VK Logger Ham Radio Forum Archive

Schmick indeed, Justin.

You'll have to dress up a presentation for Gippstech 2013 !

73, Roger Harrison VK2ZRH

Crikey - an FT-817 jack stand for a tractor !


Is that a 'front-firing', decent-size speaker in there as well ?

Tough !

Neat !

Can I have it ?

Bill VK5ACY
Bowhill S.A
PF95sb

Yes Justin, internal pictures would be nice.

Very nice. There's an awful lot of engineering in those boxes. I reckon that Fergie might meet it's match trying to run over those boxes.

VK2CU wrote: Would you settle for one under the Kingy?
Justin

Yes but don't break anything.

Hi all!
Posting from the other side of the globe (Greece).

I use VK3XDK's transverter for 10GHz:
http://sv1ixp.wordpress.com/10ghz-transverter/

For 2320MHz I built one based on W1GHZ's board:
http://sv1ixp.wordpress.com/13cm-transverter/

Now I am designing one for 23cm.

We are a relatively small group of microwavers here in Greece but we are getting more and more!
I would also like to add that this forum is very informative and I read it often, although this is my first post

73 de SV1IXP, Kostas

Neat idea Justin.


Andrew Davis VK1DA & VK2UH
Sent using Tapatalk

"Microwave Row" - the microwave transverter set-up at VK3UHF/P during this weekend's Summer VHF/UHF field day. How many transverters can you spot? Can you list them by band?

Chas
VK3PY

from furthest to closest 2.4G, 3.4G, 5.7G, 10G, 24G, 47G, 3.4G, 24G

Not fair Jenny - you have insider information, and you've visited our field station in the past.



Here's a close-up shot of David VK3QM's 47GHz transverter.
Chas
VK3PY

Greetings to all.

This posting follows some e-mail discussion on the VK-Microwave reflector during which a request was made to 'have a look' at what Rex VK4REX and I have been making for use on the 76 GHz band. A video (~40 MB) of VK4OE using the transverter he made to establish the initial VK4 distance record for this band can be accessed at:
https://www.dropbox.com/s/i06z91xq4ydxw ... s.m4v?dl=0

The images posted below show some detail of the various components of this transverter. I understand that Rex will soon add another posting showing pics of his gear. It will become quite clear that these units are quite different in design. They have been independently conceived and constructed - it has only been during the recent few months of optimisation activity that we have got ourselves together to compare and improve things.

Rex's transverter generally follows the published DB6NT design with an IF in the 70 cm band, and has a Kuhne electronics 76 GHz amplifier that's used in both RX and TX. My transverter is a double conversion design with a first IF of around 4.3 GHz, mixing then down to 1282 MHz. Mixer and pre-amplifier are from "the rf guy" (US eBay) and the pre-amplifier is also used in both RX and TX by way of the WR12 waveguide switch that's there at the 'front' of the assembly.

Here is a view of the VK4OE transverter on the same side as, but closer than that shown in the video:
Note the rifle sight and the (small) rotating machining table for azimuth adjustment.

Here is a general view of the 'other side':
Note the waveguide switch, and the bank of DC connections. The dish itself is a machined offset one (not 'spun') that was originally used in a 38 GHz link. The position of the 76 GHz feed in front of the dish was determined by the relative position of the original 38 GHz feed horn.

Here is a closer-up view of this same side of the whole unit:
The large bubble level for setting the azimuth rotation plane horizontal can be faintly seen 'down inside' the assembly, and the fine screw adjustment for optimising elevation can also be seen. The 12 GHz to 36 GHz tripler can easily be identified on top, and one of the micro switches monitoring the position of the waveguide switch can also just be seen (used for only powering up the pre-amplifier when it's 'safe' to do so!).

So there's a summary.....the journey of making all this and getting it to work has been a very satisfying 'labour of love' during the last year or so. Actually having contacts with it is just the 'icing on the cake'. I feel sure that Rex will agree with that observation!

