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Author Topic: Why can't you buy an hf amp in the USA running more than the legal limit?  (Read 25453 times)
ZENKI
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Posts: 1648




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« Reply #45 on: November 20, 2015, 05:21:18 PM »

Running big amplifiers is what all CB'ers dream  about. They buy expensive radios, 10kw amplifiers and then run  their purchases into  a 5/8th vertical antenn. They dont have  a systems HF planning approach towards HF propagation. Never once  would these  dumb CB'ers think,and say what do I need to propagate my signal for short skip distances and  how do I generate the  gain at high angles without a 10kw amp. For hams its simple answer, 4 stacked yagis driven out of phase and 1kw would do the same  or better job than 40kw into a vertical. Surprised that hams even think that a 10kw amplifier is even needed.

Hams unfortunately are falling into this same downward spiral in ignorance, and everything appears to be related to the size of ones amplifiers.  I hear these comments all the time from stations  about certain hams who have big signals. " I heard W6xxxxxxxx,, he had a massive signal, he had a big antenna and i can only imagine what the size of his amplifier is giggle giggle". This  is the typical comment that you hear about big signals these days. These comments typically come from people running a G5RV  that hangs just above the house gutter. Its the G5RV and Windom era in ham radio. Stations that have never run anything but pieces of wire, verticals and whom own expensive 10,000 dollar radios and amplifiers and who have never experienced running a beam   at more than 70ft above ground.  I dont hear big signals from hams running a G5RV at 10 meters with 10kw. I hear lots of hams with big signals running 1kw or even 100watts and big long boom yagis  up very high. Even if you think that  they are running high power and your S-meter is calibrated take off 6db and they still have a big signal. Turn your 10kw amplifier off on your low g5rv and  you wont be heard . thats the laws of physics! Then is it a surprise that these same station think that the only answer is a 10kilowatt amplifier and thats the toy that they most desire not a high gain antenna or tower.

I hear more people whining about other hams supposed big amplifiers, yet never once do I hear them seriously say I need to get a big long boom yagi or stacked array up on a 200ft tower. These are the stations who spend 150000 on a radio 8000 on a amplifier and say its too hard  and expensive to put up a 70ft tower or yagi. These are the same stations now in Europe who sit their jamming stations with stacked arrays and big signals. Yeah, you know the ones scratching their microphones. calling ooooorrrrrrlahhh the dog, coughing and so on. These are the jealous ones with 15,000 dollar radios, 10,000 amplifiers and a G5RV who want a 10kw amplifier because they cant hear or work anyone even after spending 30,000 dollars on equipment. The solution is easy for their technical  incompetence, buy or dream about a 10kw amplifier while not wanting to do the hard work installing decent antennas and towers. I actually heard a station with IC785, 2kw SPE amplifier and he was using a Comet vertical with resistor loading! I looked him up on QRZ and he had QTH where he could easily install a tower and a beam. Is his next purchase a 10kw amplifier?

You never hear these stations who want to own 10kw amplifiers ask the question, "how much gain do I  have at the take off angle of 5 degrees and how do I achieve more gain at 5 degrees" The only thing in their technical mentality is that the 10kw amplifier is the better solution to all their problems  like the Cb'ers.

You dont need more than 1kw, for most communications circuits and if you do you have  bad antennas and thats where you need to spend the money. Then even if you could afford
a 10kw amplifier or you are capable of building one, do you have the antennas to radiate the power at the takeoff angle that is required to support the communication path. Thats before you start talking about the technical challenge of issues like IMD. A issue that most hams dont understand are are typically dismissive of. We get this stupidity  in this forum all the time. Hams who dont want know about  IMD, as if it does not exists in their world  and therefore its not a problem. To them all that is important is what the power output is and have very little care for the specifications or what interference it causes. We see this debate with the SPE amplifiers. They happy with them, dont care about IMD and everyone else can go to hell because they super smart shopper hams who do what they want with little technical expertise or regard for others.

