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Filters for K3?

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Martin-2

Filters for K3?

Elecrafters,
i am about to order filters for my K3 and would like to hear from the
group what filters i should go for.
I am a ragchewer as well as a contester, ssb & cw. Rarely data modes.
I do weak signal work on 160/80 cw.
I have
2.8khz ssb in main & sub
400hz cw in main & sub
Should i order the 200hz 5-pole filter for their narrower bandwith or
the 250hz 8-pole with steeper skirts? Add 2.1khz or 1.8khz for ssb?
What is your recommendation?
Should i add filters for both rx's (-> diversity) ?
If i go for the 5-pole filters,should they be matched by elecraft or is
there a method to tweak it in the K3 ?

Thanks

Martin

--

73, DM4iM

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N8CEP

Re: Filters for K3?

I have the 2.8/8-pole, the 1.8/8-pole and the 400/8-pole. So far I have not felt the need for a narrower CW filter although I have not contested with mine yet. I currently do not own the 2nd receiver.
73 Keith W8GX

On Dec 27, 2009, at 7:00 PM, Martin Schmiedel wrote:

> Elecrafters,
> i am about to order filters for my K3 and would like to hear from the
> group what filters i should go for.
> I am a ragchewer as well as a contester, ssb & cw. Rarely data modes.
> I do weak signal work on 160/80 cw.
> I have
> 2.8khz ssb in main & sub
> 400hz cw in main & sub
> Should i order the 200hz 5-pole filter for their narrower bandwith or
> the 250hz 8-pole with steeper skirts? Add 2.1khz or 1.8khz for ssb?
> What is your recommendation?
> Should i add filters for both rx's (-> diversity) ?
> If i go for the 5-pole filters,should they be matched by elecraft or is
> there a method to tweak it in the K3 ?
>
> Thanks
>
> Martin
>
> --
>
> 73, DM4iM
>
>
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

AC6JA

Re: Filters for K3?

In reply to this post by Martin-2

I have the 8-pole 2.8, 1.0, and 400 in both the main and sub receivers.
The only other one that I've been debating on is the AM filter. Otherwise
no regrets.

Mike AC6JA
K3 #03215

In a message dated 12/27/2009 4:27:25 P.M. Pacific Standard Time,
[hidden email] writes:

I have the 2.8/8-pole, the 1.8/8-pole and the 400/8-pole. So far I have
not felt the need for a narrower CW filter although I have not contested with
mine yet. I currently do not own the 2nd receiver.
73 Keith W8GX

On Dec 27, 2009, at 7:00 PM, Martin Schmiedel wrote:

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Don Wilhelm-4

Re: Filters for K3?

In reply to this post by Martin-2

Martin,

The DSP filters will handle most filtering needs for signals less than
S9+20 to S-9+30. However when the signals within the roofing filter
passband are greater than that level, the hardware AGC will be activated
and you will experience 'pumping' of the receiver gain even though you
are not hearing the signals within the roofing filter passband, but
outside the DSP filter passband.

So, consider the signal strength of signals that you are likely to
encounter during your periods of contesting and DXing, and that will
tell you which filters you will need. If you want insurance against
nearby strong signals, you may want a filter in the 250 Hz range as well
as one in the 400 Hz range for more casual CW operation. For SSB, go
for the 1.8 filter in addition to the 2.7 or 2.8 kHz filter if you will
be receiving in very crowded band conditions. I personally do h\not
think the 2.1 kHz filter offers much advantage over the 2.7 standard filter.

If you do not have the subRX installed, changing/adding filters is not a
big deal, so you may want to go with the minimum set until you get a
feel for what you actually need. With the subRX installed, you must
lift the subRX assembly to install filters in the main K3 board.

73,
Don W3FPR

Martin Schmiedel wrote:

Fred Atchley

Re: Filters for K3?

In reply to this post by Martin-2

Martin, I have the 2.8 for transmit which I believe gives me the best
likelihood of being heard. I like low-power contesting and due to CC&Rs I
use a stealth "mystery" antenna.

I also have the 2.1, 1.8, 400 and 200Hz 8-pole filters. By far my favorites
are the 2.1 and 400Hz because of their sharp edges and "easy listening"
characteristics. I seldom use the 1.8 or 200Hz but they are there if I need
them.

