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K3 filter performance

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DaveL G3TJP

K3 filter performance

Sorry to ask this of the list, but there's been so much comment on K3 filters, I seem to be going round in circles trying to find where, if anywhere, evaluations have been done on the 5-pole filters. I'm resigned to never getting my detectve's badge, Sherlock. HI!

Elecraft have (most of?) the 8-pole ones on the website but I'd like to compare those details with similar tests done on the 5-pole.

Also, there has been mention of variable filters. As new orders placed now are estimated for May shipping, perhaps the varibles would be available by then, so is there any technical information on them yet, please?

73 all. DaveL G3TJP
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Greg - AB7R

RE: K3 filter performance

I believe Eric will be posting plots for the 5-pole filters this week
sometime.

73
Greg
AB7R

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]]On Behalf Of David Lankshear
Sent: Sunday, January 27, 2008 9:11 AM
To: [hidden email]
Subject: [Elecraft] K3 filter performance

Sorry to ask this of the list, but there's been so much comment on K3
filters, I seem to be going round in circles trying to find where, if
anywhere, evaluations have been done on the 5-pole filters. I'm resigned to
never getting my detectve's badge, Sherlock. HI!

Elecraft have (most of?) the 8-pole ones on the website but I'd like to
compare those details with similar tests done on the 5-pole.

Also, there has been mention of variable filters. As new orders placed now
are estimated for May shipping, perhaps the varibles would be available by
then, so is there any technical information on them yet, please?

73 all. DaveL G3TJP
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Joe Subich, W4TV-3

RE: K3 filter performance

In reply to this post by DaveL G3TJP

David,

Some time ago I did a "numerical comparison" using the published
-6dB and shape factor values. Perhaps these will help until the
"official" lab results are published.

> 200 250 400 500
> -------------------------------------------------
> - 6dB 224 370 435 565 Hz
> -60dB 896 777 913 1751 Hz
> slope 6.22 3.77 4.43 10.98 Hz/dB
>
> -10dB 274 400 470 653 Hz
> -20dB 398 475 559 873 Hz
> -30dB 522 550 647 1092 Hz
> -40dB 647 626 736 1312 Hz
> -50dB 771 702 825 1531 Hz

In my opinion, the 200/500 pair is the best value. That
is reinforced by comments on IMD performance and receiver
design by people like Rob Sherwood. The only reason to
look at the 8-pole filters might be the need for a slightly
wider "narrow" filter if you were into RTTY (I don't know
if 224 Hz is too narrow for 170Hz shift RTTY - particularly
with fading and/or multipath). For a died in the wool
RTTY DXer, a steep sided 270 - 300 Hz filter would be nice
instead of 370 Hz from the "250 Hz" filter.

73,

... Joe, W4TV

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of David Lankshear
> Sent: Sunday, January 27, 2008 12:11 PM
> To: [hidden email]
> Subject: [Elecraft] K3 filter performance
>
>
> Sorry to ask this of the list, but there's been so much
> comment on K3 filters, I seem to be going round in circles
> trying to find where, if anywhere, evaluations have been done
> on the 5-pole filters. I'm resigned to never getting my
> detectve's badge, Sherlock. HI!
>
> Elecraft have (most of?) the 8-pole ones on the website but
> I'd like to compare those details with similar tests done on
> the 5-pole.
>
> Also, there has been mention of variable filters. As new
> orders placed now are estimated for May shipping, perhaps the
> varibles would be available by then, so is there any
> technical information on them yet, please?
>
> 73 all. DaveL G3TJP
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
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>
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com
>
>

Larry Molitor

RE: K3 filter performance

--- "Joe Subich, W4TV" <[hidden email]> wrote:
For a died in the
> wool
> RTTY DXer, a steep sided 270 - 300 Hz filter would
> be nice
> instead of 370 Hz from the "250 Hz" filter.

Over the years I've spent a lot of time looking at
this issue. My interest is primarily digging weak RTTY
DX out of the noise but I do occasionally get into a
contest.

I've played with a lot of radios and filters but most
of my real testing was done with a FT-980, a TS-2000,
and a FT-2000.

