Langstone Update 16/10/20

Forum for discussion about the Langstone Microwave Transceiver that shares some features with the Portsdown. Wiki: https://wiki.microwavers.org.uk/Langstone_Project
G4FRE
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Re: Langstone Update 16/10/20

Post by G4FRE » Sun Jan 17, 2021 12:29 pm

In my DFS50 unit G4HUP did times 5 with a single pair of diodes

If you are using a 10 MHz square wave source the 50MHz component is already there, just filter and amplify it, no diodes needed. This is what i do for my other pluto where the 50MHZ was only 14dB down on the fundamenta (just not quite enough to just filter and use)l The 20 and 40MHz are much lower (>40db down)

The multiplier building and surgery on the pluto was the easy bit (around an hour) Persuading the pluto that it had a 50MHz reference AND getting it to remember it had a 50MHz at power up, took 6 hours visiting a number of "non-solutions"!
g0mjw wrote:
Sun Jan 17, 2021 10:17 am


I would have thought even harmonics quite easy using a doubler (diode) multiplier. 4 x 10 = 40 so a couple of doublers would work, but do you really need to? Won't the Pluto work with a 10 MHz input?

G8GKQ
Site Admin
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Re: Langstone Update 16/10/20

Post by G8GKQ » Sun Jan 17, 2021 1:26 pm

Concerning correcting the frequency of the Pluto:

I have an admission to make. As far as I can tell, I forgot to implement the functionality behind the Pluto frequency reference setting screen in the Portsdown SigGen. Even if I had implemented it, it would only change the calibration for the SigGen, not for the Langstone.

The correct way to change the calibration for the Langstone is to adjust the LO frequency stored in the Pluto, as detailed elsewhere on this Forum.

Dave, G8GKQ

G8GKQ
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Re: Langstone Update 16/10/20

Post by G8GKQ » Thu Jan 28, 2021 4:29 pm

I tried to implement the Pluto Frequency Reference Setting in the Portsdown today, and found that it was already there!

From the Pluto config menu on the Portsdown, you can enter a new Pluto reference frequency. This is stored on the Pluto, so does affect Langstone, Portsdown Pluto DATV and Portsdown Pluto SigGen.

So I did do it properly (even though I had forgotten that I had) so you can easily change the Langstone Pluto reference frequency from the Portsdown menus.

Dave

w0iy
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Joined: Sat Jul 04, 2020 2:38 am

Re: Langstone Update 16/10/20

Post by w0iy » Sat Jan 30, 2021 2:49 am

Is the ref freq feature intended for minor adjusts only? I wonder if I can change the ref to 10Mhz and use my GPSDO directly.

g0mjw
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Re: Langstone Update 16/10/20

Post by g0mjw » Sat Jan 30, 2021 9:48 am

You can also do this on the Pluto if you like and set it permanently too. There are two settings. fw_setenv ad936x_ext_refclk or fw_setenv xo_correction. The former to set a clock frequency, e.g. 20 MHz or 40 MHz. The latter to correct that frequency slightly. Look at the Wiki for the Pluto for more details. https://wiki.analog.com/university/tool ... vs/booting

e.g. 20 MHz reference

fw_setenv ad936x_ext_refclk 20000000

Minor 1 Hz adjustment to 40 MHz ref

fw_setenv xo_correction 40000001

Take care to use the right waverform. 10 MHz clocks have given problems if not square enough or the wrong levels.

Mike

G4FRE
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Joined: Fri May 26, 2017 6:57 am

Re: Langstone Update 16/10/20

Post by G4FRE » Sat Mar 06, 2021 9:59 am

before i forget how I did it, I have written up how i managed (eventually) to get my pluto to accept (and remember to accept) an external 50MHz reference

https://g4fre.blogspot.com/2021/03/lock ... ernal.html

https://g4fre.blogspot.com/2021/03/lock ... nal_6.html

https://g4fre.blogspot.com/2020/11/lock ... ernal.html

Dave
G4fre

w0iy
Posts: 27
Joined: Sat Jul 04, 2020 2:38 am

Re: Langstone Update 16/10/20

Post by w0iy » Sat Mar 20, 2021 3:37 am

A friend kc0tyd is working on using a Gpsdo 10MHz to a clock multiplier, which will generate 40MHz. Has anyone else tried this?

https://www.digikey.com/en/products/det ... FT/1916106

This is a simple low cost device. Will post more as things develop.

g4eml
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Joined: Thu Apr 26, 2018 9:36 am

Re: Langstone Update 16/10/20

Post by g4eml » Sat Mar 20, 2021 11:50 am

The Amsat DL forum has a thread about trying to use the similar ICS512 chip. The results were not good. The phase noise was too high.

radiogareth
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Joined: Wed Jan 06, 2016 9:46 am

Re: Langstone Update 16/10/20

Post by radiogareth » Sat Mar 20, 2021 1:15 pm

Another option may be to use the 10MHz as clock for a SI5381 (several variants I think) and programming it to deliver 40MHz. I have used this approach to generate stable LNB reference oscillator which worked very well for NB on QO-100. But I don't now about the phase noise qualities of the signal it outputs, that's beyond my pay grade atm....
Gareth

w0iy
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Joined: Sat Jul 04, 2020 2:38 am

Re: Langstone Update 16/10/20

Post by w0iy » Sat Mar 20, 2021 6:52 pm

Ok thanks for the info. I'll take a look for the Amsat reference.

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