Determining best roofing filter with DSP??

[callen1155]

Hello guys.

Sorry about all the questions but I think this is the last one before I press the "buy" button for a K3.

Once again a question about cw roofing filters.

I am initially ordering the K3 without the 2nd receiver but do plan on getting one within a year.

That said, and knowing it's best to have 'matching roofing filters' for both receivers, even after all the reading I still have no idea what would be the best roofing filter to get. It seems to be such an individual choice. Ideally, I'd prefer to purchase only one filter (or one for each receiver) and want to make the best filter choice for my operating.

So if I order the K3 with no roofing filters, can I determine from operating with just the DSP which cw roofing filter would be the optimal one for me.

Or is the above an exercise in futility and I just need to order say a 400 and see how that does before I'll know?
But then again I guess it wouldn't be 'matched'' when I get one for the second receiver.

Too many decisions!

thanks again.
chuck
af4xk

[Dick Dievendorff]

A 2.7 kHz 5-pole filter is included with each K3 and each KRX3.  (See the K3
price list/order form at http://www.elecraft.com/elecraft_prod_list.htm#k3)

You may replace that 2.7 kHz 5-pole filter with a 2.8 kHz 8-pole filter at
the time of initial order for an additional amount that is slightly less
than a new 2.8 kHz filter. (see the KFL3A-2.8_2.7sw item on the K3 order
form).  

If you're ordering both main and sub, you should consider "matching" the
filters if you decide on the 2.7 kHz 5-pole filters. (see KFLMATCH on the
order form). Matching is not required for two 2.8 kHz 8-pole filters.

A 2.7 or 2.8 kHz filter is required in the main K3. It is used as the
transmit filter for CW, Data and SSB modes. Even if you're a 100% CW
operator, you'll need one of these two filters, 2.7 or 2.8 kHz, on the K3
main RF board.

If you're uncertain, the smallest initial investment would be to order the
"default" 2.7 kHz 5-pole filters for both main and sub.  If you plan to use
diversity, investing in a matched pair would be a good idea.  Some users
feel that starting with two 2.8 kHz 8-pole filters is a better investment
than the matching fee.  Others are quite happy with the 2.7 kHz 5-pole
filters.

I chose 2.8 kHz 8-pole filters as my initial filters in main and sub.

If you're primarily a CW operator, you should also consider a narrow filter,
somewhere around 400-500 Hz.  There are several to choose from; Elecraft
offers a 400 Hz 8-pole filter and a 500 Hz 5-pole filter, and I think Inrad
may offer a 500 Hz 8-pole filter.  

You don't have to get this right on day one.  You can start with what you
know you need and add filters later.

73 de Dick, K6KR



-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of callen1155
Sent: Wednesday, February 24, 2010 2:30 PM
To: [hidden email]
Subject: [Elecraft] Determining best roofing filter with DSP??



Hello guys.

Sorry about all the questions but I think this is the last one before I
press the "buy" button for a K3.

Once again a question about cw roofing filters.

I am initially ordering the K3 without the 2nd receiver but do plan on
getting one within a year.

That said, and knowing it's best to have 'matching roofing filters' for both
receivers, even after all the reading I still have no idea what would be the
best roofing filter to get. It seems to be such an individual choice.
Ideally, I'd prefer to purchase only one filter (or one for each receiver)
and want to make the best filter choice for my operating.

So if I order the K3 with no roofing filters, can I determine from operating
with just the DSP which cw roofing filter would be the optimal one for me.

Or is the above an exercise in futility and I just need to order say a 400
and see how that does before I'll know?
But then again I guess it wouldn't be 'matched'' when I get one for the
second receiver.

Too many decisions!

thanks again.
chuck
af4xk

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[Bob - W0GI]

I ordered mine with a 250Hz 8-pole, and with it punched in, close signals disappear. That said, I will probably add a 1500Hz and 500Hz later on.

Now that I have played with the DSP, I am thinking that either a 500Hz or 400Hz is plenty good enough, as the roofing filter protects the DSP from close signals, but it will still go down to 50Hz brick wall with the DSP.

I really can't say what my preference will be, until I try them. The K3's use of roofing filters is much different the the Mark-V, where I have a 500 on the 455kHz IF, and a pair of 250's on both the 8.2mHz IF and the 455kHz IF. Even then my K3 just blows the Mark-V away blocking close signals.