While I have seen good weak signal performance with a
250 Hz filter, it was the exception not the rule. As
an example, the improvement on the FT-980 going from
the stock SSB filter to the dual CW filter was
dramatic. But going to the 250 Hz CW filter lost about
6 dB in ability to properly decode weak RTTY signals.
It was even worse on signals that had polar flutter. I
no longer have the plots of these FT-980 filters but
as I recall, the 250 Hz filter was a bit peaky in the
middle and had poor group delay characteristics
extending well in from the corners.

As you say Joe, the determining factor is the passband
ripple/group delay. In a typical bandpass filter the
group delay goes to heck at the corners. But the shape
of the "corners" varies from filter to filter. I've
run a number of "ham filters" on a network analyzer
and plotted group delay. Seems like no two filters are
the same even if the same part number. This I believe
is due to ham filters being so cheap and manufacturing
process control being minimal to keep the sell price
down to what we can afford.

So I would say, if you have a 250 Hz filter, no matter
where it's placed in any radio, give it a try on very
weak signals. Switch between a wider filter and the
narrow filter and see if there is any degradation. If
not, use the narrow filter.

Other wise, plan on not using any filter less than 300
Hz in passband width (note - this is NOT the 6 dB down
width!!! very important!!) if you want optimum weak
signal performance.

The DSP filters and DSP modems following the IF
filters cannot re-constitute the "distorted" signal so
it is important to keep the RTTY (and CW) signals well
away from any spot in the passband that can cause
phase distortion and/or pulse stretching.

Detailed high resolution plots of the filter passbands
in question would make these decisions a lot easier.
(hint, hint)

73,

Larry - W7IUV

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Don Wilhelm-4

Re: K3 filter performance

Larry,

You are quite correct that all filters are not created equal. For
digital modes, the group delay is just as important (if not more
important) than a flat passband and steep filter skirts. In fact, those
filters with steep skirts often sacrifice group delay to achieve the
steep skirts - but I am generalizing here, and that may not be a
universal truth.

Unfortunately, group delay plots are not common for filters since steep
skirts seem to be the 'criteria of choice' for most amateurs. A
Gaussian to 6 dB filter has a nice rounded nose and gentle skirts, but
has a great group delay characteristic, OTOH, Cohn filters usually have
great skirts and poor group delay in the passband. Group delay will
make a difference in the ability to decode digital signals.

73,
Don W3FPR

Larry Molitor wrote:

> --- "Joe Subich, W4TV" <[hidden email]> wrote:
> For a died in the
>
>> wool
>> RTTY DXer, a steep sided 270 - 300 Hz filter would
>> be nice
>> instead of 370 Hz from the "250 Hz" filter.
>>
>
> Over the years I've spent a lot of time looking at
> this issue. My interest is primarily digging weak RTTY
> DX out of the noise but I do occasionally get into a
> contest.
>
> I've played with a lot of radios and filters but most
> of my real testing was done with a FT-980, a TS-2000,
> and a FT-2000.
>
> While I have seen good weak signal performance with a
> 250 Hz filter, it was the exception not the rule. As
> an example, the improvement on the FT-980 going from
> the stock SSB filter to the dual CW filter was
> dramatic. But going to the 250 Hz CW filter lost about
> 6 dB in ability to properly decode weak RTTY signals.
> It was even worse on signals that had polar flutter. I
> no longer have the plots of these FT-980 filters but
> as I recall, the 250 Hz filter was a bit peaky in the
> middle and had poor group delay characteristics
> extending well in from the corners.
>
> As you say Joe, the determining factor is the passband
> ripple/group delay. In a typical bandpass filter the
> group delay goes to heck at the corners. But the shape
> of the "corners" varies from filter to filter. I've
> run a number of "ham filters" on a network analyzer
> and plotted group delay. Seems like no two filters are
> the same even if the same part number. This I believe
> is due to ham filters being so cheap and manufacturing
> process control being minimal to keep the sell price
> down to what we can afford.
>
> So I would say, if you have a 250 Hz filter, no matter
> where it's placed in any radio, give it a try on very
> weak signals. Switch between a wider filter and the
> narrow filter and see if there is any degradation. If
> not, use the narrow filter.
>
> Other wise, plan on not using any filter less than 300
> Hz in passband width (note - this is NOT the 6 dB down
> width!!! very important!!) if you want optimum weak
> signal performance.
>
>

P.B. Christensen

K3 Sub-receiver

I just read Wayne's 1/16 update concerning progress made toward the release
of the K3 sub-receiver where he states in part:

"Isolation between the receivers is critical to usability. For example, if
you're listening to an extremely strong signal on one receiver, none of it
should leak into the other's I.F. After extensive testing, we concluded that
we were close, but needed more isolation."

