Langstone Update

Forum for discussion about the Langstone Microwave Transceiver that shares some features with the Portsdown. Wiki: https://wiki.microwavers.org.uk/Langstone_Project
g4eml
Posts: 186
Joined: Thu Apr 26, 2018 9:36 am

Re: Langstone Update

Post by g4eml » Thu May 21, 2020 3:11 pm

Hi Dave,

The format does change sometimes but it should recover automatically.
I have just removed Langstone.conf from Github so it will never be downloaded again.
Unfortunately that means GIT might delete it on the next update. (Just this once)
If it does not exist on a new system it will be created with default settings by the GUI program.
If you have spent time adjusting all the settings for you Langstone it is worthwhile making a copy of Langstone.conf before you update.

Colin.

g4eml
Posts: 186
Joined: Thu Apr 26, 2018 9:36 am

Re: Langstone Update

Post by g4eml » Thu May 21, 2020 3:32 pm

Another Update posted on Github.

AM receive and transmit added.
(I know it's not really needed but it was easy to add!)

Improved CW Transmission.
Previously this was done with a keyed 800 Hz audio tone in SSB mode, now it is done with direct keying of the carrier. The spectrum looks much cleaner and latency is reduced.

Popup buttons added for Band and Mode selection.
When you touch the BAND or MODE buttons a second row will appear allowing direct selection instead of having to scroll through the list.

Number of Bands increased to 12.
This was done to make maximum use of the popup buttons.

Note that when you do this update you may loose any settings you have previously made.
This is because I have removed the Langstone.conf file from Github and the first update may remove it from your system. If you need to save your settings make a backup copy before updating. If you are not concerned it will be recreated with default settings on the first run.

Note also that the 12 'Bands' are really just 12 VFOs. You can re-tune any one to any frequency you want.

73
Colin G4EML

P.S. I did try to add WBFM as an extra mode but it consumed a massive amount of processor time so I decided not to add it.
If anyone really needs WBFM it can probably be added with a separate GNU Radio Flowgraph just for that mode.

G8GKQ
Site Admin
Posts: 1533
Joined: Sun Mar 22, 2009 1:21 pm

Re: Langstone Update

Post by G8GKQ » Thu May 21, 2020 4:19 pm

Thanks Colin

What a great update! Next time I open the Portsdown code, I'll add a couple of buttons/functions in the Portsdown (Menu 3, Langstone Config) to back-up/restore the config file.

Dave

PS - for those of you who already have the Portsdown A27 code loaded, you can apply Colin's update by Menu 3, Langstone Config, Update Langstone. Simple as that!

G4FKK
Posts: 35
Joined: Sun May 05, 2019 12:15 pm

Re: Langstone Update

Post by G4FKK » Thu May 21, 2020 5:28 pm

Hi all,

Only discovered this forum today! Firstly, thanks Colin for the Langstone project - great fun and a lot of work by the look of it. I built a version last week and updated it it earlier today; before your latest mods evidently :) I'll do it again shortly.

I've not had a chance yet to plough through all the posts so apologies if this has already been noticed:- I've been running my Langstone on 4m all afternoon and I noticed the latency of the audio building up from virtually unnoticeable to around 2.5 seconds as the afternoon wore on. Rebooting puts it back to mS again. I remember this happening using SDR-Console and a Lime Mini but the effect seemed to vanish with later versions of SDR-Console. As I said, if this is a known effect then apologies for the waste of forum space.

Apart from that and a slight 'digital whine', presumably from the soundcard, the Langstone has been working very well, is not being upset by my running 120W on 4m SSB and looks spectrally very clean. I might try it out on the ACs this evening - they'll soon let me know if there's anything going out which shouldn't be :)

Thanks again Colin and to BATC for providing this forum.

73, Martin - G4FKK

g4eml
Posts: 186
Joined: Thu Apr 26, 2018 9:36 am

Re: Langstone Update

Post by g4eml » Thu May 21, 2020 6:11 pm

Hi Martin.

It is still very much an experimental project but it does seem to have quite a few people trying it now.

