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Author Topic: Why can't you buy an hf amp in the USA running more than the legal limit?  (Read 25444 times)
OZ8AGB
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Posts: 586




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« Reply #15 on: November 16, 2015, 04:31:32 AM »

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WA4DOU
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« Reply #16 on: November 16, 2015, 09:27:58 AM »

Back in the 1970's there was a ham near Chicago running over 50KW. I know that for a fact. I still remember him in the pile ups. PORTUGAL PORTUGAL JAPAN. If he came on everybody else might as well go QRT.

I guess you could ask Wizzard to build one for you. His 25KW amps are all over youtube.

Dick AD4U

PS: MANY on this site (myself included) have the knowledge to build a 25++KW amp. Some do but most do not. Even though I have an Alpha 77SX (2X8877) with external Peter Dahl transformer that will run the legal limit X 3, it has not been used in several years. I am having too much run running a 50+ year old Drake 2B receiver and a Drake 2NT 50 watt transmitter. So far 293 countries on 40M CW. After over 50 years hamming, this has put the fun back into radio for me.

While anticlimactic compared with the 50KW you spoke of, I once knew an old ham from the '30's that revealed that he knew of one at the 13KW level. The highest power I ever ran was 700 watts output and that was for less than a year, back around '79-'80. Working primarily cw, I typically run 400-500 watts max, if at all. You can sure tell when rare DX shows up on 30 meters, because there are a lot of full gallon amplifiers to be heard there. Wonder how some folks can feel any sense of achievement by cheating?
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W1VT
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« Reply #17 on: November 16, 2015, 10:19:48 AM »

Given that "CBer's" running illegal amps have adversely affected what hams can buy, why would you want bring up this sort of issue when selling an amplifier?  There are specific rules in Part 97 that limit amplifier performance designed to make amateur amplifiers less useful to "CBers."
« Last Edit: November 16, 2015, 10:22:34 AM by W1VT » Logged
NO2A
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« Reply #18 on: November 16, 2015, 12:35:37 PM »

There are numerous HF amplifiers, made and sold in the USA, that are very capable of more than 1.5 KW.  Why one would want one is beyond me.  With a good antenna system much less than max legal can usually work through most pileups
Exactly. If they can't hear you with 1500 watts,or more, your amp is not the problem. 
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KD0UN
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Posts: 97




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« Reply #19 on: November 16, 2015, 01:26:49 PM »

Nail struck directly on the head.
Canada has a "legal limit" of 2.25 kW output,

You understand that is only 1.5 KW in US watts, don't you?
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W5CBO
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Posts: 98




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« Reply #20 on: November 16, 2015, 01:36:25 PM »

Quote:  He only bought it to play around and see what it was built like, NOT to flood the waives with illegal power.

Another good one I heard recently was ISIS is contained.
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W7VO
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« Reply #21 on: November 16, 2015, 02:02:46 PM »

I have an Ameritron AL-1500, but the main reason I love it is that I can run my FT-2000 exciter at half power or less for 1500 watts out of the amp, keeping the exciter's finals cool and stress free. In fact, the FT-2000's internal cooling fan almost NEVER comes on, even during contest running.

I ran the CQWW RTTY test with my FT-2000 running at about 25 watts output, and still had over 1000 watts out of the amp. Both ran cool as a cucumber, despite the RTTY duty cycle.

Nothing like "Max Headroom" to make the equipment last!   ;-)

73;

Mike, W7VO
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M0HCN
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« Reply #22 on: November 16, 2015, 02:07:12 PM »

I wonder if the UK 400W measured at the feedpoint is real or apparent power.....
Makes a big difference with an electrically short vertical, and as I recall the clarification note that OFCOM put out did not state which!

Regards, Dan.
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AD4U
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« Reply #23 on: November 16, 2015, 04:02:20 PM »

To carry this absurdity to a higher level.........The most powerful tube that I am aware of that can be run in simple grounded grid configuration is the 3CX20,000A7. There may be others.

Building a grid driven 35+++KW amp running AB1 for example will require some additional skills to tame it that many do not have.

Anybody who can build a 750 watt grounded grid amp running a single 3-500Z can apply the same exact same design principals (with much heavier components) using a 3CX20,000A7 and have a 35KW amp. In grounded grid gain should be at least 13-15 dB. Drive it with a 1500 watt amp and get 25-40 KW out

Such amps are "out there" and being used every day. Many on this site are capable of building such an amp, myself included, but most don't. Personally I could not afford the parts even if I wanted one.

Like it or not, going "horse racing" on the ham bands requires a lot more power than the legal limit.

But then I will still put my $$$ on a good operator running the legal limit or less than a poor operator running brute power.

Dick AD4U
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KK5DR
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« Reply #24 on: November 16, 2015, 04:08:32 PM »

Contesters and DXers will pay whatever it costs to be number one.
To me, it's a mindless persuit.
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K2OWK
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Posts: 1279




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« Reply #25 on: November 16, 2015, 04:32:51 PM »

Why a super high output amp. When you can use ERP (effective radiated power). A good multi element beam with 10 db. gain will give your amp of legal power the ERP of 15KW. Want more then stack two of them for an ERP of 30KW. Want even more then co-phase a 4 bay stack for 60 KW ERP. The beam will be narrow, but the overall gain will be in both directions. Receive as well as transmit, and you will be legal.

73s

K2OWK
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KD0REQ
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Posts: 2404




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« Reply #26 on: November 16, 2015, 06:03:41 PM »

3-phase... if you have it nearby, and have a room full of money, you can have it.

alternatively, install a dry transformer with 240 v in, and 3-phase out, and all you need is the money.

for decades, the standard for mainframe power worldwide has been a rotary power converter, as it maintains service if flywheeled for enough seconds for the inverter to kick in and spin the rotary back up.  so massive inefficiency has been promoted for a long time.
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VR2AX
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Posts: 1016




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« Reply #27 on: November 17, 2015, 05:17:05 AM »

Why sell or buy a 200 mph Maserati when you have a 70 mph limit. That's for each to answer and there are legitimate answers. Each to their own. If you don't mind 1000 US per tyre that is fun to some.

If or when you smell something burning that may be the time to take a check.

As others have noted ham radio is not regulated like some sports else the California Kilowatt would have been deemed non-PC much longer ago. But who did they harm.
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G3RZP
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Posts: 1319




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« Reply #28 on: November 17, 2015, 05:54:17 AM »

Quote
I wonder if the UK 400W measured at the feedpoint is real or apparent power.....
Makes a big difference with an electrically short vertical, and as I recall the clarification note that OFCOM put out did not state which!

The original concept was to allow for feeder loss at VHF, where coax feed is pretty well 'de rigeur', and so - at least in theory - the ubiquitous Bird Thruline could be used. My 160m antenna is something around 1200 + j200 so measuring the actual antenna feed power to any real degree of accuracy is somewhat academic!
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W1VT
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Posts: 3398




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« Reply #29 on: November 17, 2015, 05:57:08 AM »

You need to consider the antennas used by hams today.  Most new hams want an antenna that work on all bands.  It is surprisingly hard to come up with a good all band compromise that will take the legal limit without blowing something up.

Bottom line--you can't sell a box that someone can just plug into their station to become "really, really loud."  

It is a waste of time trying to educate your customers who are always right.

Zack W1VT
« Last Edit: November 17, 2015, 07:37:30 AM by W1VT » Logged
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