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Author Topic: Cheap 10 meter amp  (Read 78546 times)
W9FIB
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Posts: 2506




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« Reply #15 on: June 09, 2014, 08:07:56 PM »

Seems like it would require a lot of parts and labor to be of much use. By the time I get done with a retrofit, I could build one from scratch, that has useful modes on ham radio, puts out more power, and operates very clean on the bands it is going to be built for. Power supply is nothing special either. HP server power supplies are floating out there cheap. And are much higher capacity.

For me, this "find" is of little use. But maybe it would make a cool small plasma cutter for thin metal used for cases. But even then it would never pass any type of RFI specs.
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73, Stan
Wisdom is knowledge you gain after you know it all.
KA5PIU
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Posts: 446




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« Reply #16 on: June 09, 2014, 08:50:21 PM »

Hello.

First off, it does meet RFI specifications, that is the point.
And, you can not beat the cost, free, it is out of a TV.
In fact, except for the SO-239 and wooden box, it all came out of the same TV.
This is the sweep module complete from a Mitsubishi TV.
Power cord, brackets, mounts, connectors, screws, I even reused the grommets!
The wood came from some cheap furniture.
As long as it stays on 10/11/12 meters, it is fine.
It takes a cheap "export" 11 meter radio and turns it into a 500+ watt base station!
Yes, you can build one out of other things, but not as cheap.
In Mexico, the Indians love this type of thing, they will sit for hours and chat about all sorts of odd stuff.
Old wooden telephones are also popular.
Enjoy!
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N3QE
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« Reply #17 on: June 10, 2014, 06:04:18 AM »

There are bazillions of "cheap 10 meter amps" out there in the CB section of every truck stop out there.

We do not need more 10 meter amps floating around in their hands because we know that none of them will end up being used by hams.
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W9FIB
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Posts: 2506




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« Reply #18 on: June 10, 2014, 07:21:50 AM »

Hello.

First off, it does meet RFI specifications, that is the point.
And, you can not beat the cost, free, it is out of a TV.
In fact, except for the SO-239 and wooden box, it all came out of the same TV.
This is the sweep module complete from a Mitsubishi TV.
Power cord, brackets, mounts, connectors, screws, I even reused the grommets!
The wood came from some cheap furniture.
As long as it stays on 10/11/12 meters, it is fine.
It takes a cheap "export" 11 meter radio and turns it into a 500+ watt base station!
Yes, you can build one out of other things, but not as cheap.
In Mexico, the Indians love this type of thing, they will sit for hours and chat about all sorts of odd stuff.
Old wooden telephones are also popular.
Enjoy!

Then keep them in Mexico. America is overloaded in 11 meter noise amplifiers.

And I have a hard time believing without a properly tuned and matched input and output they are "clean". No amplifier is that clean without some type of filtering.
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73, Stan
Wisdom is knowledge you gain after you know it all.
KA5PIU
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Posts: 446




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« Reply #19 on: June 10, 2014, 10:31:10 AM »

Hello.

The trick is to keep it in ONE band.
Amplifiers can be clean without complicated filtering, think of really old radios.
How did they do it?
First off, a CW signal, properly produced, is clean.
Take this clean signal and amplify it, you have a strong clean signal.
Now, take only the final section and modulate it with true AM, you have a strong AM signal.
FM, not a problem.
Try SSB, and you are going to have to filter out the trash created.
That is due to the fact that SSB creates artifacts, and is, as a rule, low level modulation.
So, this thing can never be anything but a ONE band cheap amplifier.
I will give you a hint, that is the title.
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KA4WJA
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Posts: 1098




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« Reply #20 on: June 10, 2014, 02:38:33 PM »

Rudy,
Please understand that I'm not trying to be argumentative here at all, I just wanted to point out a few things that might help others reading this thread...

I'm surprised few have chimed-in here....perhaps many think (like I do) that this is just a ruse to stir up a heated discussion...
And, I don't wish to spend a great deal of time discussing your "Cheap amp" idea....but, thought it might be prudent to point out a few things for others contemplating this sort of thing....

 
Quite a bit of what you wrote here, even in one post, is contradictory, and smells an awful like "CB Math"....and then further, you add more contradictory info?

That is the dissipation, and yes, 100%.
The nominal 50 volt supply is more like 57 volts.
The actual figures are.
58 volts.
10.6 amps.
Almost exactly 500 watts on a "quality" dosy TR-2000 meter!
Why this CB stuff?
The "load bank" is this 25 ohm globar resistor pair in a steel pipe with a UHF connector I made years ago.
The resistor is rated to 1000 watts and has a HV ceramic standoff on each end and filled with transformer oil, so it can handle 10,000 watts for a few seconds
2000 watts all day, real world.
We measure the average power by the temp rise.
It does have a tap for 50% of power.
But, yes, not 100% efficient, but the fact that it is a TV sweep amplifier with NO FILTERING and "10" meters should put you on warning.

