Modulation

[Drifter]

Ok what is the correct way and level to set my modulation.... and still be heard above the hash, trash and ducks :?: I am trying to prevent bleed over, and splatter, and most of all I want to keep out of my neighbor's phone and TV. :shock: This is what I have... Texas Ranger TR696 FSSB base radio, Dead key set to 2 watts swing 15 watts by Copper Elect.. I hope they did not clip anything :x . Galaxy base echo mic, Workman W/MOD/SWR meter, and a XForce 2x4 pill with the variable at min. dead keying at about 50 watts but swingging to 1000 watts. I also have a low pass filter on the output of the amp. Antenna and equipment grounded well I think.

TIA Drifter

 

[Switch Kit]

well Drifter ...have been told over the years that there really isn't anything over 100% modulation anything over is bleed/splatter to adjasent channels above and below from the one your on as well as a waste of power on the operators radio as well , Copper huh ? I really can't speak for them but VR-16 is the AMC in that radio (audio up and down pot.) I personally doubt they clipped the limiter in there ? but I suppose the pot could be turned up to go over the 100% mark as well .....2 to 15 could also take the audio off the charts if not adjusted correctly ....trying to prevent bleedover / splatter is a good thing I would agree ....What kind of coax are you using ? .....It's to my understanding that 9913 is one of the best coax out there and that it can also help the bleed/splatter factor ....other then all of that mumbo jumbo ....I suppose your radio might do better to be put on a bench of a trust worthy radio guy and have it checked for not being over the 100% mark if that's truly what you looking for ? Can't see anything wrong with a second opinion all the same. Are you using the Mighty D-104 lolly pop ? .....could be a plus for you to turn that puppy down a little while your at it. (-: Sounds to me like you have yourself a pretty big station out there dude ..2 driving 4 huh ? ......you go Drifter !! SK

 

[riq165]

Hi Drifter-

What kind of antenna on the base? How high? Coax? Are your phone lines on a pole or underground? How close is the antenna to the phone / power poles? All of this, and more, factors into potential TVI and Phone RFI. The real test is to try it and see what happens. Hopefully you have neighbors who will work with you on solving the problem so you can have your fun without disturbing theirs.

From a purely technical stand point 100% modulation is the absolute limit for the negative peaks, anything past that and your are generating "splattering". The positive peaks can go higher IF you are able to control the 2 independently. Over modulation is very easy to correct... turn down the mic gain. The best way to truly know what is going on is with a scope.

Oh, and is that amp class C or AB?


73

riq165

 

[Drifter]

well Drifter ...have been told over the years that there really isn't anything over 100% modulation anything over is bleed/splatter to adjasent channels above and below from the one your on as well as a waste of power on the operators radio as well , Copper huh ? I really can't speak for them but VR-16 is the AMC in that radio (audio up and down pot.) I personally doubt they clipped the limiter in there ? but I suppose the pot could be turned up to go over the 100% mark as well .....2 to 15 could also take the audio off the charts if not adjusted correctly ....trying to prevent bleedover / splatter is a good thing I would agree ....What kind of coax are you using ? .....It's to my understanding that 9913 is one of the best coax out there and that it can also help the bleed/splatter factor ....other then all of that mumbo jumbo ....I suppose your radio might do better to be put on a bench of a trust worthy radio guy and have it checked for not being over the 100% mark if that's truly what you looking for ? Can't see anything wrong with a second opinion all the same. Are you using the Mighty D-104 lolly pop ? .....could be a plus for you to turn that puppy down a little while your at it. (-: Sounds to me like you have yourself a pretty big station out there dude ..2 driving 4 huh ? ......you go Drifter !! SK

I use RG213U..... Thanks... I get alot of compliments, and locals wanting to see my station. I might buy some 9913 If it will allow me to unleash my full 1200 watts without bothering the neighbors. Funny thing is I do not have any TVI in my house. I only have two complainers. I bought them some ferrite clamps. One lady has not come knocking since. The other said she heard me again... I wonder if she installed the beads correctly...... Then again my antenna might be just too close to her house. I am thinking she is also mad because the antenna went up.... If thats the case she will never be happy

 

[Drifter]

Hi Drifter-

What kind of antenna on the base? How high? Coax? Are your phone lines on a pole or underground? How close is the antenna to the phone / power poles? All of this, and more, factors into potential TVI and Phone RFI. The real test is to try it and see what happens. Hopefully you have neighbors who will work with you on solving the problem so you can have your fun without disturbing theirs.

From a purely technical stand point 100% modulation is the absolute limit for the negative peaks, anything past that and your are generating "splattering". The positive peaks can go higher IF you are able to control the 2 independently. Over modulation is very easy to correct... turn down the mic gain. The best way to truly know what is going on is with a scope.

Oh, and is that amp class C or AB?


73

riq165

I use a Coily Base Enforcer Ground Plane Antenna, Up 40' I can get it up to 48' if it will help. The amp is a class B, RG213U will upgrade if it will help. The Utilities are underground.

 

[C2]

50 swinging 1000 sounds like a lot for 4 transistors.

Just a straight up tune goes like this:

Connect a 1 kHz AF tone generator to the mic audio input, then adjust for a 30 mV peak.

Set the radio's carrier power to what you want, say 2W into a resistive 50 ohm load. (I don't do it like that, and don't forget to turn off the AF gen)

With the radio keyed, monitor the signal on an O-scope and note the peak voltage (you will need to tap the RF from the resistive load).

Turn on the AF tone generator and adjust the modulation until the peak envelope voltage is twice the carrier. (you might need to trigger the scope)

You should see a nice audio envelope with peaks at twice the carrier voltage and valleys that just pinch to 0 volts. That is 100%.

If you continue to increase the modulation, the valleys will widen and eventually the peaks will start to clip. This continues until you end up with something that looks like a square wave (pulse) envelope.

To set the radio for your amp, I would do the same thing, except for where you set the radio's carrier level. To set the radio for the amp, I would monitor the amp's output on the scope (under 100% modulation) and increase the RF level just until the peaks start to clip. Here is where the amp starts to saturate. From here, I would back down the RF to just below the clipping point.

I would then go back and retune for 100% modulation.

If your always running the amp, I would set the internal RF adjustments lower and the RF Power control higher so that I could use the RF Power control to turn the RF drive down. That way I do not always have to run full open.

If you run the amp only when you really want the power, I would set the radio's high RF the same way I set it for the amp, except peak the radio with the amp off (internal RF adjustments up). Then I would set up the amp with the RF Power control turned all the way down. That way I could easily switch between the amp and barefoot. (you might need to find a happy medium with these adjustments)

Notice that I do not use a power meter to get a specific number of watts for anything. Whatever it does, it does. I'll measure it later to see if its doing what is really should and then work from there.

 

[Drifter]

50 swinging 1000 sounds like a lot for 4 transistors.

???? It is a 2pill driving 4pills... Rated at 1200watts peak. 8)
Thanks for the info on setting the Mod though.