linear....really?????

[222DBFL]

LeapFrog, read his first post, he says it's a 2 pill amp. I've one like it and it likes a 2w dead key and about 8w max pep on AM. On SSB I ran 8-12 watts PEP into it and it sounded good.
This is with the 2 pill 1446 amp. A black knockoff Palomar. It's not a bad little amp, just don't overdrive or it will sound like crap for sure!!
And yes, I would definitely start with a lower deadkey for a 1 pill and keep the PEP power down as well. They will do about 75-85 watts PEP per transistor at 27MHz, just from my experience, and not sound like crap. I used mine mostly for SSB. Driven with a uniden 980. AM PEP was about 8 watts and 10 watts on SSB. Worked well together.

 

[Tallman]

I'll betcha it is a class "C" amp.

 

[LeapFrog]

222, I've re-read the posts from redbeast, I just don't see any mention of a 2 pill from the original poster, now Pappas and Beer on the other hand suggested it could be a 2 pill just like the one he has.

Just from looking at the pictures that redbeast posted, i'm going to say it looks like a wonderful one pill unless there's another one hiding on the underside of the PCB.


I Hope everybody who reads This Thread has a great day today. Take care & stay safe.
73

 

[redbeast]

I'll betcha it is a class "C" amp.

Ok, so let me back up one.....I assumed 2 pill due to the 2sets of jumpered whats(?). But now leapfrog and tallman appear to be right, single pill as a preamp. What exactly are the units with the jumpers? My bad about 2pill, im used to seeing transistors marked with #s. Please bear in mind, im not dtupid, but not a radio tech either..makes sense, like using a preamp to drive a big Mardhall head! The guy that gave this to me is, lets say, radio challenged. I dont guess but what he just ran it on the back end of a stock radio and talked. Since right now im using a stock cobra 25for a mobile, would the 5 watts be too much or not enough? I dont need a splatterbox, just wondering. Also, good point about low power for mobile amp, my ride has a 55A alt, so not looking to run into an issue there. Unit only has a 15A glass fuse, so ill assume it will only draw about 10A in use. Preamp on to drive big box, preamp off for radio, sound right? Again guys, im not a radio tech, and sure appreciate the input!!!!! Could you clue me as to "class C"?

 

[LeapFrog]

Ok, so let me back up one.....I assumed 2 pill due to the 2sets of jumpered whats(?). But now leapfrog and tallman appear to be right, single pill as a preamp. What exactly are the units with the jumpers? My bad about 2pill, im used to seeing transistors marked with #s. Please bear in mind, im not dtupid, but not a radio tech either..makes sense, like using a preamp to drive a big Mardhall head! The guy that gave this to me is, lets say, radio challenged. I dont guess but what he just ran it on the back end of a stock radio and talked. Since right now im using a stock cobra 25for a mobile, would the 5 watts be too much or not enough? I dont need a splatterbox, just wondering. Also, good point about low power for mobile amp, my ride has a 55A alt, so not looking to run into an issue there. Unit only has a 15A glass fuse, so ill assume it will only draw about 10A in use. Preamp on to drive big box, preamp off for radio, sound right? Again guys, im not a radio tech, and sure appreciate the input!!!!! Could you clue me as to "class C"?

Okay let me start off by saying that my description of your amplifier being a one transistor amp is inaccurate due to the fact that your model has a preamp, there will be two or three very tiny transistors for this and keying circuit.

I should also point out the distinction for the term pill many hobbyist and enthusiasts use this term because of the shape of the RF power transistors they resemble a round white pill while it is true that your amplifier will contain other transistors these other transistors are not referred to as pills, that term is reserved for the round white ones.

Generally speaking the amplifier will be attached in between the radio on the antenna if you're using a small amplifier to drive a bigger one of course it would go in line before the big amp.

One thing to keep in mind when you have an amplifier that also has a preamp function the amplifier will move the active path of RF by using a relay this is so the signal coming into your radio is present for reception and when you transmit the preamp is taken out of line as to not damage it. If it is switched on the preamp comes back into play as soon as you unkey.

Although the physical location of the amplifier never changes , the signal path through the amplifier does change. Basically if everything is working right the amplifier does this seamlessly.

I'm going to say that five watts input is going to be creating some harmonic distortion by driving a transistor into saturation point, overdriving/driving it too hard.


Running it like this with so much input ( if it is a one pill amplifier) is going to severely shorten the life of that transistor and will most definitely lead to an early failure compare to driving it with much a lower power level.

