Digilite pics

[M0DTS]

Hi All,

Here's an example of what you can get away with! and maybe some ideas for people wondering how to build the system up.

Seeming quite easy to do, building the PA into the same box as the Transmitter and VCO itself, i had my doubts it would work but no problems...!
I did put a screen between the PA and Digilite itself which will help a lot i'm sure.

Ideally could do with a bigger heatsink but it sits ~45C so i'm happy enough!

Basically the digilite is used here with the Ultram VCO. The output of the Digilite is fed into another mmic amplifier SBA5086Z and pcb from rf-bay on ebay.
This provides enough drive for the RA18H1213G PA Kit from minikits which runs at ~10W and is mounted on the rear of the box.
You could probably get away with more than 10W but it's very clean at that power level.

Hope it's useful information to someone!

Rob

[M0ATV]

Looks great Rob, there seems to be plenty of options for people to tailor fit their own designs around the various board configs, I have mine in a similar container, but haven't screened the vco off yet, only a few inches away from digilite board with no noticeable effects, waiting to do the vco pic mod before I screen it off properly, mounted my voltage regs on a small graphic card heatsink & have an internal switchable fan to draw the warm/hot air out when & if required, but have noticed mine seems to output 10% more pwr when running slightly warm than cold, just need to build a small add on extra mimmic amp to boost the pwr output up to M68719 amp low input levels.

[mm0mgb]

Haven' got mine going yet but I've just received ultram vco in case my vco had too much phase noise. What is the vco supply voltage please? 12v?

[g0uhy]

DON'T USE 12V !!!!!!!!!. VCO is designed to run on 6-9V. When we were designing the DigiLite the 8V regulator was included on the board to run the VCO so power it from that supply.

73

Malc

G0UHY

[mm0mgb]

thanks. I couldn't find anything telling what the VCo shoudl be on. I'll give it a go now.
12v would have been an expensive flash for fireworks night!!!

[w0fms]

Second on "don't run on 12V". If I remember correctly there is a small voltage regulator on the PLL Osc board.. the PLL chip is a 3.0-3.3V device and the board probably would run on 12V.. at least for a while. You are likely pushing the regulator at that point. I ran my 1152 MHz osc board at 5V for a while and currently run it on 8V. (A linear regulator is built into the box as I use that one for a microwave WSS.) For the DigiLite I'm going to run it at around but less than 9V. 5V is close to the drop-out point of the regulator on the PLL board and because of that isn't recommended either.

I increased my voltage regulator for the MMIC on my DigiLite board to 10V to substitute a MSA-0886 for the MAR-6/MSA-0685. I *SUSPECTED* that is why that regulator and the MAR-6 was both selected. The DigiLite apparently needs the gain and 8V is about perfect for the PLL board. I didn't want to put in a separate special order for the MAR-6's so I am substituting the MSA-0886's for that but then 10V was needed for the biasing.

To get "around 9V" to the VCO I'll either (and probably because I have them) use another 7808 (Or a 7805 with a diode or two in the ground lead to make it 6-ish V) or maybe three-four 1N4002's in series with the board and 10V to get it somewhere betweem 8 and 9V.

Anyway... could you give us a link to the e-bay MMIC amplifier? That's pretty much perfect for what eventually I want to build mine up to.

I am awaiting a 1255.0 MHz board from Ultram. I ran the DigiLite just a few minutes ago with no LO and according to the software and the blinking LED's it seems quite happy. In fact I adjusted the setting a bit for NTSC and 3K 1/2 FEC and took a video which will end up on my blogs. I also got WINTV6 working and for this use it's much easier to use. I need to figure out how to delete the pre-sets that didn't work though.. you can't seem to do that nor edit them..

Nice Packaging of the project. Impressive...

Thanks guys for such a neat little project...

73, Fred W0FMS