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2.7 vs 2.8

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Edward R Cole

Re: 2.7 vs 2.8

When I ordered my K3, I opted for the 2.8 KHz 8-pole filter assuming
it had a better filter shape. Since I bought the aux Rx it got one,
too. I left room for a narrower SSB filter in the main radio (2.1 or
1.8 will be the question). I bought the 400-KHz for CW and man is it
sharp! I wanted the wider SSB bw for using it with wide spectrum
display sw (WSJT, ARGO, SpectraJT) on my computer (for weak-signal
work: 600m and eme). Doing causal listening on 20m phone the DSP
controls work well. I tend to make a small shift and narrow down to
2.0 KHz. NR is working nice, too.

On my FT-847 I only had the stock SSB filter and DSP. I used the NR
there quite often, but the K3 NR seems less distorting. The filters
on the K3 run rings around the Ft-847 (no surprise).

I ordered two 13-KHz FM filters (extravagant) to get an even wider
spectrum display using sw (Linrad). This will be used with both Rx
locked to one VFO for dual-polarity diversity Rx on 2m using two
converters locked to the same LO. Linrad calculates the polarization
angle of the 2m signal when dual Rx is used.

I have wondered about getting the 200-Hz CW filter, but will see how
well the DSP+400 Hz filter do.

73, Ed - KL7UW
--------------------------------------------------------------------------------
Message: 31
Date: Mon, 12 Apr 2010 06:23:51 -0600
From: "Bill VanAlstyne W5WVO" <[hidden email]>
Subject: Re: [Elecraft] 2.7 vs 2.8
To: "David Ferrington, M0XDF" <[hidden email]>, "Bob Garceau"
<[hidden email]>
Cc: [hidden email]
Message-ID: <1C1781E7080B4D238DE2054A04AD9DF2@BILLHP9250>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=original

I think David has hit upon the crux of the matter with the tag line in his
sig: "There is no pillow so soft as a clear conscience." Will you be able to
tell the difference in actual single-receiver operation between the 2.7 kHz
5-pole and the 2.8 kHz 8-pole filters? Almost certainly not. But will it
make you feel more comfortable, knowing you have the better 8-pole filter in
all slots? Undoubtedly, based on reading between your lines! Is it worth the
cost differential? For you, sure, probably.

If and when I decide to buy the KRX3, I plan on replacing the 5-pole 2.7 kHz
filter in my main K3 with the 8-pole 2.8 kHz, along with an 8-pole in the
added KRX3. In the meantime, I'm finding the 5-pole filter works very
adequately. (I already have the 8-pole 1.8 kHz filter installed for narrow
SSB work, however, which works great in crowded bands.)

Bill W5WVO

73, Ed - KL7UW, WD2XSH/45
======================================
BP40IQ 500 KHz - 10-GHz www.kl7uw.com
500-KHz/CW, 144-MHz EME, 1296-MHz EME
DUBUS Magazine USA Rep [hidden email]
======================================

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Arie Kleingeld PA3A-2

Re: 2.7 vs 2.8

In reply to this post by bobgarceau

No need for 2.8

I have 2.7 in both main and sub rx. A joy to use. It is nice that it is just
a bit wider than the 2.8 for some broader audio.

73,
Arie PA3A

-----Oorspronkelijk bericht-----

Is is worth taking the hit and replacing the 2.7 khz 5 pole with the 2.8 khz
8 pole?

Bob, W1EQ

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Arie Kleingeld PA3A-2

the easy panadapter

In reply to this post by Edward R Cole

Hi all,

Just sharing this with you.

I have made a panadapter set-up with the K3. For many people nothing new,
but for me the first steps into SDR, and the fun thing is, at low cost.

The following set-up is working in my shack:
K3, IF-softrock pcb , Asus Xonar D1 soundcard , 2.6G Pentium IV computer(6yr
old), Power SDR-IF software.

This delivers a very nice and inexpensive panadapter with mouse point and
click tuning. Of course, it most probably does not have the super quality of
the lp-pan and emu soundcard combo or a P3(?.
BUT... IF you want to try out a panadapter with your K3, try this set-up.
Power-SDR-IF in combo with the K3 is absolutely wonderful, simply amazing.

Total cost (in EU: 14 euro for the softrock pcb and 55 euro for the
soundcard.)

