RF Prototypes for Transverters

[tipofthesowrd]

I'm currently looking into getting on 10 GHz for some small signal DX and rainscatter work  O0
Mostly also looking into doing some microwave experiments.

Still evaluating wheter I want to buy ready made transverters
- DB6NT
- VK3XDK
- Down East Microwave

or build something myself. I have enough professional design experience but I'm wondering about PCB manufactering.
I haven't found a source of 'cheap' RF PCB with Rodgers laminate for a few prototypes.
Minimum seems to be eurocircuits which is around 250, 300 EUR for a 100mm x 80mm PCB for 5pcs

My own CNC machine for fabricating MW PCB's would be the ultimate dream but I'm not versed enough in CNC specs to make an informed decision for hobby use.

What do the microwave experimenters on this forum usually do?

[mathias]

Laminates you can find on http://www.rf-microwave.com/en/home.html

Fabrication... stay away with a router. Teflon based substrates will perform horribly, the copper will peel away, you basically have zero accuracy in track width, ...
Better to just use some dry film photoresist and etch like in the old days.

Most transverters are not much more than a mixer, an amplifier and some filters. The actual receiving part is done at much lower frequency. Making stable amplifiers might be tricky, but the mixers can be deadsimple. Look up "rat-race mixer" for example, I made one that outperformed a Mini-Circuits mixer (though that was a broadband one) first time right (i.e. no tuning required).

If you want something more advanced: http://lea.hamradio.si/~s53mv/zifssb/block.html

Have fun!

[G0HZU]

or build something myself. I have enough professional design experience but I'm wondering about PCB manufactering.
I haven't found a source of 'cheap' RF PCB with Rodgers laminate for a few prototypes.
Minimum seems to be eurocircuits which is around 250, 300 EUR for a 100mm x 80mm PCB for 5pcs

My own CNC machine for fabricating MW PCB's would be the ultimate dream but I'm not versed enough in CNC specs to make an informed decision for hobby use.

What do the microwave experimenters on this forum usually do?

At work I've had access to T-Tech or LPKF milling/routing machines for about 25 years. They do work very well if you want to make a quick prototype circuit on Rogers 4003 or 4350. About 12 or so years ago I bought my own (used) T-Tech 7000S machine to use at home and it is still working really well. You can pick these machines up quite cheaply but you run the risk of buying one that will be worn out or damaged. If you want to buy one of these then it's best to be very very patient and wait for a bargain. I bought a second 7000S machine about 10years ago just for long term spares backup.

[cdev]

There are some microwave transverter designs/ideas here: http://www.croatia-microwave.blogspot.com/

[tggzzz]

Are you aware of http://microwavers.org/ ? Many back issues of their newsletter are available free of charge.

[ThomasDK]

I haven't found a source of 'cheap' RF PCB with Rodgers laminate for a few prototypes.
Minimum seems to be eurocircuits which is around 250, 300 EUR for a 100mm x 80mm PCB for 5pcs

Haven't tried them myself yet, but this is the cheapest place I have found in Europe for RO4003:
http://www.micron20.com/en/orders/calculator-production

~94 EUR for 5 pcs 100x80mm 

Thomas

[tipofthesowrd]

At work I've had access to T-Tech or LPKF milling/routing machines for about 25 years. They do work very well if you want to make a quick prototype circuit on Rogers 4003 or 4350. About 12 or so years ago I bought my own (used) T-Tech 7000S machine to use at home and it is still working really well. You can pick these machines up quite cheaply but you run the risk of buying one that will be worn out or damaged. If you want to buy one of these then it's best to be very very patient and wait for a bargain. I bought a second 7000S machine about 10years ago just for long term spares backup.

Thanks, I'll keep a lookout for the T-Tech. I can image that Teflon laminates are quite hard to mill but with the current performance of Rodgers materials I'm not really looking into other laminates right now.

I actually found a bargain Chinese CNC6040 with a Kress 1050W router on eBay which was modified by its previous owner for more stability. However, it never arrived. My intention with this machine was also to mill out some waveguide parts/feeds/slot antenna. Mostly WR90 and above. I was looking into milling some WR12 for work.
But for PCB's I was worried about the Z-axis stability.

I guess the T-Tech Z-axis is stable enough since you've been using it for quite some time?

Are you aware of http://microwavers.org/ ? Many back issues of their newsletter are available free of charge.

There are some microwave transverter designs/ideas here: http://www.croatia-microwave.blogspot.com/

I know both sites quite well  Last time I went on Holiday I downloaded a bunch of old Scatterpoints to read. 
I have the feeling more recent issues are a little less technical though. 

Haven't tried them myself yet, but this is the cheapest place I have found in Europe for RO4003:
http://www.micron20.com/en/orders/calculator-production
~94 EUR for 5 pcs 100x80mm 
Thomas

And we have a winner for some prototypes! Very nice.

[cdev]

Sort of unrelated, but I have to say this, I have always thought that microwave hardware at times begins to take on elements of art. Its not without good reason people call it "an art".