Another thing that's relevant here please do not be confused by the term preamplifier when I'm using this term I do not mean to describe the driver or modulator (the 1 pill power output part of the amp) as some people would call your one pill amplifier. The preamp is reserved for when you're describing the receive signal being Amplified not to describe the power coming out of the amplifier into your antenna, basically you have two amplifiers in one one for your reception and one for your transmit.

So I would say you have "1 pill driver box" with a builtin preamp.
People can build or buy preamplifiers separately as they can with power amplifiers it is just more convenient to have both in one box.

The alternator in your vehicle should be fine.

 

[redbeast]

Okay let me start off by saying that my description of your amplifier being a one transistor amp is inaccurate due to the fact that your model has a preamp, there will be two or three very tiny transistors for this and keying circuit.

I should also point out the distinction for the term pill many hobbyist and enthusiasts use this term because of the shape of the RF power transistors they resemble a round white pill while it is true that your amplifier will contain other transistors these other transistors are not referred to as pills, that term is reserved for the round white ones.

Generally speaking the amplifier will be attached in between the radio on the antenna if you're using a small amplifier to drive a bigger one of course it would go in line before the big amp.

One thing to keep in mind when you have an amplifier that also has a preamp function the amplifier will move the active path of RF by using a relay this is so the signal coming into your radio is present for reception and when you transmit the preamp is taken out of line as to not damage it. If it is switched on the preamp comes back into play as soon as you unkey.

Although the physical location of the amplifier never changes , the signal path through the amplifier does change. Basically if everything is working right the amplifier does this seamlessly.

I'm going to say that five watts input is going to be creating some harmonic distortion by driving a transistor into saturation point, overdriving/driving it too hard.


Running it like this with so much input ( if it is a one pill amplifier) is going to severely shorten the life of that transistor and will most definitely lead to an early failure compare to driving it with much a lower power level.

Okay let me start off by saying that my description of your amplifier being a one transistor amp is inaccurate due to the fact that your model has a preamp, there will be two or three very tiny transistors for this and keying circuit.

I should also point out the distinction for the term pill many hobbyist and enthusiasts use this term because of the shape of the RF power transistors they resemble a round white pill while it is true that your amplifier will contain other transistors these other transistors are not referred to as pills, that term is reserved for the round white ones.

Generally speaking the amplifier will be attached in between the radio on the antenna if you're using a small amplifier to drive a bigger one of course it would go in line before the big amp.

One thing to keep in mind when you have an amplifier that also has a preamp function the amplifier will move the active path of RF by using a relay this is so the signal coming into your radio is present for reception and when you transmit the preamp is taken out of line as to not damage it. If it is switched on the preamp comes back into play as soon as you unkey.

Although the physical location of the amplifier never changes , the signal path through the amplifier does change. Basically if everything is working right the amplifier does this seamlessly.

I'm going to say that five watts input is going to be creating some harmonic distortion by driving a transistor into saturation point, overdriving/driving it too hard.


Running it like this with so much input ( if it is a one pill amplifier) is going to severely shorten the life of that transistor and will most definitely lead to an early failure compare to driving it with much a lower power level.

Okay let me start off by saying that my description of your amplifier being a one transistor amp is inaccurate due to the fact that your model has a preamp, there will be two or three very tiny transistors for this and keying circuit.

I should also point out the distinction for the term pill many hobbyist and enthusiasts use this term because of the shape of the RF power transistors they resemble a round white pill while it is true that your amplifier will contain other transistors these other transistors are not referred to as pills, that term is reserved for the round white ones.

Generally speaking the amplifier will be attached in between the radio on the antenna if you're using a small amplifier to drive a bigger one of course it would go in line before the big amp.

One thing to keep in mind when you have an amplifier that also has a preamp function the amplifier will move the active path of RF by using a relay this is so the signal coming into your radio is present for reception and when you transmit the preamp is taken out of line as to not damage it. If it is switched on the preamp comes back into play as soon as you unkey.

Although the physical location of the amplifier never changes , the signal path through the amplifier does change. Basically if everything is working right the amplifier does this seamlessly.

I'm going to say that five watts input is going to be creating some harmonic distortion by driving a transistor into saturation point, overdriving/driving it too hard.


Running it like this with so much input ( if it is a one pill amplifier) is going to severely shorten the life of that transistor and will most definitely lead to an early failure compare to driving it with much a lower power level.

Another thing that's relevant here please do not be confused by the term preamplifier when I'm using this term I do not mean to describe the driver or modulator (the 1 pill power output part of the amp) as some people would call your one pill amplifier. The preamp is reserved for when you're describing the receive signal being Amplified not to describe the power coming out of the amplifier into your antenna, basically you have two amplifiers in one one for your reception and one for your transmit.

