[EE]:: RF Attenuation in Foliage

My Stack Exchange answer re RF Attenuation in Foliage
Properly formatted answer here
<https://electronics.stackexchange.com/a/766820/3288>
(https://electronics.stackexchange.com/a/766820/3288)

Also pasted below.
Main value is (probably) in the two ancient papes 1965 and 1978
Some other links also of possible interest.

zzzzzzzzzzzzzzzzzz

LORA websearch <https://tinyurl.com/LORARF>
LORA images with links to web pages here <https://tinyurl.com/LORARF2>

Best frequencies for foliage penetration web search
<https://www.google.com/search?q=what+rf+frequencies+best+penetrate+foliage%3F&rlz=1C1ONGR_enNZ1148NZ1149&oq=what+rf+frequencies+best+penetrate+foliage%3F&gs_lcrp=EgZjaHJvbWUyBggAEEUYOTIHCAEQIRigATIHCAIQIRigATIHCAMQIRigATIHCAQQIRiPAjIHCAUQIRiPAtIBCTExNzQyajBqNKgCALACAQ&sourceid=chrome&ie=UTF-8>


US military report which is both helpful and confusing - see fig 1 and 2.
Main useful point is that the lower the frequency the better (probably) the
results.
Here
<https://web.archive.org/web/20090524205748/http://stinet.dtic.mil/cgi-bin/GetTRDoc?AD=ADA055391&Location=U2&doc=GetTRDoc.pdf>
1978!

Older still Here <https://apps.dtic.mil/sti/tr/pdf/AD0648859.pdf> 1965
report - "The jungle as a communications network" (sounds good :-) ) MAY be
useful. See fig 1 and 2 .
"mc/s" in key = MHz.
A key point is that at short distances 2 MHz is much better than eg 100 MHz
but as range increases difference decreases.

_________________________________

**hcheung provided these references in a comment**

A Guide to Wildlife Tracking Technologies
<https://wildlifeactinnovations.com/wp-content/uploads/2021/05/A-Guide-to-Wildlife-Tracking-Technologies.pdf>
  -
37 pages

History of wildlife tracking technology - wikipedia
<https://wiki2.org/en/History_of_wildlife_tracking_technology>

Direction finding <https://wiki2.org/en/Direction_finding>  wikipedia

An introduction to directionj finding methodologies
<https://cdn.rohde-schwarz.com/am/us/campaigns_2/a_d/Intro-to-direction-finding-methodologies.pdf>
Rohde & Schwarz - 26 pages

Charts from olde papers.

https://i.sstatic.net/5Kauw6HO.png
https://i.sstatic.net/Ol8ZGZL1.png

____  Bad format version of SEEE post  ________________________

Directional aerials are highly desirable - in a fading environment. Signal
levels may vary with very slight receiver motion, or none at all, due to
multi-path signals through foliage which mutually interfere.

RSSI tells you signal strength at a point - you need to move to change the
strength and small distance changes are vanishingly hard to distinguish.

A directional receiver antenna - either scanned mechanically (preferred) or
based on rover direction, gives you significant directional information
from a single location, even with a quite broad antenna pattern.
"For extra points" a steered array antenna would be useful, but the
complexity and cost probably make a mechanically scanned aerial more
attractive. At eg 2.4 GHz a 10 dB scanner array is probably realistic.
Increasingly less so as frequency decreases.

Even at 100's of MHz aerials can be compact enough to make a rotary scanner
possible with quite a high gain aerial. At say 50 MHz and below antenna
sizes are liable to be increasingly cumbersome, unless loaded elements are
used which decrease antenna gain but may have advantages due to lower
foliage attenuation - see below.


As the transmitter is on the target hikers, small transmit aerial sizes are
desirable.
If you are using "legal" ISM (Industrial Scientific Medical band)
frequencies and power levels you may be restricted in regulatory allowed
transmit power levels. You probably want reduced duty cycle transmit to
reduce energy use.
Higher power pulses (maybe a few milliseconds) may allow higher effective
signal strength. In many administrations the absolute power allowed in the
2.4 GHZ band may be substantially higher than in other bands. This, and the
small aerial size, *may* make 2.4 GHZ more attractive despite higher
attenuation rates.

If you have not met "LORA" technology have a look.
LORA provides very long range in adverse conditions for given aerial and
power, at the expense of data rate.

Start [here](https://tinyurl.com/LORARF).
And [here](https://tinyurl.com/LORARF2) - every image links to a related
page.

A rover sounds like an autonomous land vehicle - if so, that would be a far
greater challenge to build than the RF tracking.
An aerial drone would be very much more capable - and easier and cheaper.

I mention LORA technology because, regardless of the vegetation answer,
LORA is reasonably likely to provide a good result for range for a given
frequency. It uses a complex spread spectrum modulation scheme and has
"best in class" range capability in adverse conditions. Increasingly good
results give lower data rates - not an issue here.
LORA modules are available off the shelf down to the ~ 460 MHZ ISM band.
Best results are probably achieved with frequencies well below where LORA
is easily avaiable BUT its characteristics may offset that.

For best frequencies for foliage penetration [start here](
https://www.google.com/search?q=what+rf+frequencies+best+penetrate+foliage%3F&rlz=1C1ONGR_enNZ1148NZ1149&oq=what+rf+frequencies+best+penetrate+foliage%3F&gs_lcrp=EgZjaHJvbWUyBggAEEUYOTIHCAEQIRigATIHCAIQIRigATIHCAMQIRigATIHCAQQIRiPAjIHCAUQIRiPAtIBCTExNzQyajBqNKgCALACAQ&sourceid=chrome&ie=UTF-8)
- there are a number of good looking links.

[Here](
https://web.archive.org/web/20090524205748/http://stinet.dtic.mil/cgi-bin/GetTRDoc?AD=ADA055391&Location=U2&doc=GetTRDoc.pdf)
is a 1978! US military report which is both helpful and confusing - see fig
1 and 2. Main useful point is that the lower the frequency the better
(probably) the results.

See link above for details

[![enter image description here][1]][1]

Older still [this](https://apps.dtic.mil/sti/tr/pdf/AD0648859.pdf) 1965
report - "The jungle as a communications network" (sounds good :-) ) MAY be
useful. See fig 1 and 2 .
"mc/s" in key = MHz.
A key point is that at short distances 2 MHz is much better than eg 100 MHz
but as range increases difference decreases.

See link above for details.

[![enter image description here][2]][2]

_________________________________

**hcheung provided these references in a comment**

[A Guide to Wildlife
Tracking Technologies
](
https://wildlifeactinnovations.com/wp-content/uploads/2021/05/A-Guide-to-Wildlife-Tracking-Technologies.pdf)
- 37 pages

[History of wildlife tracking technology - wikipedia](
https://wiki2.org/en/History_of_wildlife_tracking_technology)

[Direction finding](https://wiki2.org/en/Direction_finding)

**Godjhiyo provided this reference.**

[An Introduction to Direction Finding
Methodologies - Rohde & Schwarz](
https://cdn.rohde-schwarz.com/am/us/campaigns_2/a_d/Intro-to-direction-finding-methodologies.pdf)
- 26 pages

  [1]: https://i.sstatic.net/5Kauw6HO.png
  [2]: https://i.sstatic.net/Ol8ZGZL1.png