[ICOM] 751A

[W5JMW John]

John,I found that lowering the rf gain helps more than anything else.. NO 
preamp or attn,just use the rf gain to ctrl...73,john
----- Original Message ----- 
From: "John Geiger" <ne0p at lcisp.com>
To: "ICOM Reflector" <icom at mailman.qth.net>
Sent: Tuesday, September 20, 2005 9:17 PM
Subject: Re: [ICOM] 751A


>I will agree that my 756 original with the preamp off on 20 meters is very
> quiet.  The NR helps alot also, but probably not as much as the IF DSP in
> the PRO series.  Still seems sensitive enough with the preamp off also.
>
> However, it does seem a little noisy on the lower bands, especially 30 and
> 40 meters.  Do others who have used this rig actually add 6db or so of
> attenuation on the low bands?  It seems more than sensitive enough.
>
> 73s John NE0P
>
> ----- Original Message -----
> From: "Adam Farson" <farson at shaw.ca>
> To: "'ICOM Reflector'" <icom at mailman.qth.net>
> Sent: Wednesday, September 21, 2005 1:57 AM
> Subject: RE: [ICOM] 751A
>
>
>> Hi Blair,
>>
>> Yes indeed - reciprocal-mixing noise manifests itself as out-of-band 
>> noise
>> mixing with the noise pedestal of the 1st LO (synthesiser) to raise the
>> idle-channel noise level in the IF passband.
>>
>> The IC-756Pro series use a very up-to-date DDS scheme which yields
> excellent
>> reciprocal-mixing noise numbers. The Pro2 is a little better than the
> 756Pro
>> in this area, and the Pro3 a little quieter than the Pro2. Even the
>> "original" IC-756 DDS is quieter than any of its PLL-only predecessors.
>>
>> The DSP NR in the 756Pro series improves the S/N at the receiver's audio
>> output even further.
>>
>> 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 Ynkedragon at aol.com
>> Sent: 20 September 2005 11:59
>> To: icom at mailman.qth.net
>> Subject: [ICOM] 751A
>>
>> In a message dated 9/20/05 2:21:12 PM Eastern Daylight Time,
> farson at shaw.ca
>> writes:
>>
>> << The SSB filtering and PBT operation on the 751A was far superior to
> that
>> of  its predecessor in my shack . . . . However, I did find that the
> 751A's
>> PLL  synthesizer was somewhat noisy as compared to newer radios using a
> DDS
>> design (-104 dBc/Hz at 2 kHz offset, as compared to -111 for the IC-765
> and
>>  -125 for the IC-756Pro2). This led to relatively poor close-in 
>> reciprocal
>> noise mixing performance. >>
>>
>> Hi Adam,
>>     Regarding the '751A, you mentioned a noisy synthesizer.  Perhaps that
> is
>> what I noticed--something I had had always attributed to a noisy audio
>> chain.
>> A good friend had one which I frequently used.  When he upgraded he
> offered
>> the '751A to me at an attractive price.  I thought about it for an hour
> and
>> decided against it because of its omnipresent "white noise".  It could
> have
>> been unique to that particular radio, but I found that listening to the
>> '751A became very tiring after just a few hours.
>>     FWIW, the '756PRO series [all flavors] seems to lack that
>> (annoying-to-me) "white noise" component.
>>
>> 73,  Blair k3yd
>>
>>
>>
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>
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