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What's on your Workbench?

Posted: Mon Apr 08, 2013 7:06 pm
by VK3YE
(Arising from a suggestion by Andrew VK6WAX, it is hoped that this thread will be long, popular and enduring)

Amongst the mess is a complete software defined radio for 7.002 - 7.096 MHz. It uses $10-15 worth of discrete parts, including just 2 transistors. The 7.050 MHz local oscillator signal is split into two output signals, one 90 degrees out of phase. These feed two diode mixers whose output goes into a good quality sound card with a stereo input.

Alignment needs a continuous carrier signal - just adjust the phase splitter's two potentiometers to null the signal on the unwanted side of the carrier (I'm getting 30 - 35 dB down). Buildable in a few hours and requiring no test equipment to align, the result is a receiver that works suprisingly well, despite no front end RF filtering or amplification.
whats on your workbench 001.jpg
whats on your workbench 002.jpg
(click for bigger picture)

Note that the receiver is simpler than it looks - the 4 diode mixer on the matrix board is not used.

Re: What's on your Workbench?

Posted: Mon Apr 08, 2013 8:34 pm
by VK6WAX
That was quick off the mark Peter and many thanks.

This is a FET multimeter which got a bit erratic. Analog I know but it's the first one I bought and still get's regular use.
fetmeter.jpg
DSE Fet multimeter
The fault was traced to a couple of trimpots, now removed on the left, similar to the one on the right.
fetmeterdetail.jpg
Trimpot detail
Underneath the green plastic cap is (was) a glue to attach it to the trimpot. This had disintegrated and wedged itself under the wiper.
After replacing these the next task will be to calibrate it, which begs the question what do you calibrate your multimeters with? Does anyone even do that anymore?

Cheers
Andrew
vk6wax

Re: What's on your Workbench?

Posted: Mon Apr 08, 2013 8:35 pm
by VK4WDM
Nothing, I just cleaned it up! :D

Wayne VK4WDM

Re: What's on your Workbench?

Posted: Mon Apr 08, 2013 9:58 pm
by VK3DXE
I wish I had a workbench :( :( :oops:

Current shack gives me just enough room for a desk big enough to fit 2 smallish monitors, keyboard and mouse. Any repairs and/or construction are either done on the floor or balancing on my lap.

Re: What's on your Workbench?

Posted: Mon Apr 08, 2013 10:06 pm
by VK4TI
VK4WDM wrote:Nothing, I just cleaned it up! :D

Wayne VK4WDM
Mines not terribly tidy but....

Re: What's on your Workbench?

Posted: Mon Apr 08, 2013 10:07 pm
by VK4TI
VK3DXE wrote:I wish I had a workbench :( :( :oops:

Current shack gives me just enough room for a desk big enough to fit 2 smallish monitors, keyboard and mouse. Any repairs and/or construction are either done on the floor or balancing on my lap.
time to move into the living room

Re: What's on your Workbench?

Posted: Mon Apr 08, 2013 11:48 pm
by VK2DDS
This was my last project:
279805_10151531085356154_91903426_o.jpg
It's a DSP speech processor (discussed elsewhere on this forum). So far I've had 3 positive reports (after setting it up with a local receiver) and one negative (setting with a random guess, no local listening). The PCB was milled by the tech staff at uni, double sided. It performs high pass filtering, compression (well, more of an AGC) and gating in DSP with adjustable cutoff frequency, AGC speed (5sec to 1ms) and gate level. Analogue circuitry is a mic preamp and anti-aliasing/reconstruction filters. CPU is an ATMEGA168P which can *just* handle the above DSP at 8kHz.

Re: What's on your Workbench?

Posted: Tue Apr 09, 2013 4:43 pm
by VK7JG
Hello Peter
It's nice to see another very busy untidy bench .
I have been modifying a couple of UNILAB KL70 for 50Mhz operation .
Today I got a Replacement for VK7RAA 6M repeater working plus a 6M Beacon .

The best piece of gear is the MDRC variable current and voltage power supply that I built about 20 Years ago .
I shudder whenever I see people fixing gear with a fixed 20A power supply as the slightest slip can do untold damage .

Re: What's on your Workbench?

Posted: Wed Apr 10, 2013 12:23 pm
by VK7DB
Which band is that UHF RX from? I have one that needs 440-470MHz BPFs and a 440-470 VCO..

Dion :)

Re: What's on your Workbench?

Posted: Wed Apr 10, 2013 5:00 pm
by VK7JG
Hello Dion.
You are very observant 8)

From memory it was a 400-430 unit you can get it operational to 450 .
I will remove them for you also have the 440-470Mhz receiver that I took out of VK2RSF beacon that you also can have .


Regards.
Joe

Re: What's on your Workbench?

Posted: Sun Apr 14, 2013 9:59 am
by VK2ZRH
workbench 14Apr13.jpg
Lots of technical papers and publications on, or related to, sporadic E . . . continuing my research into the topic.

The more I learn, the more I realise there's more to learn :roll:

Posted in the interests of illustrating a different workbench.

73, Roger Harrison VK2ZRH
PS: the soldering iron and other, traditional, tools are in the "other" workroom (was once a garage) :mrgreen:

Re: What's on your Workbench?

Posted: Sun Apr 14, 2013 6:15 pm
by VK2XQ
Broken Shure 444D desk mic, been busted for around five years now, just haven't got around to looking at it. Besides, enjoying CW only on HF with the FT-1000D, don't really miss the desk mic.