So I would say you have "1 pill driver box" with a builtin preamp.
People can build or buy preamplifiers separately as they can with power amplifiers it is just more convenient to have both in one box.

 

[LeapFrog]

From the pictures alone it will be a little difficult to tell you for certain if it's a class-c box.
Unfortunately I have to say that many of those amps from that time are class C.

Someone more familiar with the palomars will have to chime in.

An experience builder could probably look at some high resolution photos and tell you right off the bat if there's any biasing circuit in there or if they're just taking the (base?) leg directly to ground through an inductor or resistor.

(Class C configuration, in the amateur radio world these amplifiers are reserved for FM & CW operation, that's not to say that many people run them on am in the CB world and to this day Builders are still making class c boxes because they produce more watts and use less energy in that configuration the cost of this efficiency is increased distortion and a non linear signal)

 

[redbeast]

Sorry, not good at typing on phone, old school fingers. Leap, youre right, and now i get the "pill" routine, im used to calling them power transistors, but they do look like pills, huh? Dont guess but what my guy did was just plug and play. So to use this for a stock cobra 25 means ill have to turn the cobra down as not to overdrive the power transistor, correct?

 

[LeapFrog]

Disclaimer: The content in this post is for educational and scientific research purposes only, I am not responsible for what another individual does with this knowledge.

I would say so, (lower power input) but seeing as how I'm having a little trouble interpreting the datasheet it would be best to confirm this with another forum member, you may be just fine running a four watt dead key into it, but I would start very small on any power input, it seems to me like your Cobra doesn't have any kind of variable modification done to it. You could try running the factory radio into it but I'm forwarning you if you overdrive the transistor and blow it up you're going to spend more money buying the replacement pill and repairing that amplifier then it's worth in the resale market, so chose wisely.

In a Cobra 25 LTD the final output adjusmemt for power is L10, it's going to be a cylinder looking thing by the final, kind of in the middle of the heat sink if that makes sense the heat sink has an odd shape, you're going to need a watt meter, depending on that individual radio, you may be able to drive the dead key down to two watts but that's not likely, use a (nonmetal)preferably a plastic straight edge or flat head type tool, normally you drive the "ferrite slug core" (black thing) clockwise to go deeper into the inductor to lower the power, you rotate counter-clockwise to raise the power. This adjustment Point has more effect on the pep or modulated Carrier then it directly affects the carrier but it will lower your deadkey some.

If the radio has never been Peak and tuned before and is a factory virgin, you're going to see bees wax covering the slug this needs to be carefully removed before any attempts are made at adjusting the slug, when you do remove the wax you must be certain to take caution when braking the slug loose from its sealed position, ( I find that a few drops of isopropyl alcohol help to loosen the seal) if you crack the ferrite slug in half or break a quarter off of it you will affect the tuning ability and characteristics of L10.

If your Cobra 25 is the GTL model the part designation may be different, but the location and physical appearance will be the same.


How mutch this adjustment affects your deadkey depends on the particulars of the radio in question.

 

[LeapFrog]

RedBeast, if you have any friends in the area or local operators that can help you, it may be best to have somebody help you match that radio to that device if you are certain that you want to use it, if you're good at soldering you could do the necessary modifications to add variable dead key to your Cobra it's not a very complicated process but it takes some confidence with a soldering iron and a watchful eye to observe for incidental short circuits.

I must say this though anytime the dead key has been lowered on a Cobra radio using L10 without the use of an oscilloscope it looked fine if the amc(modulation) is still set @ factory adjustment.

BUT, 9 out of 10 times they look like trash
and will splatter bad when the method used to lower the carrier
is the common resistor and capacitor combination added at jp36 (A jumper is removed cobra 29 at this designation, same location for the 25 but different name) Also you really have no way to adjust carrier up beyond 4-5 watts unless you shorten the coil @ L10 (25LTD) or add capacitance at a certain place.

The method I use to lower the carrier (dead key) and it looks respectable on the scope is with a with a TIP120 transistor mod with a 1K Ohm or 500 Ohm pot, 220uf electrolytic cap (dc side faces the back of the radio), and a 120 ohm resistor. But the dead key has to he set LOW like 0.5 with 1-2 watts of maximum forward avg power "swing" using normal voice modulation. The AMC diode must not be clipped, you will need to adjust it for "less bird swing" I know it's counterintuitive to what CB'rs will tell you but you but its true. Also Eitner says (it worked for me also) to replace the 220uf electrolytic by the AMC (modulation) VR (vaRiable Resistor) to a 33uf, this helps the positive peaks to stay clean and less distortion, less harmonics.
I did 1800 TOLL FREE's keep alive circuit also but that's in another thread on this forum also.(search bar ∆) the amc adjust, mic gain, and carrer setting will help you produce factory rated perfomance, when dialed in correctly it can do maybe 5% better on previous max output and sound great @ 105% modulation with clean negative peaks on the oscilloscope or you could make the same radio sound l crap loads worse and splatter like hell just by turning two knobs the wrong way, so this tune is not pratical for most operaters because it is so damn finicky.


