[ICOM] Dual Watch heterdyne

[Adam Farson]

Hi Bob,

This beat note is normal Dual Watch behaviour. If you look at a simplified
block diagram of the Dual Watch receiver:

http://www.qsl.net/ab4oj/icom/dw.html

you will see that the outputs of the A and B 1st mixers are combined, and
feed a common IF chain. If you tune in the two AM signals' carrier
frequencies on A and B, respectively, their carriers will zero-beat. If
there is a slight frequency error between them, the DSP will demodulate the
delta as a slow beat. If you offset one of the stations by 1 kHz, the DSP
demodulation process will resolve the offset as a 1 kHz tone.

By the same token, if you select SSB or CW and tune in a single tone (e.g.
the Cal Marker) on A and B, offsetting A or B will produce a beat tone equal
in frequency to the offset.

So, as my Dad used to say to me when I was a wee bairn, "Och, laddie, dinnae
fash yer wee heid o'er it!"

Cheers for now, 73,
Adam VA7OJ/AB4OJ


-----Original Message-----
From: icom-bounces at mailman.qth.net [mailto:icom-bounces at mailman.qth.net] On
Behalf Of Bob Lang
Sent: 05 February 2006 19:43
To: ICOM Reflector
Subject: [ICOM] Dual Watch heterdyne

Greetings,

Would like to hear if anyone else is experiencing what I am on my pro2 when
using the dual watch function.

I tune to an AM station on 7290 and in the sub band another AM station on
7295.

If  I tune either off its center frequency I get a beat note at a frequency
equal the offset I entered.
ie: I tune to from 7295 to 7296 and get the two audios plus a 1khz tone.
I tried other frequencies 7285&7315,  same results.

This should not be the case, just wondering if its my unit or a radio flaw.

Thanks,
Bob - N3UR 

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