Ok...I feel like a complete idiot

[blindfire]

They say confession is good for the soul. That is good, assuming I have a soul.

Anyway, I started that other thread about noise levels on 75m.

Well, I figured it ALL out.

First, the cause of my 30db over issue is my LED lights x 3 in our kitchen/dining room. Those lights are on a dimmer switch as well. As soon as I turn off the lights, the 30db drops back down to S9.

And here is where I feel like a complete idiot/boob/fool/insert your own term.

I started studying for my Extra recently using the KB6NOA (Gordon West) audio CDs. His section on amps was very enlightening. He demonstrated what impact an amp has on your signal. He also commented on the subject of pre-amps. He pointed out that pre-amps are nice for helping you dig out signals in the noise in that it boost the signal...but also boosts the noise level. I kinda knew that all along, but until he restarted it, I didn't put 2 and 2 together. My Icom IC7100 has 3 pre-amp settings...OFF, Pre-Amp 1 and Pre-Amp 2. When I first got the radio, I found that Pre-amp 2 worked really well....so I just left it there. I never really paid attention to the S meter until I started doing serious HF.

Well, as you'd expect, when I turn off the pre-amp, my signal level drops to S4-S5 at 75m.

GOOD GOD, DO I FEEL DUMB!

All I can say is, "Lesson learned". That is why I love being a ham...you never stop learning how much you don't know.

Thank you all for the help on this "problem" and feel free to chuckle at my expense.

 

[cockpitbob]

So, not a plasma TV but LED lights. Same concept though. A new technology thing was brought home, plugged in and started spewing RF all over. Good lesson for all of us.

And your preamp confession will probably save some new Icom owner the same headache. Of course the real lesson is to RTFM.

 

[blindfire]

So, not a plasma TV but LED lights. Same concept though. A new technology thing was brought home, plugged in and started spewing RF all over. Good lesson for all of us.

And your preamp confession will probably save some new Icom owner the same headache. Of course the real lesson is to RTFM.

Yeah...I did read the fine manual, but the Icom manual is sparse on helpful content outside of what each menu or button does.

So, yeah...that was fun...but a useful lesson. I should know better...I'm in tech support and I seem to ALWAYS ignore the obvious. Oh well.

 

[Zappa]

GOOD GOD, DO I FEEL DUMB!

 

[Buggin]

GOOD GOD, DO I FEEL DUMB!

Well you sound dumb also.
Just kidding.
I had one of those moments not too long ago.
We had bought a new ceiling fan/light for the kitchen. One with a remote. For some reason, whoever build the house put the only interior light switch all the way across the room. It's either leave a light on, add a lamp, rewire a log cabin, or get something with a remote.
I installed it. It never worked right. Got a hold of the manufacturer. They had a problem with the signal unit. Sent it out.
I replaced it. Worked great. About two weeks later, the wife calls and tells me the remotes not working again.
"Did you drop it?" (It's holstered in a plastic holder next to the door)
"Yes"
"Great, now we need a new remote for it"
About a week goes by and I was sporadically looking for a replacement. I hadn't called the manufacturer yet.
She's bitching up a storm. (Not like she does much cooking anyways)
I'm walking down the hall like I do a couple dozen times a day and stopped dead in my tracks. There's a light switch on the wall just outside the kitchen.
I knew it was there. It's what we used to use before we got the ceiling fan.
Click. Light. I start laughing. She comes out of the room. I show her. Both had a good laugh.
My mother had come down for the weekend and shut it off when she left. It was just a coincidence that the wife had dropped the remote.
Dumbass.

 

[AHM]

...Gordon West ... was very enlightening. He demonstrated what impact an amp has on your signal. He also commented on the subject of pre-amps. He pointed out that pre-amps are nice for helping you dig out signals in the noise in that it boost the signal...but also boosts the noise level. I kinda knew that all along, but until he restarted it, I didn't put 2 and 2 together. My Icom IC7100 has 3 pre-amp settings...OFF, Pre-Amp 1 and Pre-Amp 2. When I first got the radio, I found that Pre-amp 2 worked really well....so I just left it there. I never really paid attention to the S meter until I started doing serious HF.

Well, as you'd expect, when I turn off the pre-amp, my signal level drops to S4-S5 at 75m. ...

Paraphrasing the Yaesu FT-857 manual:

... [deactivating the preamp] will provide substantial protection against intermodulation and other problems associated with strong signal input to the receiver. Rule of thumb: so long as the S-meter is moving on background noise, additional front-end gain is not necessary.

Emphasis mine.


So one approach to front-end management is to tune to a frequency with no usable signal present, then back off on RF Gain until the S-meter stops moving, then use the AF Gain to adjust the final volume. That way, you're not using the rig to amplify the floor of noise present in the band - only signals that rise above the noise. The effect is much like having a squelch.

One must be prepared to tweak the settings if one tunes into a region of a band with splatter from a strong station, or if you're listening so long that conditions change. And all bets are off on those settings if you change to a different band with different ambient noise.

Warning: if you're going to play this game, be sure to zero the RF gain before you firewall the AF gain. Otherwise, you'll blow your brains out when you crank the volume control.

I can't swear this is the best approach for your much fancier rig. But it may be valid under some conditions.

73's

 

[blindfire]

Paraphrasing the Yaesu FT-857 manual:



Emphasis mine.


So one approach to front-end management is to tune to a frequency with no usable signal present, then back off on RF Gain until the S-meter stops moving, then use the AF Gain to adjust the final volume. That way, you're not using the rig to amplify the floor of noise present in the band - only signals that rise above the noise. The effect is much like having a squelch.

One must be prepared to tweak the settings if one tunes into a region of a band with splatter from a strong station, or if you're listening so long that conditions change. And all bets are off on those settings if you change to a different band with different ambient noise.

Warning: if you're going to play this game, be sure to zero the RF gain before you firewall the AF gain. Otherwise, you'll blow your brains out when you crank the volume control.

I can't swear this is the best approach for your much fancier rig. But it may be valid under some conditions.

73's

This is pretty much what I've started doing.

Thanks!

 

[AHM]

This is pretty much what I've started doing.

Thanks!

Glad it seems to work for you.

73's