[ICOM] IC756 PRO 3 PROBLEM with DSP

[Steve N4LQ]

Thanks. I tried sending this to the reflector last night but it never posted 
for some strange reason. Anyway, I called AES this morning and have orders 
to ship it in for them to evaluate. I already know they won't be able to 
duplicate the problem hence the reason for the jpg. I may even make a .wav 
file for them to QSX.
No the Omni VI+ has a very wide roofing filter, 2 poles at 15khz. The 
problem here isn't filtering. The DSP is working but I think it is actually 
producing the spikes as a result of clipping. The spikes do not seem to 
affect the agc either because they are too fast, or because they are beyond 
the last agc loop.
I can hear these through anything including speakers, headphones but by 
feeding the audio out to the PC's sound card and using hi-fi speaker, they 
really show up!
Steve N4LQ
----- Original Message ----- 
From: "Dave Meitzen" <dmeitzen at comcast.net>
To: "ICOM Reflector" <icom at mailman.qth.net>
Sent: Monday, December 20, 2004 6:31 PM
Subject: RE: [ICOM] IC756 PRO 3 PROBLEM with DSP


> Does the Onmi VI+ have a narrow CW roofing filter? Think heavy QRN bleed 
> in
> to the PRO III IF? Thanks for shareing this with the group -- excellent
> info. Like to know the resolution I have a Pro III :>))
> Thanks
> Dave
>
>
> -----Original Message-----
> From: icom-bounces at mailman.qth.net
> [mailto:icom-bounces at mailman.qth.net]On Behalf Of Steve N4LQ
> Sent: Monday, December 20, 2004 5:20 PM
> To: ICOM Reflector
> Subject: [ICOM] IC756 PRO 3 PROBLEM with DSP
>
>
>
> Subject: IC756 PRO 3 PROBLEM with DSP
>
>
> I received a new PRO-3 last Thursday from AES. The DSP has a problem
> especially when using the NR. The problems is distortion products 
> resulting
> in large noise spikes, far outside the bandwidth setting.
> Last night I made some recordings using Spectrogram. Band, 80m, 
> Conditions-
> Heavy QRN, BW-250hz, NR ON, DSP CW-soft. I recorded both  the OMNI VI+ and
> PRO-3 connected to the same antenna. Please see the scope patterns at this
> link:
>
> www.webham.com/PRO3.jpg
>
> When listening through wide range headphones which are plugged directly 
> into
> the PRO3, the spikes are very annoying and make copy almost impossible.
> Turning off the NR helps some. There is certainly a problem with the DSP. 
> At
> this time I do not know if it's just my rig or an engineering problem.
>
> Note: Before this, I owned a PRO2 for 2 years so I am quiet familar with 
> how
> the radio SHOULD function.
>
> I am contacting AES tomorrow. Hopefully they will provide an exchange.
>
> Stay tuned for further developments.
>
>
> Steve N4LQ
>
> IC756PROIII
> IC-756PRO3
> IC756 PRO 3
> ----
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> Win a new Icom IC-756 PRO III and help QSL/QTH.net
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>
> ----
> Your Moderator: Dick Flanagan K7VC, icom-owner at mailman.qth.net
> Win a new Icom IC-756 PRO III and help QSL/QTH.net
> Details at: http://mailman.qth.net/
>