Wavelength Dependency in RF Propagation?

[Randy Yates]

In an article in a recent issue of Microwaves & RF magazine, Jack
Browne makes the following statement:

Frequency plays a part in any link budget, especially for longer links,
since long-distance links require the LONGER PROPAGATION DISTANCES of
larger-wave-length, lower-frequency signals rather than
smaller-wavelength, higher-frequency signals.

(emphasis mine).

I was miffed initially by this statement since, as far as I know, there
is nothing inherent in wavelength that impacts how RF waves travel
through space.

But I guess this was just a way (a confusing one, IMO) of referring to
the wavelength dependency of antenna aperture, as explained nicely
in this article on the Friis equation?

http://www.antenna-theory.com/basics/friis.php

@article{microwaves-and-rf-difference-between-long-and-short-haul-links,
title = "What's the Difference Between Long- and Short-Haul Links?",
author = "Jack Browne",
journal = "Microwaves \& RF Magazine",
month = "April",
year = "2018"}

[Marcel Mueller]

Post by Randy Yates
I was miffed initially by this statement since, as far as I know, there
is nothing inherent in wavelength that impacts how RF waves travel
through space.

If you are talking about vacuum then yes. In all other media the
velocity of propagation depends on the frequency. E.g. water molecules
in the air interact frequency dependent.

Post by Randy Yates
But I guess this was just a way (a confusing one, IMO) of referring to
the wavelength dependency of antenna aperture, as explained nicely
in this article on the Friis equation?

The coupling of the antenna to the free space also introduces a
frequency dependent group delay.
And last but not least a short distance link has some frequencies with
poor performance due to eigenvalues of the overall geometry.


Marcel

[Randy Yates]

Hi Marcel,

Thank you for responding and discussing.

Post by Marcel Mueller

Post by Randy Yates
I was miffed initially by this statement since, as far as I know, there
is nothing inherent in wavelength that impacts how RF waves travel
through space.

If you are talking about vacuum then yes. In all other media the
velocity of propagation depends on the frequency. E.g. water molecules
in the air interact frequency dependent.

Does the velocity of propagation affect path loss/attenuation?

Post by Marcel Mueller

Post by Randy Yates
But I guess this was just a way (a confusing one, IMO) of referring to
the wavelength dependency of antenna aperture, as explained nicely
in this article on the Friis equation?

The coupling of the antenna to the free space also introduces a
frequency dependent group delay.

I didn't know that. I can certainly see that group delay impacts the
overall response (namely, the phase response), but it doesn't cause
attenuatation.

I was mainly interested in attenutation.

Post by Marcel Mueller
And last but not least a short distance link has some frequencies with
poor performance due to eigenvalues of the overall geometry.

I love it! Applying linear algebra to wave propagation! Do you have
a reference (hopefully easy to read)?

[Les Cargill]

Post by Marcel Mueller

Post by Randy Yates
I was miffed initially by this statement since, as far as I know,
there is nothing inherent in wavelength that impacts how RF waves
travel through space.

If you are talking about vacuum then yes. In all other media the
velocity of propagation depends on the frequency. E.g. water
molecules in the air interact frequency dependent.

Post by Randy Yates
But I guess this was just a way (a confusing one, IMO) of referring
to the wavelength dependency of antenna aperture, as explained
nicely in this article on the Friis equation?

The coupling of the antenna to the free space also introduces a
frequency dependent group delay.

All necessary apologies in advance.

All group delay is inherently frequency dependent:

" Group delay is the actual transit time of a signal through a device
under test as a function of frequency."

http://na.support.keysight.com/pna/help/latest/Tutorials/Group_Delay6_5.htm

A reasonable definition.

I have the conceit that I'm not picking nits here so much as heading
off one potentially confusing interpretation of that
sentence :) The "quantifiers" for "a group delay" sort of leaves
the phrase "for all group delay" dangling.

Post by Marcel Mueller
And last but not least a short
distance link has some frequencies with poor performance due to
eigenvalues of the overall geometry.

Aka comb filtering/multipath/cosite interference?

Post by Marcel Mueller
Marcel

[Phil Hobbs]

Post by Les Cargill

Post by Marcel Mueller

Post by Randy Yates
I was miffed initially by this statement since, as far as I know,
there is nothing inherent in wavelength that impacts how RF waves
travel through space.

If you are talking about vacuum then yes. In all other media the
velocity of propagation depends on the frequency. E.g. water
molecules in the air interact frequency dependent.

Post by Randy Yates
But I guess this was just a way (a confusing one, IMO) of referring
to the wavelength dependency of antenna aperture, as explained
nicely in this article on the Friis equation?

The coupling of the antenna to the free space also introduces a
frequency dependent group delay.

All necessary apologies in advance.
" Group delay is the actual transit time of a signal through a device
under test as a function of frequency."
http://na.support.keysight.com/pna/help/latest/Tutorials/Group_Delay6_5.htm
A reasonable definition.

But unfortunately dead wrong because it ignores causality.
Group delay != true delay, in general.