73,
Arie PA3A

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Garry Shapiro

Re: 2.7 vs 2.8

In reply to this post by M0XDF

Apparently, from what has been previously discussed here, not all the
8-pole filters are "no offset" in practice and some models in particular
might benefit from offset adjustments. And one should not forget that
these filters are roofers. Unless money is no object, I would say to
leave the stock filter in place and add another, narrower SSB filter. As
to what its BW should be, there have been scads of opinions expressed on
that subject, as well.

Garry, NI6T

On 4/12/2010 5:05 AM, David Ferrington, M0XDF wrote:
> Since you seem to favour 8 pole, I'd say do it. You should be able to get a rebate on the 2.8kHz against the 2.7kHz.
> Also, if you are going to get the KRX3, it's simple to align the 8 pole filters - otherwise you need to tell Elecraft what the offset of your 2.7kHz is
>
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Don Wilhelm-4

Re: 2.7 vs 2.8

Garry,

The amount of the actual offset is small for the 8 pole filters. It is
not important on wide filters, but with the more narrow ones, it becomes
increasingly important - so yes, for maximum performance in diversity
mode (and only in diversity mode) setting the offset midway between the
measured offset of each filter is a prudent thing to do - although I
would not bother with anything wider than a 1 kHz filter - the offset
expressed as a percentage of the filter width is the 'telling' parameter
- 10 Hz at 2.8 kHz is only 0.34% which is insignificant, but 10 Hz at
250 Hz is 4% which is significant.

It is easy to determine the actual filter center (the K3 has the AFV and
dBV displays built-in) - just scan through the response to a constant
signal input level to the K3 to see where the -3 (or -6) dB points are
(the filter center is midway between those two points). Ifyou do not
have an XG2 or other signal generator, run another transmitter into a
dummy load and pick up an S-6 level signal with a short 'antenna wire'
on the K3. Nothing exotic is needed with a little bit of thought put
into what needs to be accomplished.

73,
Don W3FPR

Garry Shapiro wrote:

> Apparently, from what has been previously discussed here, not all the
> 8-pole filters are "no offset" in practice and some models in particular
> might benefit from offset adjustments. And one should not forget that
> these filters are roofers. Unless money is no object, I would say to
> leave the stock filter in place and add another, narrower SSB filter. As
> to what its BW should be, there have been scads of opinions expressed on
> that subject, as well.
>
> Garry, NI6T
>
> On 4/12/2010 5:05 AM, David Ferrington, M0XDF wrote:
>
>> Since you seem to favour 8 pole, I'd say do it. You should be able to get a rebate on the 2.8kHz against the 2.7kHz.
>> Also, if you are going to get the KRX3, it's simple to align the 8 pole filters - otherwise you need to tell Elecraft what the offset of your 2.7kHz is
>>
>>
> ______________________________________________________________
> Elecraft mailing list
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>

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Garry Shapiro

Re: 2.7 vs 2.8

Don,

Yes, I was mostly concerned with my 400 Hz filters, which are the
narrowest I have.

I do have an XG2 that I won at Dayton--still un-assembled. And I can
handle the procedure you outlined. Thanks for the response.

Garry

On 4/12/2010 4:27 PM, Don Wilhelm wrote:

> Garry,
>
> The amount of the actual offset is small for the 8 pole filters. It
> is not important on wide filters, but with the more narrow ones, it
> becomes increasingly important - so yes, for maximum performance in
> diversity mode (and only in diversity mode) setting the offset midway
> between the measured offset of each filter is a prudent thing to do -
> although I would not bother with anything wider than a 1 kHz filter -
> the offset expressed as a percentage of the filter width is the
> 'telling' parameter - 10 Hz at 2.8 kHz is only 0.34% which is
> insignificant, but 10 Hz at 250 Hz is 4% which is significant.
>
> It is easy to determine the actual filter center (the K3 has the AFV
> and dBV displays built-in) - just scan through the response to a
> constant signal input level to the K3 to see where the -3 (or -6) dB
> points are (the filter center is midway between those two points).
> Ifyou do not have an XG2 or other signal generator, run another
> transmitter into a dummy load and pick up an S-6 level signal with a
> short 'antenna wire' on the K3. Nothing exotic is needed with a
> little bit of thought put into what needs to be accomplished.
>
> 73,
> Don W3FPR
>
> Garry Shapiro wrote:
>> Apparently, from what has been previously discussed here, not all the
>> 8-pole filters are "no offset" in practice and some models in
>> particular might benefit from offset adjustments. And one should not
>> forget that these filters are roofers. Unless money is no object, I
>> would say to leave the stock filter in place and add another,
>> narrower SSB filter. As to what its BW should be, there have been
>> scads of opinions expressed on that subject, as well.
>>
>> Garry, NI6T
>>
>> On 4/12/2010 5:05 AM, David Ferrington, M0XDF wrote:
>>> Since you seem to favour 8 pole, I'd say do it. You should be able
>>> to get a rebate on the 2.8kHz against the 2.7kHz.
>>> Also, if you are going to get the KRX3, it's simple to align the 8
>>> pole filters - otherwise you need to tell Elecraft what the offset
>>> of your 2.7kHz is
>> ______________________________________________________________
>> 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
>>
>

