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KX3 Roofing Filter Question

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stan levandowski

KX3 Roofing Filter Question

I am going to order another KX3 this week. Probably tomorrow. The last
one I ordered in 2012 did not have the roofing filter option and I do
not THINK I missed it.

I use ONLY CW and I do NOT contest. I like to CASUALLY chase DX and I
play in low stress sprints like NAQCC but mostly I just like to RAG
CHEW.

My antenna is an EFHW installed as a "half square" in trees at 30 feet
(MyAntennas 4010).

I have reviewed the Elecraft site notes, and done a fair amount of
Googling and I now am more confused than ever. It seems that the real
value lies in dealing with strong signals, crowded bands and ferocious
contesting conditions.

My bottom line question is this: If I DO NOT get the roofing filter
option will my KX3 receiver be LESS SENSITIVE? The Sherwood report
shows a pre-amp off sensitivity of .9 uv which improves to a very
impressive .09 with the preamp on. Is this somehow related to the
roofing filter?

I am especially concerned because I remember doing an A/B comparison on
a weak signal between my previous KX3 and my 55 year old Drake 2B and
the 2B beat the crap out of the factory built KX3. I can't help
wondering if the roofing filter I didn't buy in 2012 had something to do
with this.

I sure could use a real simple answer: buy it or don't buy it? CW
sensitivity is my ultimate goal because if I can't hear 'em I can't work
'em.

Thanks and 73,
Stan WB2LQF
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Don Wilhelm

Re: KX3 Roofing Filter Question

Stan,

I am not going to give you a terse answer, but I can say that the
sensitivity of the KX3 does not depend on the roofing filter.

However, the roofing filter will give you more rejection of unwanted
signals that you may encounter in crowded band conditions.

If you do not operate when the bands get crowded, you will not notice
the difference with or without the roofing filter option.

If you do choose the roofing filter, be certain you do the calibration
if it is a kit. If you order the factory built KX3 with the roofing
filter option, that calibration will have been done at the factory.

73,
Don W3FPR

On 1/29/2018 4:20 PM, stan levandowski wrote:
> I am going to order another KX3 this week. Probably tomorrow. The last
> one I ordered in 2012 did not have the roofing filter option and I do
> not THINK I missed it.
>
> I use ONLY CW and I do NOT contest. I like to CASUALLY chase DX and I
> play in low stress sprints like NAQCC but mostly I just like to RAG CHEW.
>
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Elecraft mailing list

Re: KX3 Roofing Filter Question

Re: "If you do choose the roofing filter, be certain you do the calibration
if it is a kit."

Don,

My kit build KX3 instruction manual says that I don't have to do the calibration if I ordered the filters WITH my KX3 kit:

"If you received the optional KXFL3 filter with your kit, you do not need to perform theReceiver Sideband alignment procedure referenced in the Owner’s manual and describedin detail in the KXFL3 option manual. That procedure was done for you at the factory."

That was back in 2013, so maybe things have changed.

Mark,
KE6BB

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Bob McGraw - K4TAX

Re: KX3 Roofing Filter Question

In reply to this post by stan levandowski

In general, filters have little to do with sensitivity.   On the other
hand, filters do provide selectivity.   In crowded band conditions where
one is attempting to dig out a weak signal among stronger signals, the
roofing reduces the likelihood that the stronger signal will impact the
overall AGC, thus diminishing the apparent strength of the weaker signal.

Otherwise, the added roofing filter certainly can't diminish the
receiver performance but may, under certain conditions, enhance receiver
performance.

Conclusion:   buy it!

73

Bob, K4TAX

On 1/29/2018 3:20 PM, stan levandowski wrote:

