[ICOM] Icom rigs and atmospheric noise

[Jim Isbell]

On 40 meters I find noise levels as high at S8 regularly in the evening 
on a Collins 75S-1  I don't think you can judge a receiver by the noise 
level which is always above the no signal level of the receiver.  Try 
removing the antenna and see if the noise level drops to your 
expectation.  If it does then what you are seeing in normal of that 
band.  If it remains high then its the receiver.

John Geiger wrote:

>Here is a question for the list about there
>experiences with Icoms.  I recently picked up an Icom
>740 based on its reputation for having a quiet
>receiver and a great NB.  I am thinking that I have a
>problem with power line noise, or something like that,
>and so far the power company has done nothing really
>to try and fix it.  I am now wondering if maybe my
>expectations are too high.
>
>According to the ARRL review of the 740, its MDS
>(noise floor) is -133dbm with the preamp off, and
>-141dbm with the preamp on.  They don't mention what
>bad that is on.  On the higher bands, with the preamp
>off, I am seeing a noise level around S1 or so.  Very
>nice and quiet, and the notch filter will remove that
>even more.  When I turn the preamp on, the noise level
>will rise to S4 or S5 sometimes.  I noticed this
>yesterday during the NAQP.  It pretty much sounds like
>regular static, though.  No buzzing or anything like
>that.  Given the MDS numbers from the ARRL review,
>would S4 be an expected atmospheric noise level with
>the preamp on?  I generally run it with the preamp off
>on the lower bands, and it does seem fairly quiet
>there, although I was seeing some S8 bursts on 75
>meters last night.  
>
>I guess I am starting to think that maybe I really
>don't have much power line noise.  Maybe I just have a
>sensitive rig with some good old mother nature static,
>and a little bit of the crud you get from living in
>the city with neighbors on every side.  I have been
>driving myself half crazy trying to find a rig with a
>S1 or lower noise level, and maybe I just have too
>high of expectations.  I have a short memory and
>cannot really remember what things were like in other
>locations I lived in. Of course I probably had less
>sensitive rigs also.
>
>Any opinions?
>
>73s John NE0P
>
>
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