Portsdown wish list - output attenuator

Discussion about this major DATV Project. See also https://wiki.batc.tv/The_Portsdown_Transmitter
g8gtz
Posts: 764
Joined: Wed Apr 07, 2010 6:26 pm

Portsdown wish list - output attenuator

Postby g8gtz » Sun Sep 17, 2017 6:56 am

It would be very desirable to be able to back off the Portsdown Tx output when driving amplifiers.

I know the existing hardware cannot do that, but would it be possible using one of ebay programmable attenuators as seen regularly on the KLB show? Not sure what the control interface is but could be worth investigating...

73 Noel

g0mjw
Posts: 330
Joined: Sat Sep 20, 2014 9:15 am

Re: Portsdown wish list - output attenuator

Postby g0mjw » Sun Sep 17, 2017 9:33 am

The Ebay units I have been using have buttons but may well be modifiable as my "OLED 6G Digital programmable attenuator " has what looks like a serial interface. There are also modules available based on the obsolete PE4302 that might be useful but given the chip has been replaced by the PE4312 may not be around for much longer.

The underlying attenuatior is usually a Peregrine, Analog Devices or Hittite chip - e.g. the aforementioned PE4312 http://www.psemi.com/pdf/datasheets/pe4312ds.pdf and the Analog Devices HMC1119 http://www.analog.com/en/products/rf-microwave/attenuators/digital-step-attenuators/hmc1119.html have both SPI and parallel interfaces and cost under £10. Unfortunately these are in SMD packaging with the connections on the bottom, so difficult to use.

Mike

MN-tech
Posts: 42
Joined: Thu Aug 30, 2012 6:01 pm

Re: Portsdown wish list - output attenuator

Postby MN-tech » Sun Sep 17, 2017 12:39 pm

Hi Noel,

The PE4302 board project Colin and I did is in the Wiki. Later the same board was used with the PE43703 which has 1/4 dB steps but the new code never made it to the Wiki. The IC uses the same type interface as the ADF4351 local oscillator so it could share the control lines with the addition of another latch enable line (LE).

John

M0YDH
Posts: 67
Joined: Sat Dec 31, 2016 5:59 pm
Location: Wolverhampton IO82WO

Re: Portsdown wish list - output attenuator

Postby M0YDH » Tue Oct 03, 2017 7:31 pm

Hello Colin and John
I liked the look of this and made the controller over the weekend on Veroboard as pictured. My PE4302 is on the slow boat from China. I hope to fit the controller [complete with the missing M2 stand-offs] into the lid of my Portsdown and mount the attenuator board on a bracket above the filter modulator. Thank you for all your hard work.
73
David M0YDH
Attachments
PE4302 controller by M0YDH.jpg
PE4302 controller by M0YDH.jpg (397.49 KiB) Viewed 635 times

M0YDH
Posts: 67
Joined: Sat Dec 31, 2016 5:59 pm
Location: Wolverhampton IO82WO

Re: Portsdown wish list - output attenuator

Postby M0YDH » Sun Oct 15, 2017 3:09 pm

What are the DIP switch settings to make the controller change the level of attenuation? As received all 8 are on and the attenuator remains bypassed aka no attenuation when RF is applied.
The Chinglish descriptions on Ebay mention switch changes but I don't understand.

Regards
David M0YDH

MN-tech
Posts: 42
Joined: Thu Aug 30, 2012 6:01 pm

Re: Portsdown wish list - output attenuator

Postby MN-tech » Sun Oct 15, 2017 6:45 pm

Set the solder jumpers for serial
https://wiki.batc.tv/File:PE4302_Attenuator.pdf

Set the DIP switches for max attenuation.

G4KLB
Posts: 196
Joined: Wed May 28, 2008 10:46 am

Re: Portsdown wish list - output attenuator

Postby G4KLB » Sun Oct 15, 2017 11:48 pm

Glad to hear your attenuator is working now David, as mentioned above they come configured for parallel.
For the benefit of others, there should only be a solder blob on J4 to enable serial operation.

M0YDH
Posts: 67
Joined: Sat Dec 31, 2016 5:59 pm
Location: Wolverhampton IO82WO

Re: Portsdown wish list - output attenuator

Postby M0YDH » Mon Oct 16, 2017 7:53 am

Thank you John and Colin. Here's the picture that Colin sent me. My eyes were drawn to the switches. The attenuator came with 8 on switches. The J thingies are the solder pads across the bottom of the PCB. Solder blobs were on J5 and J6 as supplied. I removed these with solder wick and soldered J4. Et voila!
One for the Wiki to save others anxiety?

Cheers
David M0YDH
Attachments
PE4032 DIP & SOLDER BLOB Settings.JPG
PE4032 DIP & SOLDER BLOB Settings.JPG (75.04 KiB) Viewed 467 times

g8gtz
Posts: 764
Joined: Wed Apr 07, 2010 6:26 pm

Re: Portsdown wish list - output attenuator

Postby g8gtz » Mon Oct 16, 2017 8:24 am

Hi David,

Before you start drilling holes in the Portsdown case, I believe our RSGB construction competition winning Portsdown guru is implementing attenuator control in to the Portsdown software :-)

73 Noel

M0YDH
Posts: 67
Joined: Sat Dec 31, 2016 5:59 pm
Location: Wolverhampton IO82WO

Re: Portsdown wish list - output attenuator

Postby M0YDH » Mon Oct 16, 2017 11:55 am

Thanks Noel. I was having second thoughts on placing this unit in the Portsdown case. Besides at CAT17 we were told that speakers go in the lid!

I'm sure that I'm the only individual who has built the first and second place entries. Well done to team Crump and to Heather's powermeter.

73
David M0YDH


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