SVXSpot an SVXLink Analog Hotspot for the Raspberry Pi Zero

RF.Guru Analog Hotspot 70CM (UHF) 500mW Power

RF.Guru Analog Hotspot 2M (VHF) 500mW Power

RF.Guru Analog Transceiver 70CM (UHF) 1.3W Power (added a Low Pass filter) needs additinal power best used with an external power source like RF.Guru Pi Zero PSU

RF.Guru Analog Transceiver 2M (VHF) 1.3W Power (added a Low Pass filter) needs additinal power best used with an external power source like RF.Guru Pi Zero PSU

Used PIN's:

• 3 GPIO2
• 6 GPIO3
• 35 GPIO19
• 8 TX
• 10 RX
• 12 CLK
• 32 GPIO12 -> COS input from the radio chip
• 36 GPIO16 -> PTT pin
• 38 GPIO20
• 40 GPIO2

These boards are also suitable for conducting analog ham radio experiments within the 70cm and 2m ham radio frequency bands. (Like APRS iGate/Digipeater, packet etc...)

Antenna

The hotspot is not suitable for connecting an outdoor antenna because it lacks a sufficient low-pass filter. However, the transceiver version is equipped with a low-pass filter and is suitable for transmitting via an outdoor antenna.

The RF 50 ohm output requires an antenna with a SWR (Standing Wave Ratio) of less than 4:1, which is considered reasonable. If you experience sound distortion, it could indicate that the antenna being used has a high SWR, leading to common-mode currents that may affect the RF chip. To test, use a 50-ohm dummy load (for UHF) and consider using a more suitable antenna. We recommend and sell antennas that work without any issues.

Barebone

If you prefer to handle everything manually, you can find the necessary resources here:

• RF Module (SA818) can be programmed via https://github.com/Guru-RF/SA818.
• The I2C audio chip kernel module can be found here https://github.com/waveshare/WM8960-Audio-HAT.

SVXLink Bookworm Image

Bookworm 32Bit Lite 2024-01-29 Image (only for Raspberry Pi Zero 2W, Raspberry Pi 4 and Raspberry Pi 5)

Utilize PI-Imager to write the image to your MicroSD card! Don't use svxlink or svxspot as a username, these are system usernames, using them will result in a broken installation !

You can set username/password and wifi credentials in the Raspberry PI Imager tool ... there is no default username/password !

Use the latest release of PI-Imager Github

Youtube demonstration of how to use PI-Imager on Windows 11

Youtube demonstration of how to use PI-Imager on MacOS X

Boot the hotspot with a descent power supply that can provide enough current and has a stable voltage > 5v !

It appears that the Raspberry Pi freezes after resizing the file system. Currently, after the initial boot, wait for 10 minutes, disconnect the power, and then restart. We suspect this issue is a bug and anticipate it will likely be resolved in a future release of pi-shrink.

To complete the final configuration step, SSH is required. For Linux/Mac, SSH is installed by default. Open a terminal and type ssh username@ip. However, for Windows, you'll need an additional application, such as Putty.

Youtube how to install putty on Windows 11

Ensure that you download Putty for the correct architecture; for the majority, it will be x86 64-bit.

Once connected, you can execute:

sudo hotspot-config

as illustrated in this video:

hostspot-config2.mp4

To activate the default talk group, just press PTT once, the second PTT will go to the network.

The chip has a deviation of 2.5khz ... for best audio experience send with Narrow FM (FM-N), it will sound better !

To activate another talk group send DTMF 91 talkgroup #

To leave the active talk group send DTMF 91 0 #

To specify various talkgroups for monitoring within the 'hotspot-config', you can indicate them as follows: 8++,23+,50,51,52,53,54,55

The plus signs denote priority levels.

The hotspot also has a local portal you can access it via it's hostname if you network support this or via his ip adress.

For adding additional networks you can use the

sudo nmtui 

provided by the Pi OS.

Choosing a frequency and ctcss tone

We advice a frequency not in use by nearby repeaters, also do not use ISM frequency 433Mhz ... we use 439.100 on 70cm and 145.250 on 2m

For CTCSS tone ... use a tone not localy used ... we use 88.5

Modify talk groups on the dashboard

Edit the following file:

sudo vi /var/www/html/include/tgdb.php

Hotspot with enclosure

hotspot.mp4

Manual SVXLink and Radiomodule install scripts

(not needed when using the image, this is preinstalled on the image)

Prepare your sd-card with Raspberry PI OS (Bookworm 32Bit Lite) (Youtube)

Login to your system with ssh add run following commands:

Install GIT

sudo apt -y install git

Clone repostory

git clone https://github.com/Guru-RF/SVXSpot.git

Audio and Radio module installation script

cd SVXSpot
sudo bash install-radiomodule.sh

SVXLink installation script

cd SVXSpot
sudo bash install-svxlink.sh

Tuning Input Volume

(modify /usr/sbin/hotspot_volume to the desired volume)

systemctl stop svxlink
/sbin/hotspot_volume
arecord -V stereo -r 44100 -f S16_LE -c 2 /dev/null

Modify RF Module settings

(modify /usr/sbin/hotspot for rf module changes)

Simple Test

Sending D1# dtmf on the configured frequency starts the parrot.
(On Anytone DTMF ABCD -> P1 = A P2 =B up button =C down button =D)

Hostpot Full Audio / RF module Test

curl -L -o - https://raw.githubusercontent.com/Guru-RF/SVXSpot/master/test-hotspot.sh | sudo bash

SVXLink Hotspot in action

Svxlink.Hotspot.rPiZero.mp4