IQ Mode help

[M0YDH]

I'll substitute my VCO filter for the one in Dave 's Portsdown on my next visit to isolate the problem. We can do scope and power measurements at 71MHz all being well.
I've the Chip-quik set for what may come next.....
Thank you David.

73
David M0YDH

[G8GKQ]

Hi Dave and David

Really pleased that you have a picture and have isolated the fault to the VCO filter board. The best way ahead is probably to make comparative voltage measurements between your 2 VCO filter boards.

The coupling question is now irrelevant! What I was asking is what connection you had between the Portsdown and the Minitiouner, or were you just using 2 aerials? I use 60dB of attenuators for testing.

73

Dave

[M0DHP]

Hi Dave G8GKQ

Please try connecting the output of the ADF4351 directly to the input of the Filter-modulator board, so that you bypass the VCO filter. Then see if you have any RF output (or even pictures).

Was there something in Dave G7MEG's voltage readings that made you suspect the VCO filter?

Thanks

Ray M0DHP

[G8GKQ]

Hi Ray

No, the voltages were all normal, so I reviewed Dave's posts and noticed that he had mentioned that he had no output. I should have spotted it before!

Dave

[cashy666]

Hi Dave,
thank you for all your help..
hopefully now its been narrowed down to the VCO
it should be appearing in the success stories in the
very near future with the help of David M0YDH.

regards

Dave
G7MEG

[cashy666]

Hi Dave, (G8GKQ)

Just an update on my IQ problem.

David M0YDH arrived on Monday armed with test gear and his Lo Filter.
The first thing he noticed that my filter was not powered! It shows no connection
on the diagram on Wiki.
I put 12v to it and powered it up.... unfortunately I had put LO7 on the board (doh)
which resulted in smoke signals coming from the board!!!!!
The obvious damage is the fried 220NH inductor, David M0YDH has very kindly just dropped off a replacement.

Would it have damaged any other components?

Thanks for your help.
73
Dave
G7MEG

[G8GKQ]

Hi Dave

I fear that it might have done. The only way to tell is to put it on a variable power supply and slowly wind up the voltage, checking current consumption, smoke and performance as you go.

Dave

[M0YDH]

On a brighter note the G7MEG portsdown with my filter card fitted did Tx IQ mode signals. Great rejoicing.
Dave's RF output select card was bypassed but is powered so don't know what that does yet.....