Re: RF Gain control


Charles W. Powell
 

An opportunity to design a mod for the radio?

72,

Chas - NK8O

On Jan 30, 2019, at 12:08 PM, Jim Pruitt <jpruitt67@...> wrote:

The idea is a good one and has been for decades. The one question I had was...what do we use with most of the current homebrew and direct conversion rigs that have no separate RF gain controls to allow us to do this magic?

Thank you.

Jim Pruitt
WA7DUY


On 1/29/2019 11:19 PM, Charles W. Powell via Groups.Io wrote:
Bill,

Having said all that, I discovered working last month that what “the old timers” say about dealing with noise. We are all used to cranking the AF gain to try to hear signals. That works fine on upper bands, but on 60, 80, and 160, the adjustment should be primarily through the RF gain. Why? Let me put it this way: If you have S9 noise and you turn up the AF gain on the radio, the noise becomes overwhelming. You know there is a signal that you can hear, but the noise is so loud, you can’t listen for more than a few minutes before you want to throw your headphones across the room. If you reduce the RF gain to where the noise is at a tolerable level, then that signal is suddenly audible at a reasonable level over the noise. You have optimized your signal-to-noise ratio by reducing the noise in the mix. You might ask, “Doesn’t this reduce the sensitivity of the receiver?” Well, yes, it does. But if your noise is S-whatever, everything below that level is useless to you. So why amplify the noise and increase your level of fatigue? The only thing to remember is to turn the RF gain back up when you change bands. Otherwise you’ll think the front-end of your radio is blown!

Chas - NK8O


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