12KW on HF Ham bands ?!? - Page 1
Forum section: electronics / rf-microwave

author: A.Z.
author_rank: Super Contributor
timestamp: August 11, 2024, 10:00:40 am
content: I was looking herehttp://www.dc9dz.de/en/katana12k.htmlnow, those amplifiers are built for the Ham bands, I can't make sense of them, I can understand using an overpowered linear at 50% of its power, so remaining legal but "sparing" the amp, but those are FAR above, how do they make sense ? What's the point in using one of them ?

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: August 11, 2024, 03:09:46 pm
content: Here in the US there are lots of CBers who use amplifiers that make the 12 KW amp look quite small.There is quite a market for these types of ampsI do not know of any Hams who would use it but lots of CBers would.I think that in some other countries Hams would use it. But I really do not know for sure....

author: coppercone2
author_rank: Super Contributor
timestamp: August 11, 2024, 03:37:30 pm
content: there is always the situation of the steam boiler (flooded coaxial cable) requiring a bit more power to radiate ~150 wattsyou know, when your antenna is in parallel with a 250mOhm water load

author: iMo
author_rank: Super Contributor
timestamp: August 11, 2024, 04:48:04 pm
content: Not all ham bands world-wide are exclusive for ham radio. There could be services using the bands as primary/secondary to hams.For example diplomatic services, military, etc. And their allowed output power might be those 12kW easily..

author: radiolistener
author_rank: Super Contributor
timestamp: August 11, 2024, 09:30:23 pm
content: I hear that some ham-amateurs using more than 100-200 kW power at short wave, that is not legal and of course eats a lot of mains electricity, but this is not an obstacle for the desire to do what you love... I remember one guy said that he had specially installed a dedicated three-phase line from a high-voltage power transmission line for this purpose. When someone on the air asking which equipment they are using because their stations have very strong signal, they boasts a very good antenna and a 100 Watt transmitterWhen they saying "100 Watt", they actually meaning 100 kiloWatt, but newbies thinking that they really using 100 Watt and don't understand why their own 100 W signal isn't heard the same strong.Often these guys are highly skilled RF professionals and may working on government or military RF monitoring services and some of them even can use very large government or military antenna fields for ham-amateur communications. So, don't surprise if your correspondent working at 500 kW power from a large antenna field...I know one ham-amateur in our city who like very high power. When he transmits on VHF band, it requires to add 30-40 dB attenuation on my receiver to avoid overloading... Currently he is working on a new power supply for his new power amplifier on high power tubes... He likes that stuff...In other words, everyone has their own hobbies.And some guys have the opportunity to use equipment that a usual ham-amateur could never dream of.

author: vk4ffab
author_rank: Frequent Contributor
timestamp: August 11, 2024, 11:04:49 pm
content: Quote from: A.Z. on August 11, 2024, 10:00:40 amThere is a guy that runs a US net on 40m, I hear him most says, S9 + 20 to 40 over. His antenna a G5RV. I am using a 1/4 wave vertical on 48 radials and 100w. Last time I called in he gave me a 3 by 3 report. Now he is in a remote area so no major noise issues, so you do the math and work out how much power he is running, because its obviously not legal limit, it is a lot more than that.So i have no doubt there are some who are running those sorts of power levels and many others who are running a little more than whatever is legal for them. End of the day, none of this matters because in most jurisdictions there is no enforcement and as long as you do not cause harmful interference to some commercial user, you can get away with whatever you want.As a home brewer, I am a dx taker and could not give 2 craps if anyone hear me LOL. There is more to radio than talking bollocks with the same idiots every day on the I am not dead yet, bed wetters net, being touched on the frequency when someone comes close to the frequency they own.

author: RFDx
author_rank: Regular Contributor
timestamp: August 11, 2024, 11:59:45 pm
content: Quote from: A.Z. on August 11, 2024, 10:00:40 am2.8kW RTTY and 6kW CW from a 7000VA transformer on a 230V/16A line I 'm (barely) willing to accept, but 12kW SSB? Even if it is only PEP, how does that work?

author: radiolistener
author_rank: Super Contributor
timestamp: August 12, 2024, 12:41:20 am
content: Quote from: RFDx on August 11, 2024, 11:59:45 pmProbably something like that:https://frank.pocnet.net/sheets/140/8/8281.pdfYou can drive it with typical 1-2 kW ham-amateur amplifier. Such amplifiers usually using 3-phase mains supply.