Knowing that Wayne & Eric are immersed in the product launch, does anyone
know if the forthcoming KRX3 change will require existing K3 transceivers to
be modified? Or, is the isolation issue wholly determined by the
sub-receiver module and not the main receiver?

My apologies if this topic was already covered but I did not see this point
covered in the archives and boy was there a lot to filter after the
announcement. Tnx!

Paul, W9AC (K3 on order)

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WILLIS COOKE

Re: K3 Sub-receiver

I don't know the answer to that question Paul, but I
am an engineer. My best guess is that no one knows
the answer for sure until the problem is solved. I am
confident that they will do their best to confine the
changes to the sub-receiver module, but the best laid
plans of mice and men often go asunder. All that we
customers can do is let them do their work and hope
for the best.

Cookie, K5EWJ, 31 Xs on the calender since my K3
order.

--- Paul Christensen <[hidden email]> wrote:

> I just read Wayne's 1/16 update concerning progress
> made toward the release
> of the K3 sub-receiver where he states in part:
>
> "Isolation between the receivers is critical to
> usability. For example, if
> you're listening to an extremely strong signal on
> one receiver, none of it
> should leak into the other's I.F. After extensive
> testing, we concluded that
> we were close, but needed more isolation."
>
> Knowing that Wayne & Eric are immersed in the
> product launch, does anyone
> know if the forthcoming KRX3 change will require
> existing K3 transceivers to
> be modified? Or, is the isolation issue wholly
> determined by the
> sub-receiver module and not the main receiver?
>
> My apologies if this topic was already covered but I
> did not see this point
> covered in the archives and boy was there a lot to
> filter after the
> announcement. Tnx!
>
> Paul, W9AC (K3 on order)
>
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>

Stephen Prior

Remotely controlling a K2

In reply to this post by Don Wilhelm-4

Having just got around to installing skype, I thought I'd patch the audio
through from my K2 then via skype to a remote computer. I'm very pleased
with the sound of the audio as relayed over the internet and it has set me
wondering how I could remotely control my K2 as well as receiving audio via
skype. I'm only interested in rx at the moment.

The problem is this, at home we are exclusively (Intel) Macs but work is a
Windows environment. Not surprisingly, I have the audio working fine
between pc and mac versions of skype but I'm short of ideas as to how to
remotely control with running a PC on one end and a Mac on the other. I do
have XP on my mac but don't want to have to go down that road unless I
really have to!

Anyone been there and done it? I'd be grateful for any advice!

Thanks and 73

Stephen G4SJP

K1, K2 and K3 on order.

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David Fleming-2

Re: Remotely controlling a K2

I can get you half way there.

I've written a fairly full featured K2 control app for
Mac OS X that will control the K2 over a network. I've
been using iChat for the audio. I haven't tried Skype.
I enjoy lying in bed and working CW using my Macbook.
The K2 is downstairs being controlled by an iMac.
Works like a charm.

I haven't tried this, but it's written in REALBasic,
which is cross platform, so I should be able to
compile it for Windows and it should work. I would
probably have to do some tweaking to get the UI to
look right, but it should work. I'm presently knee
deep in getting the K3 Utility for Linux ready to go,
but if you can give me a few weeks, I'll see what I
can come up with. This has been on my to-do list for
some time now. I want to be able to work CW while I'm
at work (PeeCees only). :)

David, W4SMT

--- Stephen Prior <[hidden email]> wrote:

> Having just got around to installing skype, I
> thought I'd patch the audio
> through from my K2 then via skype to a remote
> computer. I'm very pleased
> with the sound of the audio as relayed over the
> internet and it has set me
> wondering how I could remotely control my K2 as well
> as receiving audio via
> skype. I'm only interested in rx at the moment.
>
> The problem is this, at home we are exclusively
> (Intel) Macs but work is a
> Windows environment. Not surprisingly, I have the
> audio working fine
> between pc and mac versions of skype but I'm short
> of ideas as to how to
> remotely control with running a PC on one end and a
> Mac on the other. I do
> have XP on my mac but don't want to have to go down
> that road unless I
> really have to!
>
> Anyone been there and done it? I'd be grateful for
> any advice!
>
> Thanks and 73
>
> Stephen G4SJP
>
> K1, K2 and K3 on order.
>
>
>
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>
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>

Barry McWilliams

Remotely controlling a K2

In reply to this post by Don Wilhelm-4

Here's a configuration that may work. It incorporates a K2 radio
control program running on your Mac and a means to control you Mac via
the Internet from your Windows operating system PCs. (You've got the
audio part figured out.)