While I am a advocate for  having the best transmitter  IMD specifications, I am happy that we have such poor IMD specifications and little regard for for IMD standards on the ham bands. These poor standards means that these very stupid hams who run excessive power all eventually get run off the air and do get caught because of their lack of understanding of the issue of TX IMD. Poor IMD does have one good outcome, it gets rid of lids on the ham bands who break the law and who cause harmful interference. I can give you a endless list of hams who have been run  off the air or  lost their license by running excessive power with broad signals because of their technical stupidity and arrogance. Its the same stupid mentality  like the hams who run CB amplifiers who think that their signals are clean and that IMD is not a issue. These days with SDR radios its easy picking out these fools from the crowd. Its even easier picking up the  clown with the 10kw splattering amplifier, most of them barely last 6 months.

The bigger question is not  if you need 10kw amplifier the question should be how do you get gain at at the takeoff angles below 15 degrees and radiate what power you have at the angles below 15 degrees. Having a 100kw ERP at wrong takeoff angle is stupidity at its best  especially for the  ham bands. Its mostly stations who radiate their power at the wrong takeoff angles or dont have  towers and antennas to radiate down at these low angles who dream about 10kw amplifiers. All I can say is go back to the drawing board and think about high antennas and low angles. Once you have achieved this objective first, you can think about the miserable true S unit you going to get from a pick amp and will be smart enough to figure out that the expense and effort is not worth it.  At the end of the day most government and military HF stations dont run more than 4kw on HF because because in excess of 6db over 1kw buys you very little when you have a good antenna up high. Hams certainly dont need more than 1kw if you have decent antennas.

The only reason for owning amplifier that is capable of many times your legal limits is too run it conservatively so that the amplifier is never driven into saturation at whatever your legal limit is. It does however appear to be common sense to sell amplifiers with 60,000 lines of code that can be driven into saturation and call it the greatest amplifier since sliced bread was invented. I though cb'ers invented driving amplifiers into excessive power output and well into saturation? Ham manufacturers have learned a CB marketing trick? lets hope that they dont produce the 10kw version very soon!
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KB4QAA
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« Reply #46 on: November 20, 2015, 08:15:45 PM »

*Bonus length IMD Rant from Zenki this week.  Woohoo!  Smiley
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KA0HCP, ex-KB4QAA Relocated to Ks. April 2019.
KD8MJR
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« Reply #47 on: November 20, 2015, 09:53:47 PM »

Yep but he does make a valid point.
It really is stupid to have a ton of power when you can't hear the stations that you need the power for.  Also the IMD just gets so much worst that it just kills the band for those who have good antennas that can actually hear and work the guy.

73s
Rob
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“A lie can travel half way around the world while the truth is putting on its shoes.”  (Mark Twain)
DL8OV
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« Reply #48 on: November 21, 2015, 01:02:07 AM »

I run a single antenna, a 130m run of wire from my building to another apartment building at the end of the complex. Why? Our lease includes a total ban on antennas, even satellite dishes are banned. I therefore resorted to stealth and ran my antenna using very VERY thin wire and it was up for over a year before the building superintendent had a quiet word in my ear and said "I know what you have done, this wire is OK but please, no more".

I would love to put up a 70m tower and a three element StepIR but this is just not possible in my present situation. If I want a bigger signal I could buy or build a power amplifier but all of that power going into a poor antenna would be an RFI nightmare and pretty quickly people would start searching for the reason why their cable TV and their radios were being interfered with. So, no amplifier for me.

Zenki is almost right here, some hams do use an amplifier as a substitute for a tower and a beam, but he needs to remember that not everybody is capable of putting that tower in the back yard due to circumstances beyond their control.