> I am going to order another KX3 this week. Probably tomorrow. The
> last one I ordered in 2012 did not have the roofing filter option and
> I do not THINK I missed it.
>
> I use ONLY CW and I do NOT contest. I like to CASUALLY chase DX and I
> play in low stress sprints like NAQCC but mostly I just like to RAG CHEW.
>
>
> My antenna is an EFHW installed as a "half square" in trees at 30 feet
> (MyAntennas 4010).
>
>
> I have reviewed the Elecraft site notes, and done a fair amount of
> Googling and I now am more confused than ever. It seems that the real
> value lies in dealing with strong signals, crowded bands and ferocious
> contesting conditions.
>
>
> My bottom line question is this: If I DO NOT get the roofing filter
> option will my KX3 receiver be LESS SENSITIVE? The Sherwood report
> shows a pre-amp off sensitivity of .9 uv which improves to a very
> impressive .09 with the preamp on. Is this somehow related to the
> roofing filter?
>
>
> I am especially concerned because I remember doing an A/B comparison
> on a weak signal between my previous KX3 and my 55 year old Drake 2B
> and the 2B beat the crap out of the factory built KX3. I can't help
> wondering if the roofing filter I didn't buy in 2012 had something to
> do with this.
>
>
> I sure could use a real simple answer: buy it or don't buy it? CW
> sensitivity is my ultimate goal because if I can't hear 'em I can't
> work 'em.
>
>
> Thanks and 73,
> Stan WB2LQF
> ______________________________________________________________
> 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
> Message delivered to [hidden email]

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Barry K3NDM

Re: KX3 Roofing Filter Question

In reply to this post by stan levandowski

Stan,
If you use the 8 KHz receive offset, you can not use the roofing filter;
it is disables when you invoke the SHFT. So, having it will do you no
good. And, that's the simple answer.

I have my KX3 set to the offset as it cleans up the spectrum display
that I use; I've never looked into the performance difference of using
the offset or not. I did use my KX3 for causal DX, contesting, and
everything in between. It's a wonderful radio. I have since purchased a
K3s, so the KX3 has been relegated to Field Day use only.

Be careful of system sensitivity specs. Most receivers are more
sensitive than ambient conditions will allow. The .9 uV number you show
is absolutely fine for the lower end of HF, but you could use a little
more at the upper end. I live in an urban environment with power lines
and neighbors with noisy TVs, heat pumps, and solar arrays. I'd be more
than happy if I could use a sensitivity of a 1 uV on 80.

73,
Barry
K3NDM

------ Original Message ------
From: "stan levandowski" <[hidden email]>
To: [hidden email]
Sent: 1/29/2018 4:20:06 PM
Subject: [Elecraft] KX3 Roofing Filter Question

>I am going to order another KX3 this week. Probably tomorrow. The last
>one I ordered in 2012 did not have the roofing filter option and I do
>not THINK I missed it.
>
>I use ONLY CW and I do NOT contest. I like to CASUALLY chase DX and I
>play in low stress sprints like NAQCC but mostly I just like to RAG
>CHEW.
>
>
>My antenna is an EFHW installed as a "half square" in trees at 30 feet
>(MyAntennas 4010).
>
>
>I have reviewed the Elecraft site notes, and done a fair amount of
>Googling and I now am more confused than ever. It seems that the real
>value lies in dealing with strong signals, crowded bands and ferocious
>contesting conditions.
>
>
>My bottom line question is this: If I DO NOT get the roofing filter
>option will my KX3 receiver be LESS SENSITIVE? The Sherwood report
>shows a pre-amp off sensitivity of .9 uv which improves to a very
>impressive .09 with the preamp on. Is this somehow related to the
>roofing filter?
>
>
>I am especially concerned because I remember doing an A/B comparison on
>a weak signal between my previous KX3 and my 55 year old Drake 2B and
>the 2B beat the crap out of the factory built KX3. I can't help
>wondering if the roofing filter I didn't buy in 2012 had something to
>do with this.
>
>
>I sure could use a real simple answer: buy it or don't buy it? CW
>sensitivity is my ultimate goal because if I can't hear 'em I can't
>work 'em.
>
>
>Thanks and 73,
>Stan WB2LQF
>______________________________________________________________
>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
>Message delivered to [hidden email]

Don Wilhelm

Re: KX3 Roofing Filter Question

In reply to this post by Elecraft mailing list

Mark,

If the roofing filter was added to your original order, it will be
calibrated at the factory (even if it is a kit).

If you add the roofing filter later, you will have to do the calibration
for optimum results.

73,
Don W3FPR

On 1/29/2018 5:31 PM, Mark Petiford via Elecraft wrote:

> Re: "If you do choose the roofing filter, be certain you do the calibration
> if it is a kit."
>
>
> Don,
>
> My kit build KX3 instruction manual says that I don't have to do the calibration if I ordered the filters WITH my KX3 kit:
>
> "If you received the optional KXFL3 filter with your kit, you do not need to perform theReceiver Sideband alignment procedure referenced in the Owner’s manual and describedin detail in the KXFL3 option manual. That procedure was done for you at the factory."
>