1) Install a K2 control program on you Mac. This will allow you to
control the frequency, mode and other parameters of your K2. Here are
two possible programs.

a) David's (W4SMT) program that he mentioned here on the reflector
earlier today. (I don't know where it's available. This is the first
I've heard about his work ... sounds interesting.)

b) A program from NI5V ->
(http://www.machamradio.com/software/ni5v/mack2/index.html)

2) Install on you Mac a VNC (Virtual Network Computer) "server" that
allows you to capture your Mac's screen and keyboard. With this, you
can control your Mac, and thus it's applications from another computer
via the internet.

Here's a link to a free VNC servere for OSX ->
http://www.redstonesoftware.com/products/vine/server/index.html

3) Finally, you need a VNC "viewer" that runs on the Windows PCs to
connect to the above VNC "server", control you Mac and run K2 control
program.
Here's a link to a VNC "viewer" that run on Windows ->
http://www.realvnc.com/products/free/4.1/winvncviewer.html

Here's the schematic ...

Windows -> VNC Viewer -> internet -> VNC server -> K2 control program

Hope this gives you some ideas,

Barry, WK2S
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Jack Brindle

Re: Remotely controlling a K2

Just a warning here to be careful. VNCs are notorious for being
unsecure. You are probably OK on the Mac for quite a while, but the
Windows component may open up pandora's box. For this reason many, if
not most, companies have banned VNC from their internal networks.

Yeah, yuck!

On Jan 28, 2008, at 3:05 PM, Barry McWilliams wrote:

> Here's a configuration that may work. It incorporates a K2 radio
> control program running on your Mac and a means to control you Mac
> via the Internet from your Windows operating system PCs. (You've
> got the audio part figured out.)
>
> 1) Install a K2 control program on you Mac. This will allow you to
> control the frequency, mode and other parameters of your K2. Here
> are two possible programs.
>
> a) David's (W4SMT) program that he mentioned here on the
> reflector earlier today. (I don't know where it's available. This is
> the first I've heard about his work ... sounds interesting.)
>
> b) A program from NI5V -> (http://www.machamradio.com/software/ni5v/mack2/index.html
> )
>
> 2) Install on you Mac a VNC (Virtual Network Computer) "server" that
> allows you to capture your Mac's screen and keyboard. With this,
> you can control your Mac, and thus it's applications from another
> computer via the internet.
>
> Here's a link to a free VNC servere for OSX ->
> http://www.redstonesoftware.com/products/vine/server/index.html
>
> 3) Finally, you need a VNC "viewer" that runs on the Windows PCs to
> connect to the above VNC "server", control you Mac and run K2
> control program.
> Here's a link to a VNC "viewer" that run on Windows ->
> http://www.realvnc.com/products/free/4.1/winvncviewer.html
>
> Here's the schematic ...
>
> Windows -> VNC Viewer -> internet -> VNC server -> K2 control program
>
> Hope this gives you some ideas,
>
> Barry, WK2S
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David Fleming-2

Re: Remotely controlling a K2

In reply to this post by Barry McWilliams

The VNC thing should work. There may be some latency
issues, but maybe not. *Heed Jack's warning*. VNC's
can be very risky.

> David's (W4SMT) program
> (I don't know where it's available.

It's on my hard drive. :)

I've been meaning to release it, but I never got
around to it. Here are some screenshots.

http://sight.net/ik2

If there's enough interest, I'll bundle it up and make
it available for download.

