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 <mailto:[email protected]>
*Sent:* Sunday, October 26, 2014 10:24 AM
*To:* [email protected] <mailto:[email protected]>
*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 <[email protected]
<mailto:[email protected]>> 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 <[email protected]
<mailto:[email protected]>> 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
--
All parts should go together without forcing. You must
remember that the parts you are reassembling were disassembled
by you. Therefore, if you can't get them together again, there
must be a reason. By all means, do not use a hammer. -- IBM
maintenance manual, 1925
