2017 SVHFS CONFERENCEApril 29, 2017

CHARLOTTE, NC

By: Ben Lowe, K4QF/K4VOW

TREESFOLIAGE ATTENUATION AT

V/UHF & MICROWAVE

TREES

“I THINK THAT I SHALL NEVER SEE, A

POEM AS LOVELY AS A TREE.”

– JOYCE KILMER, 1886-1918

A MOMENT OF HISTORY

REVISED HISTORY

RADIOS

“I THINK THAT I SHALL NEVER KNOW,

A POEM AS LOVELY AS A RADIO.”

– BEN LOWE, K4VOW/K4QF, 1958

IDEAL COMMUNICATIONS SYSTEM

E-SKIP

DUCTING

TROPOSCATTER

METEOR SCATTER

MOONBOUNCE

RAIN SCATTER

TOWER REFLECTIONS

AIRCRAFT REFLECTIONS

TRANSMITTER

RECEIVER

SIGNAL

GENERATION

& DETECTION

IMPEDANCE

MATCHING,

FOCUSING, &

COUPLING TO

PROPAGATION

MEDIA

PROPAGATING

MEDIA

REAL LIFE COMMUNICATIONS SYSTEM

TREES AND SHORT RANGE

FOLIAGE ATTENUATION

THE VIEW FROM DIXIE!

(OR JUST ABOUT ANYWHERE EAST OF THE MISSISSIPPI)

HOW MUCH ATTENUATION?

HIGHEST POINT IN SOUTH CAROLINA

SASSAFRAS MTN., 3554 ft. ASL, EM85ob

ANTENNA HEIGHT BELOW THE TREE LINE

EXAMPLES OF SHORT RANGE

FOLIAGE INTERFERENCE (1)

ROVING TO HIGH POINT BLOCKED BY TREES

EXAMPLES OF SHORT RANGE

FOLIAGE INTERFERENCE (2)

EME ANTENNA BELOW THE TREE LINE (@MY HOUSE)

EXAMPLES OF SHORT RANGE

FOLIAGE INTERFERENCE (3)

MOON

ATTENUATION MODELS; TAKE YOU CHOICE

METHODOLOGY

• OBTAIN SIGNALS ON THE FOLIAGE FREE PATH IN

APPROXIMATELY 6 dB STEPS. THIS IS USED AS A

“VALIDITY” CHECK.

• REPEAT SIGNAL MEASUREMENTS WITH TREES IN THE

PATH BY TURNING THE SOURCE ANTENNA 180 DEGREES

TO PROPAGATE THROUGH THE FOLIAGE USING THE

SAME INSTRUMENTATION.

• CHANGE TO THE NEXT FREQUENCY AND REPEAT

THE PROCESS.

• CALCULATE THE ATTENUATION JUST FROM THE FOLIAGE

TEST APPROACH FOR MEASUREMENTS

TWO SIGNAL PATHS; ONE WITH TREES, ONE WITHOUT

VIEW OF BOTH SIGNAL PATHS

FOLIAGE FREE PATH FOLIAGE PATH

TEST EQUIPMENT

SIGNAL SOURCE & SUPPLY ANTENNA

TEST EQUIPMENT (2)

CLOSEUP OF BATTERY ALONG WITH 10 MHz SOURCE

RAW DATA

FREQUENCY 144 MHz 432 MHz1296 MHz

2304 MHz

5800 MHz

RANGE, ft. 100 200 400 100 200 400 100 200 400 100 200 400 100 200 400

FREE SPACESIGNAL, dBm -60 -68 -75 -60 -66 -72 -69 -74 -78 -50 -57 -61 -58 -65 -76

FOLIAGE PATHSIGNAL, dBm -60 -68 -75 -81 -98 -105 -71 -82 -90 -61 -74 -88 -79 -87 -97

MEASUREDFOLIAGEATTEUNATION, dB 0 0 0 21 32 33 2 8 12 11 17 27 21 22 21

DATA SUMMARY

0

10

20

30

40

0 1000 2000 3000 4000 5000 6000

ATTENUATION, dB

FREQUENCY, MHz

FOLIAGE LOSS VS. FREQUENCY

100 Ft. 200 Ft. 400 Ft.

144 432 1296 2304 5760

144 432 1296 2304 5760

SURPRISE FINDINGS

• 144 MHz ATTENUATION WAS NEGLIGIBLE.

• 432 MHz ATTENUATION APPEARED TO BE HIGHEST OF

ALL FREQUENCIES TESTED.

• 2304 MHz WAS ANTICIPATED TO BE THE HIGHEST

ATTENUATION AS THIS IS THE FREQUENCY USED FOR

MICROWAVE COOKING; I.E. WATER MOLECULE

EXCITATION. IT WAS NOT!

• 5760 MHz ATTENUATION DID NOT APPEAR TO BE VERY

RANGE DEPENDANT AS IF THOSE WAVELENGTHS

PASSED THROUGH THE FOLIAGE.

PERTINENT POINTS

WHAT DOES IT ALL MEAN?

MODE S/N CONDITIONSFM 20 dB (FULL QUIETING)SSB 10 dB (GOOD COPY)CW* - 3 dB (EVERY OPERATOR)CW* -10 dB (BEST OPERATORS)

* - Adjusted for optimum tone ~ 700 Hz

* - Adjusted for optimum speed 10 - 12 wpm

COLLINS RADIO WEAK SIGNAL TEST, ~1964

REAL LIFE COMMUNICATIONS SYSTEM

PERSONAL TESTIMONY(NOT SCALPH’S INDIAN RIVER MEDICINE, NOT

CARTER’S LITTLE LIVER PILLS, AND NOT HATICOL)

WINDROCK MTN. ~ 3500 Ft. ASL

POSITION #1DIRECTION TO

W4ZRZ (200 mi.),20 WATTS CW, 1296 MHz, SIGNAL JUST AT THE NOISE LEVEL

POSITION #2DIRECTION TO

W4ZRZ (200 mi.),20 WATTS SSB, 1296 MHz, S-4 TO S-5

SIGNAL, 100% COPY

• ALL OPERATIONS ABOVE 2 METERS SHOULD BE FREE

OF FOLIAGE, ESPECIALLY 432 MHz.

• FOLIAGE ATTENUATION TESTS SHOULD BE REPEATED

BY A “TEAM” SO THAT PARTICIPANTS CAN BE ON

BOTH ENDS OF THE PATH TO ADJUST FREQUENCIES

AND AIM SOURCE ANTENNA. (THIS PROCESS IS

SOMEWHAT LABOR INTENSIVE FOR ONE PERSON.)

• WHEN REPEATING TESTING, INCLUDE 10 GHz.

EQUIPMENT WAS NOT AVAILABLE FOR THIS EFFORT.

• PUBLISH RESULTS TO BE AVAILABLE TO THE WEAK

SIGNAL COMMUNITY.

RECOMMENDATIONS

QUESTIONS?

THE REST OF THE STORY

RADIOSI think that I shall never know,a poem as lovely as a radio.

Where the tubes light up, and the dial does too.

And you can tune in the station that pleases you.

Just turn the dial and pick a station,For music, news, and weather information.

So anyone can plainly see,A radio is better than a tree!

© - K4VOW/K4QF, 1958