How pure is the signal?
It needs to be run around 300 watts for anything close to a nice signal, and it is a 100% class C amp, don't even think about anything but CW or FM! even at 300 watts.
But, at 500 watts CW, it is clean!

And, it is constant duty.
My guess is that around 700 watts is the upper limit.
The power supply can do almost 19 amps without any sag or excess heat on the 50 volt output.
So, 4 watts of drive gives 500 watts nominal out.
Remember that this is loose experimenting.

Steve and Bryan have already mentioned this "linear", isn't... Smiley
And, these figures just don't ring anywhere close to being "true"...
81% eff? isn't the only thing that makes no sense... Smiley


Plus, you write about "no filtering"?
(I assume you are not aware that close-in spectral purity, such as IMD products, are not "filterable"?, but are noise/products produced on-channel/in-band...)

Then you reference Wikipedia for an explanation of "AM".... Smiley
Perhaps you're not aware that many of these folks here actually "know" these things and have decades of experience with them?





And, when Mike tried to get some actual info....
You then posted more confusing/contradictory nonsense....

First off, only the schematic for the TV is available.

It is not configured for anything but 24 to 32 MHz, no low pass or high pass filtering is required.
The second harmonic of the lowest frequency would be 48 MHz, well outside the range of the transistors to amplify.
Uh, I wouldn't bet on that...


The second harmonic is down 100+ Db.
The third harmonic? there is NO third harmonic!
IMD? 50+ dB down.
You're not serious here, are you?


Again, I am using the idea that this is a 10 meter amp.
God help 10 meters!


True, class C biased, it can NOT deal with an AM or SSB signal!
Linear? not hardly!
In a TV set, yes, it is linear, but in this  application? no!
What they mean by linear is the ability to control power output over a broad range of frequencies, not an RF application.
Again, this is a TV sweep unit, NOT an HF amplifier.
But, aren't you actually touting this AS an HF amp?


The way I get away with it is the fact that it is run on one limited area.
Think of it as a super clean 11 meter amplifier.
Can 'ya say oxymoronic? Smiley


The power control circuit can accept an AM signal.
That was your first hint.
The fact that it can do AM with external modulation?
Or FM?
"CW is possible"?
No, you are expecting WAY to much, it is a cheap 10 (Or 11) meter amp.
Nah, it seems more like a RF noise generator to me... Smiley


And, to make this clear, in Mexico, running 1000 watts on 11 meters is perfectly legal.
That is the market for something like this.
You do understand that "11 meters" signals do travel past the borders of Mexico?  Thank goodness this is one of our ISM bands...and PLEASE do NOT promote this as a "ham radio" amp, PLEASE... 





There is NO "trick" to this....and here again you are being contradictory and melding things to fit some sort of narrative?
The trick is to keep it in ONE band.
Amplifiers can be clean without complicated filtering, think of really old radios.
How did they do it?
First off, a CW signal, properly produced, is clean.
Take this clean signal and amplify it, you have a strong clean signal.
Now, take only the final section and modulate it with true AM, you have a strong AM signal.
FM, not a problem.
Try SSB, and you are going to have to filter out the trash created.
That is due to the fact that SSB creates artifacts, and is, as a rule, low level modulation.
So, this thing can never be anything but a ONE band cheap amplifier.
I will give you a hint, that is the title.
I will give you a hint, this is not a 10 meter amp! 
And, please understand that you cannot "filter out" the trash created!
And, SSB doesn't "create artifacts"....






And, I suspect whatever you think you're measuring....you're mistaken...
I used a Motorola service monitor to look at purity of signal, and that is excellent, but at about 80% modulation.
What procedure are you using to verify the "purity of signal"? [sic]
And, what "specifications" are you asserting that it meets?






Are you aware that "RFI specs" (I assume from the old TV set), are about the TV set, and its power supplies and modules, etc. not radiating interference beyond what the "part 15" specs say, but these have NOTHING at all to do with your "cheap amp's" ability to produce a "clean" signal, neither close-in/in-band, nor harmonically!!
First off, it does meet RFI specifications, that is the point.

As long as it stays on 10/11/12 meters, it is fine.

It takes a cheap "export" 11 meter radio and turns it into a 500+ watt base station!
Here again, more contradictory statements....(and nonsense)....it is NOT fine "as long as it stays on 10/11/12 meters"....
And, it seems like it turns a TV set into a RF noise/distortion generator....






The title of this thread is "Cheap 10 meter amp", but at best you seem to be promoting a cheap, dirty 11 meter amp....
Perhaps, you should ask the eham moderators to allow you to change the title accordingly?