Now, if the straight key chucked it in, it would be fixed straight away. Also busted five element 50MHz beam which blew down in a storm about six years ago, laid in the backyard for around three. Again, still haven't got around to looking at it. 8)

There was an IC-736 HF/50MHz transceiver that suffered a grand PSU failure, sat on the bench for around six weeks, did have a look at that, just a cursory glance mind you. Gave the radio away to Peter VK2DYN and shouted myself an FT-2000D base radio. :wink:

Jack D. Haden VK2XQ (QF-56ne) Sydney NSW.

Re: What's on your Workbench?

Posted: Sun Apr 14, 2013 7:15 pm
by ZL2BKC
I have plenty of irons in the fire at the moment.

For the last few evenings the following project has been occupying my workbench after being promoted from the drawing board.
DSC_9088.JPG
Work in progress
This is a prototype JT4 digital beacon exciter, which has just succeeded its proof of concept test by successfully transmitting both JT4D and JT4G messages on 432MHz. The fractional-N PLL used is capable of directly generating the small frequency offsets making this an elegant solution. So far the limits appear to be JT4D upto 432MHz and JT4G upto 3.4GHz band. It may also be possible to do JT65 on the lower bands (2m or lower), but I have not explored that option yet.

The prototype uses an existing PLL design (which will be unchanged), but since there is a relatively large firmware footprint and a GPS interface requirement I have used another one of my project boards as a development board to prove the concept.

Next step is to layout the circuit board and do a lot more firmware work. The board will contain an Atmel micro, LCD Interaface, a GPS receiver and interfaces for driving upto 4 PLL boards which makes a 4 band beacon possible (6/2/70/23cm) or any band combination upto 3.4GHz.

It will probably take a month or two before it gets onto its proper circuit board..... The fun is only just starting!

Oh: It can also do CW in the "odd minutes" :)

73,
Wayne ZL2BKC

Re: What's on your Workbench?

Posted: Sun Apr 14, 2013 7:42 pm
by VK4GHZ
ZL2BKC wrote:Next step is to layout the circuit board and do a lot more firmware work. The board will contain an Atmel micro, LCD Interaface, a GPS receiver and interfaces for driving upto 4 PLL boards which makes a 4 band beacon possible (6/2/70/23cm) or any band combination up to 3.4GHz.
Wayne, very, very impressive! :D
ZL2BKC wrote:Oh: It can also do CW in the "odd minutes" :)
Nice. A "dual mode" beacon.

Dual mode as in: 20th century / 21st century :wink:

Re: What's on your Workbench?

Posted: Sun Apr 14, 2013 8:13 pm
by ZL2BKC
Thanks Adam

I still need to shake a few trees on this side of the pond, but if all goes to plan there could be one pointing towards Aus for next summer :wink:

--
Wayne

Re: What's on your Workbench?

Posted: Mon Apr 15, 2013 10:32 am
by VK4CDI
Where do I start!
1 uwave power meter, waiting on a PCB to be made.
2 3.4Ghz 30watt PA built but needs to be tested.
3 control gear for new 4.9Mx dish
4 4.9mx dish
5 mount for dish
6 432 patch feed and 1296 septum feed
7 Just finished 'fixing' a HP 5245l counter, anyone want one? seems a pity to rat it for the OCXO....
8 Got a Marconi TF144 sig gen to look at....once again, to good to let it go to the tip.....

Cheers
Phil VK4CDI

Re: What's on your Workbench?

Posted: Mon Apr 15, 2013 3:01 pm
by VK3BJM
At the moment I have:
Workbench April 2013.JPG
1) New LNA for the 2m EME array, with the bypassing relays one either side; ready to go up the tower to replace the venerable VK5 ESC BF981 pre-amp.
2) The second 500 watt 70 cm LDMOS pallet, all machined/drilled/tapped, ready to have the LDMOS sweated into place and the PCBs populated.
3) Three VK3XDK Agile PLLs (two visible, one back in the protective A4 wrapping), after a quick check that all was on frequency, clean and at a good level (which, of course, they were). They are for the 1296, 2403 and 3400 MHz transverters that are under construction - and under the bench, because the top of the work bench is TOO SMALL... :lol:
4) And on the breadboard in front of the Weller soldering station is a Ring Modulator I built with my son, after he read about them being used to produce various affects in early episodes of Doctor Who (Daleks, etc). Makes a mess of a signal from an electric guitar, too, funnily enough. He did enjoy that...

73,
Barry
VK3BJM

Re: What's on your Workbench?

Posted: Mon Apr 15, 2013 6:09 pm
by VK4KL
Currently on my workbench is
1. an FC757AT with blown drive chain to load capacitor (trying to source replacement parts)
2 25 amp ps
3. Mutek 6m transverter with 50w amp
Bench too messy to take photo :shock:

Adrian

Re: What's on your Workbench?

Posted: Mon Apr 15, 2013 8:40 pm
by VK4GHZ
Image

:D

Re: What's on your Workbench?

Posted: Mon Apr 15, 2013 10:57 pm
by VK6WAX
Great to see so many projects, please keep those photos coming not matter the mess!
For those who like photos of electronics and plenty of toroids, this Elecraft K2 project makes it's way on and off the workbench as time allows. So far it's been about six months and just about ready for the last adjustments. I'm really enjoying the building of it and notwithstanding its shortfalls, was a major decision in it's purchase.
k2phase3.jpg
Taken with a phone camera, I've shrunk the image from it's original 2MB, hope it's not too big.
(At some point I'm going to have to tackle the antenna situation, not looking forward to that, still to-ing and fro-ing with the council.)
Cheers
Andrew
vk6wax