no worries, Exit13 is very capable. I've talked with him on the phone before and he has the experience to help you out i.m.h.o.
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i got this friend...
- Thread starter longhaireddwb
- Start date
Don't worry grenades were deflected and disarmed.
Edit: I think Tallman was talking about the SP1a speech processor, my apologies for going Rambo..
Its clear what everyone was talking about, "Top gun modulator",
its nothing special unless you like distorted audio,
you can do more or less the same thing with a few cents worth of components,
The sp1 speech processor won't give npc / ppe or big swing from 2w deadkey but it will work in a 66.
its nothing special unless you like distorted audio,
you can do more or less the same thing with a few cents worth of components,
The sp1 speech processor won't give npc / ppe or big swing from 2w deadkey but it will work in a 66.
Thank You, bob85.
I would like to add that I have seen similar results in the older EPT 3600 radios, I believe it was with one diode and one variable resistor, it was swinging like a banshee, but then special attention was paid to the driver bias in order to reduce IMD and make the final PA "more linear".
It looked asymmetrical on the scope.
Neat little hat-trick, made driving the box real fun.
I have not found a stand-alone solution to produce results similar to this in a Cobra 29 or PC-66, the closest thing I have found so far is the modulation transformer replacement circuit, and then computer interface. That's more geared for base station operation and higher fidelity stuff, wide-banding and all that.
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Nice results for a lot less $$$, he is measuring RF volts, not watts.
I built the circuit to replace the transformer, and did a standard "Gold Finger Cap Change" using the stock pre-amp in a 29, it works great and gets compliments all the time, only it's nowhere near as pure on the scope (AMC needs re-design), but when running the computer interface "Direct Inject", it's MMM/Asymod clean.
My radio uses the TA7222, and that little audio I.C. can make some nice music.
The 29 in the videos has a custom audio amplifier, but the mod works great with the factory chip.
Notice the peak voltage remains about the same, that's because this is controlled carrier A.M. in so far as that the modulation ratio is directly affected by the carrier level, carrier level doesn't affect the peaks. So the lower the carrier, the higher the mod%, the processing from the PC is keeping everything sinusoidal and producing the asymmetry.
At this point, if I'm running a computer into the Cobra 29, I no longer care about communications grade audio; I want to "broadcast" a seriously different kind of signal, one that stands out with the best of 'em. This is what I call the poor (or Technical) man's "DaveMade digital transmitter" you build it out of an old 29, and step up & into the world of Hi-Fi A.M.
73
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There has been plenty of talk about npc & ppe on here years ago Leapfrog, i seem to remember one guy saying he invented it for exports,
goldfinger is one of the good guys, i have heard radios he modified sounding good on air, its been a long time since i last talked to him or motormouth.
goldfinger is one of the good guys, i have heard radios he modified sounding good on air, its been a long time since i last talked to him or motormouth.
Yes there has been, fair enough; just trying to share something "new" for the AM only rigs.
(Shout-out to CB Phreaker in California who re-designed the 148 GTL AM reg circuit for the open 29 mod, thank you brother)
Was it Billy D. who said that?
Didn't RF limited produce a clean radio? Or was it a splatter box with the modulator turned on? I can't imagine they would sell a splatter-box
, this leads me to believe they "worked the kinks out" of the NPC-RC modification and made it a factory feature in some radios, switchable.I like the Gold Finger cap changes, opened up the 29 nicely.
Yup all this excitement for plastic radios, yet I keep being drawn towards this.
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yes i think it was billy that claimed he invented it,
i have had many good conversations with goldfinger and motormouth on paltalk,
people were talking about swapping transformers in cb's since that's the bottleneck even if you open the amplifier bandwidth,,
i don't know anything about RF limited rigs
The direct injecting plastic radios came about one night when some of the guys in primes room kept saying plastic radios will always sound plastic,
i disagreed & decided to try and prove it with what i had lying around,
i hooked my wifes portable cd player playing "BUMP IT DOWN" through a 4.7uf audio grade cap directly to a president ar144's AM reg mod circuit & used my JRC hf set on wide AM to record what i was transmitting & sent the file to prime.
at first he said gtf out of here bob that's no plastic radio, its got bass & trebble,
i explained what i did to get rid of the plastic sound, the rest is history.