I do not have a sub RX.

73, Fred, AE6IC

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Richard Ferch

Re: Filters for K3?

In reply to this post by Martin-2

Martin,

As a general rule, before adding roofing filters I'd suggest that it
would be a good idea to first operate for a while with the DSP filtering
at the width of the proposed roofing filter to see whether you are
comfortable with that bandwidth. In the case of SSB, my understanding is
that you should narrow the bandwidth by reducing the HI cut and leaving
the LO cut unchanged, not by reducing the width and leaving the FC
unchanged.

If you are comfortable with a narrow bandwidth but find that nearby
strong signals are getting through your wider roofing filters and
causing IMD or gain pumping, then you should look for the narrowest
roofing filter that is the same as or wider than your preferred
operating DSP bandwidth. Remember that the purpose of the roofing
filters is not to set the filter bandwidth you listen with (the DSP
filters do that); it is to set the bandwidth outside which strong
signals will be rejected in order to give you the desired dynamic range.
If you don't need a lot of dynamic range at a particular signal
separation, then you don't need a roofing filter at that separation.

You should also consider how you use the sub-RX before deciding whether
to get two filters or only one for the main RX. In a pileup, you can use
either receiver to listen to the DX and the other one to listen to the
pileup (using the SPLIT button to control which VFO is used for
transmit), so if you have only one roofing filter at a particular
bandwidth you can decide which of the two frequencies needs it the most.
Of course, if you find yourself needing the close-separation dynamic
range at both frequencies, then you need both roofing filters.

If you already have the 400 Hz 9-pole filters, note that the 400 Hz
filter BW6 is 435 Hz and the 250 Hz BW6 is 370 Hz (look at the plots at
<http://www.elecraft.com/K3/K3_8_pole_plots.htm>). That's a rather small
difference, especially if you configure both roofing filters to switch
in at the next DSP bandwidth below the roofing filter's actual BW6. If
you really need narrower roofing filters because strong signals are
getting through inside the 400 Hz roofing filter bandpass but outside
the DSP filter bandpass, then I'd suggest you consider the 200 Hz filter
unless you never operate with bandwidths as low as 200 Hz.

The filter skirts probably do not matter, as the DSP filter skirts are
much steeper anyway.

If you need these roofing filters in both receivers, and if you will be
using bandwidths that narrow during diversity receive, then you should
probably purchase a pair of matched filters. There is no way for the
user to tweak this - you can pretend the offsets are the same in the
configuration, but if the hardware filter offsets are different enough,
that won't work, especially at 200 Hz bandwidth where even small
differences in the offset will make a large audible difference.

On the other hand, if you are operating with a 200 Hz DSP filter
bandwidth using a 200 Hz roofing filter in the main RX and a 400 Hz
roofing filter in the sub-RX, that might be OK for diversity receive. My
understanding, subject to correction as always, is that the offset
problem during diversity receive is most audible with two 5-pole filters
with slightly different offsets, rather than with one 5-pole and one
8-pole filter. Again, though, if you find yourself suffering from gain
pumping in the sub-RX because of very strong signals outside the DSP
filter but inside the sub-RX's roofing filter, that's when you will need
a narrower roofing filter in the sub-RX, and in that case you will want
to match its offset with the one in the main RX.

73,
Rich VE3KI

DM4IM wrote:

> i am about to order filters for my K3 and would like to hear from the
> group what filters i should go for.
> I am a ragchewer as well as a contester, ssb & cw. Rarely data modes.
> I do weak signal work on 160/80 cw.
> I have
> 2.8khz ssb in main & sub
> 400hz cw in main & sub
> Should i order the 200hz 5-pole filter for their narrower bandwith or
> the 250hz 8-pole with steeper skirts? Add 2.1khz or 1.8khz for ssb?
> What is your recommendation?
> Should i add filters for both rx's (-> diversity) ?
> If i go for the 5-pole filters,should they be matched by elecraft or is
> there a method to tweak it in the K3 ?

Philippe Trottet

Re: Filters for K3?

