With respect Ron, as far as I know the term Roofing Filter was in use many
years before up-conversion superhet receivers with a fist IF at VHF started
to appear in the market. It was at least fifty years ago when I first ran
across the term, which was used to describe the first IF filter used
Geoffrey Mackenzie-Kennedy wrote:
With respect Ron, as far as I know the term Roofing Filter was in use
many
years before up-conversion superhet receivers with a fist IF at VHF
started
to appear in the market.
Correct Geoff. The first up-conversion ham rigs were introduced in the
Bill and group - Can't say it was first, but has to be the first US
designed and produced ham rigs to use up conversion. The DRAKE TR-7
has no RF Amplifier and uses a diode ring up converter to 43 mhz as
the first IF. The design was in the late 60s, early 70s. Bob Drake and
his company
Racal's RA-17 was an up-converting receiver, with a first IF at 40 MHz.
However, the 40 MHz IF filter was wideband, with the real selectivity
applied at 1.6 MHz and 100 KHz. With the Wadley Loop tuning system, it
was an extremely advanced design for 1955, all done with vacuum tubes,
of course.
Thanks for the clarification Geoff.
The fellow with the original question asked what why he was still hearing
QRM even when using the 1.8 kHz crystal filter (presumably listening to SSB)
and David responded, The purpose of the roofing filter is...not to provide
selectivity.
I was respectfully
I purchased a K3 with the standard 2.7 Khz SSB filter plus the 1.8 Khz SSB
filter. I did not purchase a cw filter because I operate very little cw. But
that may change. The 2.7 is in slot #1 and the 1.8 is in slot #2. I know that
if I push the FILT button that I can switch filters. But I
Hi Mark
Try reducing the bandwidth further using the width control, then the DSP
filtering will be responsible for narrowing the bandwidth. You could also
try adjusting the shift control to slide the passband one way or the other.
Although I have all my filter slots filled, I never use the xfil
Hi,
I agree with forgetting about the XFIL button and use the passband controls
exclusively. But using SHIFT/WIDTH on SSB is very awkward as you constantly
have to touch up both controls. Use HiCut/LoCut instead. Leave LoCut at
300Hz and use HiCut as the QRM fighting tool. If you have the 1.8kHz
Subject: [Elecraft] Roofing Filter Usage
I purchased a K3 with the standard 2.7 Khz SSB filter plus the 1.8 Khz
SSB filter. I did not purchase a cw filter because I operate very
little cw. But that may change. The 2.7 is in slot #1 and the 1.8 is
in slot #2. I know that if I push the FILT button
The purpose of the roofing filter is to reduce receiver generated
distortion products, not to provide selectivity. Are you sure that that:
1) the strong signals are completely out of band;
2) the only distortion products are those generated by the K3 itself,
and not the transmitter.
That's why the Elecraft doesn't call the first I.F. crystal filters roofing
filters. Unlike some receivers, the first I.F. crystal filters in the K3
are there for selectivity to isolate the desired signal. That is further
enhanced in the second conversion with the variable DSP filter, but the
Unfortunately, they do. Personally I dislike the term.
For example:
A A narrow roofing filter -- compatible with the communications bandwidth
required -- will protect downstream stages. The K3's
shift/width/hicut/locut controls automatically select and properly
position the optimal
Good point Wes, but clearly Wayne used it in that context answering
someone's query who called the first I.F. filter by that name. He's picked
up that name (in parenthesis) in the latest Owner's manual as well in the
interest of communicating with people who think roofing simply means the
first
Yes, they do. Elecraft presents it's position on the term Roofing Filter here:
http://www.elecraft.com/K3/Roofing_Filters.htm
where the protective function is emphasized.
Bob NW8L
On Thu, Oct 28, 2010 at 5:37 PM, Wes Stewart n...@yahoo.com wrote:
Unfortunately, they do. Personally I dislike
That paper explains why Elecraft has begun to call it roofing when it is
not what most designers think of when they speak of a roofing filter.
Call it what you want, the primary function of the first I.F. crystal filter
in the K3 is selectivity.
The term roofing filter came into use when
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