Metric

English

Remarks

Frequency (MHz)

145.650

Wavelength

2.058

6.749

Antenna Height (Tx) (meters or feet)

30487.805

100000.000

Balloon at Burst height

Antenna Height (Rx) (meters or feet)

9.146

30.000

Receive antenna on house

Horizon Distance (Max Range Tx to Rx)

829062.015

447.247

Based on Burst height

Desired Path Length (km or miles)

55611.000

30.000

Rough Slant range requirement

Free Space Path Loss (dB)

-110.620

Attenuation due to inverse square law

Tx Power (dBm)

10.000

Transmit Power in db WRT 1mW

Tx Antenna Gain (dBi)

0.000

Assume worst case no gain in antennas

Rx Antenna Gain (dBi)

0.000

RX Cable Loss (dB)

-4.000

Rx Input Power (dBm)

-104.620

Signal power into receiver

Fade Margin (dB)

0.000

Not an issue for high elevations

Rx Noise Figure (dB)

7.000

Typical for VHF receivers

Rx BW (Hz)

30000.000

Determined by NBFM Filter

Rx BW (dBHz)

44.771

10*log10(Rx BW)

Rx Noise Power (dBm)

-122.229

-174+Noise Figure + Rx BW(dB)

S/N (dB)

17.609

Receive Power(dBm) -Noise power (dBm)

Data Rate (Baud)

1200.000

Same as Bits per second in our case

Bits/Symbol

1.000

Simple AFSK modulation

Eb (dBm) (Energy/bit: equals sig pwr/rate)

-135.412

No (dBm/Hz) (Noise Density:=Pn/BW)

-167.000

Eb/No (dB) Determines Bit Error Rate

31.588

Eb/No is used to find the Bit Error Rate (BER) of

the system. Some complicated probability

equations relate Eb/No to BER. Fortunately, there

are curves published trhat are close enough

for our project.

Anything above about 15 dB Eb/No

Should give us a BER < 10^-6