This here seems like a great find for the junk box....but, why would you try to make a
Cheap amp", that has horrible spectral purity?

This is the really large Mitsubishi Diamond-Vision with the SVGA connector.
I had no concern over the TV proper, just the audio section at first.
I took the HV as it was connected to this nifty power supply.
It was only after I took it apart that I saw the module.
This set yielded 2 tuners, 3 power supplies, 6 speakers, and a host of parts such as the input panel and its PC board.
Remember that this was all free.
In my opinion, it would be best to put these old TV's to better use...







Please forgive any perceived rudeness on my part, but hear stuff like this talked about on-the-air as well, and I'm wondering where in the world do all of these misconceptions come from?



I could go on, but I think I got the point across....


73,

John,  KA4WJA

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KA5PIU
Member

Posts: 446




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« Reply #21 on: June 10, 2014, 08:17:43 PM »

Hello.

First off, I checked the CW carrier with a spectrum analyzer, clean.
The amplifier module simply does not amplify much past 32 Mhz, at 35 MHz, no  gain,
And, the reason for CW is that the amp itself is modulated, no AM or CW signal enters the amp.
SSB Does indeed cause all sorts of problems with a class C biased amp.
This is NOT intended for use as a CB amp in the USA.
I hang out on 28.385 MHz on 10 meters, and put out a very clean signal.
I do NOT operate on other bands as a rule, 10 meters or 160 is it for HF/MF for me.
I do have an HF/MF/LF amp,AM ONLY, rated for 10,000 watts, a shipboard unit.
It has a built in 500 kHz and 2182 transmitter.
In normal use, CW is fed to the thing and the Amplifier is modulated, classic AM fone.
Running 1000 watts, it runs cool.
It is on the basis of this that I look at stuff like this.
As a rule, I run ONLY AM or FM or CW.
And, no, this really is intended for legal use.
If you ever listen to me operate, I am perhaps a model operator, looking for RFI/TVI.
You see, in Mexico, OTA TV is the norm, and you cause TVI in Mexico, and don't fix it and you are likely to come home and find your radio gone!
CB and 10 meters in the US and Mexico mean differing things.
In Mexico, this type of radio is used to communicate between villages, it is NOT a hobby.
I have a Mexican call, but that stays in Mexico.
I am not a ham in Mexico, I am the community communications guy.
The last US ham who tried to get in actual contact with me was arrested.
The Mexican authorities have me as their comm guy in Sinaloa, and drugs are a real problem.
So, by giving the communities a voice, crime is reduced.
In the USA, people talk about what if communications quit.
I am going to places where there is nothing to quit!
Again, way different thinking.
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W9FIB
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Posts: 2506




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« Reply #22 on: June 10, 2014, 08:42:07 PM »

Is it just me, or is this guy seem to be rambling on with nonsense? The tune has changed so many times it has broken my BS meter. Or is the way he tells it the problem? And when someone points out a problem, it seems like he makes something up so he "sounds" right.

Last time I saw such crazy things it was from a guy that runs his generator inside his garage and says it is impossible for the exhaust to get inside his house.
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73, Stan
Wisdom is knowledge you gain after you know it all.
KA5PIU
Member

Posts: 446




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« Reply #23 on: June 10, 2014, 09:58:48 PM »

Hello.

Again, read the title, Cheap 10 meter amp.
It is NOT a full range HF amp, mono band.
It is NOT a CB amp, clearly intended for 10 meters.
It just happens to work well on 10 meters.
There is no low pass filter, none needed, the transistors drop out much past 10 meters.
The second harmonic of 28 MHz is 56 MHz, well past the passband of the device.
Note that I said passband, it simply does not pass 56 MHz.
On 12 meters, 24 MHz, the same is true, the second harmonic is 48 MHz, and outside the pass band.
Will it work below 24 Mhz, perhaps, but I did not try, filtering would be needed.
Again, read the title Cheap 10 meter amp.
http://educate-yourself.org/be/upperharmonicsexplained22may02.shtml
So, if PURE sine waves are introduced, such as a CW signal, there is no problem, and why CW transmitters need so little in the way of filtering.
Lets say we have this strong CW signal after passing it through an amplifier, a sine wave.
Now, modulate this in the final section, and the signal will be distorted, but this will be very limited, as there is no further amplification.
All transmitters produce artifacts, noise.
The trick is to have them far enough down to meet requirements, FCC, etc.
Again, if operated as a mono band amplifier, no problem.
CW, FM or high level AM.
No SSB, no other bands.
Again, Cheap 10 meter amplifier.
The title is fine, if you can not figure it out, that is your problem.
I have also built 160 meter amplifiers.
The more common TV sweep transistors MIGHT be able to do 3 MHz, if that.
But that is fine for 160 meters.
Again, AM FONE.
There are plenty of old MF marine radios with dead finals.
People try and "Test" them without an antenna.
So, 60 watt AM radio? why not?
No SSB, 2 MHz AM marine was the norm and they moved to VHF FM.
The key advantage of AM is that it sounds natural, FM has no, or little static.
The disadvantage is that it takes up more bandwidth and so shorter range.
But, CB, no, that is limited to 4 watts.
4 watts on VHF, such as 2 meters, has a good range.
If you listen to 2 meters, even the repeaters, they are dead!
10 meters? I can pick a frequency, like 28.385 MHz, and listen for hours, nothing.
And, why 28.385 MHz?
Like it or not, a lot of hams started in CB, and to move a CB up 1 MHz is easy.
But, once converted it is a ham radio, FCC rules do not permit dual use radios.
The point being, to sell amateur radio, you have to SELL amateur radio.
Make it interesting, enjoyable, and,,, if need be, cheap.
Remember, not everyone wants HF, the antennas, etc.
The Cheap Chinese talkies? some are happy with them.
I think most "Elmers" sniff too much glue!
Read about Dayton.
Now, with that in mind, how are you going to introduce people to radio.
I explain it is a hobby and you can buy or build.
This is an example.
True, it is never going to be good for SSB, or anything but 10 meters, but it is super cheap!
Again, this is something out of a discarded TV!
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KA5PIU
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Posts: 446




