Portsdown wish list - output attenuator

Discussion about this major DATV Project. See https://wiki.batc.org.uk/The_Portsdown_Transmitter
G8GKQ
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Re: Portsdown wish list - output attenuator

Post by G8GKQ » Tue Oct 17, 2017 3:20 pm

I now have one of these attenuators and will be writing some additional code for the Portsdown so that the attenuation can be set for each band. It may be a few weeks yet, but it would be worth making room for it in the case (between the F-M board and the RF Switch).

Dave

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M5TXJ
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Re: Portsdown wish list - output attenuator

Post by M5TXJ » Thu Nov 02, 2017 1:00 pm

I now have one of these boards the same as pictured earlier in the thread, I await developments with interest.

73 Dave.
...are you sure I can't use a pair of 813's?... :shock:

M0DHP
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Re: Portsdown wish list - output attenuator

Post by M0DHP » Fri Nov 24, 2017 2:46 pm

G8GKQ wrote:I now have one of these attenuators and will be writing some additional code for the Portsdown so that the attenuation can be set for each band. It may be a few weeks yet, but it would be worth making room for it in the case (between the F-M board and the RF Switch).
Hi Dave, have you decided yet how the attenuator will interface with the Pi (in terms of connectors, wiring)?

Thanks and 73
Ray M0DHP

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Re: Portsdown wish list - output attenuator

Post by G8GKQ » Fri Nov 24, 2017 3:48 pm

Hi Ray

RF-wise it will go between the filter modulator board and RF switch, so just one extra SMA male-to-male lead required. Control wiring will be 3 wires from the attenuator board to the GPIO board. Exact connections are still tbd, but at least one wire will go on the "DigiThin" connector.

Sorry, I've been distracted by other projects! There will be an unrelated software update in the next few weeks.

Dave

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Re: Portsdown wish list - output attenuator

Post by GI4DOH » Wed Apr 18, 2018 5:50 pm

I have connected a PE43703 attenuator board up to my Portsdown as per the wiki info with DATA and CLK shared with the ADF4351 board and LE from GPIO pin 10. When I turn the attenuator on and off on the touch screen I can see the CLK pulses and then the LE pulse at the attenuator side of the 1K resistors in series with the lines. There is no corresponding DATA signal (either side). When I turn the ADF4351 on and off I can see the CLK and DATA for the ADF4351 OK at the PE43703 end - obviously no LE pulse for the attenuator board at this point.

I am using a RPi 3B+ with Portsdown TX Version 201804060 and PE43713 is selected for the attenuator type.

Is this a know problem or is there something else for me to check?

73 Richard GI4DOH

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Re: Portsdown wish list - output attenuator

Post by G8GKQ » Thu Apr 19, 2018 8:57 pm

Hi Richard

Last time I touched this code, it worked. However, I have not yet been able to test it explicitly with an RPi 3B+, and won't get the chance for a day or 2.

Please check if it works with the SigGen (select from Menu 2). You should see data on the attenuator every time that you change the output level with the attenuator on.

Dave

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Re: Portsdown wish list - output attenuator

Post by GI4DOH » Fri Apr 20, 2018 4:26 pm

Hi Dave
Thanks for the reply. I had tried withSigGen on and off and I also had an RF meter on the output of the attenuator too but no change.
Unfortunately we have family arriving for the weekend so I have had to put my toys away. I will try a clean build on the RPi when I get my 'workshop' space back again just in case and I will try combinations while specifically in SigGen.
Richard

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Re: Portsdown wish list - output attenuator

Post by G8GKQ » Sun Apr 22, 2018 4:25 pm

Hi Richard

I have just checked the attenuator functionality on an RPi 3B with Portsdown TX Version 201804060 and it works perfectly. I have also monitored the Data line on an RPi 3B+ (as my attenuator is hard wired to the RPi 3B) whilst adjusting the attenuation (with the SigGen ON) and I can see the desired signals on the 'scope.

I'm puzzled - I think that you may have a wiring problem. There is nothing different in the software between the way that the ADF4351 data pulses are generated and the way that the attenuator data pulses are generated.

Please try the following:
  • select the PE43713 attenuator in the Portsdown main menu
  • Select the SigGen from Menu 2
  • Select the Portsdown Output and the Attenuator On
  • Select the Freq Menu and then select the Output on
  • Monitor the Data line at the RPi side of the 1K resistor whilst adjusting the the demanded output level
You should see short 3v3 pulses. Let me know how you get on.

73, Dave

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Re: Portsdown wish list - output attenuator

Post by GI4DOH » Tue Apr 24, 2018 10:24 am

Hi Dave
Thanks for the Info. It looks like operator error on my part. I hadn't twigged that when I set the attenuator value that I need to save it before leaving the screen. Also, if I didn't select the attenuator then the option to set it wasn't there. I didn't immediately associate the dBm figure with having the attenuator set - not helped by looking at the screen upside down with my prototype layout.
I needn't have spent all that time getting my USB scope set up to monitor the lines - I should have spent more time looking at the RPi screen.
The only other thing is where do I set the base value for each band to make it align with my actual value?
It has been fun getting this far - hopefully Norbreck at the weekend will turn up something in the way of antennas and amplifiers for me to get me on-air.
Richard

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Re: Portsdown wish list - output attenuator

Post by G8GKQ » Thu Apr 26, 2018 9:23 am

Hi Richard

Pleased that it is working for you.

There is no facility to set a base value for the Portsdown/attenuator output. I have built this capability into the Portsdown Signal Generator (where the output level vs frequency calibration is stored in the file rpidatv/src/siggen/siggencal.txt). For initial transmitter setup, you can adjust the SigGen output to the required level (with "Mod" selected) then read the attenuator setting from the SigGen screen, and enter it into the "band" setting in the transmitter.

Dave

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