No video on transmit

[G4HTZ]

Still trying to get portsdown working.
Using a 7 inch screen now which controls everything ok.
Initially thought the minitoune wasn't working , but that receives in ugly mode fine.

If I tx on the portsdown it goes into tx ok ..ADF board 2nd light comes on and the Dg0ve pa produces about 20w ...so it's producing rf ok....but produces no video on the minitoune...I have made sure I have right mode , frequency and no offsets on minitoune.....the carrier and sr needles on minitoune just jump about ...RF and mer show good levels about 1/2 way.
The minitoune displays a circle forming with 4 constellations.....but that's as far as it gets.

Checked wires between gpio board and FM board and they seem fine.

Any other checks I can carry out

Cheers
Steve G4HTZ

[g0mgx]

Can you post a screen shot of the MIniTioune so we can see all the settings?

Mark
G0MGX

[g0mjw]

How are you connecting these? Multipath can be a problem. Also make sure that you have selected DVBS and low SR

[G4HTZ]

Thanks for replying
Useing twisted pairs as recommended for the I Q connections .
Have minitoune set up ok ...have seen ther people's posts where they had offsets etc in the set up.
Tried it on 23cms and 70cms with various SR FEC etc .
Currently remaking all interboard connections...not a fan of the molex connectors ...considering hard wiring it
Proberly something simple ...me !!!

[g0mjw]

I MEANT how are you connecting the TX and RX. This needs to be a cable connection - not with 20W - just put some attenuators in line - say 40dB between the Portsdown output and the receiver input.

Mike

[G4HTZ]

I MEANT how are you connecting the TX and RX. This needs to be a cable connection - not with 20W - just put some attenuators in line - say 40dB between the Portsdown output and the receiver input.

Mike

Hi mike ...portsdown plus amp on 70cms feeding 18ele yagi currently at 20ft
70cms dipole with low noise preamp from at 10ft ....so should be plenty of field strength !!

Could try as you suggested got some in line attenuators

Cheers
Steve

[g0mjw]

Steve,

It has not the field strength, apart from with your description you may have far too much which could saturate the pre-amp (I hope its not a VLNA with 30dB of gain) and its possible the tuner is also overloaded. To diagnose this we need to be sure your reception is not being compromised by multipath. You can't do reliable testing using antennas like this because of all the local reflections. At the moment we have too many variables so please try connecting transmitter and receiver together directly, through a cable, without any amplifiers but with that attenuation in line. If this doesn't work, we know it is not multipath and can start diagnosing what else it might be. Also be useful to see an image of Minitioune window.

Mike

[G8GKQ]

Hi Steve

I would recommend disconnecting your linear and putting about 60dB of attenuation between the Porstdown SMA output socket (where the signal will be 5-10 mW) and the tuner input. Then try transmitting in ugly mode 333KS on 437. Get it receiving OK, and then switch to IQ mode.

If no joy, use a narrowband receiver to check the LO at 437 MHz.

Lastly, try disconnecting the 7 inch screen and controlling the Portsdown from the console on another computer.

Dave

[G4HTZ]

Thanks mike and Dave
Ok can try as you suggested over the weekend
Will update with any useful or otherwise information
Regards
Steve

[g0mjw]

Steve,

The other thing that came to mind was to check I and Q are as expected using an oscilloscope, There should be 0.6v p-p signals on each of the test points I+, I-, Q+, Q- near U41 on the filter/modulator board. Its possible to wire it incorrectly, and also possible for there to be a fault. This will show that up. See https://wiki.batc.tv/Filter_Modulator_b ... _the_board

It might be useful to reset to defaults under advanced settings via the console, just in case you have an incorrect setting. Also doing an update if you haven't recently. I would also suggest disconnecting the LCD and seeing if you can get it to work via the console, just in case this 7" screen is causing issues.

Another useful check is to use a spectrum analyser to look at the output. If you don't have access to a spectrum analyser you can do it well enough with a £20 RTL-SDR dongle and software like SDR Console and SDR Sharp or http://www.rtl-sdr.com/spektrum-new-rtl ... -software/

Mike