David, W4SMT
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Bill VanAlstyne W5WVO

Re: K3 filter performance

In reply to this post by Don Wilhelm-4

All this leaves me wondering: What will be the best filter configuration (both
TX and RX) for running FSK441 on meteor scatter? In case you're unfamiliar:

"FSK441 uses four-tone frequency shift keying at 441 baud. The frequencies of
the audio tones are 882, 1323, 1764, and 2205 Hz. Each encoded character uses
three tone intervals and therefore requires 3/441 seconds (approximately 2.3
ms) for transmission. FSK441 accommodates an alphabet of 43 characters."
-- from the WSJT manual by Joe Taylor, K1JT

Bill W5WVO

Don Wilhelm wrote:

> Larry,
>
> You are quite correct that all filters are not created equal. For
> digital modes, the group delay is just as important (if not more
> important) than a flat passband and steep filter skirts. In fact,
> those filters with steep skirts often sacrifice group delay to
> achieve the steep skirts - but I am generalizing here, and that may
> not be a universal truth.
>
> Unfortunately, group delay plots are not common for filters since
> steep skirts seem to be the 'criteria of choice' for most amateurs. A
> Gaussian to 6 dB filter has a nice rounded nose and gentle skirts, but
> has a great group delay characteristic, OTOH, Cohn filters usually
> have great skirts and poor group delay in the passband. Group delay
> will make a difference in the ability to decode digital signals.
>
> 73,
> Don W3FPR
>
> Larry Molitor wrote:
>> --- "Joe Subich, W4TV" <[hidden email]> wrote:
>> For a died in the
>>
>>> wool
>>> RTTY DXer, a steep sided 270 - 300 Hz filter would
>>> be nice
>>> instead of 370 Hz from the "250 Hz" filter.
>>>
>>
>> Over the years I've spent a lot of time looking at
>> this issue. My interest is primarily digging weak RTTY
>> DX out of the noise but I do occasionally get into a
>> contest.
>>
>> I've played with a lot of radios and filters but most
>> of my real testing was done with a FT-980, a TS-2000,
>> and a FT-2000.
>>
>> While I have seen good weak signal performance with a
>> 250 Hz filter, it was the exception not the rule. As
>> an example, the improvement on the FT-980 going from
>> the stock SSB filter to the dual CW filter was
>> dramatic. But going to the 250 Hz CW filter lost about
>> 6 dB in ability to properly decode weak RTTY signals.
>> It was even worse on signals that had polar flutter. I
>> no longer have the plots of these FT-980 filters but
>> as I recall, the 250 Hz filter was a bit peaky in the
>> middle and had poor group delay characteristics
>> extending well in from the corners.
>>
>> As you say Joe, the determining factor is the passband
>> ripple/group delay. In a typical bandpass filter the
>> group delay goes to heck at the corners. But the shape
>> of the "corners" varies from filter to filter. I've
>> run a number of "ham filters" on a network analyzer
>> and plotted group delay. Seems like no two filters are
>> the same even if the same part number. This I believe
>> is due to ham filters being so cheap and manufacturing
>> process control being minimal to keep the sell price
>> down to what we can afford.
>>
>> So I would say, if you have a 250 Hz filter, no matter
>> where it's placed in any radio, give it a try on very
>> weak signals. Switch between a wider filter and the
>> narrow filter and see if there is any degradation. If
>> not, use the narrow filter.
>>
>> Other wise, plan on not using any filter less than 300
>> Hz in passband width (note - this is NOT the 6 dB down
>> width!!! very important!!) if you want optimum weak
>> signal performance.
>>
>>
> _______________________________________________
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> Elecraft web page: http://www.elecraft.com

Greg - AB7R

RE: K3 filter performance

Seems like anything from the 1.8 kHz on up to the supplied 2.7 should work
fine.

Greg
AB7R

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]]On Behalf Of Bill W5WVO
Sent: Monday, January 28, 2008 4:43 PM
To: [hidden email]; Larry Molitor
Cc: [hidden email]
Subject: Re: [Elecraft] K3 filter performance

All this leaves me wondering: What will be the best filter configuration
(both
TX and RX) for running FSK441 on meteor scatter? In case you're unfamiliar:

"FSK441 uses four-tone frequency shift keying at 441 baud. The frequencies
of
the audio tones are 882, 1323, 1764, and 2205 Hz. Each encoded character
uses
three tone intervals and therefore requires 3/441 seconds (approximately 2.3
ms) for transmission. FSK441 accommodates an alphabet of 43 characters."
-- from the WSJT manual by Joe Taylor, K1JT

Bill W5WVO

Don Wilhelm wrote:

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Larry Molitor

Re: K3 filter performance

In reply to this post by Bill VanAlstyne W5WVO

Since I have gone through the optimization of four
different radios for WSJT use, I can make some
suggestions.

