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mtruss

Filters

I have purchased a used K3, serial number 3000 or so, it has been sent back to Elecraft for updates etc and returned to me working great so far. I would like to update some things especially the roofing filters first so the question I would like to ask is Has anybody upgraded from the 2.7 five pole filter to the 2.8 eight pole filter? I understand the 8 pole is a wider filter with 3 more filtering crystals , does it make any difference in received audio? also could I use the fm filter for use in the am position. Any other suggestions would be appreciated.
Thanks
Mike W8FLT

Jim Brown-10

Re: Filters

On Mon,1/30/2017 5:21 PM, mtruss wrote:
> I have purchased a used K3, serial number 3000 or so, it has been sent back
> to Elecraft for updates etc and returned to me working great so far. I
> would like to update some things especially the roofing filters first so the
> question I would like to ask is Has anybody upgraded from the 2.7 five pole
> filter to the 2.8 eight pole filter?

I have 2.8 kHz filters in the main receiver in both of my K3s. I like
them because they're a bit flatter in the passband, which reduces the
incidental AM when I'm transmitting RTTY. The steeper skirts also do a
bit better in the presence of strong signals.
> I understand the 8 pole is a wider
> filter with 3 more filtering crystals , does it make any difference in
> received audio?

Not that you would notice.

> also could I use the fm filter for use in the am position.

I'll let Don or Wayne answer that with respect to TX. I don't TX AM,
but I sometimes tune down to the AM BC band to verify the directivity of
my RX antennas.

73, Jim K9YC
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Don Wilhelm

Re: Filters

In reply to this post by mtruss

Mike,

Unless you are doing SSB contesting, you will likely notice little
difference between the 2.7kHz and the 2.8kHz filters. The skirts on the
2.8kHz filter are a bit steeper than for the 2.7kHz.
If you have the subRX and want to do diversity receive, it would benefit
you to use the 2.8kHz filter in both the mainRX and the subRX.

Unless you have really critical ears, you will not notice a difference.

Yes, you can use the 13kHz filter for AM.

73,
Don W3FPR

On 1/30/2017 8:21 PM, mtruss wrote:

> I have purchased a used K3, serial number 3000 or so, it has been sent back
> to Elecraft for updates etc and returned to me working great so far. I
> would like to update some things especially the roofing filters first so the
> question I would like to ask is Has anybody upgraded from the 2.7 five pole
> filter to the 2.8 eight pole filter? I understand the 8 pole is a wider
> filter with 3 more filtering crystals , does it make any difference in
> received audio? also could I use the fm filter for use in the am position.
> Any other suggestions would be appreciated.
> Thanks
> Mike W8FLT
>
>
>
> --
> View this message in context: http://elecraft.365791.n2.nabble.com/Filters-tp7626294.html
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w0mu

Re: Filters

In reply to this post by mtruss

I would say stay with the 2.7. I have used both. I also have the 2.0
ssb filters. Unless you are a super serious SSB contester the 2.7 is
probably fine.

W0MU

On 1/30/2017 6:21 PM, mtruss wrote:

Joe Subich, W4TV-4

Re: Filters

In reply to this post by mtruss

> I would like to update some things especially the roofing filters
> first so the question I would like to ask is Has anybody upgraded
> from the 2.7 five pole filter to the 2.8 eight pole filter?

You will not notice any difference going from the 2.8 KHz to 2.7 KHz
filters. The ultimate bandwidth is determined by the DSP in the
second (15 KHz) IF and the roofing filter skirts don't make much
difference once they're down 30 - 40 dB.

If you're into serious SSB contesting you may want to add either
the 2.1 KHz or 1.8 KHz roofing filter for that additional protection
from strong adjacent channel signals but in most cases the adjacent
channel garbage is often transmitter IMD (splatter) that is actually
"on channel" and can't be rejected by any filtering.

> also could I use the fm filter for use in the am position.

Yes, he FM filter (13 KHz) can be used for both AM transmit and
receive. Note: even with the 13 KHz filter, the widest receive
bandwidth will be 4.2 KHz - not 6+ KHz - as the receiver audio
chain includes a sharp 4.25 KHz low pass "brick wall" audio filter
to limit artifacts from the digital to analog converter.

73,

... Joe, W4TV

On 1/30/2017 8:21 PM, mtruss wrote:

Bill Frantz

Re: Filters

In reply to this post by mtruss

Hi Mike and congratulations on the new-to-you K3.

When thinking about filters for the K3 or K3S remember that they
are roofing filters. The DSP code also filters the signal, so
unless you have a problem with nearby strong signals, the DSP
filtering may do everything you need. For example, when I find
very close CW signals, I may dial the DSP width down to 50 or
100 Hz, which frequently eliminates the interference. On the
other hand, during a contest when a local station is calling CQ
400 Hz up from the station I'm trying to work, the 250 Hz filter
is very helpful.

The FM filter can be used for AM operations.

My filter configuration is:

13 KHz FM filter
2.7 KHz 5 pole filter
2.1 KHz 8 pole filter for SSB
.25 KHz 8 pole filter for CW and digital operation

I just let the radio pick the right filter as I change the DSP
bandwidth. It all works very nicely during contests and DX chasing.

73 Bill AE6JV

On 1/30/17 at 5:21 PM, [hidden email] (mtruss) wrote:

>I have purchased a used K3, serial number 3000 or so, it has been sent back
>to Elecraft for updates etc and returned to me working great so far. I
>would like to update some things especially the roofing filters first so the
>question I would like to ask is Has anybody upgraded from the 2.7 five pole
>filter to the 2.8 eight pole filter? I understand the 8 pole is a wider
>filter with 3 more filtering crystals , does it make any difference in
>received audio? also could I use the fm filter for use in the
>am position. Any other suggestions would be appreciated.
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