The 88-Mile Challenge

Path: Lookout Mountain, Denver → Pikes Peak Int'l Raceway 

Distance: ~ 88.33 miles

Frequency: 99.5 MHz (KQMT-FM)

Primary Obstacle: Rampart Range (7,000-9,000 ft ridge)

Objective: Characterize VHF signal persistence across extreme mountainous terrain 

The 88-Mile Challenge examined VHF propagation across an 88.33-mile obstructed path from Lookout Mountain (Denver) to the Pikes Peak International Raceway, with the Rampart Range (7,000–9,000 ft elevation) introducing significant terrain blockage and non-line-of-sight conditions.

A continuous 99.5 MHz transmission was used as a stable reference source to evaluate real-world attenuation relative to theoretical free-space path loss and line-of-sight assumptions. The analysis considered geometric path obstruction, diffraction effects over mountainous terrain, and summed theoretical path loss exceeding 110 dB.

Field observations demonstrated that, despite substantial terrain-induced attenuation, directional antenna gain and receiver system optimization materially influenced signal recoverability.

The results suggest that while large-scale topographical barriers impose severe degradation on VHF signals, practical link performance can exceed simplified line-of-sight expectations when system-level parameters are carefully engineered.

ADDITIONAL INFORMATION:

-4 Element Yagi-Uda used as control (Four Element Directional Outdoor FM Antenna 30-2460) +6dBi gain

-GQRX SDR software used with low-loss RG-6 Coax cable

-RTL SDR V4 used as an RF spectrum receiver

-RTL Low Noise Amplifier in series with feedline, immediately following antenna

-5V DC injection in RTL SDR using built-in Bias Tee

-Weather was kept as much of constant a variable as possible

-Observed received signal during midday (constant time)

-Propagation was analyzed during normal atmospheric and solar conditions with clear days

~Remarks: Intro RF project, complementary to HAM radio VHF propagation, moderate success.

overviewed by Dr. Paul Wikinson (SIEEE), in association with Pikes Peak Radio Amateur Association (PPRAA)

POTENTIAL SOURCES OF ERROR:

Non-Calibrated receiver

Unknown Transmitter ERP variations (may vary contingent upon time of day)

Multipath effects

Antenna Gain Uncertainty

* PLEASE NOTE: All equipment that was used was purchased by me for my 2025 Christmas money. Please understand that I am on a tight budget and did not have the resources to tightly control all variables. I have not gotten definitive quantitative measurements to be presented, heavily relying upon theory and online resources like those of Graphical Information Systems (GIS) and technical data.