As it turns out the same requirements apply to the
JT65 modes used for EME so you only need to have one
setup for any WSJT mode used for any propagation mode.

FSK441, JT65 A,B & C, and the new JT4 modes all
require a 2.7 kHz or greater bandwidth for optimum
performance both on TX and RX. Although the software
can compensate to some degree for passband amplitude
variations, the best performance will be obtained with
a perfectly flat passband for both TX and RX.

Even though the bandwidth of these modes is less than
the 2.7 kHz specified, you need to have the wide
filters to allow for doppler, radio drift, frequency
errors, etc. There is no downside to using the widest
filter possible for these modes as the detection
bandwidth inside the software is on the order of 1hZ!

Many EME operators use a SDR radio wide open at 96 or
192 kHz width and the beta software which will decode
multiple signals simultaneously in that passband.

Larry - W7IUV

--- Bill W5WVO <[hidden email]> wrote:

> All this leaves me wondering: What will be the best
> filter configuration (both
> TX and RX) for running FSK441 on meteor scatter? In
> case you're unfamiliar:
>
> "FSK441 uses four-tone frequency shift keying at 441
> baud. The frequencies of
> the audio tones are 882, 1323, 1764, and 2205 Hz.
> Each encoded character uses
> three tone intervals and therefore requires 3/441
> seconds (approximately 2.3
> ms) for transmission. FSK441 accommodates an
> alphabet of 43 characters."
> -- from the WSJT manual by Joe Taylor, K1JT
>
> Bill W5WVO
>
>
> Don Wilhelm wrote:
> > Larry,
> >
> > You are quite correct that all filters are not
> created equal. For
> > digital modes, the group delay is just as
> important (if not more
> > important) than a flat passband and steep filter
> skirts. In fact,
> > those filters with steep skirts often sacrifice
> group delay to
> > achieve the steep skirts - but I am generalizing
> here, and that may
> > not be a universal truth.
> >
> > Unfortunately, group delay plots are not common
> for filters since
> > steep skirts seem to be the 'criteria of choice'
> for most amateurs. A
> > Gaussian to 6 dB filter has a nice rounded nose
> and gentle skirts, but
> > has a great group delay characteristic, OTOH, Cohn
> filters usually
> > have great skirts and poor group delay in the
> passband. Group delay
> > will make a difference in the ability to decode
> digital signals.
> >
> > 73,
> > Don W3FPR
> >
> > Larry Molitor wrote:
> >> --- "Joe Subich, W4TV" <[hidden email]>
> wrote:
> >> For a died in the
> >>
> >>> wool
> >>> RTTY DXer, a steep sided 270 - 300 Hz filter
> would
> >>> be nice
> >>> instead of 370 Hz from the "250 Hz" filter.
> >>>
> >>
> >> Over the years I've spent a lot of time looking
> at
> >> this issue. My interest is primarily digging weak
> RTTY
> >> DX out of the noise but I do occasionally get
> into a
> >> contest.
> >>
> >> I've played with a lot of radios and filters but
> most
> >> of my real testing was done with a FT-980, a
> TS-2000,
> >> and a FT-2000.
> >>
> >> While I have seen good weak signal performance
> with a
> >> 250 Hz filter, it was the exception not the rule.
> As
> >> an example, the improvement on the FT-980 going
> from
> >> the stock SSB filter to the dual CW filter was
> >> dramatic. But going to the 250 Hz CW filter lost
> about
> >> 6 dB in ability to properly decode weak RTTY
> signals.
> >> It was even worse on signals that had polar
> flutter. I
> >> no longer have the plots of these FT-980 filters
> but
> >> as I recall, the 250 Hz filter was a bit peaky in
> the
> >> middle and had poor group delay characteristics
> >> extending well in from the corners.
> >>
> >> As you say Joe, the determining factor is the
> passband
> >> ripple/group delay. In a typical bandpass filter
> the
> >> group delay goes to heck at the corners. But the
> shape
> >> of the "corners" varies from filter to filter.
> I've
> >> run a number of "ham filters" on a network
> analyzer
> >> and plotted group delay. Seems like no two
> filters are
> >> the same even if the same part number. This I
> believe
> >> is due to ham filters being so cheap and
> manufacturing
> >> process control being minimal to keep the sell
> price
> >> down to what we can afford.
> >>
> >> So I would say, if you have a 250 Hz filter, no
> matter
> >> where it's placed in any radio, give it a try on
> very
> >> weak signals. Switch between a wider filter and
> the
> >> narrow filter and see if there is any
> degradation. If
> >> not, use the narrow filter.
> >>
> >> Other wise, plan on not using any filter less
> than 300
> >> Hz in passband width (note - this is NOT the 6 dB
> down
> >> width!!! very important!!) if you want optimum
> weak
> >> signal performance.
> >>
> >>
> > _______________________________________________
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> >
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> > Elecraft web page: http://www.elecraft.com
>
>