Peter DL8OV
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KD8MJR
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« Reply #49 on: November 21, 2015, 01:25:45 AM »

I think you miss the point. Unless your Rx can match your Tx ability you are pretty much gaining nothing unless your goal is just to create a big signal and excessive amounts of splatter for people who most likely can hear you just fine at legal limit.  Take that 130m run and beef it up to handle 10kw and you will make a few extra contacts but piss off a bunch of other nearby hams trying to work the same DX.
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“A lie can travel half way around the world while the truth is putting on its shoes.”  (Mark Twain)
DL8OV
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« Reply #50 on: November 21, 2015, 02:55:02 AM »

Right now my receive ability matches my transmit signal reasonably well, we have a high noise level here in the city and my transmit power is a clean 50W. Most of the time the old rule of 'if I can hear it I can work it' applies but I don't stand too much chance in a pileup.

Peter DL8OV
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KM1H
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Posts: 5541




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« Reply #51 on: November 21, 2015, 08:32:39 AM »

Quote
You would be better served by putting your bucks in the antenna.  Although if you want to overcome your crappy antenna with 5Kw of rf, terrific.  This will also be a great way to meet new neighbors.

That makes no sense as first ERP is still ERP no matter if it is via QRO or a big antenna; secondly many are not able to install a decent antenna system which I consider at a minimum a 70' tower, a 3 el tribander for 10-20M and wires for lower bands. WARC coverage is a step up the ladder as is 2el for 40.

Quote
Yep but he does make a valid point.
It really is stupid to have a ton of power when you can't hear the stations that you need the power for.

A G5RV, OCF, longwire, etc can often hear the DX but is so far down in the pileup on TX he cant get thru before propagation changes or the DX goes to a different call area. These are the type that join DX lists and really believe they have accomplished something...what morons!

OTOH DXCC is a disgrace these days anyway when anyone with the money can use a remote station, even on another continent, to work DX and get credit. I absolutely refuse to stoop that low and join the gutter dwellers.

Quote
I think you miss the point. Unless your Rx can match your Tx ability you are pretty much gaining nothing unless your goal is just to create a big signal and excessive amounts of splatter for people who most likely can hear you just fine at legal limit.  Take that 130m run and beef it up to handle 10kw and you will make a few extra contacts but piss off a bunch of other nearby hams trying to work the same DX.

High power does not have to mean worse IMD except in the case of most overated SS amps on the market. Any decent tube amp has very acceptable IMD and is only subject to what goes in to it; IOW, GIGO (Garbage In Garbage Out). An overdriven AL-80A/80B to 1000W is very noticeable on the bands but at 700W they are very clean. The AL-82, 572, 800HD, 1200 and 1500 are all very clean when run properly.....even the AL-811 series is very acceptable at 400/600W PEP respectively.

My SS xcvr is rated around -40 IMD (real and not the ARRL version) and so is the 2X 3-500Z amp which I run at only 1200W. I also use an old HP-141T spectrum analyzer to monitor my signal and watch for others on RX. When I was contesting from this hilltop with 4/4/4/4 stacks I could operate very close to others that knew how to operate without getting IMD or splatter reports. My biggest problem in SSB or CW contests was phase noise and/or spurs from a lot of very expensive garbage, usually ICOM and a few Yaesu and Elecraft.

Carl
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KM4AH
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« Reply #52 on: November 21, 2015, 10:03:52 AM »

I kind of like big amplifiers myself.
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KD8MJR
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« Reply #53 on: November 21, 2015, 10:06:54 AM »

Even if your SS transceiver has an IMD of -40db you will still have significant signal levels on either side when you multiply that by 93 dbm of even a perfect 10kw amplifier.  Yes still tiny numbers but annoying for people nearby with good antennas.

73s
Rob
« Last Edit: November 21, 2015, 10:09:39 AM by KD8MJR » Logged

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W8JX
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« Reply #54 on: November 21, 2015, 11:23:41 AM »

I kind of like big amplifiers myself.

