[Elecraft] [Bulk] 8 or5 Pole cw filters

[Mike Harris]

K3 with sub RX here.  Both with stock 2.7kHz and five pole 500Hz 
filters.  Not a contester but haunt DX and DXped piles.  I have a 
neighbour 300 metres away with a 9+60 signal from another brand 
transceiver that fills any band he is on with S5 noise, somewhat less on 
adjacent bands but still there.  Inclusion of a band filter between his 
transceiver and linear cures the adjacent band problem.  A visiting K3 
at the same location being used on SSB whilst I was on CW was not known 
to be on the band until I saw a spot.  A quick check revealed that I 
could get within +/- 35kHz before noise became a problem. At that point 
I was till copying a VE SSB mobile at S2-3 without difficulty.

The nice thing about the K3 is you can tell it lies about the filter 
setup, both width and offset.  Both my unmatched filter pairs have 
exactly the same offset, I told the K3 they had.  As far as I am aware 
this information is only used in the maths used to set the syth 
frequencies to make sure the filters are suitably positioned with 
respect to the desired audio passband.  A 500Hz filter passband window 
error of a few tens of Hz is not an issue.  I believe the "matched" 
filters are only good for 10Hz, could be wrong there.

Five pole works for me.

Regards,

Mike VP8NO


On 21/01/2015 02:55, Dr. William J. Schmidt, II wrote:
> Well let's be clear here...
>
> 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.   So the decision is driven more by the degree of loud stations operating adjacent to you... than by the type of operating you do.
>
>
> Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ
>
> Owner - Operator
> Big Signal Ranch – K9ZC
> Staunton, Illinois
>
> Owner – Operator
> Villa Grand Piton – J68HZ
> Soufriere, St. Lucia W.I.
> Rent it at: http://www.vrbo.com/487375
>
> email:  bill at wjschmidt.com
>
> -----Original Message-----
> From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Don Wilhelm
> Sent: Tuesday, January 20, 2015 11:23 PM
> To: Bill Coleman; Mike Zbrozek
> Cc: Elecraft
> Subject: Re: [Elecraft] [Bulk] 8 or5 Pole cw filters
>
> Bill,
>
> If you are not into 'hot and heavy' contesting or DXing in a pileup
> and/or diversity receive, you will find the 5 pole filters quite adequate.
>
> The "problem" is that the 8 pole filters have a better slope factor and
> do not have an offset.
> The offset is only important for diversity reception, and the slope
> factor is only important in situations where the band conditions are
> such that there are strong signals on adjacent frequencies -- as might
> be encountered in heavy contests or DX pileups.
>
> So if you are not interested in having the optimum receive capability in
> DX pileups and heavy contesting situations, save your $$$ and use the 5
> pole filters.  Some of us are more casual operators, and the $$$ savings
> can be significant.
>
> 73,
> Don W3FPR
>
> On 1/20/2015 11:17 PM, Bill Coleman wrote:
>>> On Jan 13, 2015, at 10:52 PM, Mike Zbrozek <k8xf4 at verizon.net> wrote:
>>>
>>> As a cw opr that is planning on buying a K3 next month I would
>>> like to know how many cw ops use/prefer 5 or 8 pole cw filters?
>>> Does anybody use the 1000 Hz 8 pole filter for hunting cq's then
>>> switch over to a 500 or 400 Hz filter? And how many cw ops use a sharper 200 or 250 Hz filter?
>>>
>>> Tnx in Advance
>>>
>>> Mike Zbrozek, K8XF
>> I’m going to buck the trend a little bit. I only have one 8-pole filter — the 13 kHz FM filter.
>>
>> I see posts from a lot of guys who have a radio full of 8-pole filters. That’s nice — if you can afford it. Those filters are expensive.
>>
>> During the five years I spent dreaming of owning a K3, I had thought I only wanted to have the 8-pole filters. However, my wife (the best XYL ever!) ordered a very stock K3 for me for Christmas, and it came with the 2700 Hz (5-pole) filter. Swapping out this filter after the fact for the 2800 (8-pole) filter is even more expensive than ordering it in the first place.
>>
>> Because of the expense, I used the stock filter for about six months before contemplating anything. I bought the 13 kHz filter because it gave me FM and AM receive and transmit capability. I got the 500 Hz (5-pole) filter because someone offered it on this list at a greatly discounted price.
>>
>> The key thing to remember about the K3 is that the DSP IS your filter! You don’t have to buy any of those expensive crystal filters. PERIOD. The radio works great with just the stock filter.
>>
>> Do the expensive crystal filters make a difference? Yes. The 500 Hz filter makes a difference. I’ve got it configured to kick in at 450 Hz. There’s a distinct difference in the audio background noise switching to 450 from 500. During the 160m CW contest, this filter knocks down a lot of adjacent channel interference. I’m glad I have a narrow roofing filter available for CW, PSK and RTTY work.