author: CaptDon
author_rank: Super Contributor
timestamp: August 12, 2024, 02:07:35 am
content: 12kw from the amplifier pictured? Look at the tank coils! Look at the ratings. Very ICAS rated. Those coils would have a melt down and the loading cap would arc over at 12KW. Is that 12KW input with maybe 8KW outut at the RF connector? I'd love to see that thing do 12KW AFSK SSB!!! Where is the HV filtering? Probably has a crap load of A.C. ripple at full output. I'm not buying one.

author: CaptDon
author_rank: Super Contributor
timestamp: August 12, 2024, 02:16:37 am
content: You don't get 100KW from a single 4CX20,000!!!! (unless it is a pure squarewave 100%THD for about a millisecond key down)I think these should be called wet dream amplifiers. Kind of like the D.J. audio amplifiers claiming 6 kilowatts RMS output using a 5 amp slo-blo fuse on 120VAC. Do the math!!

author: A.Z.
author_rank: Super Contributor
timestamp: August 12, 2024, 08:47:01 am
content: Quote from: CaptDon on August 12, 2024, 02:07:35 amWell, set aside that, the output power would still be far outside the legal limit in most (if not all) countries, also, those amplifier are built (and SOLD) specifically for the Ham bands, so I can't still understand the whole purpose or reason why one would buy and use one of them, I've read the "full story" herehttp://www.dc9dz.de/en/tsunami.htmland then, considering it as an "experiment" could probably make (some) sense, but then the folk behind the whole thing decided to "monetize" it and not only sell the original design one, but also expand the models range and sell those too, but... who's buying them and... why ?

author: Solder_Junkie
author_rank: Frequent Contributor
timestamp: August 12, 2024, 09:18:52 am
content: The amp specification from DC9DZ doesn't make sense, on the web page it says "Measured with a Bird Power Meter, Model 43, PEP, on a single 230 V line with 16 A fuse" and shows an output power of 10 KW for 100 Watts drive, in order to obtain 10 KW you need to supply around 17 KW of mains input to the amplifier, which by my maths comes to around 74 Amps at 230 Volts... that is close to the maximum you can obtain directly from most domestic electricity supplies at the incoming feed to the house!The legal power limit for amateur radio varies from country to country, in Europe it is up to 1 KW output, depending on country and amateur band. From memory it is 700 Watts in Germany (DC9DZ appears to be a German callsign, but that call is not listed, is it a pirate?).SJ

author: iMo
author_rank: Super Contributor
timestamp: August 12, 2024, 10:23:33 am
content: I see him in the qrz.com..PS: there might be a de-jure difference in "operating a 100kW amplifier by a licensed HAM on amateur bands" and when a licensed HAM is "manufacturing and possessing and having on stock and selling a 100kW amplifier"..Quote from: Solder_Junkie on August 12, 2024, 09:18:52 am

author: Solder_Junkie
author_rank: Frequent Contributor
timestamp: August 12, 2024, 10:28:27 am
content: Sorry, my mis-typing. He is listed

author: vk6zgo
author_rank: Super Contributor
timestamp: August 12, 2024, 10:58:51 am
content: Quote from: radiolistener on August 11, 2024, 09:30:23 pmMy feeling is that as well as using govt or military antenna fields, to get those power levels, they are probably also using the associated transmitters & the taxpayers' electricity.

author: A.Z.
author_rank: Super Contributor
timestamp: August 12, 2024, 11:02:17 am
content: Quote from: vk6zgo on August 12, 2024, 10:58:51 amIstronglydoubt that any gov/mil entity operator is using one of those amplifiers or is "playing" on Ham bands

author: Phil1977
author_rank: Frequent Contributor
timestamp: August 12, 2024, 11:06:28 am
content: Quote from: A.Z. on August 12, 2024, 11:02:17 amBut they have lots of bands next or near to the Ham bands or they just use the frequency without any assignation.And why shouldn't they buy what´s available on the free market if it matches the requirements?

author: A.Z.
author_rank: Super Contributor
timestamp: August 12, 2024, 12:28:19 pm
content: Quote from: Phil1977 on August 12, 2024, 11:06:28 amIt doesn't work that way

author: Phil1977
author_rank: Frequent Contributor
timestamp: August 12, 2024, 01:21:50 pm
content: Says who? Because all governments just buy from consiprationally selected agents???For sure, these things will probably mostly sit in the shack of some CB or HAM enthusiast who just thinks power is sexy. But e.g. at university we had some setups that needed lots of RF e.g. to heat a plasma. And for this reason we just selected what was in budget and in performance requirements. And a university is also some kind of government agency, at least in Europe.