Brett Howard

Re: 2.7 vs 2.8 vs 1.8 & 2.1

In reply to this post by Bill K9YEQ

Before you plunge have you seen that there are 1.5's available?

~Brett

On Mon, 2010-04-12 at 14:56 -0500, Bill K9YEQ wrote:

> Skip my question.... should have read the archives first. I have my
> answer... 1.8 for me.
>
> Bill
> K9YEQ
>
>
> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Bill K9YEQ
> Sent: Monday, April 12, 2010 2:47 PM
> To: 'David Ferrington, M0XDF'; 'Bob Garceau'
> Cc: [hidden email]
> Subject: Re: [Elecraft] 2.7 vs 2.8 vs 1.8 & 2.1
>
> I am using a pair of 8 pole 2.8 and am very happy. There is at times tons
> of qrm on 75 meters in the evening. Question: Is anyone using the 2.8 and
> 2.1/1.8 filters and what is the on-the-air experience?
>
> Bill
> K9YEQ
>
> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of David Ferrington,
> M0XDF
> Sent: Monday, April 12, 2010 7:06 AM
> To: Bob Garceau
> Cc: [hidden email]
> Subject: Re: [Elecraft] 2.7 vs 2.8
>
> Since you seem to favour 8 pole, I'd say do it. You should be able to get a
> rebate on the 2.8kHz against the 2.7kHz.
> Also, if you are going to get the KRX3, it's simple to align the 8 pole
> filters - otherwise you need to tell Elecraft what the offset of your 2.7kHz
> is

Jim Brown-10

Re: 2.7 vs 2.8

In reply to this post by k6dgw

On Mon, 12 Apr 2010 11:24:54 -0700, Fred Jensen wrote:

>I thought the xtal roofing filter[s] are at the 1st IF [~8 MHz], and
>their purpose is to restrict the passband coming out of the 1st mixer so
>that strong adjacent signals don't make it to the 2nd mixer and DSP.
>Thus, it seems to me that tweaking the roofing filters will only have
>noticeable effects if you are plagued with very strong neighbors close
>in on your frequency ... often.

You're sort of right, Fred, but there's a bit more to it. While the
PRIMARY function of a roofing filter is to protect the DSP from overload
by strong signals off frequency, the roofing filter cascades with the
response of the DSP filter. That is, the total rejection by the filters
is the rejection of the roofer PLUS the rejection of the DSP. When the
two filters are of comparable bandwidth, the result is considerably
better rejection of strong interfering signals.

As a simple example, consider a signal 300 Hz off frequency with a 400 Hz
roofing filter and 400 Hz DSP setting. If each filter is 7dB down at that
frequency, their combined (cascaded) response would be 14 dB down. Take
that out to 800 Hz and each might be 20dB down, combining to 40 dB. This
can be a very big deal when the interfering stations are 40dB over S9 and
you're trying to read an S5 signal, or when lots of big guns are squeezed
into a narrow DX window. :)

I started with 400 Hz filters as my narrowest roofers, and while I was
reasonably happy, I recently added 250 Hz 8-pole filters. For the reasons
noted above, I'm very glad that I did.

BTW -- one good reason for using the 8-pole 2.8 kHz filter is that it's
alleged to be a bit flatter in the passband (less ripple) than the 5-pole
filter. Rigs with 2.7 kHz filters tend to have some incidental AM when
transmitting RTTY, and a flatter filter would help that. Other than that,
I can't think of a good reason for spending the money. I nearly always
run with a 1.8 kHz roofer for SSB contesting.

73,

Jim K9YC

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