Garmin Astro GPS Dog Tracking Systems

Improving Signal Range for the Garmin Astro 220

Not many users of the Garmin Astro dog tracking system know that you can switch frequency to gain signal range. The Garmin Astro operates on five (5) different frequencies. These five frequencies are selectable in the Garmin Astro 220 Receiver handheld unit.

The Garmin Astro DC-30 and DC-20 transmit a radio signal to the Garmin Astro 220 handheld on 5, 10, or 30 second intervals. The range of that radio signal depends on the terrain where you are tracking. If you are in a flat terrain like a field, you will experience the best results in signal range. But if you are tracking in a rough terrain with hills and valleys, you will experience a signal range that is reduced.

The signal range is also dependant on a few technical factors:

1. the output power on the Garmin Astro DC-30 or DC-20 transmitter
2. the transmitter and receiver antennas
3. the frequency you have chosen on your Garmin Astro 220 receiver

Output Power: The output power on the Garmin Astro DC-30 and DC-20 is 2 Watts. This output power is a function of the product design and not changeable. When a radio transmitter operates on such a low output power, the main rule is to use the lowest radio frequency possible. The higher the frequency, the higher the output power it takes to deliver the signal.

Antennas: Choice of the antennas on the transmitters and receiver will have an effect on signal quality. One improvement of the new Garmin Astro DC-30 design over the original DC-20 was the inclusion of a longer, higher performance, transmission antenna. If you have a DC-20, there are higher performance antennas from aftermarket companies available that can be mounted on a collar or on a harness. Some users have also experienced improved signal range when using the Garmin Magnetic Mount Antenna with their Astro 220 handheld instead of the original stock antenna.

Frequency: With the US version of the Garmin Astro, there are five (5) MURS* radio frequencies to work with:

151,82Mhz (ID code: 0-9)
151,88Mhz (ID code: 10-19)
151,94Mhz (ID code: 20-29)
154,57Mhz (ID code: 30-39)
154,60Mhz (ID code: 40-49)

The Scandinavian version of the Garmin Astro has only one frequency available: 155,42Mhz, transmitting on 2 Watts of output power.

*MURS stands for Multi-Use Radio Service and consists of these five frequencies in the VHF spectrum. As defined by the FCC, it is a private, two-way, short distance voice or data communications service for personal or business activities of the general public. In 2000, these frequencies were moved to become part of the new Citizens Band Radio Service (CB) which has been renamed MURS.

How to Switch Frequencies

Switching frequency on the Astro 220 handheld unit is very easy and it is not published in the Garmin Astro User Manual. To change it, you simply need to change the pre-programmed ID code that your Garmin Astro DC-30 or DC-20 is using. For example, if your unit is currently set to ID code: 43, you can see on the frequency table above that the radio frequency you are using is 154,60Mhz. In this example, for better signal range, you should try an ID code between 0 and 9 (e.g. 5) so the unit is set on the lowest frequency: 151,82Mhz.

To assign a new ID code to your unit.

1. With the "Dog Tracker" page open, and the Garmin Astro DC-30 or DC-20 transmitter powered on, press MENU.
2. Select Change Comm. Settings.
3. Follow the on-screen instructions.
4. Select the desired ID-code and press OK
5. Choose the update rate you desire.
6. Follow the on-screen instructions to finish the setup.

User Experience

A Garmin Astro user that was instructed about switching frequencies gained 2.4 miles by just performing the frequency change. The factory ID code on his DC-20 unit was preset on: 48 (154,60Mhz), and the maximum signal range that he had experienced was about: 1.3 miles. After he changed the ID code to: 4 (151,82Mhz), he experienced a signal range of 3.7 miles in the exact same area...a 284% improvement!

In some other cases, depending on where you are hunting, the lowest frequency might not be the ultimate one. It is recommended that you to try all 5 frequencies to see which one is performing the best in your specific area of the world. When you try out the different frequencies, just be sure that you test each in the exact same area. Hang the Garmin Astro DC-30 or DC-20 transmitter in a tree and take a ride with your car or bicycle. Please note that whenever you actually change the frequency, you must have the Garmin Astro 220 handheld unit and the Garmin Astro DC-30 or DC-20 very near each other.

This article was co-authored by America's Pet Store and may not be reproduced without permission. It has been written to provide general information on product selection and training. It is not intended to be a substitution for the information that comes with your product.