IQ Mode help

[cashy666]

Hi All,
I have now got to the stage of build to run my Portsdown in IQ mode.
unfortunately after several weeks of trying, rewiring, rewiring and rewiring no joy.
I have followed all the instructions on the forum..still no joy.
It puts out a carrier on 437 but still no lock in.
Fellow Portsdown builder David M0YDH has been around with his test gear and it
would appear there is no power output in IQ mode. The ADF4351 is showing both leds lit.
Frustration levels are through the roof and it was almost filed under bin..........

Any help would be much appreciated, please note though I am technically challenged!!!!!

Regards
Dave
G7MEG

[g0mjw]

It puts out a carrier on 437 but still no lock in.

What exactly do you mean by this ? I assume you are seeing CW. That's a good start. Have you put a scope on the IQ outputs from the PI?

Do you have a photo?

Mike

PS = make sure you have replaced the software from defaults as it's possible you have some settings mixed up.

[G8GKQ]

Dave

Do not despair! Using the touchscreen (or console), select Pattern, FEC 7/8, SR4000, 1255 MHz, and then TX.
Please measure the voltage at the following points on the Filter-Mod board with a voltmeter:

Starting next to the heatsink, measure the voltage on:

J02 pin 1
J02 Pin 2
J02 pin 3
J02 pin 4

then continuing round the board measure

J01 pin 1
J01 pin 2
J01 pin 3
J01 pin 4

Then on the PCB between the input and output SMAs there are some testpoints:

I-
I+
Q-
Q+

After that I can offer some clues.

Dave, G8GKQ

Photos will help as well!

[cashy666]

Hi Dave, Mike

thank you for your response...
Mike,
the 437 referred to is the signal received on a handheld with the Portsdown tx in IQ mode
no I have not put a scope on it.
I have checked all the software settings and the seem fine.
Ill attach some photos.

Dave
attached is the readings as requested

J02 pin 1 0.06v
J02 Pin 2 0.05v
J02 pin 3 3.37v
J02 pin 4 3.37v



J01 pin 1 0.05v
J01 pin 2 1.67v
J01 pin 3 0.03v
J01 pin 4 1.67v


I- 0.05v
I+ 1.69v
Q- 0.05v
Q+ 1.69v
attached are photos as requested

73
Dave G7MEG

[G8GKQ]

Hi Dave

Can you confirm that you measured the I+, I- Q+ and Q- voltages while you were transmitting? Please re-check them. If so, we are tracking your problem down.

Next, please measure the voltage on R15 (at the end without the capacitor soldered on) on transmit and then the same point on receive. Repeat for R16, so that you come back with 4 voltages.

Dave

[cashy666]

Hi Dave,

measurements as requested.

Q- 0.77v
Q+ 0.77v

I- 0.78v
I+ 0.78v

R15 tx 2.51v
R15 rx 2.68v

R16 tx 3.45v
R16 rx 3.42v

hope this helps...

thanks

Dave
G7MEG

[F5SWB Dimitri]

Hi dave,
according to Evariste, in h264, you must put autopid off = you are on
pid video 1001
pid audio 1000 (there is no transport stream for the audio at this moment)

I know it's not your trouble because you've got no signal s/n mer ....
But i could help you later

73's qro / Dimitri.

[G8GKQ]

Dimitri, Dave

That is not my experience with Portsdown.

AutoPid On has always worked best for me. The only time AutoPid does not work is when viewing a multi-channel satellite stream.

Dave

PS still thinking about what your problem might be!

[G8GKQ]

Dave

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).

How are coupling the output of the filter-modulator board to your receiver?

Dave

[cashy666]

Hi Dave, Dimitri,

Dimitri, thanks for the information, its noted for future use.

Dave,

attached the ADF4351 directly as advised...hey presto a picture, locking in
quite quickly.

"How are coupling the output of the filter-modulator board to your receiver?"

not sure what you are asking here, sorry....

regards
Dave