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Sensitivity Reality Check: What Our $500 Telescope Can and Cannot Detect
HONEST SENSITIVITY ASSESSMENT
RTL-SDR + LNA + grid dish specifications:
System noise temperature: ~100-200 K
Bandwidth: 2.4MHz (raw), 0.14Hz (processed)
Dish gain: ~15-20dBi at 1420MHz
Effective aperture: ~0.3m²
Integration time: 1-24 hours practical
Bandwidth: 2.4MHz (raw), 0.14Hz (processed)
Dish gain: ~15-20dBi at 1420MHz
Effective aperture: ~0.3m²
Integration time: 1-24 hours practical
Minimum detectable signal (radiometer equation):
ΔT = T_sys / √(Δf × τ)
With T_sys=150K, Δf=1Hz, τ=3600s (1 hour):
With T_sys=150K, Δf=1Hz, τ=3600s (1 hour):
ΔT = 150 / √(3600) = 2.5 K
With τ=86400s (24 hours): ΔT = 0.51 K
WHAT THIS MEANS:
We can detect signals that raise the antenna
temperature by ~0.5-2.5 K above noise.
Natural hydrogen line from Milky Way: ~5-50 K.
So we CAN detect galactic hydrogen (proven).
temperature by ~0.5-2.5 K above noise.
Natural hydrogen line from Milky Way: ~5-50 K.
So we CAN detect galactic hydrogen (proven).
WHAT ABOUT AN ARTIFICIAL SIGNAL?
Depends entirely on the transmitter power.
For an Arecibo-class transmitter (1MW, 300m dish)
at 8.6 light-years: flux ~10⁻²⁶ W/m²/Hz
= about 0.001 K with our dish.
BELOW our detection threshold.
For an Arecibo-class transmitter (1MW, 300m dish)
at 8.6 light-years: flux ~10⁻²⁶ W/m²/Hz
= about 0.001 K with our dish.
BELOW our detection threshold.
For a civilization-scale phased array
(our pyramid network model, N=50 sites,
N²=2500× power gain): flux ~10⁻²³ W/m²/Hz
= about 1 K with our dish.
NEAR our detection threshold!
(our pyramid network model, N=50 sites,
N²=2500× power gain): flux ~10⁻²³ W/m²/Hz
= about 1 K with our dish.
NEAR our detection threshold!
HONEST ASSESSMENT:
Probability of detection with $500 setup: LOW.
But NOT zero. And the exercise proves:
But NOT zero. And the exercise proves:
- The method works (calibrate on galactic H)
- The prediction is specific and falsifiable
- Professional follow-up can improve 10,000×
- YOU will have built a radio telescope and done real radio astronomy for $500.
- Even a null result is PUBLISHABLE if the method and frequency prediction are novel.
THE REAL POWER:
This is not about finding the signal yourself.
It is about MAKING THE PREDICTION and
DEMONSTRATING THE METHOD.
Then professionals with ALMA, VLA, or SKA
can follow up with the required sensitivity.
It is about MAKING THE PREDICTION and
DEMONSTRATING THE METHOD.
Then professionals with ALMA, VLA, or SKA
can follow up with the required sensitivity.
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