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KX3 Roofing filter question

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Joshua Gould, K8WXA

KX3 Roofing filter question

All,

Would the roofing filters help reduce atmospheric noise? I'm having a heck
of a time hearing anything over the S5 noise levels that I seem to be
dealing with of late. But at least it's better than the S9 noise I was
getting from switching power supplies under my desk...

72,
Joshua Gould
K8WXA
EM89pn

KX3# 7480
NAQCC # 7704
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k6dgw

Re: KX3 Roofing filter question

Joshua, Probably not. The ultimate BW of your receiver is set by the
DSP and noise power is "sort of" proportional to BW. The purpose of the
roofing filters is to protect the ADC sampler at the head end of the DSP
from very strong signals that could drive it to saturation.

Noise, other than atmospheric and galactic, needs to be attacked at the
source. Like getting rid of your switching wall warts and power
supplies. So long as the atmospheric noise is not saturating the ADC,
reducing the DSP BW is the only really effective way to reduce it's
impact, and that's a lot easier on CW than on SSB. Different roofing
filters are not likely to make much difference at all unless they're
more narrow than your DSP setting.

On 3/24/2015 7:24 PM, Joshua Gould wrote:

> All,
>
> Would the roofing filters help reduce atmospheric noise? I'm having a heck
> of a time hearing anything over the S5 noise levels that I seem to be
> dealing with of late. But at least it's better than the S9 noise I was
> getting from switching power supplies under my desk...
>
>
> 72,
> Joshua Gould
> K8WXA
> EM89pn

Chester Alderman

Re: KX3 Roofing filter question

Joshua,

If you primarily operate CW or other digital modes, try using Rx
Equalization and drop anything above about 800 Hz by anywhere from 0 to
-16dB. I think if you operate primarily SSB you are stuck with having to
have Rx Equalization pretty much open above 800 Hz.

73,
Tom - W4BQF

-----Original Message-----
From: Elecraft [mailto:[hidden email]] On Behalf Of Fred
Jensen
Sent: Tuesday, March 24, 2015 10:49 PM
To: [hidden email]
Subject: Re: [Elecraft] KX3 Roofing filter question

Joshua, Probably not. The ultimate BW of your receiver is set by the DSP
and noise power is "sort of" proportional to BW. The purpose of the roofing
filters is to protect the ADC sampler at the head end of the DSP from very
strong signals that could drive it to saturation.

Noise, other than atmospheric and galactic, needs to be attacked at the
source. Like getting rid of your switching wall warts and power supplies.
So long as the atmospheric noise is not saturating the ADC, reducing the DSP
BW is the only really effective way to reduce it's impact, and that's a lot
easier on CW than on SSB. Different roofing filters are not likely to make
much difference at all unless they're more narrow than your DSP setting.

On 3/24/2015 7:24 PM, Joshua Gould wrote:

> All,
>
> Would the roofing filters help reduce atmospheric noise? I'm having a
> heck of a time hearing anything over the S5 noise levels that I seem
> to be dealing with of late. But at least it's better than the S9
> noise I was getting from switching power supplies under my desk...
>
>
> 72,
> Joshua Gould
> K8WXA
> EM89pn

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vk2rq

Re: KX3 Roofing filter question

In reply to this post by k6dgw

If you have lots of atmospheric noise, you may have too much gain in your revive chain, and should maybe consider switching off the preamp/switching on the attenuator.

There is also the "NR" noise reduction feature which may be useful. However on CW I find that narrowing the PBT bandwidth cuts out a lot of the band noise. As someone else stated, a roofing filter is not going to help you with this sort of problem; a roofing filter is to protect against strong stations on nearby frequencies so you don't get problems like AGC pumping and undesired mixing products.

73, Matt VK2RQ

> On 25 Mar 2015, at 1:49 pm, Fred Jensen <[hidden email]> wrote:
>
> Joshua, Probably not. The ultimate BW of your receiver is set by the DSP and noise power is "sort of" proportional to BW. The purpose of the roofing filters is to protect the ADC sampler at the head end of the DSP from very strong signals that could drive it to saturation.
>
> Noise, other than atmospheric and galactic, needs to be attacked at the source. Like getting rid of your switching wall warts and power supplies. So long as the atmospheric noise is not saturating the ADC, reducing the DSP BW is the only really effective way to reduce it's impact, and that's a lot easier on CW than on SSB. Different roofing filters are not likely to make much difference at all unless they're more narrow than your DSP setting.
>
>> On 3/24/2015 7:24 PM, Joshua Gould wrote:
>> All,
>>
>> Would the roofing filters help reduce atmospheric noise? I'm having a heck
>> of a time hearing anything over the S5 noise levels that I seem to be
>> dealing with of late. But at least it's better than the S9 noise I was
>> getting from switching power supplies under my desk...
>>
>>
>> 72,
>> Joshua Gould
>> K8WXA
>> EM89pn
>
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