Understanding amp designs: Texas Star

[unit_399]

WireDawg-

If you're looking for design info on transistorized linear amps, the best source for this type of information is the MOTOROLA RF DATA MANUAL. The one I have was published in 1978. It was reprinted by Radio Shack in 1984 (catalog # 62-1380). I've seen them listed on Ebay. There are several Application Notes (AN) and Engineering Bulletins (EB) pertaining to amplifier design written by the legendary Motorola RF design engineer Helge Granberg.



EB-63 "140 watt amateur radio linear amplifier."
and
AN-762 "Linear amplifiers for mobile operation."
have most of the design info you're looking for, but they were written for engineers and are really heavy on the technical lingo.. EB-63 was reprinted in the 1999 ARRL Handbook (and maybe other years), but the text was rewritten and is much easier to understand.

I would scan these articles for you, but have no way to do it here. You might try googling Helge Granberg. Maybe some ANs and EBs are online. Hope this helps. 73s

 

[Wire Dawg]

If it's brand new, the instructions should have come with it. If not, go to the MFJ website and download and print a copy of the instructions. It's there.

Mr. Beetle: While I can interpret certain legal & medical literature related to my job, as well as answer questions about the subject without making a jackass out of myself, I admit that when it comes to electronics I am not the brightest bulb on the tree. In case that you lack the intuition, the reason I'm asking questions in this forum is because I'm interested in the hobby, want to learn more and I have found many real people in here that are willing to share their knowledge without spewing sourness. I can read, speak & write multiple languages, however, the instructions that came with the artificial ground unit are written beyond my understanding in electronics: perhaps directed to geniuses like you appear to pretend to be. It does not bother me to accept that I was unable to obtain any + or - results from the gadget, and that is why I have asked for help. Your sarcasm is passé, and a lame attempt to seek recognition among those with the same rotten attitude towards other enthusiasts. I know that you have a lot to offer to this forum, but your interventions would be a lot more effective if you leave the stinking 'holier than thou' attitude behind.

 

[Wire Dawg]

WireDawg-

If you're looking for design info on transistorized linear amps, the best source for this type of information is the MOTOROLA RF DATA MANUAL. The one I have was published in 1978. It was reprinted by Radio Shack in 1984 (catalog # 62-1380). I've seen them listed on Ebay. There are several Application Notes (AN) and Engineering Bulletins (EB) pertaining to amplifier design written by the legendary Motorola RF design engineer Helge Granberg.

View attachment 9639

EB-63 "140 watt amateur radio linear amplifier."
and
AN-762 "Linear amplifiers for mobile operation."
have most of the design info you're looking for, but they were written for engineers and are really heavy on the technical lingo.. EB-63 was reprinted in the 1999 ARRL Handbook (and maybe other years), but the text was rewritten and is much easier to understand.

I would scan these articles for you, but have no way to do it here. You might try googling Helge Granberg. Maybe some ANs and EBs are online. Hope this helps. 73s

I appreciate the offer. Maybe after retirement, I will have the leisure time to take a course in electronics to decipher these books. The mere fact that a bunch of transistors, resistors, diodes etc can be thrown together and allow communications across the world, is fascinating. I worked in electronics during my military years, however, I did the “brawny” part rather than the ‘’brainy” one. Had the pleasure of going TDY to the US embassy at your QTH and others in SA/CA. Enjoyed every minute of every trip. Still have beautiful emeralds and a can of Bustelo coffee from Bogotá (1980's).

 

[Mudfoot]

I don't understand. I read this thread twice. At no point, did I see where beetle had his foot stepping on your nuts.

 

[towerdog]

Ok: Texas Star amplifiers have no output filtering. 1) Will somebody please outline any inherent pros/cons to such design approach? 2) Are the terms intermodulation distortion, harmonics, spurious signals, splatter & TVI one and the same? 3) What effect does a Bencher YA-1 LPF have when connected at the output of these amps? 4) What effect does a coax choke balun have when used at the antenna end? 6) If TS is used within their limitations (not overdriven), will there still be discernible adverse effects? I’m asking because, in addition to grounding my station & antenna, I have implemented all these measures to obtain the cleanest output possible (barring the purchase of amateur radio equipment). All was fine ‘till yesterday when, for the first time in my years in this hobby, I heard my voice coming out of the old toaster & PC speakers. It was not a hallucination. The hair on my terrier rose like a frightened porcupine and my ball python stood up like a flag pole. Even the rooster’s crow sounded like CQ, CQ, CQ when I keyed the radio this AM! Is the TS amp causing this anomaly? If so, how come it never happened before?