Group delay is d phi / d omega, and is useful as a leading-order
approximation to how a nice wide smooth pulse propagates through a
network. It's exactly analogous with group velocity in radio or optical
propagation, which is d(omega)/d k, where k is the wave vector.

You can see the distinction in two ways. First, group delay can be
negative, which true delay cannot.

Second, networks can have group delay without having true delay. You
can undo the effect of a 1-pole RC lowpass with an RC highpass, for
instance.

Post by Les Cargill
I have the conceit that I'm not picking nits here so much as heading
off one potentially confusing interpretation of that
sentence :) The  "quantifiers" for "a group delay" sort of leaves
the phrase "for all group delay" dangling.

Post by Marcel Mueller
And last but not least a short
distance link has some frequencies with poor performance due to
eigenvalues of the overall geometry.

Aka comb filtering/multipath/cosite interference?

Post by Marcel Mueller
Marcel

Cheers

Phil Hobbs

[Phil Hobbs]

(This weirdly came up as a new message--silly me.)

Post by Phil Hobbs

Post by Les Cargill

Post by Marcel Mueller

Post by Randy Yates
I was miffed initially by this statement since, as far as I know,
there is nothing inherent in wavelength that impacts how RF waves
travel through space.

If you are talking about vacuum then yes. In all other media the
velocity of propagation depends on the frequency. E.g. water
molecules in the air interact frequency dependent.

Post by Randy Yates
But I guess this was just a way (a confusing one, IMO) of referring
to the wavelength dependency of antenna aperture, as explained
nicely in this article on the Friis equation?

The coupling of the antenna to the free space also introduces a
frequency dependent group delay.

All necessary apologies in advance.
" Group delay is the actual transit time of a signal through a device
under test as a function of frequency."
http://na.support.keysight.com/pna/help/latest/Tutorials/Group_Delay6_5.htm
A reasonable definition.

But unfortunately dead wrong because it ignores causality.
Group delay != true delay, in general.
Group delay is d phi / d omega, and is useful as a leading-order
approximation to how a nice wide smooth pulse propagates through a
network.  It's exactly analogous with group velocity in radio or optical
propagation, which is d(omega)/d k, where k is the wave vector.
You can see the distinction in two ways.  First, group delay can be
negative, which true delay cannot.
Second, networks can have group delay without having true delay.  You
can undo the effect of a 1-pole RC lowpass with an RC highpass, for
instance.

Post by Les Cargill
I have the conceit that I'm not picking nits here so much as heading
off one potentially confusing interpretation of that
sentence :) The  "quantifiers" for "a group delay" sort of leaves
the phrase "for all group delay" dangling.

Post by Marcel Mueller
And last but not least a short
distance link has some frequencies with poor performance due to
eigenvalues of the overall geometry.

Aka comb filtering/multipath/cosite interference?

Post by Marcel Mueller
Marcel

Cheers
Phil Hobbs

[boB]

On Sat, 26 May 2018 01:40:39 -0400, Randy Yates

Post by Randy Yates
In an article in a recent issue of Microwaves & RF magazine, Jack
Frequency plays a part in any link budget, especially for longer links,
since long-distance links require the LONGER PROPAGATION DISTANCES of
larger-wave-length, lower-frequency signals rather than
smaller-wavelength, higher-frequency signals.
(emphasis mine).
I was miffed initially by this statement since, as far as I know, there
is nothing inherent in wavelength that impacts how RF waves travel
through space.
But I guess this was just a way (a confusing one, IMO) of referring to
the wavelength dependency of antenna aperture, as explained nicely
in this article on the Friis equation?
http://www.antenna-theory.com/basics/friis.php
@article{microwaves-and-rf-difference-between-long-and-short-haul-links,
title = "What's the Difference Between Long- and Short-Haul Links?",
author = "Jack Browne",
journal = "Microwaves \& RF Magazine",
month = "April",
year = "2018"}

I don't suppose he could have been referring to ground wave or
ionospheric propagation associated with low frequency transmissions
?..... Or, how higher frequencies have more of a line of site
characteristic ?

boB

[Eric Jacobsen]

On Sat, 26 May 2018 01:40:39 -0400, Randy Yates

Post by Randy Yates
In an article in a recent issue of Microwaves & RF magazine, Jack
Frequency plays a part in any link budget, especially for longer links,
since long-distance links require the LONGER PROPAGATION DISTANCES of
larger-wave-length, lower-frequency signals rather than
smaller-wavelength, higher-frequency signals.
(emphasis mine).
I was miffed initially by this statement since, as far as I know, there
is nothing inherent in wavelength that impacts how RF waves travel
through space.
But I guess this was just a way (a confusing one, IMO) of referring to
the wavelength dependency of antenna aperture, as explained nicely
in this article on the Friis equation?
http://www.antenna-theory.com/basics/friis.php

For the most part you're right, the frequency effects are
predominantly associated with antenna characteristics. I wrote and
article about it about a decade ago:

https://www.dsprelated.com/showarticle/62.php

There are some atmospheric effects, etc., that are frequency
dependent, and materials penetration/reflection is frequency
dependent, but for the most part free space propagation is independent
of frequency.

