if it is anything similar to what the old yaesu's have, such as the 101 
series, they are for speaker output, and phone patch functions.
There is probably a recorder line out as well and perhaps jacks for external 
meters and possibly a short wave receiving antenna.
the manual would make all clear i'm sure.
bear in mind that the lower bands wil have a higher noise level then higher 
bands, especially if you are using a vertical antenna.
an s9 noise level is not uncommon on 75 and 80M with a vertical...and s 3 to 
s6 on 40 with a vertical.  the noise level will be higher during the day 
time hours due to atmospheric noise.
I still suspect you are getting noise off the power lines in your area 
unless they are underground.

73
Colin, V A6BKX
----- Original Message ----- 
From: "John Miller" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, July 08, 2009 8:34 AM
Subject: Re: hf interference news


>
> All the older icoms have that setup with the RCA jacks, I don't know what 
> it
> is but the bolt below it is the grounding hookup.
> ----- Original Message ----- 
> From: "Gery Gaubert" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Wednesday, July 08, 2009 10:25 AM
> Subject: hf interference news
>
>
>> Thanks to all who answered.  This is a really great list full of great
>> peop=
>> le who are willing to help.  Thanks for that first.  A little more info 
>> on
>> =
>> the grounding issue
>> The pool pump is off, all computers and the fridge is off. The ac unit 
>> got
>> =
>> turned off for a few minutes for the experiment and still static is 
>> there.
>> =
>> At least on the lower bands.  I have parts of 40 meter band with the
>> stati=
>> c and including that and lower seem to be effected.  Now for any one who
>> ma=
>> y have this radio or can figure out what I am talking about since they 
>> are
>> =
>> quite knowledgable.
>> On the back of the icom 751A  when I am looking at the front of it, I
>> reach=
>> around the right side I found a ground.  It is a bolt with a nut.  To my
>> s=
>> urprise right above this I found 3 sets of jacks that feel like they are
>> rc=
>> a plugs.  There are 6 total but it looks as if the middle 2 are in use.
>> Th=
>> ere is a wire with an rca plug on each end that goes from 1 jack to
>> another=
>> .  The wire between the 2 plugs is really short.  Any idea or better
>> explan=
>> ations, please let me know.  I am so confused now.