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Brett Howard

RE: Remotely controlling a K2

In reply to this post by Jack Brindle

I run VNC with no real problems. The secret is to only allow that port
access to specific IP addresses. Granted someone can spoof the IP and gain
access but a lot of different holes have to line up just right for someone
to first know what the number is and second know how to exploit the system.

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Jack Brindle
Sent: Monday, January 28, 2008 3:23 PM
To: Elecraft List
Subject: Re: [Elecraft] Remotely controlling a K2

Just a warning here to be careful. VNCs are notorious for being
unsecure. You are probably OK on the Mac for quite a while, but the
Windows component may open up pandora's box. For this reason many, if
not most, companies have banned VNC from their internal networks.

Yeah, yuck!

On Jan 28, 2008, at 3:05 PM, Barry McWilliams wrote:

(http://www.machamradio.com/software/ni5v/mack2/index.html

> )
>
> 2) Install on you Mac a VNC (Virtual Network Computer) "server" that
> allows you to capture your Mac's screen and keyboard. With this,
> you can control your Mac, and thus it's applications from another
> computer via the internet.
>
> Here's a link to a free VNC servere for OSX ->
> http://www.redstonesoftware.com/products/vine/server/index.html
>
> 3) Finally, you need a VNC "viewer" that runs on the Windows PCs to
> connect to the above VNC "server", control you Mac and run K2
> control program.
> Here's a link to a VNC "viewer" that run on Windows ->
> http://www.realvnc.com/products/free/4.1/winvncviewer.html
>
> Here's the schematic ...
>
> Windows -> VNC Viewer -> internet -> VNC server -> K2 control program
>
> Hope this gives you some ideas,
>
> Barry, WK2S
> _______________________________________________
> Elecraft mailing list
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-Jack Brindle, W6FB
=======================================================================

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David Woolley (E.L)

Re:K3 filter performance

In reply to this post by Larry Molitor

Larry Molitor wrote:

> The DSP filters and DSP modems following the IF
> filters cannot re-constitute the "distorted" signal so

Do not, rather than cannot.

Firstly, the Finite Impulse Response (FIR) filters used need not, and
are almost certainly constructed so that they do not, introduce any
group delay distortion of their own. That means that you can still use
narrow DSP filters, even if you have to compromise the roofing filter.

Moreover, it has been standard practice for at least a couple of
decades, to use adaptive versions of such filters mitigate group delay
distortion in telephone modems. In that context, they generally require
synchonrous transmission, because the standard adaptive equalizers only
fully cancel inter-symbol interference at the actual sampling points.
Although synchronous operation does make the adaptive process easier,
I'm not sure that the longer filters that can be implemented in modern
fast DSPs, combined with the relatively fixed distortion the the receive
filters, cannot compensate for non-synchronous signals.

--
David Woolley
"The Elecraft list is a forum for the discussion of topics related to
Elecraft products and more general topics related ham radio"
List Guidelines <http://www.elecraft.com/elecraft_list_guidelines.htm>
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GW0ETF

Re: K3 filter performance

In reply to this post by Don Wilhelm-4

Hi,

No mention has been made in this thread about group delay and the dsp filtering; my limited knowledge of dsp tells me that FIR filters are linear phase so does that mean we should be using the (newly selectable) FIR setting for data modes rather than the original IIR....?

