Are you trying to be annoying, or just succeeding?
From: Josh Reynolds via Af
Sent: Sunday, October 26, 2014 10:14 PM
To: af@afmug.com
Subject: Re: [AFMUG] questions about filters
Then post the correct formula, IYHO, so it can be fixed.
Josh Reynolds, Chief Information Officer
SPITwSPOTS, www.spitwspots.com
On 10/26/2014 06:20 PM, Ken Hohhof via Af wrote:
That doesn’t address my complaints about the USE of those formulas. Do you
agree that WiFi bits/sec/Hz should be divided by 3 but LTE should not, because
of assumptions about frequency reuse? In the context of a WISP application
which may use GPS sync? How about assuming one spatial stream for WiFi but 8
for LTE? And what about treating LTE Advanced like a current technology but
802.11ac as a future technology?
And 802.11n is capable of more than 1.2 bits/sec/Hz. If the formula
disagrees with reality, it’s the formula (or the numbers plugged into the
formula) that must change, not reality. It’s not like a Looney Toons cartoon
where the character falls to the ground once you point out they can’t walk on
air.
From: Josh Reynolds via Af
Sent: Sunday, October 26, 2014 8:59 PM
To: af@afmug.com
Subject: Re: [AFMUG] questions about filters
The formulas are at the top of the chart.
Josh Reynolds, Chief Information Officer
SPITwSPOTS, www.spitwspots.com
On 10/26/2014 05:31 PM, Ken Hohhof via Af wrote:
I think those numbers are flawed. Especially dividing the 802.11n numbers
by 3 due to “frequency reuse” factor. And using SISO for 802.11n but 8x8 MIMO
for LTE. Not to mention using 802.11n and not 802.11ac.
Saying 802.11n is only good for 1.2 bits/sec/Hz is saying it can only do 24
Mbps in a 20 MHz channel. Hogwash.
From: Josh Reynolds via Af
Sent: Sunday, October 26, 2014 5:49 PM
To: af@afmug.com
Subject: Re: [AFMUG] questions about filters
Well...
http://en.wikipedia.org/wiki/Spectral_efficiency
802.11n has a spectral efficiency of around 1.2. LTE advanced has a
spectral efficiency of _30_.
If we could get some fairly cheap radio chipsets with even a 10-15 in
spectral efficiency at this point, we would probably all be incredibly happy.
Doing that would likely cause us to (A) Not be compatible with 802.11 (fine
by me), and (B) would require mass market adoption.
Josh Reynolds, Chief Information Officer
SPITwSPOTS, www.spitwspots.com
On 10/26/2014 02:40 PM, Mike Hammett via Af wrote:
That's what I was hoping for but I was told to sit down.
-----
Mike Hammett
Intelligent Computing Solutions
http://www.ics-il.com
----- Original Message -----
From: "Bill Prince via Af" mailto:af@afmug.com
To: af@afmug.com
Sent: Sunday, October 26, 2014 12:36:58 PM
Subject: Re: [AFMUG] questions about filters
Perhaps some innovation in improving efficiency? Maybe takes someone thinking
outside of the current box(es).
bp On 10/26/2014 9:55 AM, Chuck McCown via Af wrote:
I was just going to mention that. Make a clean signal and you don’t have to
filter so much. Anyone remember what a Class A amplifier is? (45% efficient at
best) Cavity filters?
I would think that in this day and age, you ought to be able to go DSP direct
to antenna up to a 5 volt p-p signal. Or if you had to use a PA, inject a
pre-distortion component. The cable TV guys have been dealing with these issues
for decades.
And then there is the issue with physical size of filters. A nice filter, with
decent response and low insertion loss is large. SAW filters are about as small
as you can get but they are higher loss than, for example, a waveguide filter
however they are maybe 1% of the volume.
You want a small radio that consumes very little power, then ... it will be
more noisy than a large radio that consumes more power. That said, modern tech
is unbelievable in performance and it just keeps getting better. Perhaps Chuck
will get to come to AnimalFarm this year and show us something fun.
From: Chuck Macenski via Af
Sent: Sunday, October 26, 2014 10:24 AM
To: af@afmug.com
Subject: Re: [AFMUG] questions about filters
Hi again,
Another factor that causes expense is the linearity of the final stage output
amplifiers...these puppies are linear for most modern radios and more linearity
= more cost and higher power consumption. I will stop now...
Chuck
On Sun, Oct 26, 2014 at 10:47 AM, Chuck Macenski < ch...@macenski.com > wrote:
Hi,
There are many questions (explicit and implicit) in your question. Focusing on
the tx side only (since we are talking about band edge), the filters you are
talking about are electromechanical. Do a wikipedia search on SAW filters and
you will get a sense for what you are dealing with. There are many other
factors involved in meeting band edge requirements and other filtering that is
or can be performed, but, the expense is often in the electromechanical
components.
Chuck
On Sun, Oct 26, 2014 at 1:45 AM, That One Guy via Af < af@afmug.com > wrote:
with the changes in the 5ghz rules, it may force innovation in filtering
technology to bring cost down, assuming the innovators arent stuck in a mindset
of the only thing that would work is what there is.
How do filters works?
Are there electronically adjustable filters?
Where does the cost come from on filters? It is not new technology, so recovery
of R&D on a new tech has long since past, what is it that drives the cost up?
Is it primarily a matter of it being something needed, so its more valuable, or
is it something in the physical properties of the filters that drives up the
cost?
Can you filter electronically a transmitter using something along the same
lines of noise cancelling headphones
