8 or5 Pole cw filters

[Bill-3]

Hoorah!  I thought this is a technical forum - not an elitist venue. Can
we move on?

Flame if you want - it just warms the bandwidth and wastes your time.

Bill W2BLC K-Line

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[NK7Z]

Could we move this to the above topic please...  I was enjoying the
filter discussion...

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On Wed, 2015-01-21 at 08:58 -0500, W2BLC wrote:

> Hoorah!  I thought this is a technical forum - not an elitist venue. Can
> we move on?
>
> Flame if you want - it just warms the bandwidth and wastes your time.
>
> Bill W2BLC K-Line
>
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[w7aqk]

Hi All,

Maybe I misinterpreted the data, but when I selected my filters, I opted for the 8 pole 400 hz, plus the 5 pole 200 hz.  I selected the latter one simply because the actual width seemed more compatible in relation to what the 400 hz filter provided.  The 250 hz filter almost overlapped the 400 hz filter.  Besides, the 5 pole filters are not slouches!  The 8 pole filters may have somewhat steeper skirts, but not to the point that they make the 5 pole filters a bad idea, or a serious compromise.  In any event, I wasn’t trying to save the slight difference in cost.  However, maybe I erred in my assessment, which I often do!!!  I rarely have to go to the 200 hz filter, but when I do, it seems to do the job very nicely.

Dave W7AQK

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[Edward R Cole]

Since I operate very little on HF, then why did I buy the 8-pole filters?

Because:
1.  I figured they had steeper skirts for extreme operating
conditions where adjacent strong signals were encountered.  (very
rarely happens in my neighborhood though a multi- super contesting
station lies 10mi north of me).  But someday I may be operating
portable/mobile in the lower-48 where it will be appreciated.

2.  I bought the KRX3 sub-receiver; matched filters were recommended.
3.  I figured it would help re-sale value, someday.

I bought:
13-KHz for FM (on VHF)
2.8-KHz (K3 required either 5 or 8-pole SSB filter)
400-Hz CW
2.8-KHz for KRX3.

I wrongly bought an extra 13-KHz filter for the KRX3, not thinking
clearly that the KRX3 would not be used for FM - I sold it here on
the reflector after realizing my error.

In practise I mostly use the 2.8-KHz roofing filter and set bw with
the DSP, even on CW, which is mainly used for VHF or eme.  The 400-Hz
filter does appear to improve the sensitivity when running 200-Hz on
CW-eme.  Probably knocks down the noise bw of the receiver before the
A/D converters.

I avoid the HF contests and only participate in the Elecraft
Net.  Occasional psk-31 on 14.070, and very occasional general
chatting on (mostly 20m).  99% activity is eme oriented which is 90%
building/fixing and 10% operating.  QRV on 17-bands 600m/3cm.

73, Ed - KL7UW
http://www.kl7uw.com
     "Kits made by KL7UW"
Dubus Mag business:
     [hidden email]

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[Guy Olinger K2AV]

On Wed, Jan 21, 2015 at 12:55 AM, Dr. William J. Schmidt, II <
[hidden email]> wrote:

> These are roofing filters, so you will only notice a difference in
> adjacent frequency rejection of loud signals... so if you live out in the
> country and don't have any loud stations near you, it’s not likely you will
> ever perceive a difference between 5 pole and 8 pole filters.


Will beg to differ here. It certainly is not just the loud local at issue.
Another is the dB between the very weak desired IN-channel signal and the
very loud close-in UN-desired station that is just barely up or down from
you.

If I had a dollar bill for every time I was trying to copy a very weak 40m,
in-the-noise EU QRP station running a noodle antenna on the floor of his
basement, with a 10 kW mildly clicky Italian station up 300 Hz with a three
element beam up 180 feet aimed at the US, I could buy a lot of new
equipment.

Of course, we were using a five element full sized quad on 40m, but the K3
showing 45 over 9 for his signal seemed high. Between DX contests I did a
complete alignment and calibration. The next time I ran into that station
he was only (?) 40 over 9. Or maybe that was propagation. The ambient noise
was S4. That's S4 in the 350 Hz 8 pole filter ("250"). So I'll give the
argument the benefit of the doubt here call the QRP station S4, although
probably he was only S3 at best. That's a 65 dB difference (probably 70)
between the wanted and unwanted. What the 5 poles do NOT have, and the 8
poles DO have, is sharply steep skirts.

The problem is to drop 65-70 dB in about 170 Hz. And do it without tuning
off your run frequency. Knowing those kinds of situations, the other ops
would not let me put a rig with 5 pole filters on the line. The 8 pole 350
with the DSP at 350 drops 65 dB off center zero in 250 Hz. With the NB set
for medium key click cancel, that takes out my 40 over 9 up frequency
neighbor and most people calling him and allows me to strain to copy the
noodle QRP station with nothing but ambient noise as the enemy.

Do I need that in mild casual operating?  Heck no. But it serves me in many
more situations than just when I have another station within a quarter mile.

If I took my K3 out to the contest station with 5 pole filters for CW
running bandwidth, the other ops wouldn't let me put it on the line. It
would be an emergency spare only.

As for SSB contesting, I use the 8 pole 1.8 roofers, and it just barely
uncovers some signals from interference up and down.

73, Guy.
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[Eric Swartz - WA6HHQ]

This thread is closed. Joe's earlier posting was inappropriate and violated list
guidelines.

Please refrain from discussing this further. Please address complaints to the
list manager (me), rather than posting here.

73,

Eric
elecraft.com

On 1/21/2015 5:58 AM, W2BLC wrote:
> Hoorah! I thought this is a technical forum - not an elitist venue. Can we
> move on?
>
> Flame if you want - it just warms the bandwidth and wastes your time.
>
> Bill W2BLC K-Line

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[Eric Swartz - WA6HHQ]

This technical part of the discussion is of course, OK. My prior thread closure
just posted under this topic referred to the improper postings in reference to
maritime nets etc.

Carry on. :-)

73,

Eric
elecraft.com

On 1/21/2015 6:42 AM, dyarnes wrote:
> Hi All,
>
> Maybe I misinterpreted the data, but when I selected my filters, I opted for the 8 pole 400 hz, plus the 5 pole 200 hz.  I selected the latter one simply because the actual width seemed more compatible in relation to what the 400 hz filter provided.  The 250 hz filter almost overlapped the 400 hz filter.  Besides, the 5 pole filters are not slouches!  The 8 pole filters may have somewhat steeper skirts, but not to the point that they make the 5 pole filters a bad idea, or a serious compromise.  In any event, I wasn’t trying to save the slight difference in cost.  However, maybe I erred in my assessment, which I often do!!!  I rarely have to go to the 200 hz filter, but when I do, it seems to do the job very nicely.
>
> Dave W7AQK
>

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