Cheap speakers suck, had some when I was young and NPR classical 88.1 would always come through when the computer was off, sometimes enough to wake me up and night til they finally pissed me off so bad i woke up and ripped the cord out the back.

Simple solution, rent a spectrum analyzer or check harmonic frequencies with a scanner as you drive around the block.
It's 2013, Obamas having his second term in office and the worlds turned upside down. This is the era of the television interfering with the CB radio, a world where old analog television antennas with built in preamps amplify wimax and unknowingly retransmit it to jam LTE, only for shady hotels to intentionally jam whatever the wimax dont to cling to their failed business model of $$$ for long distance.
Dun Dun Dun, check your grounds, ground loops especially, make sure your antennas is higher than your toaster oven, do a quick check and roll with it.
And never, ever, ever, mention on any amateur frequency you are running a Texas Star, or it will instantly splatter all over the band and cause your rig to start drifting frequency.

 

[The Bruce]

So your saying that CB is the only band that uses illegal amplifiers ?

I can't speak for every band out there but, yes, technically and legally speaking, any and all amplifiers for 11-meters are illegal.

 

[W5LZ]

Wire Dawg and all,
If you want to know why something works, and why it sometimes doesn't work, then that's good and I think you should do so. If/when speaking about electronics that isn't done by just asking questions, at least not on internet forums unless you already have a foundation (the basics) to make the answers understandable, for them to make sense. That same thing is true for anything, not just electronics. Can you imagine trying to explain about engine timing to someone who doesn't have any knowledge about engines at all? Just the terminology of it can bring it to a screeching halt. "Ain't no body got time for dat!", well, you'd better make time cuz it won't happen otherwise. One of the 'catches' to that learning process is finding someone who does know how and why that stuff works correctly. If you pick the wrong 'teacher' then you learn all of the 'wrong' ways of doing/thinking about it that teacher learned too. There's nothing 'fast' or 'easy' about it. There's a huge difference between knowing 'how' to do something and knowing 'why' it's done that way.
As for the legal/illegal thingy, think about it. Where will you find the most stuff done illegally, and why? It always involves 'limits'. What radio service has limits? They all do, the differences are what those limits are about and why. You don't like those limits? Hey! Join the club, not many of us like them either, but they are there and there are penalties (as unlikely as they may be). I can't think of anything that doesn't apply to so you'd better get used to it, you know?
No one is trying to make this stuff hard to learn. It's just hard to learn...
- 'Doc

 

[Wire Dawg]

I don't understand. I read this thread twice. At no point, did I see where beetle had his foot stepping on your nuts.

It may not be so obvious to someone that consistently adds value to the forum by bringing witty humor (cartoons/ comments), constructive debate and by sharing experiences that enhance the collective knowledge of all readers. I enjoy your threads because they either bring a smile or awareness of issues/ equipment affecting radio hobbyists. I do not condone bragging rights for citizens that meet licensure criteria for certain skills (driving a truck/ talking on radio) or regulated professional endeavors (practicing law/ medicine). I admire those that share their skills & knowledge: whether by explaining antenna theory in layman’s terms or writing about their subject of expertise. However, it is a totally different issue when bragging rights are turned into a weapon to demean and belittle others. Arrogant Debbie Downers that act as if they hold the Holy Grail for having passed a test, often have to be reminded that there is no license to explicitly or implicitly be insolent to others. There are other forums that cater to such mindset. If the illegality of CB amps is cited as the empowering ticket to be “judge & jury”, then these people need to be reminded that many laws have been proven to be immoral, unethical or unfair, such as the ones that brought about our civil war. If you still don’t see the trending attitude, please refer to historical threads in this forum.