i have had many good conversations with goldfinger and motormouth on paltalk,
people were talking about swapping transformers in cb's since that's the bottleneck even if you open the amplifier bandwidth,,
i don't know anything about RF limited rigs
The direct injecting plastic radios came about one night when some of the guys in primes room kept saying plastic radios will always sound plastic,
i disagreed & decided to try and prove it with what i had lying around,
i hooked my wifes portable cd player playing "BUMP IT DOWN" through a 4.7uf audio grade cap directly to a president ar144's AM reg mod circuit & used my JRC hf set on wide AM to record what i was transmitting & sent the file to prime.
at first he said gtf out of here bob that's no plastic radio, its got bass & trebble,
i explained what i did to get rid of the plastic sound, the rest is history.
I got on paltalk for a short while, like 1 or 2 days but I then uninstalled it.
Well I have to pause for the cause, bob85 and thank you for doing that, that fateful evening.
If you hadn't of done that I probably wouldn't be here typing this post.
I had my first experience injecting audio into a galaxy 66, my jaw dropped at thinking about the possibilities of feeding a signal from my computer!
The transformer really is the bottle neck in AM only rigs, I found-that-out by injecting a signal to the input pin of the TA7222 in my 29 LTD, the signal was not good enough; not nearly wide-enough for the type of fidelity I was looking for.
I tried the Rev Bow Bastard Modulation Engineering transformer replacement (shout-out), and admittedly one half drunken night I fubar'ed the install and walked away from it for a while, lost interest.
Several months went by, then one day I got an email, and a schematic for a "cobra29audiomod"!
Now with about $25 worth of discrete components, PCB included, my plastic radio can "BUMP IT DOWN" too, & l didn't have to pay several hundreds of dollars for MMM/Asymod to get asymmetrical wide-band audio out of a 29 LTD!
I might join paltalk again and try to shout out to GoldFinger and give him a "thank you", because his cap change suggestions are great for opening up the bandwidth, I really like the results.
I emailed John once or twice but, i'm not a whale so... yeah I get crafty and "build it, not buy it."
I'm sure he is a very helpful and great person, I just ain't paying his price. People can call me cheap I don't mind that, and nobody calls my audio "cheap" when they hear it, so I think I'm doing alright, headed in the right direction.
Now I just need to get to work on my antenna system, lol.
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Looks as if you need only copy the two-transistor AM-modulator circuit from the original Cobra 148-type radios. The tiny pc board sure looks like that's what it is. A 2N3904 driving a 2N6487. The Cobra used a 2SC945 driving a 2SC1419.
Just one drawback. The peak modulated voltage to the final transistor will be cut roughly in half. Should drop the modulated PEP to a lot less than the transformer provided.
Don't get me wrong. My attitude is "Damn the wattmeter, full audio ahead".
The original modulation transformer puts a peak audio voltage roughly twice the power-supply voltage onto the final and driver's collector circuit. The transistor-only setup in the Open HiFi circuit can't deliver more than the power-supply voltage, dropped by about 1.5 or 2 Volts.
Just how he gets 32 Watt peaks by feeding no more than 12 Volts to a Cobra 29 final is not terribly clear.
Cool trick, though.
73
Just one drawback. The peak modulated voltage to the final transistor will be cut roughly in half. Should drop the modulated PEP to a lot less than the transformer provided.
Don't get me wrong. My attitude is "Damn the wattmeter, full audio ahead".
The original modulation transformer puts a peak audio voltage roughly twice the power-supply voltage onto the final and driver's collector circuit. The transistor-only setup in the Open HiFi circuit can't deliver more than the power-supply voltage, dropped by about 1.5 or 2 Volts.
Just how he gets 32 Watt peaks by feeding no more than 12 Volts to a Cobra 29 final is not terribly clear.
Cool trick, though.
73
He drew inspiration from the 148 GTL, why re-invent the wheel right?
The 2N6487 is a beast of a part, all things considered.
That one drawback is the first thing I noticed after replacing the transformer, but it is more about audio fidelity than watts.
He has removed the reverse polarity diode, and D8, IRF520N conversion, he also bypassed the on/off switch, input is 13.8 volts.
Nomad, it's going to require more than 2 amps.
I believe in the IRF520N, that it can produce 32 watts of instantaneous peak energy.