Cheers and 73,

--Doug, VK4OE.

Totally agree with Doug it's been a lot of fun learning new ways to achieve things.

Instead of including pictures of the transverter (the basic design can be seen in Dubus) I thought a couple of pictures of how I implemented things may be interesting.

The 76Ghz mixer board from Khune needs to be shaped to fit the DL2AM mixer housing to ensure a reliable placement. I made a small led assembly and screwed it to the front of the circular waveguide so it shone thru to the mixer cavity. Then shaped the pcb with a diamond file to make it fit correctly and to get the probe length into the correct position for maximum coupling. (This measurement was a separate exercise and took a bit of experimentation). Once completed the pbc could be reliably inserted into position each time I tested it. The red led also allowed me to see that no silver epoxy was encroaching the waveguide hole. Placed the silver expoy on the pcb and "glued" it to the housing then baked in an oven for 4 hours to set the expoy.


PCB in housing with alignment led.

Putting the antiparallel diodes onto the pcb after it had been baked was another interesting exercise. For those not familiar with the diodes they measure .65mm x .35mm. Silver epoxy has to be placed on the two mounting points and the diode slid into place. I found a simple ohm meter check to measure the forward drop of the diodes (.6v forward and reverse) ensured they were in the correct place on the transmission lines and connected. Once done I set the pcb aside to naturally cure the silver epoxy, this takes around 5 days.

Once done the rest of the mixer was assembled and testing was done. I chose a 420.1Mhz IF and didn't use the Kuhne IF board but used my standard sequencer board that has a PGA103 LO NF preamp and a 420-450Mhz bandpass filter. By using 420Mhz the LSB was further away and filtering was marginally easier. The good matching of the diodes from Ma-com gave an LO suppression of -18dB compared to the USB signal. Final USB output from the mixer was -6dBm. After the filter the final output from the amplifier is 14.5dBm. A second mixer was build and exhibited similar performance.

I was fortunate to get a Kuhne LNA/PA last December (Limited production run) that was of a similar form factor to my 47Ghz system so was able to use the same switching technique to go from Tx to Rx. Video shows the system.

https://www.dropbox.com/s/l6onzwqkkpifj ... h.mp4?dl=0

The LO is derived from a modified Elcom unit and then fed to a 2 wire tripler to generate the 38Ghz signal for the mixer. From measurements the 2 wire tripler performed better than the 3 wire unit in the configuration I was using. The harmonic levels for the 2 wire unit are different to the 3 wire unit. The 2 wire is the better unit to use for building a beacon as it has a slightly higher second harmonic on 76Ghz.

The other interesting issue we found on final testing is Trimble Thunderbolt units appear they are not all equal (Especially when multiplied up this far). Using an OCXO based beacon on 76Ghz that Doug built, one Thunderbolt exhibited a slow drift of about 10-20Hz giving a do - do - do type noise on the cw carrier whereas the other didn't. When I connected my reference to Doug's unit he lost the funny noise indicating his Thunderbolt may be a different version to mine. I suspect there are differences and based on KE5FX's site he refers to software versions and which type of OCXO is installed in the Thunderbolt (Tribmle v/s Piezo). I suspect the version 3 software and Trimble OCXO are the better based units but we need to examine the suspect unit to see what it is using.

Hope this helps any budding builders

Rex

Awesome workmanship gentlemen! me thinks I best up the anti somewhat! excellent.

Some time ago I built a small 10GHz transverter out of discrete components, in a small instrument case, about 230 x 150 x 50mm. I modified two LNB's, one to act as the Rx preamp, and the other to be the Tx amplifier. It worked OK, with about 15mW Tx out, and Rx sensitivity was excellent. BUT, it was plagued with instability, receiver 'warbling' when it liked, and Tx power varying (also 'warbling' I was told!

I put it in a cupboard, and thought nothing more about it, until two months ago, after I purchased a 5W amplifier from Israel.

