[INRAD] IMPRESSIVE] (Charlie Mazoch Jr.)

[Giancarlo Moda]

Hi Charlie,

CONGRATULATIONS !!!!!

If you like to try  some other improvements please do
not forget I am available to put you and your Icom
PRO2 in danger .. replacing the 2nd mixer...

Please do not fall to sleep having reduced some
noise...hi

73 and have anice weekend

Gian
I7SWX 
> 
> Message: 1
> Date: Thu, 15 Mar 2007 07:32:56 -0500
> From: "Charlie Mazoch Jr." <w5vin at earthlink.net>
> Subject: [INRAD] [Fwd: Re: IMPRESSIVE]
> To: List at inrad.net
> Message-ID: <45F93CF8.7080108 at earthlink.net>
> Content-Type: text/plain; charset="us-ascii"
> 
> Thought I'd forward this e-mail to the group.
> George, W2VJN and I had 
> modified my Icom Pro2 for an INRAD roofing filter.
> We started off 
> putting the filter further downstream and ended up
> in it's present 
> location. The after results are phenomenal and quite
> visible on the rigs 
> pan adapter. Wide band noise is suppressed and
> signals are very visible. 
> The modification is not that hard for a technically
> inclined person and 
> is certainly worth the effort. The RF board does
> need a trace cut and a 
> couple of miniature coaxial cables soldered onto it.
> George found a spot 
> in the rig to mount the board and filter. It is
> activated by  "Dual 
> watch" and rotating the balance control fully CCW.
> If both receivers are 
> set to the same frequency and dual watch is
> activated the balance 
> control can be rotated CCW for narrow band and CW
> for wide ban 
> receiving. Recently I read an article about the Pro
> series of Icom rigs 
> and how wonderful the DSP worked in relation to
> crystal filtering. I beg 
> to disagree with the author of this article. DSP
> isn't the only cure for 
> intermod. The IF strings still perform a lot better
> when the signal to 
> be amplified is narrow.  73's
> Charlie  W5VIN
> 
> -------- Original Message --------
> Subject: 	Re: IMPRESSIVE
> Date: 	Wed, 14 Mar 2007 19:55:18 -0700
> From: 	George Cutsogeorge <w2vjn at rosenet.net>
> To: 	Charlie Mazoch Jr. <w5vin at earthlink.net>
> References: 	<45F8B1C5.2070008 at earthlink.net>
> 
> 
> 
> Charlie,
> 
> Thanks for the comments.  That wide band noise you
> see is intermod from all 
> the strong signals.  I never measured the isolation.
>  The point I cut is a 
> low impedance, so there is not much trouble there. 
> You can see from the 
> curve that there is adequate isolation.
> 
> George
> ----- Original Message ----- 
> From: "Charlie Mazoch Jr." <w5vin at earthlink.net>
> To: "George Cutsogeorge" <w2vjn at rosenet.net>
> Sent: Wednesday, March 14, 2007 7:39 PM
> Subject: IMPRESSIVE
> 
> 
> > Hi George:
> >  I took some time this evening to listen to an
> extremely noisy band with 
> > the Icom Pro2. One has to be in "Dual Watch" and
> the balance control CCW 
> > to receive through the roofing filter. I set both
> VFO's to the same 
> > frequency and rotated the balance control right or
> left while in dual 
> > watch. On tonight's noisy 75 meter band the
> results of the INRAD roofing 
> > filter were very impressive. Watching the pan
> adapter while rotating the 
> > balance control from one receive path to the other
> I noticed the broad 
> > band noise displayed between signals was much less
> with the roofing filter 
> > inline. There is definitely a visual indication of
> the receivers 
> > improvement. Very, very impressive. Putting the
> roofing filter right after 
> > the 1st mixer certainly gets rid of a lot of broad
> band  noise being 
> > amplified  and IMD generated in the RF amplifier
> after the receive 
> > combiner. Smart thinking. Thanks and 73's
> > Charlie  W5VIN
> >
> > PS:  What sort of isolation were you getting after
> cutting the circuit 
> > trace where you tied in? According to the
> literature you didn't cut it in 
> > two places and ground the center trace.
> > 



 
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