If you really want the variable that came out I will give you a picture of the schematic and explain what is happening on the schematic (@ least what info you need to make it work) l.m.k. I can add it to this thread.
or google it

This is the part that I hate to say but it is necessary for this set up to be done correctly and not interfere/splatter terribly, an oscilloscope to do the final tune or at least have access to one is a necessity, otherwise you can very easily create a square wave monster. And with that comes all the splatter it might as well have a clip limiter at that point so I can tell you that many people do lower their dead key and run an amplifier without the use of an oscilloscope but this is just the wrong way to do it, they are going in the blind and they are probably splattering all over the band, You could put a low pass filter after the amplifier and before the antenna that will help to reduce anything over 30 megahertz getting out and causing RFI/TVI

When you start learning about power the plot thickens, now you have to worry about common mode currents, RF grounding, DC grounding, power requirements, and high powered setups you may have to worry about "microphone bite"/RF burns. I'm going to say the generality though because running 100 - 200 watts are not really experiencing these problems when they get a 500 watt - 1KW and above range these become very serious concerns, when you run lower power the weaknesses in your feedline and your antenna system do not present themselves as well as with the high-powered setup, and I say that as a generality because if you have a proper input and output tune on the amplifier and a good standing wave ratio with the antenna, the SWR should not increase while running increasing power that's an indication of a problem somewhere that may not have presented itself when simply running barefoot.

Edit: After this thread guys I think I'm gonna have to lay off the coffee, came back after a few hours and seen that I basically have created the great wall of China only in text though.

 

[Pappas and Beer]

I would suggest using in the area of 1/2 to 2 watts. If you run a deadkey of 5 watts I bet the rms out of the amp will be in the area of 40 watts or so which will give it a 2:1 ratio to PEP which is bad on the amp. That amp looks like it's seen a few all nighters.

 

[jon666]

i have a few of them one is 1 pill
the other is mosfets 2 driving 4..
its a 100 watt amp.. i bought them years ago. never even hooked them up. there sitting in the closet

 

[9C1Driver]

Definitely not a Palomar Elite 300, not even close. Nice cheap little 1 pill that does not draw a lot of amperage. It probably has an auto SSB delay but who knows. The 1446 final is probably worth more then the amplifier these days lol.

 

[Tallman]

Could you clue me as to "class C"?

Class "C" amps do not generally as a rule have a bias applied to the base of the transistor. The term pill refers to the ceramic top of the final transistor in the transmit section. Class "C" amplifiers sound okay on AM signals but the sound quality suffers on SSB. It is a very efficient as far as power consumption is concerned. For more detail click the link below. Other classifications of amp you can study are "A", "AB1","AB2", and class "D".
http://www.circuitstoday.com/class-c-power-amplifier

 

[redbeast]

Class "C" amps do not generally as a rule have a bias applied to the base of the transistor. The term pill refers to the ceramic top of the final transistor in the transmit section. Class "C" amplifiers sound okay on AM signals but the sound quality suffers on SSB. It is a very efficient as far as power consumption is concerned. For more detail click the link below. Other classifications of amp you can study are "A", "AB1","AB2", and class "D".
http://www.circuitstoday.com/class-c-power-amplifier

Okay, first off thanks for akl the good input. Having an automotive background i get a lot of the data, and as I figured.....the radio should definitely be setup with this amp. As always in my past as well as yours theres always the crowd that just plugs stuff in with no thought, and we all know what they sound like even if they dont. So that being said, sounds like a project a) for my future, and b) over my expertise level. The radio im using right now is a stock (to my knowledge) cobra 25 ltd classic. Question.....is it possible to set the 25 up using the ch9 switch to control the deadkey hi/lo....im thinking this would make a nice combo, esp for a slipseat setup. I know that the 25s and 29s were good, solid units and modded would really talk tall, thinking ill just shelve this til after the holidays, and finding a good "wrench" to go through and set it up. Will be sending out anther post re: the rk56 igot free with the linear, since a couple of you asked. Im definitely going to reread all your posts again, i really appreciate your input. Also have some info to pass along re: newer charging systems....a lots changed in the auto world . Thanks again.......oh, BTW-anyone know exactly what the large cap looking devices with the wires coming out the top are...my bad in thinking they were transistors