Saturday, December 24, 2011

Tinkering on Chrismas eve

Yesterday I tinkered with some vintage germanium transistors. I chased my tail for hours trying to figure out why the distortion was so bad on the audio I was trying to amplify! Not to mention that the gain was miserably small...

With lots of reading I have come to the conclusion, that the main reason you would ever want to tinker with vintage germanium transistors is to reproduce the distortion effects of "that era".

I set about measuring the Beta on them, they vary so much across the same model!

The AX9000 run from a Beta of 19 up to 36! The ACY21 vary from 70 up to 150! So getting a balanced pair out of these is a bit more difficult that I was expecting.

I might just put these back in their box and tinker with some "modern" silicon transistors, that date to the early 1970's. I picked them up last year at the AHARS HAM radio buy'n'sell here in Adelaide. This year I picked up some old school headphones and a 1960's microphone.

Saturday, October 22, 2011

October updates

Right, so a few things this time.

I put the MEPT together, set up a dipole cut for 10.140 MHz and with a 12v7A SLA, let it run for a while. None of the 30 meter QRSS grabbers were picking it up though. I set up the frequency counter and it registered 10.140010 MHz. I exchanged a few emails on the list, had a phone call about it... Still was not getting into any of the grabbers in ZL, VK2 or VK7. I though, perhaps the frequency counter is not accurate.

I arranged to take the counter to Barry, VK5BW. He compared it to his rubidium standard. Surprisingly it was only 10Hz off at 10MHz. So with that sorted I moved onto the next task, which is finishing the VK5JST antenna analyser... Its not finished yet, hopefully I can get some more time in on it over the weekend. Then I think its organising a decent feed line up to the dipole and an insulated box =)

Much time has been taken up with emergency plumbing. Yeah, the fun variety of "why is my backyard full of water all of a sudden?" So much digging revealed a split pipe and conveniently a tap I'd put it to aid changing things around later =) Its all fixed now, but that was two days work to get it all dug up and repaired... but not yet filled in the hole. Another few hours of fun on the morrow.

Some time back I talked about my new acquisition. A mobile-ground-plain. Well, a ute actually. One day I will do some mobile radio with in it. In short I have invested a lot of time with paint striper, a scraper, sand paper and etch primer to get rid of the aging paint, some bog and a bit of surface rust. Its coming along nicely. However the big news for today is, it runs! I have had several attempts to get it running over the last couple of months. Just could never get it to fire. Thought it was an electrical problem. Today I noticed the choke cable going to the carby for the first time. Its always been there, but as I have an automatic choke on the car, I hadn't thought to fiddle with the choke lever. Anyhow it runs and its bloody loud! The only problem is it doesn't idle. Its a start. Running is good =) Its a big step forward and is just more motivation to get the front locking hubs replaced so its a four wheel drive again ;) All in good time. I have a big trip in January I hope to have it on the road for.



Monday, September 26, 2011

QRSS MEPT kit on the workbench

Some months back I ordered a couple of Hans Summers QRSS kits. They arrived a couple of weeks back, but I've been too sick to really get much done. So during the WIA broadcast on Sunday morning I started putting one together. More to come ...


Monday, August 1, 2011

Project: receive antenna for 2200 meters or 137KHz

I've been eyeing off the 2200 meter band for some time. One of the reasons that I decided to sit the Advanced theory exam instead of the Standard theory exam. Then I would be access to a lot more bands, especially 30 meres and 2200 meters =)

There has been plenty of discussion on the lofexp and 600m yahoo groups recently about getting new folks in the door to experiment in the band.

The following is one of the articles recommened; A Receiving Loop for Long Waves: Cancelling Out Unwanted Noise Sources.

I wonder about the JFET, its a BF245C. After some searching on the net I am still unsure what a suitable replacement would be. Possibly a J201 or a MPF102? I have some J310's and some MPF102's, I think I will just build a version for a plug-able transistor and go from there.

Maybe later I can modify it for 80 meters as published in AR by VK5TR...?


Sunday, July 17, 2011

New callsign

Today the ACMA call sign search confirms what the WIA callsign search alluded to on the weekend.

My new callsign has been allocated!