I have a feeling that the K3 with the 500Hz 5-pole filter performs better then just about any other receiver.

Good luck, as you may have to flip a coin. :>)

73, Bob

[Cookie]

Chuck, you don't need to match the filters if you buy the 8 pole filter which the 400 Hz is, but the extra cost to match the filters is less than the difference between the 8 pole and 5 pole.  I have the 2.7K, 500 and 250 and I am happy.  The narrow filters only are effective when there is a strong signal in the bandpass of the wider filter.  The DSP filter will handle signals that are not really strong.  You need the 2.7K for sure but one comes with the K3 and another with the sub-receiver.  So the best thing to buy for CW is the 500 Hz 5 pole or the 400 Hz 8 pole.
 Willis 'Cookie' Cooke
K5EWJ




________________________________
From: callen1155 <[hidden email]>
To: [hidden email]
Sent: Wed, February 24, 2010 4:30:15 PM
Subject: [Elecraft] Determining best roofing filter with DSP??



Hello guys.

Sorry about all the questions but I think this is the last one before I
press the "buy" button for a K3.

Once again a question about cw roofing filters.

I am initially ordering the K3 without the 2nd receiver but do plan on
getting one within a year.

That said, and knowing it's best to have 'matching roofing filters' for both
receivers, even after all the reading I still have no idea what would be the
best roofing filter to get. It seems to be such an individual choice.
Ideally, I'd prefer to purchase only one filter (or one for each receiver)
and want to make the best filter choice for my operating.

So if I order the K3 with no roofing filters, can I determine from operating
with just the DSP which cw roofing filter would be the optimal one for me.

Or is the above an exercise in futility and I just need to order say a 400
and see how that does before I'll know?
But then again I guess it wouldn't be 'matched'' when I get one for the
second receiver.

Too many decisions!

thanks again.
chuck
af4xk
--
View this message in context: http://n2.nabble.com/Determining-best-roofing-filter-with-DSP-tp4629030p4629030.html
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[Brett Howard]

I see the best bet is to get the 2.8Khz rock to start with.  Just pony
up the upgrade price and start there...  Trust me if you decide you want
to use 5 pole filters instead I GUARANTEE you that you can sell the 2.8
and you'll find plenty of people willing to sell you a 2.7K 5 pole
filter (as they pulled them out of their radio to upgrade to the 8 pole
models)...

Recently I had the 1.8K filters in my radio for SSB contesting.  I
decided I was interested in the 1.5K filters from INRAD.  What I did is
I then dialed my DSP down to 1.5K and I listened to some SSB stations on
a relatively calm day (no big strong guys right next to the stations I
was listening to).  I then determined that 1.5K was wide enough with
proper tuning to copy an SSB station.  So I then sold my 1.8K filters
and bought the 1.5K filters.  

I recommend you do just that!  Buy the 2.8K filter upgrade with your K3.
Then play with the K3 as it is and listen to some stations.  Neck down
on these stations with the DSP alone and find out where it is you like
to use your K3.  Then if you are patient enough try doing the same
during a contest.  You may find that you're perfectly happy with the
DSP's performance alone.  Then think of all the money you've saved...

But then I've got 10 8-pole filters in my radio as of today when I just
installed the last of them...

~Brett (KC7OTG)

On Wed, 2010-02-24 at 14:30 -0800, callen1155 wrote:

>
> Hello guys.
>
> Sorry about all the questions but I think this is the last one before I
> press the "buy" button for a K3.
>
> Once again a question about cw roofing filters.
>
> I am initially ordering the K3 without the 2nd receiver but do plan on
> getting one within a year.
>
> That said, and knowing it's best to have 'matching roofing filters' for both
> receivers, even after all the reading I still have no idea what would be the
> best roofing filter to get. It seems to be such an individual choice.
> Ideally, I'd prefer to purchase only one filter (or one for each receiver)
> and want to make the best filter choice for my operating.
>
> So if I order the K3 with no roofing filters, can I determine from operating
> with just the DSP which cw roofing filter would be the optimal one for me.
>
> Or is the above an exercise in futility and I just need to order say a 400
> and see how that does before I'll know?
> But then again I guess it wouldn't be 'matched'' when I get one for the
> second receiver.
>
> Too many decisions!
>
> thanks again.
> chuck
> af4xk

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[callen1155]

Thanks guys.

Great information.

73.
chuck
af4xk