Extending Langstone to include 10GHz

Forum for discussion about the Langstone Microwave Transceiver that shares some features with the Portsdown. Wiki: https://wiki.microwavers.org.uk/Langstone_Project
g4eml
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Joined: Thu Apr 26, 2018 9:36 am

Re: Extending Langstone to include 10GHz

Post by g4eml » Sat Oct 03, 2020 9:37 pm

Hi Barry,

At present only the 5th harmonic can be selected for receive. As the top frequency for the Pluto is 6 GHz that sets a limit of 30Ghz.

Probably the only practical use for the 24GHz mode is as a test source or local monitor receiver. I suspect it would need a lot of external gain to make it into a usable transceiver.

Colin.

G8AGN
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Re: Extending Langstone to include 10GHz

Post by G8AGN » Sun Oct 04, 2020 11:22 am

Hi Colin

I notice that on the 24GHz band setting, x2 can be selected on TX as well as x1 and x5 but only x1 and x5 on RX.

This morning I unearthed my very old WB 24GHz rig based on a Plessey Gunn diode module and fired that up.
As you can see in the photo, the Gunn is not very stable (as expected but OK for WB) and is low in frequency but at least I can now see a signal on Langstone at 24GHz. That's today's progress.

73 Barry, G8AGN
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g4eml
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Re: Extending Langstone to include 10GHz

Post by g4eml » Sun Oct 04, 2020 11:42 am

The X2 selection on transmit is to support the Hydra 10GHz module by OE8FNK. that has a simple doubler for transmit and a PLL satellite down converter for receive. Because it doubles the output frequency of the Pluto it cannot be used for SSB and FM has double the deviation. This is the main advantage of using the harmonic mixing method, SSB and FM remain usable. The disadvantage is that the output power is much lower.

G8AGN
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Re: Extending Langstone to include 10GHz

Post by G8AGN » Mon Oct 05, 2020 7:49 am

I have now tried receiving the second harmonic of an Elcom 1295 synthesiser running at 12.240GHz. This is normally used to provide a marker for 122,4 GHz for use with the VK3CV 122GHz transceiver boards. The frequency multiplication is done using a double diode mixer chip from an old SatTV LNB soldered across a piece of 141 semi-rigid coax.

As expected, this signal is very stable!

73 Barry, G8AGN
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g3yjr
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Re: Extending Langstone to include 10GHz

Post by g3yjr » Thu Oct 15, 2020 1:35 pm

That does look astonishingly stable!

73 Graham

G8GKQ
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Re: Extending Langstone to include 10GHz

Post by G8GKQ » Sun Oct 18, 2020 4:40 pm

Thanks to Colin for some outstanding research on this capability.

I have just added a "5th Harmonic" mode to the Portsdown Signal Generator. Described here: https://wiki.batc.org.uk/Portsdown_4_Signal_Generator

Dave, G8GKQ

IW1EPY
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Joined: Fri Apr 23, 2021 8:40 pm

Re: Extending Langstone to include 10GHz

Post by IW1EPY » Fri Apr 23, 2021 9:09 pm

Maybe someone with more knowledge of IQ mixers could comment on this. Is this the expected behaviour of the mixers when using Harmonics? Or is it just an indication of poor balance at frequencies outside the normal range?
I was working with Alberto for Satsagen software and enter in the same problem. At the end Furier solved the problem . If you applay the furier transform to the 2 square wave sin cos of the LO you sea that the phase of the 3 , 7 etc .. harmonics is reversed so IF you send trought I&Q DAC an USB sognal on 3 and 7 you will obtain a LSB info.
The harmonic contemt of a 50% duty cycle square wave is only odd so 2 , 4 do not have power .
By the way i have install your SW on Raspberry and Pluto works well , i plan to install 2 switch 1 to 6 on Rx and Tx and will be interesting to add the possibility of full duplex ( example Tx on 144 receive at 1296) , do you think is possible modifiing SW?
Ciao 73 de IW1EPY

m1cdq
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Re: Extending Langstone to include 10GHz

Post by m1cdq » Sat Apr 24, 2021 2:27 pm

just out of curiosity. Would I be able to modulate this from portsdown for a 10ghz signal
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g4eml
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Re: Extending Langstone to include 10GHz

Post by g4eml » Sat Apr 24, 2021 8:26 pm

IW1EPY, Thanks for your comments. That confirms my theory about the harmonic mixing. The 5th harmonic is the easiest to use as it does not invert the signal.

Regarding Duplex operation. That is already supported when working QO-100. It is made available when there are different offsets for Tx and Rx. It would be difficult to use it for operation on two bands because there is currently no method of individually tuning two bands at the same time.

Colin.
Last edited by g4eml on Sat Apr 24, 2021 8:35 pm, edited 1 time in total.

g4eml
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Re: Extending Langstone to include 10GHz

Post by g4eml » Sat Apr 24, 2021 8:30 pm

M1CDQ,

I do not think it would be possible to use that signal generator for Digital Tv. However it might be possible to use it as a local oscillator driving a mixer. Then it could convert the output of a Portsdown up to 10GHZ.

I doubt that it would be stable enough for any narrowband modes.

Colin.

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