[g***@gmail.com]

Post by boB
On Sat, 26 May 2018 01:40:39 -0400, Randy Yates

Post by Randy Yates
In an article in a recent issue of Microwaves & RF magazine, Jack
Frequency plays a part in any link budget, especially for longer links,
since long-distance links require the LONGER PROPAGATION DISTANCES of
larger-wave-length, lower-frequency signals rather than
smaller-wavelength, higher-frequency signals.
(emphasis mine).
I was miffed initially by this statement since, as far as I know, there
is nothing inherent in wavelength that impacts how RF waves travel
through space.
But I guess this was just a way (a confusing one, IMO) of referring to
the wavelength dependency of antenna aperture, as explained nicely
in this article on the Friis equation?
http://www.antenna-theory.com/basics/friis.php

For the most part you're right, the frequency effects are
predominantly associated with antenna characteristics. I wrote and
https://www.dsprelated.com/showarticle/62.php
There are some atmospheric effects, etc., that are frequency
dependent, and materials penetration/reflection is frequency
dependent, but for the most part free space propagation is independent
of frequency.

I find that interesting. I am always told that using higher frequencies means lower distances. So what must you do to the antenna to fix things? eg if you are using wi-fi at 5 gig versus 2.4, the 2.4 one has greater coverage

[Eric Jacobsen]

Post by g***@gmail.com

Post by boB
On Sat, 26 May 2018 01:40:39 -0400, Randy Yates

Post by Randy Yates
In an article in a recent issue of Microwaves & RF magazine, Jack
Frequency plays a part in any link budget, especially for longer links,
since long-distance links require the LONGER PROPAGATION DISTANCES of
larger-wave-length, lower-frequency signals rather than
smaller-wavelength, higher-frequency signals.
(emphasis mine).
I was miffed initially by this statement since, as far as I know, there
is nothing inherent in wavelength that impacts how RF waves travel
through space.
But I guess this was just a way (a confusing one, IMO) of referring to
the wavelength dependency of antenna aperture, as explained nicely
in this article on the Friis equation?
http://www.antenna-theory.com/basics/friis.php

For the most part you're right, the frequency effects are
predominantly associated with antenna characteristics. I wrote and
https://www.dsprelated.com/showarticle/62.php
There are some atmospheric effects, etc., that are frequency
dependent, and materials penetration/reflection is frequency
dependent, but for the most part free space propagation is independent
of frequency.

I find that interesting. I am always told that using higher frequencies means lower distances. So what must you do to the antenna to fix things? eg if you are using wi-fi at 5 gig versus 2.4, the 2.4 one has greater coverage

Regulatory effects often matter more. e.g., in many regions the
maximum amount of allowed transmitted power for unlicensed devices is
different at 2.4GHz than it is at 5GHz. This can make more
difference in coverage area than propagation effects.

Nevertheless, a good 5GHz stick antenna will be smaller than a 2.4GHz
antenna, so it will collect less energy.

With a reflective, i.e., dish, antenna, higher frequencies means MORE
gain. Satellite and many fixed point-to-point applications that use
reflective, directive antennas like to go to higher frequency because
of this. In the old days the limitation was that the rf electronics
got prohibitively expensive as the frequency went up.

[m***@yahoo.com]

Post by Eric Jacobsen
With a reflective, i.e., dish, antenna, higher frequencies means MORE
gain. Satellite and many fixed point-to-point applications that use
reflective, directive antennas like to go to higher frequency because
of this. In the old days the limitation was that the rf electronics
got prohibitively expensive as the frequency went up.

here is marks rule of thumb..
depends on the type of antenna at each end of the link

omni to omni, lower frequencies are better
omni to dish frequency independent
dish to dish higher frequencies are better

(better means less spreading loss)

mark

[Steve Pope]

Post by Randy Yates
In an article in a recent issue of Microwaves & RF magazine, Jack
Frequency plays a part in any link budget, especially for longer links,
since long-distance links require the LONGER PROPAGATION DISTANCES of
larger-wave-length, lower-frequency signals rather than
smaller-wavelength, higher-frequency signals.
(emphasis mine).
I was miffed initially by this statement since, as far as I know, there
is nothing inherent in wavelength that impacts how RF waves travel
through space.
But I guess this was just a way (a confusing one, IMO) of referring to
the wavelength dependency of antenna aperture, as explained nicely
in this article on the Friis equation?

It's a pretty sloppy statement at best.

The Friis pathloss assumes 0 dBi antennas, and the aperture of
a 0 dBi antenna is about 0.05 times the wavelength squared.
(Some sources say 0.07.) The aperture of a parabolic dish is
roughly the area of the dish, so a given size dish has more
gain (in dBi) at shorter wavelengths. This is why space communications
uses short wavelengths.

The (perfectly executed) New Horizon mission to Pluto operated at 6 GHz.

I'm betting Jack Bronwe never worked on a space datalink? That
or they just slipped up when they wrote this.

Steve