The slowly increasing latency was there on earlier versions but it has got a lot better in the last couple of versions. I hesitate to say it is fixed totally but I have certainly not noticed it recently. The big improvement was splitting the GNU radio SDR code into separate RX and TX tasks. I now freeze the one that is not active which frees up a lot of CPU time. It seems to help a lot and I think the Pi runs a bit cooler as well.


The background noise seems to be a problem with the recommended USB sound module. It doesn’t seem to be very well filtered against power supply noise. I have a more expensive type that seems to be a lot better on a PC. I am planning to try that on the Langstone soon.

73
Colin.

G4FKK
Posts: 35
Joined: Sun May 05, 2019 12:15 pm

Re: Langstone Update

Post by G4FKK » Thu May 21, 2020 7:33 pm

Very successful experiment so far Colin! It's already very usable. I've just re-updated to your latest version and I'll run it for a few hours and see if I get the latency build-up again. I'm currently listening to the local club 4m FM net. I might call in later and see what they think of the audio.

I've been through all the previous posts now and you mentioned running a separate GNU Radio Flowgraph for WBFM. That would be a "nice to have" at this time of the year on 4m when the FM broadcast stations are coming through via sporadic e from the NE. Really not urgent though :)

Thanks again for sharing all your hard work. I now need to update my Portsdown!

73, Martin - G4FKK

G4FKK
Posts: 35
Joined: Sun May 05, 2019 12:15 pm

Re: Langstone Update

Post by G4FKK » Fri May 22, 2020 5:34 pm

A quick update from here Colin,

I left the Langstone (latest update applied), running all day on receive on 4m, mainly because my Wife had me slaving away in the garden for most of it. When I came back and started transmitting the latency was fine. I then started droning on with G3NPI and after around half an hour of fairly lengthy overs (alright; waffling), the latency had built up to around 2.5 to 3 seconds. I'm not sure if this is a technical issue or whether I'm just boring the Langstone into extreme lethargy :)

I've tried several microphones and there appears not to be enough audio gain on FM. The tx frequency response seems rather LF heavy on all voice modes. My high impedance Shure 444 sounds quite woolly whereas a 500R dynamic has a bit more top end so I suspect the sound card has a low impedance input. Rx frequency response is fine.

These are not, by any means, complaints, just observations and I hope they may be helpful.

For my next trick I'm going to install Dave's Portsdown additions.

Great fun and many thanks,

Martin - G4FKK

radiogareth
Posts: 452
Joined: Wed Jan 06, 2016 9:46 am

Re: Langstone Update

Post by radiogareth » Fri May 22, 2020 6:03 pm

And I had a brief play with this little bargain.....(QSO with self), +42dBm output at -10db TX reduction.
Vhttps://www.ebay.co.uk/itm/433MHZ-335-480MHz-13 ... 2749.l2649
Whilst designing touch-screen front panel and parts to mount in in my box...
https://www.ebay.co.uk/itm/Sloping-Box- ... 2749.l2649

I'm better at designing things than tidying the shack ;-)

Gareth

g4eml
Posts: 186
Joined: Thu Apr 26, 2018 9:36 am

Re: Langstone Update

Post by g4eml » Fri May 22, 2020 7:46 pm

Hi Martin,

I think that confirms that the latency builds up the longer the transmitter is used. Previously the transmit was actually running all the time even when receiving. I suspect it is caused by a slight difference in sampling rates between the sound card and the Pluto as it sounds like the output is gradually falling behind the input.

As for the mic audio, I know that Dave has added an external preamp for his mic. It may be some need that. I am using an Icom mic with mine and that is fine but I think Icom mics tend to have higher output levels than some. I could increase the available gain setting but I think that would just raise the background noise. I think the USB audio device probably needs a higher input level.

Colin.

G4GUO
Posts: 655
Joined: Tue Feb 16, 2010 12:51 pm

Re: Langstone Update

Post by G4GUO » Fri May 22, 2020 7:52 pm

I get a similar issue with the constant envelope SSB code I wrote for Express, my problem is the other way round which causes under runs
which appear as broadband clicks on transmit every few seconds which is far more objectionable.

- Charles

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