I then thought how to fit this amplifier and all of the other "goodies" in a case. One time at a field day, I bought an old "Cybernet" chassis CB radio, thinking that I might make use of the case, even though it was steel!

I stripped the case, and made a new chassis, front and back out of sheet aluminium. Then to fit it all in... LO, 4x multiplier, splitter, 2x mixers, Tx mixer filter,10MHz reference, RF preamp, various power supplies, sequencer, and headlight relay for the amplifier supply. Not to mention a "correct polarity" relay on the 12V input! And an isolator, with 30dB isolation on the output of the amplifier!
I haven't labelled the front panel yet, but the two switches are for 'Power On', and 'LO On', and the BNC socket for 'IF In'. If I am travelling, I can connect 12V (13.8V) and turn on the Local Oscillator and 10MHz reference and have it warm up, without having all the rest of the transverter on, drawing lots of current.

The best part... it all fits easily in the case, and with 0dBm out of the Tx pipecap filter, considering the isolator insertion loss, and losses in my attenuators and connecting cables, it is close to +38dBm out (which is marked on the amplifier)! The 12V fan is run off an 8V regulator, and only switched on in transmit. Under the amplifier there is a 6.5mm plate which is above the speaker holes (now empty) in the bottom of the case. When the fan operates, it draws air right through the case from the bottom, to the outside rear.

On the rear panel, there are two BNC sockets, one is '10MHz Out' (from an internal Isotemp 131-100 block), and the other is '10MHz In', which is either linked to the Isotemp, or connected to my portable 12V Trimble reference, which I described earlier in "What's on Your Workbench". Also there is an SMA socket, for RF in/out, and an RCA socket for DC in.

I gave the case several coats of spray paint. Testing it on receive with my reference signal source (14.4MHz TCXO), and FT-817 with a TCXO9 over 36 hours, it didn't move more than 20Hz!

Now for some real testing, on air!

73 Bruce VK2EM

The 5W+ 10GHz transverter shown above is for sale, as are my other 4 transverters, including a 20W+ Tvtr for 3.4GHz. I have yagis, dishes and hornfeeds for 5 bands to 10GHz, plus other bits and pieces for making transverters, etc. I am getting too old to wait for "the bands to open" to here, so have decided to dispose of it all! Watch the 'other' radio website for my 'For Sale' items.
If you need microwave bits, call or email me... I might have it!

73 Bruce
VK2EM

Today i got the build completed for the panel antenna version of a vk3xdk 2.4GHz transverter. Grahams kits are brilliant and easy to get going and i used a excommercial datamodem panel antenna as the backplane for this transverter, and connectors to make it plug and pray compatible with the excellent geelong club 3.4GHz transverters.
All went well after solving a horrible pll noise problem , i had used a ebay cheapy variable voltage regulator pcb to run the 10 volt line to the MDS pll module.
That was a bad mistake as tiny high frequency ripple ended up modulating the 1969MHz output and no matter what filter caps i added didnt completely solve it.
A 7808 fixed it, so dont use those little switchmode regs, use linear instead and 8 volts instead of 10 works just fine. It took my spectrum analyser to actually see what was going on...
The 10 MHz reference comes from an atomic standard, one of the squarewave types. A good way to clean up the output is to use a filter-splitter unit scrounged from ex MDS transmit gear from bmarc field day, or use a 10MHz crystal filter using computer pc crystals.
Otherwise use a Isotemp or trimble cheap ocxo reference from ebay to provide the reference signal.
The IF radio is ft817nd, the panel is receiving a tiny signal on the 5th harmonic from a small si570 signal source bouncing off the watertank in the picture. The signal source is hundreds of metres away only radiating microwatts with no antenna.
The whole setup runs from the 12volt battery shown in the photo and is charged from a 20 watt solar panel
Microwaves are astounding to experiment with.
I hope you try them too
73 Dave vk2jds