 

[Wire Dawg]

Wire Dawg and all,
If you want to know why something works, and why it sometimes doesn't work, then that's good and I think you should do so. If/when speaking about electronics that isn't done by just asking questions, at least not on internet forums unless you already have a foundation (the basics) to make the answers understandable, for them to make sense. That same thing is true for anything, not just electronics. Can you imagine trying to explain about engine timing to someone who doesn't have any knowledge about engines at all? Just the terminology of it can bring it to a screeching halt. "Ain't no body got time for dat!", well, you'd better make time cuz it won't happen otherwise. One of the 'catches' to that learning process is finding someone who does know how and why that stuff works correctly. If you pick the wrong 'teacher' then you learn all of the 'wrong' ways of doing/thinking about it that teacher learned too. There's nothing 'fast' or 'easy' about it. There's a huge difference between knowing 'how' to do something and knowing 'why' it's done that way.
As for the legal/illegal thingy, think about it. Where will you find the most stuff done illegally, and why? It always involves 'limits'. What radio service has limits? They all do, the differences are what those limits are about and why. You don't like those limits? Hey! Join the club, not many of us like them either, but they are there and there are penalties (as unlikely as they may be). I can't think of anything that doesn't apply to so you'd better get used to it, you know?
No one is trying to make this stuff hard to learn. It's just hard to learn...
- 'Doc

I only seek too enhance my enjoyment of this hobby, but at the same time, wish not to bother others that live near me (that's why I initiated this thread). I seek advise here because I've found that this forum is one of a kind, for not been sponsored by a manufacturer, distributor or promoting a rigid one-sided view/philosophy of the hobby. Many of the explanations to technical question, including those that you have proferred, are often given in laymans terms that are easy to digest. I'd like to take the opportunity to thank you and others that do the same. I have added a course in electronics to my bucket list, as I find it increasingly interesting while studying for my test (still learning about color codes and Ohm's law). But until I can have domain of electronics, I will continue to seek input and advise from others.

 

[KM3F]

The original poster has asked about things that require very involved answers.
1. Filters are required to attenuate harmonics produced and passed through the amplifier that could cause interference to other equipment and services at other frequencies.
2. Intermod distortion is produced within the amplifier from the mixing of two or more frequencies due to inherent nonlinearity of the amplifier and it's design.
The FCC has spec limits for both harmonics and IMD before commercial sales can be approved or they are considered illegal to market in the US.
3. A choke balun is an attempt to stop RF current from traveling back to the radio on the outside of a Coax by presenting a high 'impedance' at the point it is connected.
4. Low pass filter is a device that passes all frequencies below a certain design frequency so harmonics above the cutoff point are attenuated to a very low level or stopped from being radiated.
And there is much more yet!
.
One has to have some background to understand the finer points of all these items.
For example an amplifier that is designed as a 'push/pull' circuit normally will not have very high 'even' harmonics in it's output because they tend to cancel out or down, in the circuit.
IMD does not respond to normal filtering in the output because of the way it's generated as an inherent part of the final signal. IMD and harmonics are a cause of splatter and interference above and below the operating frequency and tend to widen out the frequency occupied to an excessive degree..
Hope it helps you see there is more to all this than just simple explainations.
Electronics is a complex hobby beyond ragchewing and plug and play.
Good luck.

 

[Wire Dawg]

The original poster has asked about things that require very involved answers.
1. Filters are required to attenuate harmonics produced and passed through the amplifier that could cause interference to other equipment and services at other frequencies.
2. Intermod distortion is produced within the amplifier from the mixing of two or more frequencies due to inherent nonlinearity of the amplifier and it's design.
The FCC has spec limits for both harmonics and IMD before commercial sales can be approved or they are considered illegal to market in the US.
3. A choke balun is an attempt to stop RF current from traveling back to the radio on the outside of a Coax by presenting a high 'impedance' at the point it is connected.
4. Low pass filter is a device that passes all frequencies below a certain design frequency so harmonics above the cutoff point are attenuated to a very low level or stopped from being radiated.
And there is much more yet!
.
One has to have some background to understand the finer points of all these items.
For example an amplifier that is designed as a 'push/pull' circuit normally will not have very high 'even' harmonics in it's output because they tend to cancel out or down, in the circuit.
IMD does not respond to normal filtering in the output because of the way it's generated as an inherent part of the final signal. IMD and harmonics are a cause of splatter and interference above and below the operating frequency and tend to widen out the frequency occupied to an excessive degree..
Hope it helps you see there is more to all this than just simple explainations.
Electronics is a complex hobby beyond ragchewing and plug and play.
Good luck.