73,

Stewart Rolfe, GW0ETF (K3 145)

Don Wilhelm wrote

Larry,

You are quite correct that all filters are not created equal. For
digital modes, the group delay is just as important (if not more
important) than a flat passband and steep filter skirts. In fact, those
filters with steep skirts often sacrifice group delay to achieve the
steep skirts - but I am generalizing here, and that may not be a
universal truth.

Unfortunately, group delay plots are not common for filters since steep
skirts seem to be the 'criteria of choice' for most amateurs. A
Gaussian to 6 dB filter has a nice rounded nose and gentle skirts, but
has a great group delay characteristic, OTOH, Cohn filters usually have
great skirts and poor group delay in the passband. Group delay will
make a difference in the ability to decode digital signals.

73,
Don W3FPR

ac0h

Re: Remotely controlling a K2

In reply to this post by Brett Howard

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Unless he's in a very small company, owns the company and doesn't mind
the risk, and/or works for someone who isn't paying any attention to
network security, "ain't no way that's going to happen" should be the
answer.
My company does allow remote connection but only through a properly
designed and secured (expensive) Cisco tunnel. It's how our remote users
connect back to the company network. It also takes about 2 weeks and a
long list of approvals. You basically have to prove,

#1. That you need it for company business.
#2. That your running approved, meaning taken apart byte by byte by our
apps engineers and scrutinized, software.

Failing either one of those conditions brings about the "ain't no way
that's going to happen" response from we network security types.

Brett Howard wrote:
| I run VNC with no real problems. The secret is to only allow that port
| access to specific IP addresses. Granted someone can spoof the IP and
gain
| access but a lot of different holes have to line up just right for someone
| to first know what the number is and second know how to exploit the
system.
|
|
| -----Original Message-----
| From: [hidden email]
| [mailto:[hidden email]] On Behalf Of Jack Brindle
| Sent: Monday, January 28, 2008 3:23 PM
| To: Elecraft List
| Subject: Re: [Elecraft] Remotely controlling a K2
|
| Just a warning here to be careful. VNCs are notorious for being
| unsecure. You are probably OK on the Mac for quite a while, but the
| Windows component may open up pandora's box. For this reason many, if
| not most, companies have banned VNC from their internal networks.
|
| Yeah, yuck!
|
|
| On Jan 28, 2008, at 3:05 PM, Barry McWilliams wrote:
|
|> Here's a configuration that may work. It incorporates a K2 radio
|> control program running on your Mac and a means to control you Mac
|> via the Internet from your Windows operating system PCs. (You've
|> got the audio part figured out.)
|>
|> 1) Install a K2 control program on you Mac. This will allow you to
|> control the frequency, mode and other parameters of your K2. Here
|> are two possible programs.
|>
|> a) David's (W4SMT) program that he mentioned here on the
|> reflector earlier today. (I don't know where it's available. This is
|> the first I've heard about his work ... sounds interesting.)
|>
|> b) A program from NI5V ->
| (http://www.machamradio.com/software/ni5v/mack2/index.html
|> )
|>
|> 2) Install on you Mac a VNC (Virtual Network Computer) "server" that
|> allows you to capture your Mac's screen and keyboard. With this,
|> you can control your Mac, and thus it's applications from another
|> computer via the internet.
|>
|> Here's a link to a free VNC servere for OSX ->
|> http://www.redstonesoftware.com/products/vine/server/index.html
|>
|> 3) Finally, you need a VNC "viewer" that runs on the Windows PCs to
|> connect to the above VNC "server", control you Mac and run K2
|> control program.
|> Here's a link to a VNC "viewer" that run on Windows ->
|> http://www.realvnc.com/products/free/4.1/winvncviewer.html
|>
|> Here's the schematic ...
|>
|> Windows -> VNC Viewer -> internet -> VNC server -> K2 control program
|>
|> Hope this gives you some ideas,
|>
|> Barry, WK2S

- --
R. Kevin Stover, ACØH
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jwsteven@concentric.net

RE: Remotely controlling a K2

In reply to this post by Barry McWilliams

Consider using a personal VPN such as Hamachi to tunnel your control
software through. It is encrypted end-to-end and works very well.

73 john k5js

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