EM/EW Project Journal

I am keeping a journal of my EM/EW build project here.  I would be interested in getting feed-back on the PCB layout that I came up with.  I am trying to make it work on a single sided board so that I can eventually photo etch the board myself.

I didnt look too closely but it looks good.     Personally, I think that it would be a better design if the antenna coils were on separate boards and closer to the antenna- but 1 board is how Moog does it.

I didn't look too closely either but I would put current mirrors at the common emitter points for the transistor pairs.  This would limit the current (this oscillator topology can draw significant current when slightly mistuned, so says my simulations) and would likely increase stability.  I'd also buffer the oscillator outputs going to the mixer to reduce coupling/locking near the null point.

I agree with all Charlie and Dewster say above.. Particularly with regard to bufferring the oscillators.

Not sure about the way the coils are placed - I thought the EW and EW had the coils positioned differently, but you have one at 90 degrees to the others - This may affect the coupling and total inductance or perhaps even Q.. But I am just talking here - I really dont know.. On the EM/EW bits I have built I never followed the layout, and used off-board coils.

Fred.

Thanks for feed back.

I am aware of the mod for buffering the outputs.  I haven't strayed too far from the original design as of yet but I do have a short list of mods I'd like to add, but first I'd like to get it working as-is so I have some kind of baseline to work from.

As for the coil arrangement, here is a pic of the more recent EW design that I was working from.  One thing I noticed right off from this pic is that there a few new components that are not part of the hot-rodded schematic, particularly the addition of Q9, C34, R41 and one or more capacitors.  They appear to be part of the fixed pitch osc/turning circuits but have no clue how.  If anyone has any ideas please let me know.

Thanks.

"As for the coil arrangement..."

Ok, If thats how the new EW's have the coils, may as well copy it! ;-) .. As for adding modifications - I personally would include buffers on your layout now - they need to connect to highly sensitive bits of the circuit and adding them later could perhaps give problems.. There is no reason you need to fit the buffer components at first - just put a bypass link in until everything in the standard build is tested, then take this link out and fit the buffer..

But thats just what I would do.. ;-) -

I would also make the PCB a bit bigger and put down some empty "breadboard" pads to allow adding modifications - if nothing else, a few rows of 0.1" spaced pads sprincled over the board - these allow one to solder small vertical mounted breadboards onto the main board - a great way to implement modifications / extensions.

Fred.