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« Reply #24 on: June 11, 2014, 03:03:41 AM »

Hello.

Had someone ask a member of the Tokyo Radio Club.
Mitsubishi was an RF module intended for Marine HF radios.
To be precise, it is for the JRC 500 watt MF/HF transceiver.
Operating at 500 watts, it should be clean!
Band filters would need to be installed for anything but 10 meters.
But, this was installed in a TV set.
Nominal output impedance? 50 ohms.
Nominal input impedance? 450 ohms.
In RF service, a T pad is installed to buffer the module from the driver section.
I referred this thread to them and they said in effect 'Get a Job!'  or  'Get a Life!'.
But, no, this is by far not a truck stop special.
Again, there are NO filters, so operating it at anyplace but 10 meters would be a problem.
The low pass and high pass filtering is the fact that anything above about 32 MHz faces a very steep drop off, nothing is at the output terminals.
That is in the design of the device.
I looked at the thing, and it looked like there was a place for a SO-239, There is.
Just like any large TV set, it was one module of several.
The audio section is the same way, the audio section on the main board is unpopulated, and an external board is present.
This is the same with GM cars with the "Bose" sound system, a large amp in the trunk but little but a tuner up front.
So, the moral of the story? follow your training when encountering used electronics.
I have a console TV/HiFi with the record player missing and the TV had a bad CRT.
Now, a laptop sits where the Record player was, and an LCD computer monitor where the TV was, and it is nice wood to boot!
Router and access point, cordless phone base, surge protector, all that crap, is inside this unit.
Reuse, repurpose, recycle, be good to the environment!
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W9FIB
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Posts: 2506




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« Reply #25 on: June 11, 2014, 04:29:17 AM »

Clueless! I give up trying to understand this dribble.
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73, Stan
Wisdom is knowledge you gain after you know it all.
DL8OV
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Posts: 1054




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« Reply #26 on: June 11, 2014, 07:49:51 AM »

I have a use for old CRT TV sets. The electrolytic capacitors get removed from the PCBs as do the large inductors. The scan coils are unwound and I recover what connectors I can. Finally I remove all the power transistors I can see and then the rest goes in the recycling bin where our local municipality recover the heavy metals.

A 28 MHz class C linear?

No thank you, I do not want the Bundesnetagentur knocking on my door!

Peter DL8OV
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N6AJR
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Posts: 9930




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« Reply #27 on: June 11, 2014, 08:18:07 AM »

for some reason when I see Dosy meter, I automatically think CB
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N4TTS
Member

Posts: 253




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« Reply #28 on: June 11, 2014, 10:57:06 AM »

Is it just me, or is this guy seem to be rambling on with nonsense? The tune has changed so many times it has broken my BS meter. Or is the way he tells it the problem? And when someone points out a problem, it seems like he makes something up so he "sounds" right.

Last time I saw such crazy things it was from a guy that runs his generator inside his garage and says it is impossible for the exhaust to get inside his house.

It's not just you. This guy went from almost nothing to posting near gibberish all over the forum in the last few weeks.
I believe an adjustment in his medication went wrong and we're witnessing the results.

I'm not moving into ad hominem as much as I am ad nauseum.

Don N4TTS
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WA7PRC
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« Reply #29 on: June 11, 2014, 05:03:41 PM »

... class C linear?

The terms "Class C" and "linear" should not be associated with each other.  Wink

vy 73,
Bryan WA7PRC
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