Finningley rally is on!!

For ages now we have had news of rallies being cancelled or postponed so it is great to report on a rally actually happening! This is this Sunday July 25th and is outside only.  Doors open at 10am. Take and wear masks to keep yourself and others safe when with crowds. This is near J2 of the M18. Contact organisers before setting out.  The website is www.g0ghk.com/cbr21.

Rally - Finningley

Sunday 24 JULY : FINNINGLEY ARS ANNUAL RALLY
 
The Hurst Communications Centre, Belton Road, Sandtoft, Doncaster DN8 5SX There will be a talk in station and doors open at 10.30am with admittance £3. The venue is all on one level. Car parking is free. There is a large indoor and outdoor trader's area with major traders, special interest groups and an RSGB bookstall. There will be a flea market. Hot food and drinks will be available all day. More information from Kevin, G3AAF on 0783 161 4640.

A list of rallies can be found at http://rsgb.org/main/news/rallies/.

As I have said before, I get sent these regularly and reproduce them here in good faith, but contact the organisers if travelling any distance to ensure the information is correct.

Finningley optical transceiver working fine

Although I posted this on the Nanowaves Yahoo group , I forgot to update folks reading this blog on the progress with this optical transceiver kit designed by Bernie G4HJW.

Well, at the weekend I finished building the unit and started testing it. The TX part worked first time, but the RX did not. Time to find out why!

Using logic and common sense, I carefully went through the various stages (8V regulator, later audio stages etc) and tracked the fault down to an intermittent preset SMA pot that sets the FET bias. The FET stage is the very high impedance stage that follows the PIN photodiode.

The error was entirely my fault and easily fixed by removing the part and redoing the surface mount joints. Now the full transceiver is working well (but yet to be put into 100mm optics) and the RX sensitivity is close to that with my K3PGP design RX. In the coming weeks I hope to get a transition piece to connect the transceiver "tube" to a 110mm drainpipe that houses the 100mm lens. I'll then assemble this onto a stable tripod with sighting scope and I'll be ready to look for QSOs.

http://www.earf.co.uk/optoposition.JPG

One thing that puzzled me was how having the detector diode and TX LED slightly off-centre would work. In my mind I thought that the light would not be properly focused onto the devices, so losing sensitivity. Then someone pointed out that by slightly aiming "off beam" by around 1 degree the light would fall exactly onto the position on the transceiver where the LED or PIN diode are mounted.

Finningley optical transceiver progress

In the last couple of days, armed with my wife's close-up reading glasses, a magnifying glass, tweezers and a fine tipped soldering iron, I have been doing the SMA build of G4HJW's "Finningley" optical transceiver kit, designed to be used with 100mm optics (drain pipe and Poundland lenses!).

The G4HJW designed optical transceiver

Bernie's instructions were first class with all the SMA parts for the receiver and the transmitter being organised sequentially with a clear layout diagram showing where each part has to be placed. It seems to have gone together very well with no snags, although I have still to add a few discrete parts including the LED and the PIN photodiode before testing can start. All being well, I should be able to start testing on Sunday as I am tied up with our church fete tomorrow.

G4HJW "Finningley" Optical Transceiver kit

The G4HJW optical transceiver kit

Bernie G4HJW is well known for his innovative work on microwaves and optical comms. Last year he designed a neat, part SMA, optical transceiver kit to build at the Finningley round table meeting. The transceiver is capable of very good results and several (around 70) have been built and used very successfully. I believe the best DX QSOs at 481THz have been over 60km using these in 100mm optics.

Exactly when I'll get my kit built I'm not sure but it will be good to have one of these available for optical line-of-sight tests in the autumn. Once assembled, I shall be looking for some 2-way optical QSOs beyond the 10km speech contact I achieved with my own kit last summer. In East Anglia, the issue is finding some hills to allow long line-of-sight paths.

Bernie is, I understand, considering putting together a further batch of these kits, which make a good introduction to nanowave communications. In addition to these electrical kits, all that is needed is a microphone, headset and some simple optics than can be built for a few pounds.

See http://www.earf.co.uk/nanotrx.htm for more details

Finningley Optical Transceiver (G4HJW)

Bernie G4HJW is well known for his innovative microwave designs as well as many other good projects in recent years. This year he has produced another winner for the Finningley Round Table in mid July:  a baseband optical transceiver kit designed with SMA components. For details see http://www.earf.co.uk/nanotrx.htm . I am not sure if Bernie is planning to make kits available more generally. Bernie has tested this design over a 65km line-of-sight path recently.