Langstone Update

[g4eml]

Update to improve FM Transmission.

Added deviation limiter.
Corrected Pre-Emhasis.
Adjusted Mic Gain and deviation.

Transmitted FM audio now sounds much crisper and does not over deviate.

Colin G4EML

[DL5BCA]

Hello Collin,

Thank you for the Update.
I update my system.
I tested over our city repeater.

With my Equipment (2headset, 1 Tablemicro) the sound is to low. Compared to a normal Tranceiver...

I will look for a microphone preamplifier.

Thank you for your effort.

73 Thomas DL5BCA

[g4eml]

The low level might also be caused by the low voltage supplied by the USB audio dongle. Some microphones need a higher voltage to work correctly. Those designed for Icom radios need about 8V, they do still work with the lower voltage but the output is greatly reduced.

A simple one transistor preamp would probably be sufficient.

[DL5BCA]

Hallo Collin,

thank you for your answer and help.

All 3 tested microphones are computer microphones. Extra for a sound card input.
The dongle is especially for the Raspberry, this one: https://www.rasppishop.de/USB-Soundkarte-Soundadapter

I'll try a mic preamp.

73 Thomas DL5BCA

[G8GKQ]

We have discovered in the last few days that all the audio levels on the latest Raspios build on the RPi 4 are initially set a lot lower than is sensible. Use of 'alsamixer' at the command line has been able to resolve these issues in Portsdown.

I hope to set the initial levels to something more sensible by default in a future Portsdown build (which will work on co-hosted Langstones), but need to do a bit of testing and experimentation before pushing the update.

Dave, G8GKQ