Unbelievable Cobra 148GTL 25 Watts 300% Modulation, Better than a Cobra 2000GTL... Seriously ???
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- Опубліковано 13 січ 2023
- Satire, Satirical, is it real? Maybe.... YOU HAVE TO SEE THE END, FUNNY
Read all the description below to learn more.
Yes, this can be real, it is real in this video, but in the real world most people don't have a 15 Volt system in their vehicle.
Yes most vehicles charge at somewhere from 13.8 to 14.4 volts, but that is right at the battery, and that is rarely the voltage seen inside at the places where most people connect their radios. There is almost always a significant voltage drop by the time all the accessories are turned on and the voltage finally gets to your radio.
I made this video to help people understand the significant power output (wattage) difference that will happen when the power supply voltage is changed that is supplied to the radio.
Just by changing the power supply voltage by a couple volts can change the power output by up to 40% or more.
This is a common way that some unscrupulous "radio tuners" and radio shops RIP customers off.
There is a local shop here in Southern California that shows people their radio doing X-watts on the bench and then they drive off happy and bragging about their X-watt radio. Then one day someone puts a meter on it and it isn't doing X-watts, it doing a lot less.
I had a friend drive straight to my house from a radio shop just off of Milliken Ave in Ontario next to the truck stop. He was bragging to me about his X-watts. I told him it was bull pucky and so we brought out the watt meter. It was putting out a lot less than what he saw at that shop. He was upset, so I told him lets take it in to the bench. On the bench it did the same power as in his vehicle, that's because I have my power supply set at about 13 volts. I cranked it up to almost 15 volts and guess what? The magic X-watts showed up. A simple 2 volt difference was almost exactly the difference from 75 to 100 watts. 75 watts was exactly what the radio was supposed to do, but the tech that charged him to "tune it up" showed him 100 watts.
I don't know how these crooks sleep at night. This happenes every day, and not just at this shop, they are everywhere.
So in this video what you see and hear is really me making fun of those thieves and hopefully educating some people so they do not get ripped off.
Make sure you see the voltage on the power supply when picking up your radio. Maybe even take your own volt meter and watt meter. Ask to see the power after it is installed.
Yes !!! in this video I really do have this Cobra 148gtl doing 21 watts of clean 300% modulation, but it is at 15 volts, and 15 volts might be just a little higher than you should run these radios at full time. You're gonna go thru some meter lights and make the outputs really hot!
When you see it at 25 watts that is a real meter reading also, but it's crap distortion all over the place.
Once I turn the power supply voltage down to a real world scenario, what we get is a little over 200% modulation at 16 watts. This is what I feel is a best case scenario for a Cobra 148gtl in most mobile environments.
This 148gtl has been modded with the Finals Volted and with the NPC/RC mods, and had the modulation limiter removed on AM. It does sound beautiful on AM and SSB.
Like I said before, the 15 Volt results are real. With that being said, these 148's and the Cobra 2000GTL Base Stations have almost identical boards inside, and both can be tuned with just about all the same mods. The difference is that a Cobra 2000gtl has a built in power supply, and just like you see me change the voltage in this video, the 2000gtl has an adjustment also. That means when you take your radio to the "radio man" he can just turn up the voltage and suddenly you believe he is a radio god. Don't be fooled, your radio will run hot and all your meter lights will burn out and then he can sell you some LED's. Then your capacitors will go bad, then....
OK, so leave some comments
Most car and truck alternators produce 13.8v to 14.2v when running. The battery at rest should be 12.5v-12.8v with the engine off. You went from to high to to low.
if you read my description for this video, I say 13.8 to 14.4, but this video isn't about alternator voltage, it's about showing how just a couple volts has a significant impact on the amount of power a radio can put out, and this video is specifically aimed at, making fun of, and exposing, these truck stop CB shops that tell their customers (and show them) that their radio is doing all this exaggerated power when in fact it may do that power on their 15 volt bench power supply, but the radio is not going to perform like that once installed in their truck/car.
So from what i just saw, if you're arround the 15v u will have a bit more headroom for positive peaks?
No, you have to do the NPC mod to reduce the negative peaks, otherwise the 15 volts doesn't help.
To explain, if you just up the voltage you would have something like a 6 watt carrier and 24 watts PEP, and that is still just 100% modulation. A stock radio opened up to be 100% modulation would be 4 and 16. That's the same 4:1 ratio. With 15 volts your radio will put out more power and your signal will travel a little farther, but it is still just 100% modulation, and your radios components, especially the light bulbs will burn out faster.
To explain more, you do not have to change the voltage at all. If you just do the NPC mod AND reduce the carrier you will end up with something more like a 1.5 watt carrier and 16 watts PEP, which would be well over 200% modulation. It is the NPC (negative peak compression) that allows over 100% Modulation without clipping the negative dips.
Your term "headroom" is almost correct, but the headroom as you call it, is created by reducing the carrier AND compressing the negative peaks to allow the same positive peaks without going "too low" on the negative dips and clipping the negatives.
The whole point of me showing 15 volts was simply to make fun of some unscrupulous CB Shops that show the customer their radio doing big power (on 15v) when the customer picks up their radio and pays the bill. Most CB'ers don't have a watt meter on their set up and just believe whatever the CB shop says.
Now, to add to all this, if you do crank up the voltage to say 15v, then you will also raise the carrier again, and then you will have to lower the deadkey again by changing the resistance on one side of the variable POT that controls the deadkey, then you can end up with a 1.5 deadkey once again, but now the PEP Power will be up near 25 watts, which is now pushing 300% modulation. If done right, the modulation will still be perfectly clean.
BUT BUT BUT !!!.... the higher voltage is hard on the radio and you can burn components up and bulbs out.... AND there are a lot of radios out there on the receiving end of your transmit that will not tolerate that much modulation in the their receive. That is why you may end up with some people saying your radio sounds great, and others saying you sound like poo poo. If they say you sound like poo poo, ask then to turn off their noise blanker.
Can you describe your npc/rc mod? I don't feel safe to run without clipping circuit. I don't need more than 130 to 150% modulation to preserve my 4 pills amp 😉
Very much like this, but each radio I do I spend time perfecting the mods listed here, plus audio chain mods, tuning/alignment, clarifier mods, etc... but every radio is a little different and they respond differently also. One thing that almost all the radios have in common is that if you go below 1 watt deadkey the audio gets trashed... The reason I mention that is I hear so many poeple talking about needing a 1/2 watt deadkey. I should also mention that just because a radio has 200 or 300% modulation doesn't mean it's going to sound good to other radios. Many radios can't handle all that modulation correctly. So some people may tell you that you sound great, and some other may tell you that you sound like crap. If you do have someone tell you that you sound crappy, ask them to turn off their noise blanker. Some noise blankers kill big audio. www.silicon212.org/CB/c2000.htm