I like amps but very rarely use one on 20, 17, 15 and never on 12 or 10. I have had many QSO's on 40m during day that without a amp on both ends chat would of been difficult if not impossible barefoot. On upper bands power is usually not really needed unless you are getting into shouting or splatter matches.
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Ham since 1969....  Old School 20wpm REAL Extra Class..
AB4D
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« Reply #55 on: November 21, 2015, 12:14:32 PM »

...I am happy that we have such poor IMD specifications and little regard for IMD standards on the ham bands. These poor standards means that these very stupid hams who run excessive power all eventually get run off the air and do get caught because of their lack of understanding of the issue of TX IMD. Poor IMD does have one good outcome, it gets rid of lids on the ham bands who break the law and who cause harmful interference. I can give you a endless list of hams who have been run off the air or lost their license by running excessive power with broad signals because of their technical stupidity and arrogance.

I would like to see that list.  At least here in the states, I can't remember anyone in the past 20 years who lost their license due to poor TX IMD or harmful interference due to transmitter issues.  Usually, it's just operator issues. Smiley  IMO 500 watts offers the most performance gain over a 100 watts. 99% of the time, no one on the receive end can tell the difference between 1.5 KW and 500 watts.

Jim, AB4D 
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KM4AH
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« Reply #56 on: November 21, 2015, 01:15:00 PM »

I kind of like big amplifiers myself.

I like amps but very rarely use one on 20, 17, 15 and never on 12 or 10. I have had many QSO's on 40m during day that without a amp on both ends chat would of been difficult if not impossible barefoot. On upper bands power is usually not really needed unless you are getting into shouting or splatter matches.


That is the way I operate as well. It is a pretty simple matter to put a high gain antenna up on those bands.
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KM1H
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« Reply #57 on: November 21, 2015, 04:45:02 PM »

I enjoy using the amp plus big antennas on 10-15 when the band appears dead. I often get on in the late afternoon, especially 10M SSB and AM and get CQ answers from the 5-10W crowd as far away as NYC/NJ which is a haul for 10M. Signals are often pee weak but I hear well here in the boonies on a hilltop and remember one guy was so excited as he was running 5W SSB to a mag mount on his refrigerator in the projects in the Bronx! Not bad from NH.

At sunset on a dead band I often get VK and ZL coming back and my loud signal gives many the nerve to try and work me with 100W and much less....it is fun and better than 59NH!

Carl
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K6AER
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« Reply #58 on: November 21, 2015, 05:44:33 PM »

Now what happens when both hams are running big power at each end?Huh?? 10 dB better bidirectional propagation. I always call CQ with the amp on. My location is very quiet.

Like hunting if you are good with a 500 yard shot your possibilities greatly increase.
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KM1H
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« Reply #59 on: November 22, 2015, 02:01:38 PM »

Quote
Even if your SS transceiver has an IMD of -40db you will still have significant signal levels on either side when you multiply that by 93 dbm of even a perfect 10kw amplifier.  Yes still tiny numbers but annoying for people nearby with good antennas.

Huh, what orfice did you drag 93 dBm from?

Going from 100W to 10KW is a 20 dB power increase.

If IMD 3 is -40 it could still be in the signal passband. With a good rig and amp the 5th, 7th, 9th, etc products are typically -52 dB and more so say at 5 kHz away the signal is way below that what would interfere with another QSO. Most SS and many ham legal Russian tube amps can barely make -25 dB on the 5th.

This is why the QRO gang are running Class A transceivers  include SDR's and then super clean buffer (IPA) and final amps which sound better than many with 100W. This is why the 3CX3000A7/F7 is popular with many in the 5-7 KW range, 3CX6000A7 to about 10-12KW and the 3CX10000A7 to 25 KW.

The 3CX3000A7 is the best bargain on the planet at a bit under $700 from China (same price as a 8877 from the same source) using Eimac supplied tooling, has a 225W grid structure, and can be rebuilt. At 1500W it will outlast the user.

Quote
Like hunting if you are good with a 500 yard shot your possibilities greatly increase.

And the extra power helps when antennas are not pointed properly, a whole new azimuth window opens up.

Carl
« Last Edit: November 22, 2015, 02:04:11 PM by KM1H » Logged
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