Thank you KM3F for helping with this puzzle. I recognize by your explanation that the absence of a variety of filters (not just one) in certain amps is one of the reasons why they are considered non-compliant with government standards. I guess that I may analogize the use of one of these amps to driving a car without a catalytic converter or other emission control devices required by the EPA. A Bencher LPF only provides one type of filtering to help reduce byproducts of an unfiltered amp, but not all. Adding one to the circuit does not compensate for all the shortcomings of an unfiltered amp. Likewise, the choke balun merely attenuates RF signals that may otherwise radiate thru the coax on the way back to the radio. There may not be a need for one if the antenna is well-tuned. Since I had recently worked on the ground rods for the tower and equipment, I never imagined that the toaster problem could be attached to a ground problem. The culprit appeared to have been a lose ground clamp (can’t explain how it came lose), since the toaster is no longer resonating (thanks for the suggestion North Texas Mudduck)

I’m truly grateful for your definitions and explanations. I hope that all these mysteries will slowly unravel as I progressively engage in the intricacies of electronics (although I wish not to find myself arguing over the merits of certain transistor materials). In regards to the issue of linearity, I would like to request some elaboration, if possible. The question is whether these unfiltered amps would maintain an acceptable level of linearity when not overdriven. The Texas Star amps that I've used, are said to be class AB.

 

[KM3F]

On the tube types that were used in these amplifiers, they were mostly a muti-elment type called a Tetrode that needed a screen supply.
The tube types were usually from television use where linearity was not a issue as it is for RF power application.
As well, the screen supply circuits were nearly never regulated and contribute even more to the IMD products and non linearity operation.
This, the desmise of TV tubes and tightening of the FCC rules all cause stopping the use of these tubes in Ham amplifiers.
But the illegal market still kept/keeps using them.
.
For solid state amplifiers, IMD is still an issue but now depends on the device design, the voltage regulation, the bias regulation and filtering as to the final outcome for signal quality, interference and how dirty the drive signal is into both types.
.
As for driveing these amplifiers; if over driven, there come a point where the dynamic upper limit of the amplifer is reached such that an increase in drive does not result in a increase in power.
This causes increases in harmonic and IMD outputs. A very intense example of driving into nonlinearity for both tube and solid state amplifiers..
Over driveing is often called gain compression in solid state amplifiers and flat topping in tube types.
.
An example of this in solid state amplifiers is the use on FM at full output.
If AM mode were used to drive the same amplifier, the drive has to be reduce so the 'peak AM envolope power' does not approch the max the amplifier will handle without going into gain compression/flat topping and causing unwanted by-products in the output signal..
.
This is the key missunderstanding the CB people run under for over driving amplifiers and wonder why the tubes and transistor burn out besides the other poor attributes of the illegal amplifiers..
.
Sounds like it's time for you to consider an Amatrur radio ticket, getting some good Ham equipment and expanding your pleasure in the hobby.
Make no mistake, Ham equipment can be mis-used and cause the same issues as above but you know about it and know not to permit it to happen knowing- ly by agreeing to this as a condition of the License.
Good luck.

 

[Wire Dawg]

Thank you for taking the time to elaborate! Have clarified some misconceptions and learned a few things (not so easy at my age).

 

[Ratfink]

Is CB the only place you find illegal amplifiers? Of course not, but that's where you will find all of them by definition! Those same amplifiers are not illegal on 10 meters. Which still doesn't mean that they meet normal specs/standards.
You can call them '10 meter' amplifiers if you want, but just like the '10 meter' radios they are only a 'get around'.
- 'Doc

I just had to speak up on that one lol. Carry on

 

[Ratfink]

I can't speak for every band out there but, yes, technically and legally speaking, any and all amplifiers for 11-meters are illegal.

I guess anything over 4 watts on am and 12 on SSB is illegal you don't have to have an amplifier to get more than 4/12 since there's a few radios out there that do 100+ I don't mind ham's or people that run power on 11M as long as they know what they are doing and don't splatter like the ones on Channel 6 lol.