I've gotten around 12 or 13 watts FM out of an IRF520N, stands to reason they can in-fact produce 25 watts p.e.p., how much of the last 7 watts is really a stretch?
13.8 Volts and he doesn't have a diode drop to contend with, the #'s do in fact add up, and yes asymmetrical waveform on a Cobra 29 is a "neat trick", (neat Hi-Fi also) even if this method requires a P.C.
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~Cheers!~
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longhaireddwb, don't bother doing anything or adding anything to that radio.
your friend wants to be louder because his friends are telling him to "pump it up" or he is trying to key on and talk over his rock hauler buddies.
He is used to having an amp and now feels like a wimp. so now he wants the radio "as loud as it can get" in an attempt to compensate for not having the amp anymore.
you need to tell him that it doesn't work, and that his radio is already operating correctly.
tell him that there isn't a mod in the world that is going to make his 66 talk over anyone that it can't talk over now.
after that conversation, he will lose all faith in your radio knowledge and will end up at a truck stop shop where the "tech" will be all to happy to turn up the AMC and tune for maximum smoke.
the only change you can make to that 66 that is going to make him happy is to add an RFX75 or a stinger board to it, and i am not much of a fan of either one of those built in amps.
tell him if he wants to be louder then he just needs to start yelling everything into the mic.
LC
your friend wants to be louder because his friends are telling him to "pump it up" or he is trying to key on and talk over his rock hauler buddies.
He is used to having an amp and now feels like a wimp. so now he wants the radio "as loud as it can get" in an attempt to compensate for not having the amp anymore.
you need to tell him that it doesn't work, and that his radio is already operating correctly.
tell him that there isn't a mod in the world that is going to make his 66 talk over anyone that it can't talk over now.
after that conversation, he will lose all faith in your radio knowledge and will end up at a truck stop shop where the "tech" will be all to happy to turn up the AMC and tune for maximum smoke.
the only change you can make to that 66 that is going to make him happy is to add an RFX75 or a stinger board to it, and i am not much of a fan of either one of those built in amps.
tell him if he wants to be louder then he just needs to start yelling everything into the mic.
LC
Leapfrog,
not having been on PAL myself for years i have no idea what people have been up to, its the first time i have seen the 29 type rigs with the export type modulator but it makes sense if you want wide audio without an expensive audio transformer,
Nomad,
rather than stepping voltage & impedance up before the final as in the original transformer setup, it looks to me that he has modified the tank circuit to step voltage & impedance up more than the stock radio,
you could do that by using a final operating @ a lower optimal load impedance drawing more current from the psu than the original 2078
not having been on PAL myself for years i have no idea what people have been up to, its the first time i have seen the 29 type rigs with the export type modulator but it makes sense if you want wide audio without an expensive audio transformer,
Nomad,
rather than stepping voltage & impedance up before the final as in the original transformer setup, it looks to me that he has modified the tank circuit to step voltage & impedance up more than the stock radio,
you could do that by using a final operating @ a lower optimal load impedance drawing more current from the psu than the original 2078
Yea I saw some drama, (I've come to expect it now) on paltalk between two radio groups called the bowl.. One was empty, the other was poppin', a full house!!
Yes, this is so much more affordable (& easier to locate) than finding a transformer that can pass bandwidth anywhere near that of the modulator design, this one uses an NPN as the main regulator (so like a Cobra 148 style).
Temperature on the heatsink was about 105°F after a 30 minute torture test broadcasting at 32KHz wide, more to come in a different thread.
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Sorry guys. Been on the road for a while. Thanks for the comment Loosecanon as that is about what I had told him. I'm not going to don't crazy stuff to his radio and make it sound bad. He left me alone about it now. Not sure what he wants went his employer is limiting him. I mean, a 66 works just fine when properly tuned so I dont see an issue.
Now I'm working on another radio. Just posted a question so if someone could help me on it...
This thread got a little over my head when you start talking injecting audio. I know what your talking about but in a truck I dont think this is going to help. He barely know what an RF gain is for. Ha.
Now I'm working on another radio. Just posted a question so if someone could help me on it...
This thread got a little over my head when you start talking injecting audio. I know what your talking about but in a truck I dont think this is going to help. He barely know what an RF gain is for. Ha.