# Presentation: 203838

## GPS Re-radiators

- Army Spectrum Management Office
- Stevan Jovancevic
- Date: October 28, 2005

## GPS Re-radiators

- Purpose: To examine use of GPS Re-radiators for military applications.
- GPS Re-radiators receive the GPS signal and retransmit it to users who otherwise could not be able to get a lock on the GPS signal due to superstructure blockage.
- IRAC has generated regulations for the use of these devices by the Government agencies which includes the military.
- Military has unique requirements for utilization of the GPS Re-radiating kits.

## Present Army Operations in IRAQ 

## 	Army Applications of the GPS Re-radiators

- Army troops are engaged in the present day conflict in IRAQ.
- Position Location is necessary for successful mission execution.
- Troops are being transported in the armored vehicles such as Bradley Fighting Vehicle and Stryker Brigade Combat Vehicles.
- Special Operations Forces utilization in transport vehicles and cargo planes (C-130).
- Feedback from users includes a request for utilization aboard the fixed wing and rotary wing aircraft.
- A significant number of Humvees are also armor plated.

## Reception of the GPS Signal

- GPS Signal is unable to propagate inside armored vehicles.
- Our troops are unable to receive the GPS signal inside Bradley Combat Vehicles, Humvees, or Stryker Brigade Combat Vehicles.
- Solution: Use the GPS Re-radiator to obtain a GPS signal. Troops can tolerate certain GPS signal error.

## Feedback from the troops

- Mr. Ryberg,
- 	believe me, this is one of the BEST products I have ever seen for a military application!!!!
- 	I bought one for myself about 2 years ago and used the HE** out of it!!! it was the ONLY thing on earth that allowed GPS's (garmin's and PSN-11 and other GPS's) to work inside the vehicle (armored and non armored).
- 	I went to Iraq without one (in april 2004) and drove around with my hand out the window of a armored humvee... doesnt seem like that makes much sense, but in order to know where I was going, I had to have line of sight.  Now since Nov 2004 (when i purchased mine) with the VORTECH reradiator, I can leave the 3" thick glass closed and not have to worry about getting my arm blown off by a improvised explosive device sitting on the side of the road or getting shot in the face.
- 	Justin P. Corder TSgt, USAF-TACP

## WHAT IS AT STAKE

- DoD’s ability to successfully carry out its mission.
- Our troops ability to know their location.
- Ultimately, people’s lives.

## ASMO ANALYSIS

- Army Spectrum Management Office performed EMI analysis to determine a separation distance between GPS Re-radiators and GPS Receivers.
- Utilized L1 frequency of 1575.42 MHz.
- Case 1 based on the GPS signal of -130 dBm.
- Case 2 based on the GPS signal of -124 dBm.

## CHRONOS GPS Re-radiating UNIT RA-46

## CONFIGUARTION REPRESENTATION

**Parameters **
**Amplifier Gain:                      28 dB**
**Re-transmit antenna gain:    20 dBi**
**Cable Losses:                          0 dB**
**GPS Antenna Gain case 1:      0 dBi**
**GPS Antenna Gain case 2:   2.1 dBi**

**Free Space Path Loss (dB) = 20 Log D (meters) + 20 Log F (MHz) -27.55**

## EMI ANALYSIS RESULTS CASE 1

- 1 Meter Ex: -130 dBm + Antenna gain (s) + Amp Gain – Free space Loss = -118.3 dB

