On Thursday 03 May 2007 21:29:00 Lyle Johnson wrote:
In the olden days, analog radios would use two IF filters and slide them
back and forth against each other to form variable bandwidth filters.
Yes indeed.
My Eddystone EA12 receiver that I bought from Tom Roberts, G3YTO (SK 1985)
is a
With respect Larry I must disagree about the term roofing filter being
misleading. I completely agree that a narrow filter at the first IF is
desireable if not essential, and it could be identified as a roofing filter
in some instances - see below. This approach has been the norm in the design
Hi Geoff. My post was somewhat tongue-in-cheek, and it's mostly
semantics, but I would say that the K3 filter would be a roofing filter
or not depending on your settings. I guess my opinion is that if it's
set for the same BW as the 2nd IF, then its not a roofing filter, and if
it's set wider
Hi all:
The notation below (previously posted) is referring to the final
passband filter and NOT a roofing filter. You are trying to compare
apples and oranges.
I think you would be hard pressed to discern (in real use) a
difference between the 200 and 250 hz ROOFING filter, except in LOSS
I think, still, someone needs to define what a ROOFING
FILTER is. Say for sake of argument - I have a
passive or active or crystal filter - and it is to
be used as a ROOFING FILTER. Why is it called this?
Why is the filter itself, called a ROOFING FILTER?
And where does the adjective,
The term roofing filter has been around a long time, at least 20 years.
Usually used in the context of up-converting receivers, where the first
IF is 40.455 MHz, or 45.000 MHz or even higher. The term means the first
selective filter in the receiver. If the first IF is 30 MHz, the
roofing
Roofing filters - I think the term has more to do with marketing than
engineering. Other companies have made a big deal over having them and
people have come to think of them as something special.
They are little more than filters placed early in the RX signal path to
limit bandwidth ASAP. They
A lack of understanding is also shown in the FT-2000 Yahoo! group. A fine
document which explains traditional roofing filters is here:
http://www.qth.com/inrad/roofing-filters.pdf . The FT-2000 is an
up-conversion receiver (unless I've lost the plot again).
Elecraft's design is more subtle
Just cannot resist saying this Jack, the term roofing filter has certainly
been around for a long time - close to 50 years I believe, possibly longer.
I think that I first ran across the term being used to identify the first IF
filter in an Independent Sideband Receiver which the company for
One more data point on the term roofing filter.
I have a copy of the June 1981 RSGB Radio Communications magazine that
reviewed Drake's TR7.
It describes the design as follows:
A low-noise, wide-dynamic range amplifier is used at 48.05 MHz to
precede the 10-KHz wide roofing filter.
Marketing term, I tell ya, pushed extra hard by the sales folks at
YaeComWood. :-)
-Original Message-
... it describes the filter as a roofing filter although Drake does
not use the term in its technical manual.
___
Elecraft mailing list
Oh, and no I don't think I did an apples to oranges comparison. The
filters, whether placed early or late in the signal chain, have the same
effect on bandwidth and out-of-band signal rejection. What I compared
was 8 vs. 6 pole and that showed me some things that are applicable to
the 5 vs. 8
Irrespective of the original source of the term roofing filter, it seems
clear enough that whoever made it up wanted to imply the idea of protection,
which is the word used in the RSGB document. A ROOF is a first line of
protection against having nearby high-energy stuff from the outside world
I do not know where or when the term roofing filter first appeared, when I
first came across it in the late 1950s I was working in Canada. I suspect
that the term originated in N.America, most probably in connection with the
type of equipment which I mentioned, most of which was purchased by
-Original Message-
From: Brett gazdzinski [mailto:[EMAIL PROTECTED]
Sent: Thursday, May 03, 2007 2:02 PM
To: 'Fred (FL)'
Subject: RE: [Elecraft] 8 pole vs 5 pole..I knew this would happen
I think, in the past, it was the first filter,
before all the conversions.
When
Yes, that is exactly the point I was trying to make! You can have it as
you like it (I am speculating a bit about the control options in the
firmware, of course). Some people like a wider width at the first IF to
hear signals approaching, even if it opens the window for AGC blocking
or
Discussion List
Subject: Re: [Elecraft] 8 pole vs 5 pole..I knew this would happen
I think the term roofing filter is misleading. A narrow
filter at the
first IF protects a receiver even better than a roofing filter, so
there is nothing inherently distortion reducing in using a
wider
Oak, MI.
- Original Message -
From: Fred (FL) [EMAIL PROTECTED]
To: elecraft@mailman.qth.net
Sent: Thursday, May 03, 2007 12:55 PM
Subject: [Elecraft] 8 pole vs 5 pole..I knew this would happen
I think, still, someone needs to define what a ROOFING
FILTER is. Say for sake of argument
On Thu, 3 May 2007, Lyle Johnson wrote:
In the olden days, analog radios would use two IF filters and slide them back
and forth against each other to form variable bandwidth filters. This may be
some of the PBT you were referring to.
Being as technically adroit as your average cow pie, all
Yes, that is exactly the point I was trying to make! You can have it as
you like it (I am speculating a bit about the control options in the
firmware, of course). Some people like a wider width at the first IF to
hear signals approaching, even if it opens the window for AGC blocking
or
Given that I hardly ever, but maybe now and then operate SSB, and would
like to try other digital modes, what would suggest as a reasonable
approach to filters?
I'd start with the default 2.7 kHz filter. It'll handle the new, wider
digital modes like Olivia, and handle SSTV and digital
21 matches
Mail list logo
