[ICOM] Using RF Gain

[AD5VJ Bob]

That is a gud method John:

You are essentially making your dynamic range continuously adjustable, by using a combination of attenuator settings and rf gain
control.

I would love to see a ham rig with a continuously adjustable attenuator setup and of course the rf gain control as well.

When you use the method you are using, it is really nice because. you are helping the filters, gain circuits and  noise elimination
circuits do their job better.

As you tune each particular signal, while putting the gain circuits more inline with their respective "sweet spots" for the signal
you are interested in "tuning in" at the time.

Gud method. 

Also one thing I also do that you might consider on the 775 which helps IMHO is the use of the APF. 

Once I zero in on a signal and adjust the RF gain, attenuators and filtering circuits I then use the APF to lock onto the signal and
bring up selectivity of that particular signals audio frequencies.

I have at times gotten a signal out of the noise and enhanced it using a combination of the crystal filters rf gain, attenuators
settings and the APF to where the signal was 3 s units out of the noise and completely readable, but before it was hardly readable.

I love my IC-775. 

I could not do this sort of fine tuning with *any* of the other rigs that I had. They either *only used DSP* or they were not
sensitive enough to pull it off. 

Hopefully when my IC-775 gets back from the shop it will be even better than before. Which will be amazing.

  73 fer nw,
Bob AD5VJ(AAR6VM)
Visit My Ham Blog
http://www.ad5vj.com/

10X# 37210, SMIRK#-5177, RARS #-149
Code may be taking a back seat for now,
but the pioneering spirit that put the code
there in the first place is out front of it all.




> -----Original Message-----
> From: icom-bounces at mailman.qth.net 
> [mailto:icom-bounces at mailman.qth.net] On Behalf Of W5JMW John
> Sent: Saturday, June 17, 2006 11:46 AM
> To: ICOM Reflector
> Subject: Re: [ICOM] Using RF Gain
> 
> Yes John,Also on the pro or 775.I do this often on 
> 160.Pre-amp on and vary the rf gain.While it might not help 
> with the noise floor.It appears too,and to my deag ears it 
> seems to help.Again,I have no lab evidence of this,it just 
> appears to help at times..73 john
> ----- Original Message -----
> From: "John" <w5td at lcisp.com>
> To: <icom at mailman.qth.net>
> Sent: Saturday, June 17, 2006 11:10 AM
> Subject: [ICOM] Using RF Gain
> 
> 
> > Here is a question which I should know the answer to, but 
> can't come 
> > up with it at the present time.  I have an Icom 706 
> original, which I 
> > generally run with the preamp on.  This makes HF kind of noisy, but 
> > turning off the preamp makes the radio pretty deaf (QST 
> measured the 
> > MDS at -123dbm, 20 meters, preamp off).  Can I use the RF gain to 
> > reduce sensitivity a bit to quiet things up?  A MDS of -130 or so 
> > would probably be fine, but there is no way to achieve this 
> by using 
> > the preamp and/or ATT.  Can reducing the RF gain lower sensitivity 
> > while preserving S/N ratio?
> >
> > 73s John W5TD
> >
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