| Distance Separation
Between GPS receiver
and re-transmitter | Signal Strength of
the re-radiated
signal at the GPS
Receiver | Re-transmitter
Antenna Gain | Receiver 
Antenna Gain | Power Output
from Re-transmitter
(out of the amplifier 
before antenna) | GPS Frequency
L1 | Free Space Path
Loss |
| --- | --- | --- | --- | --- | --- | --- |
| 1 meter | -118.3  dBm | 20 dBi | 0 dBi | -102 dBm | 1575.42 MHz | 36.38 dB |
| 2 meters | -124.4 dBm | 20 dBi | 0 dBi | -102 dBm | 1575.42 MHz | 42.40 dB |
| 3 meters | -127.9 dBm | 20 dBi | 0 dBi | -102 dBm | 1575.42 MHz | 45.9  dB |
| 4 meters | -130.4 dBm | 20 dBi | 0 dBi | -102 dBm | 1575.42 MHz | 48.4  dB |
| 5 meters | -132.3 dBm | 20 dBi | 0 dBi | -102 dBm | 1575.42 MHz | 50.3  dB |
| 6 meters | -133.9 dBm | 20 dBi | 0 dBi | -102 dBm | 1575.42 MHz | 51.9  dB |
| 7 meters | -135.2 dBm | 20 dBi | 0 dBi | -102 dBm | 1575.42 MHz | 53.2  dB |
| 8 meters | -136.4 dBm | 20 dBi | 0 dBi | -102 dBm | 1575.42 MHz | 54.4  dB |
| 9 meters | -137.4 dBm | 20 dBi | 0 dBi | -102 dBm | 1575.42 MHz | 55.4  dB |
| 10 meters | -138.3 dBm | 20 dBi | 0 dBi | -102 dBm | 1575.42 MHz | 56.3  dB |
| 11 meters | -139.2 dBm | 20 dBi | 0 dBi | -102 dBm | 1575.42 MHz | 57.21 dB |
| 12 meters | -139.9 dBm | 20 dBi | 0 dBi | -102 dBm | 1575.42 MHz | 57.96 dB |
| 13 meters | -140.6 dBm | 20 dBi | 0 dBi | -102 dBm | 1575.42 MHz | 58.66 dB |

## EMI ANALYSIS RESULTS CASE 2

| Distance Separation
Between GPS receiver
and re-transmitter | Signal Strength of
the re-radiated
signal at the GPS
Receiver | Re-ransmitter
Antenna Gain | Receiver 
Antenna Gain | Power Output
from Re-transmitter
(out of the amplifier 
before antenna) | GPS frequency
L1 | Free Space Path
Loss |
| --- | --- | --- | --- | --- | --- | --- |
| 1 meter | -110 dBm | 20 dBi | 2.1 dBi | - 96 dBm | 1575.42 MHz | 36.3 dBm |
| 2 meters | -116.3 dBm | 20 dBi | 2.1 dBi | - 96 dBm | 1575.42 MHz | 42.4 dBm |
| 3 meters | -119.8 dBm | 20 dBi | 2.1 dBi | - 96 dBm | 1575.42 MHz | 45.9 dBm |
| 4 meters | -122.3 dBm | 20 dBi | 2.1 dBi | - 96 dBm | 1575.42 MHz | 48.4 dBm |
| 5 meters | -124.2 dBm | 20 dBi | 2.1 dBi | - 96 dBm | 1575.42 MHz | 50.3 dBm |
| 6 meters | -125.8 dBm | 20 dBi | 2.1 dBi | - 96 dBm | 1575.42 MHz | 51.9 dBm |
| 7 meters | -127.1 dBm | 20 dBi | 2.1 dBi | - 96 dBm | 1575.42 MHz | 53.2 dBm |
| 8 meters | -128.3 dBm | 20 dBi | 2.1 dBi | - 96 dBm | 1575.42 MHz | 54.4 dBm |
| 9 meters | -129.3 dBm | 20 dBi | 2.1 dBi | - 96 dBm | 1575.42 MHz | 55.4 dBm |
| 10 meters | -130.2 dBm | 20 dBi | 2.1 dBi | - 96 dBm | 1575.42 MHz | 56.3 dBm |
| 11 meter | -131.1 dBm | 20 dBi | 2.1 dBi | - 96 dBm | 1575.42 MHz | 57.2 dBm |
| 12 meters | -131.8 dBm | 20 dBi | 2.1 dBi | - 96 dBm | 1575.42 MHz | 57.9 dBm |
| 13 meters | -132.5 dBm | 20 dBi | 2.1 dBi | - 96 dBm | 1575.42 MHz | 58.6 dBm |
| 14 meters | -133.2 dBm | 20 dBi | 2.1 dBi | - 96 dBm | 1575.42 MHz | 59.3 dBm |
| 15 meters | -133.8 dBm | 20 dBi | 2.1 dBi | - 96 dBm | 1575.42 MHz | 59.9 dBm |
| 16 meters | -134.3 dBm  | 20 dBi | 2.1 dBi | - 96 dBm | 1575.42 MHz | 60.4 dBm |
| 17 meters | -134.9 dBm | 20 dBi | 2.1 dBi | - 96 dBm | 1575.42 MHz | 60.9 dBm |
| 18 meters | -135.4 dBm | 20 dBi | 2.1 dBi | - 96 dBm | 1575.42 MHz | 61.4 dBm |
| 19 meters | -135.8 dBm | 20 dBi | 2.1 dBi | - 96 dBm | 1575.42 MHz | 61.9 dBm |
| 20 meters | -136.3 dBm | 20 dBi | 2.1 dBi | - 96 dBm | 1575.42 MHz | 62.4 dBm |

