IRLP node 8040
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2006-02-15 The antenna. I finally found a really good QTH for my IRLP link wich has been idle for about 1,5 years. Now I needed a lightweight dipole for 2m to put on a window-ledge, the QTH is a very windy place. The antenna will act as both TX/RX for IRLP node 8040, it's being run as a 2m simplex link. I somehow got the idea to use aluminium rods for the antenna part, and plexiglas for the isloator between the antenna. I didn't want to use electric pipes with wires inside becase of the bigger wind-area, plus that they are quite unstable. The total weight of this antenna is 80 grams. I cut the parts to be about the length I tought would match 145 Mhz, but added a few extra millimeters. When I set it up and tested it for tuning, it had a SWR of 1.1:1 between 143.5 - 146.5 Mhz. Sometimes you're lucky!   The antenna was put on a PVC plastic tubing to hold it (see last picture) and weather-safe using heat-glue and vaseline all around the feedpoint, I used quite a few glue sticks to accomplish that :-)  2006-05-03 Oops, this project accidentally fell asleep, time to continue - Rig & Interfacing! I got my hands on a used Kenwood TR-7950 (5/45w) 2m rig. It had a broken display unit, but that doesn't matter for IRLP, so I managed to grab it fairly cheap. When I got the rig, I quickly opened it up and, and it was no surprise the display didn't work. The connectors on the LCD was hurt, and the cable to connect the LCD to the logics was gone, so I decided to use it without the display.  I looked around a bit, and found a weird connector at the rear end of the radio - a 5 plug DIN connector that wasn't listed in any manuals nor pictures of the rig?! Some cable-following and measurements later, this plug actually provided: GND, Mic+ and PTT! Someone had been using it for some kind of link before me! Hah, pure luck? There was also a regular plug for an external speaker below it (also home-made), so a wire was quickly put between these connectors to allow the speaker to go thru the DIN-Plug also. I found out I had no DIN-5 connectors at home, so I slaughtered an old microphone from the junkbox and got a connector. Now to the tricky part - I need a SQL Open line on that DIN connector, to indicate when we have an incoming signal (Open Squelch) on the receiver.  I looked everywhere for a clean SQL Open signal, but didn't find any good signal. However, the radio contains a LED that incicates "On channel", i.e. if the RX frequency is right on the transmitter. Some kind of FM alignment help. This seems to be even better than a open squelch detector after trying it out. It does not indicate open for possible heavy QRM on nearby channels, that actually opens the squelch!  A small wire was added to a connector, according to the arrow (red wire, yellow shrinktube), the radio was assembled and tested.  Everything works okay! The radio shows +5V when "the squelch is open", and all necessary signals are coming out of the DIN-5 port at the rear, and TX works as well as it should. The internal speaker was unplugged not to put out the RX sound when not needed.  A small interface with 600:600 ohm line transformation was put together to separate the radio and the computers grounds, to avoid potential problems resulting in nasty humms.  2005-09-30 FINALLY! Time for installation. My friend who owns the QTH for the link called me and asked when we should install it. I forgot about this project after the vacation, and the stuff kinda "grew old" where they were standing. They could have been there for another year without me noticing. Anyway, we loaded all the stuff into the truck and moved to the QTH (JO67AT). We did put everything up on a locker right above the washing machine, etc. Perfect room for a noisy computer and a PSU with a big fan.  The antenna was put up using two wooden screws, seemed to be rock stable due to the light weight of the construction. The picture is kinda bad, but it's five stories up, at one of the highest QTH's in Gothenburg. We took a ride over the entire city late tonight, and found out that 5W and a small magmount will cover almost all parts of the city.  Future things to do: Tune the "high power" switch to provide only 10-12w instead of 45w, to get a better QRO mode. Possibly also install a pre-amp for receive. Current link data: Nodenumber: 8040 Frequency: 145.225 Simplex Node Call: SM6YOU/L Antenna: Dipole Power: 5w Location: JO67AT, Gårdstensberget/GothenburgMany thanks to my (not-yet-a-ham-operator) friend Björn for hosting the link! Please drop any reports of the link readability/quality in my guestbook. If you're trying it from abroad, try to give me a call! 73 de SM6U/Rick |