Ranger RCI 2995 DX Hi-Cut Mod

[nomadradio]

Not all potentiometers are created equal. In radios you find two basic types. First, a linear taper is what it sounds like. The percentage of the control's resistance that changes per degree you turn the knob is the same from left to right. This kind of pot is used for squelch, RF gain, SWR Cal, transmit power, or echo delay.

But for an audio level control, this doesn't work quite right. Never mind why, but a control meant as a volume control has a non-linear taper. Sometimes called a "log" or logarithmic taper. Usually just called an audio taper. The resistance changes very slowly per degree at the left end of rotation, and the percent increase per degree rises as the knob moves to the right. I'll skip putting everyone to sleep explaining why, but the human ear is not a linear kind of thing. A mike gain control is also an audio-taper control, as is the echo level control. A tone control works best with an audio taper control. The capacitor hooks to the middle lug of the control, the counterclockwise lug connects to the audio ground, and the other end of the capacitor connects to the clockwise lug of the radio's volume control.

Frequently you'll see the resistance value of a control marked on it, along with the letter "A" or "B". A B control is linear taper, not what you want. An audio taper control will have the letter A next to the resistance rating.

73

 

[loosecannon]

thanks buddy for the info, I don't have a sig gen. Are there any cheap ones on Amazon that would work for me?

I didn't really find anything on amazon, but here is something you can get for less than 100 dollars that should work for a beginner.

Pardon Our Interruption...

so, this will allow you to input a signal to the radio and adjust the level of that signal.

it won't be any good for calibrating an S-meter or things that need quantitative measurements, but just to peak a receiver, it will work.

there is a learning curve to using a piece of equipment like this, and you may need to attenuate the output in order to get the signal level low enough.

why do you need a super low level signal?

well, in a radio receiver, there is a feature called AGC (automatic gain control) this circuit's job is to try to make an S1 signal the same volume as an S9 signal.

it does this by detecting how strong an incoming signal is and attenuating it if it's too strong.

when you are aligning a CB radio receiver, you want the signal to be low enough so that it doesn't activate the AGC circuit.

so in general we use whatever signal level gives us an S-1 reading on the radio's meter or even lower than that.
the goal is to peak the receiver with the lowest possible signal that you can still hear/measure.


all that being said, you really don't need one of these to do the trick i mentioned earlier.

just draw a line with a sharpie on the coil indicating the slug's current orientation.

now, as long as you don't turn more than a full turn in either direction, you can put the coil back where it was if you don't like the results.

You know what is a good substitute for a signal generator?

a friend who hits you with an S-3 or lower signal!

or even another radio with a piece of wire stuck in the antenna socket. (make sure this is a junker you don't care if you burn up lol).

you can have someone key up, make a note of their signal, do the trick just as i mentioned it, and then have them key up again to make sure you haven't lost much/any sensitivity.

this trick usually only involves turning the coil a 1/2 turn or less.

good luck!
LC

 

[HavaV10]

I didn't really find anything on amazon, but here is something you can get for less than 100 dollars that should work for a beginner.

Pardon Our Interruption...

so, this will allow you to input a signal to the radio and adjust the level of that signal.

it won't be any good for calibrating an S-meter or things that need quantitative measurements, but just to peak a receiver, it will work.

there is a learning curve to using a piece of equipment like this, and you may need to attenuate the output in order to get the signal level low enough.

why do you need a super low level signal?

well, in a radio receiver, there is a feature called AGC (automatic gain control) this circuit's job is to try to make an S1 signal the same volume as an S9 signal.

it does this by detecting how strong an incoming signal is and attenuating it if it's too strong.

when you are aligning a CB radio receiver, you want the signal to be low enough so that it doesn't activate the AGC circuit.

so in general we use whatever signal level gives us an S-1 reading on the radio's meter or even lower than that.
the goal is to peak the receiver with the lowest possible signal that you can still hear/measure.


all that being said, you really don't need one of these to do the trick i mentioned earlier.

just draw a line with a sharpie on the coil indicating the slug's current orientation.

now, as long as you don't turn more than a full turn in either direction, you can put the coil back where it was if you don't like the results.

You know what is a good substitute for a signal generator?

a friend who hits you with an S-3 or lower signal!

or even another radio with a piece of wire stuck in the antenna socket. (make sure this is a junker you don't care if you burn up lol).

you can have someone key up, make a note of their signal, do the trick just as i mentioned it, and then have them key up again to make sure you haven't lost much/any sensitivity.

this trick usually only involves turning the coil a 1/2 turn or less.

good luck!
LC

thanks so much LC I really appreciate your time and help. I will look into getting one of these soon. So far the hi-cut mod really did help out a lot.

 

[19wrc333]

thanks so much LC I really appreciate your time and help. I will look into getting one of these soon. So far the hi-cut mod really did help out a lot.

A tinySA Spectrum Analyzer also has a signal generator function.
Plus it is an awesome little Spectrum Analyzer.
Bonus.. they are cheap, less than $100,-

--
Skyline