## EMI ANALYSIS RESULTS CASE 2 CONTINUED

| Distance Separation
Between GPS receiver
and re-transmitter | Signal Strength of
the re-radiated
signal at the GPS
Receiver | Re-transmitter
Antenna Gain | Receiver 
Antenna Gain | Power Output
from Re-transmitter
(out of the amplifier 
before antenna) | GPS Frequency
L1 | Free Space Path
Loss |
| --- | --- | --- | --- | --- | --- | --- |
| 21 meters | -136.73 dBm | 20 dBi | 2.1 dBi | - 96 dBm | 1575.42 MHz | 62.83 dBm |
| 22 meters | -137.13 dBm | 20 dBi | 2.1 dBi | - 96 dBm | 1575.42 MHz | 63.23 dBm |
| 23 meters | -137.52 dBm | 20 dBi | 2.1 dBi | - 96 dBm | 1575.42 MHz | 63.62 dBm |
| 24 meters | -137.88 dBm | 20 dBi | 2.1 dBi | - 96 dBm | 1575.42 MHz | 63.98 dBm |
| 25 meters | -138.24 dBm | 20 dBi | 2.1 dBi | - 96 dBm | 1575.42 MHz | 64.34 dBm |
| 26 meters | -138.58 dBm | 20 dBi | 2.1 dBi | - 96 dBm | 1575.42 MHz | 64.68 dBm |
| 27 meters | -138.91dBm | 20 dBi | 2.1 dBi | - 96 dBm | 1575.42 MHz | 65.01 dBm |
| 28 meters | -139.22 dBm | 20 dBi | 2.1 dBi | - 96 dBm | 1575.42 MHz | 65.32 dBm |
| 29 meters | -139.53 dBm | 20 dBi | 2.1 dBi | - 96 dBm | 1575.42 MHz | 65.63 dBm |
| 30 meters | -139.82 dBm | 20 dBi | 2.1 dBi | - 96 dBm | 1575.42 MHz | 65.92 dBm |
| 31 meters | -140.11 dBm | 20 dBi | 2.1 dBi | - 96 dBm | 1575.42 MHz | 66.21 dBm |

## RECOMMENDATIONS

- Modify the existing NTIA regulations for utilization of the GPS Re-radiating devices.
- Due to current regulations, resellers of the GPS Re-radiators are hesitant to sell GPS Re-radiating equipment to DoD elements.
- Reassure resellers of the GPS Re-radiators that purchase by DoD forces for OCONUS use is allowed under the current regulations.
- Make allowances for DoD to purchase GPS Re-radiators for its use Nationally for test and training on military bases and installations.