BATC Forum

Hello
I've started working on the langstone project, congratulations on this great project. I have a problem when I press the PTT it takes 3 seconds to see my modulation , I have the impression that it would have a tempo.
It has a setting or a solution to this

I use a Pluto TX/RX

73s Pierre F4JXP

There should be no significant delay when you transmit.
Make sure you are not connected to a network. High network activity can slow down the raspberry pi.
Also make sure you are using a good quality Class 10 SD card.

Colin G4EML

Hello
Thank you for your feedback. I'm going to check that the sd card is class 10. Would there be any point in using an ssd disk instead of an sd card?
Thank you

Pierre 73s F4JXP

I don't know about using a disk., I have never tried it.

Colin.

f4jxp wrote: ↑

Tue Jul 04, 2023 3:15 am

Hello
I've started working on the langstone project, congratulations on this great project. I have a problem when I press the PTT it takes 3 seconds to see my modulation , I have the impression that it would have a tempo.
It has a setting or a solution to this

I use a Pluto TX/RX

73s Pierre F4JXP

That's normal for Portsdown TV, but not for SSB/CW/FM from the Langstone. Perhaps you have the wrong firmware or wrong firmware settings in the Pluto?

Mike

Hello Colin
I checked the sd card and it is class 10.
However, when I reread the installation tutorial, I saw that a resistor had to be connected to the 3.3 v and GND to switch the PTT pin 11.
I don't know if this has any effect on the delay?

Thank you Pierre F4JXP

Both the PTT pin and the CW Key pin need resistors to 3V3.

Connecting these pins to ground will then start transmitting.

If the resistors are not fitted the inputs might pulse on and off with noise which might cause problems.

Colin.

I'm getting a delay of several seconds after PTT is asserted and teh audio is transmitted. This only occurs after langstone has been running for several hours. A reset normalises this.

I monitor this on another langstone and have tried swapping the langstones which both use the recommended sound card a sooundblaster, which works , and also using a different sound card, a soundblaster which works after setting up its input using alsa (The settings don't survive a reset).

It looks as if a sound buffer may need resetting when PTT is asserted.

Any thoughts?

Unfortunately this is a 'feature' of the use of the underlying GNURadio code. When using multiple devices each with their own clock the tiny differences in clock accuracy can cause buffers to slowly grow or shrink. There doesn't seem to be a simple fix for this and it appears to be a regularly asked question on the GNURadio forums with no good reply. GNURadio doesn't seem to have a way to clear the buffers. Or at least if it does I have not been able to find it.

I don't have time to work on Langstone at the moment, when I do I will see if there is some way of improving this.

Colin G4EML

regarding the delay we noticed that its kinda dependent on the temperature of the pi. speaking at minus 5 we have had no issues but at 15 degrees it showed up. switching sd cards of type changed it minor but not a big help.
as next step we are thinking to run it on ssd without sdcard to benefit of advanced io rate..
will report if it helped.