In reply to this post by Martin-2

Dear Martin,
I've ordered some days ago... and received yesterday the 6Khz for AM & ESSB and the 1.8K for SSB. So I installed them yesterday evening.
Considering my antenna, delta loop for 40m and the huge signals received for the ex-USSR side, 59+30 & up is common, the 1.8k in addition to the 2.8k is really helpful and I like the fact when moving the width knob it goes automatically from one filter to another. Just an example from yesterday as I made rx tests after installing the 1.8K, 2 x UA big guns were on 7.085 and 7.090 respectively and polluted the spectrum with very bad tuned amps with lot of splatters. With the K3 and the 8 pole filters I was able to distinguish and follow a qso on 7.088 performed by 2 M0 Hams. The shift was reduced on 1.00 and the bandwidth 1.6~1.7 with the 1.8K activated. Using the AFX for audio was also helpful.
Considering my cw traffic, the 400Hz is perfect for general purpose.

My actual config, all 8 poles filters
Main
FL1: 6K
FL2: 2.8K
FL3: 1.8K
FL4: 400Hz

Sub:
FL2: 2.8
FL4: 400Hz

Bst 73's & Happy New Year.

Philippe
A65BI (F5LTB)
K3#3616

>>> Martin Schmiedel <[hidden email]> 28-12-2009 4:00 >>>
Elecrafters,
i am about to order filters for my K3 and would like to hear from the
group what filters i should go for.
I am a ragchewer as well as a contester, ssb & cw. Rarely data modes.
I do weak signal work on 160/80 cw.
I have
2.8khz ssb in main & sub
400hz cw in main & sub
Should i order the 200hz 5-pole filter for their narrower bandwith or
the 250hz 8-pole with steeper skirts? Add 2.1khz or 1.8khz for ssb?
What is your recommendation?
Should i add filters for both rx's (-> diversity) ?
If i go for the 5-pole filters,should they be matched by elecraft or is
there a method to tweak it in the K3 ?

Thanks

Martin

--

73, DM4iM

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Arie Kleingeld PA3A-2

Re: Filters for K3?

In reply to this post by Martin-2

Main RX: 2.7 2.1 400 and 200
Sub RX: 2.7 2.1 400

Use of the filters:

Normal operation SSB: 2.7 (this filter is much wider than 2.7 but that's no
problem in normal band conditions)
Contest operation SSB: 2.1 (this is needed when the band is crowded)

Normal operation CW: 2.1 , listening on 500Hz BW or more (no need for other
filter if the band is normal). I use 400 if in QRM situation.
Contest operation CW: 400

Both sub and main filters have same offsets for diversity.

The 200 Hz in the main is for special occasions when the going really gets
tough in CW or data.

73 and happy new year all.

Arie PA3A

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Jim Brown-10

Re: Filters for K3?

In reply to this post by Martin-2

On Mon, 28 Dec 2009 01:00:08 +0100, Martin Schmiedel wrote:

>i am about to order filters for my K3 and would like to hear from the
>group what filters i should go for.

First, bear in mind that the DSP in the K3 does the IF filtering that
older rigs do with conventional LC circuitry, so the hardware filters
you buy are roofing filters that simply protect the DSP from getting
blown away by VERY strong signals.

I'm a serious contester, and also do some DXing. Not much rag-chewing.
I'm quite happy with the standard 2.7 kHz 5-pole, the 1.8kHz 8-pole,
and the 400 Hz 8-pole filters. IMO, the 1.8 kHz filter is far too
narrow for anything but contesting. It's really rather unpleasant to
listen to, but it does help with things are really rough. For casual
work, I'd give serious thought to either the 2.8 kHz or 2.1 kHz 8-pole
filters.

I have a second K3 so that I can do SO2R (single operator, two radio)
contesting. It has only the 400 Hz filter. I'm planning to take
advantage of Inrad's New Year's Day sale to add the 1.8kHz filter.

Whether to use 2.8 kHz 8-pole or 2.7 kHz 5-pole? Good question. I'd
like to hear from those who have tried both and critically compared
them. There IS a enough ripple in the 2.7kHz filter to cause
significant incidental AM of a RTTY signal (you will see a wattmeter
bounce a lot), and I'm told that the 2.8kHz filter has a lot less. I've
been told that it's also possible to tell the K3 to TX on RTTY through
the 1.8 kHz filter if you have one, and that this also reduces the
incidental AM. I should try that.

73,

Jim K9YC

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