZZ. The range 52,57 kilometers.

Video of our laser QSO - made by Mike OE3MZC (3MB)

Webpage of  Mike OE3MZC with our contact.

Erstkontakt zwischen OE und OM im THZ-Bereich - www.oevsv.at

Story

On Saturday 13th. Jan. 2007 I found that I can see the Vienna citylights from the balcony in my parents flat. I published the photo which I made on my web page. After that Mike OE3MZC send me an e-mail with request for the optical QSO between Stupava and Vienna.
We had to wait few days for the good weather. On Friday 19th. Jan. 2007 in Bratislava it looked that fine, so I called Mike. He told me that in Vienna is heavy rain. At 20:00 I looked out of the window and I was able to see the citylights from Vienna again.

I called Mike on the repeater that it should work. He agreed and he was QRV after a hour.

His first QTH was Jubilaeumswarte - distance over 56km to Stupava. At the beginning it was hard to find Mike, because I expected his laser about 5deg to right. After some time we found each other. I was able to copy Mikes laser opticaly and also audio. Mike was able to see my laser, but he can not hear anything in his receiver. So this was only 1way contact. This QTH was on some tower and there were very windy. Mike decided to change the location to the other one.

QTH1  -  Jubilaeumswarte

First signal from OE3MZC/1

First phone signal from OE3MZC/1

Phone message

The second QTH was Kobenzl - distance over 52km to Stupava. Kobenzl is near the TV tower, so it was easier to find Mikes light. Mike used his carlights as a spotlight and it worked good. I found him with my equipment so I was able to send the laser back for his adjustments. After a while we could see each other, but Mike can not hear me. Fortunately his colegue Guenter OE3GWW/1 with the other equipment was able to hear my signal. We could start the contact. About the midnight we succed the first amateur optical contact between OE and OM.



QTH2 - Kobenzl

Carlights        Zoomed laser 

Laser         TH2 near TV tower 

QTH2 - Kobenzl audio files        
First signal from OE3MZC/1
Contact OE3MZC/1 and OM2ZZ

Audio for video file
All recorded audio




TRX - balcony on the tenth floor

oboR frontend

Used frontend is transimpedance opamp with big feedback resistor.

Transimpedance photovoltaic opamp principle

On the simplified schematics you can see the principle of the transimpedance opamp frontend. It is voltage to voltage converter.
The bigger feedback resistor the better sensitivity.
This principle schematic is working with symetric power source ( +9V to -9V) in photovoltaic mode.

Full schematics of oboR frontend

This one works with asymetric power source (+9 to +15V). Feedback resistor is substitute with resistors network. For full sensitivity use all the feedback resistors except R17, R18 and R25. In this mode the frontend is wild animal so it could oscilate. Than I recomend bypass 6 or 12 feedback resitors with 0.5pF capacitor. I did not find TLC272 in SMD so I substitute it for LM358 which is not best but it works.

For daylight use baypass feedback network with one 1Meg resistor.

This frontend is in photoconductive mode - anode of BPW34 is connected to power ground. You can improove the sensitivity with photovoltaic mode. It is enough just cut the anode from the ground and connect it to the virtual ground for opamp - pin3. This contact was made with this improovement.

Af signal is amplified with an ordinary LM386.

This frontend is able to receive modulated wave - CW and AM.

On PCB there is lot of space for tests. Please let me know ho it works with your optics :)

Schmematics

PCB

Parts placement







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