author: A.Z.
author_rank: Super Contributor
timestamp: August 12, 2024, 03:08:31 pm
content: Quote from: Phil1977 on August 12, 2024, 01:21:50 pmw/o referring to "conspiration", it suffices to check the requirements for stuff used/installed into "mil" bases or "gov" embassies to see why I wrote "it doesn't work that way"Quote from: Phil1977 on August 12, 2024, 01:21:50 pmBut then, and again, they'll be totally illegalQuoteThat's a quite different use, isn't it ? And then I think the frequencies and requirements are different too

author: Phil1977
author_rank: Frequent Contributor
timestamp: August 12, 2024, 03:22:15 pm
content: Quote from: A.Z. on August 12, 2024, 03:08:31 pmThey are not so far away... CVD plasma or sputter chambers often operates at 13.56MHz, RF welding at 27MHz. I honestly don't know if these amplifiers here are suited, but principally there are lots of applications where you need high power RF without its far-field emission.

author: CaptDon
author_rank: Super Contributor
timestamp: August 12, 2024, 03:49:02 pm
content: I worked for a 5KW Day 1KW Night AM station that years ago signed off at midnight. It was a 4 tower directional array. By way of a matchbox tuner we used the main feed into the phasor cabinet to run ham radio on 160M, 80M and 40M. God only knows what the horrible mis-match was throughout the antenna field but the QSL cards proved their is no substitute for 'metal in the air'. This was the days of rigs from SBE Sideband Engineers, Swan and maybe Tempo or Trio/Kenwood. Output power was probably 100W PEP from a pair of 6146 or a pair of sweep tubes 6BQ6, 6DQ5 or similar.

author: radiolistener
author_rank: Super Contributor
timestamp: August 13, 2024, 07:54:36 am
content: Quote from: A.Z. on August 12, 2024, 11:02:17 amThey do, but they of course don't like to talking on the air what real equipment and antenna they are using, because it may lead to punishment for them. As one said, he simply couldn't resist using the equipment he used for work to try to make amateur communications on it, he didn't used his official call sign, but simply came up with a fake one and made a lot of DX QSO using fake callsign.

author: radiolistener
author_rank: Super Contributor
timestamp: August 13, 2024, 08:18:50 am
content: Quote from: A.Z. on August 12, 2024, 03:08:31 pmYes, from law point of view this is illegal.But if you're think that all things are strictly regulated and illegal things are impossible, just tune at 3 MHz and listen for a "free radio amateurs".They don't have license and their callsign is not registered on government services just because their ideology is that the air is free and they don't need to get permission from someone to use it.They do not interfere with government/military services bands and these services do not touch them either. Just because if they punish them and start to hunting them, they will occupy a new frequencies and it will make more disorder and troubles than order.... They already tried it in the past. So it appears that this frequency is not officially allocated for amateurs, but is used by free radio amateurs. And government service know that and don't touch them. That's how it works in real life.

author: vk6zgo
author_rank: Super Contributor
timestamp: August 13, 2024, 08:24:48 am
content: Quote from: A.Z. on August 12, 2024, 11:02:17 amIt has happened in the past on rare occasions.

author: Phil1977
author_rank: Frequent Contributor
timestamp: August 13, 2024, 08:33:08 am
content: Is the vacuum tube the right choice if you build a 12KW 30MHz amplifier nowadays?I just ask out of curiosity, I just wouldn't be surprised if you could reach this frequency range with Class-D or Class-E transistor amplifiers in a cheaper way today.

author: radiolistener
author_rank: Super Contributor
timestamp: August 13, 2024, 08:46:41 am
content: Linear solid state amplifier for a short wave and such power is possible, but I suspect it will cost a lot of money and will be a bit complicated in comparison with old school tube amplifier.Guys that I know using tube amplifiers for high power.

author: Phil1977
author_rank: Frequent Contributor
timestamp: August 13, 2024, 09:23:41 am
content: Quote from: radiolistener on August 13, 2024, 08:46:41 amYeah, dissipating the heat of linear amplifiers is for sure easier with tubes at this high power level.But what about digital amplifiers? If a CPU is switching hundreds of amps with many gigahertz, then it somehow sounds possible to get 30MHz without producing much heat.

author: radiolistener
author_rank: Super Contributor
timestamp: August 13, 2024, 10:36:07 am
content: Quote from: Phil1977 on August 13, 2024, 09:23:41 amAs I read somewhere, modern commercial 500 kW AM transmitters really using PWM. As I remember it allowed to implement solid state AM modulator with 50 kW output, but 500 kW amplifier still on the tubes.

author: vk4ffab
author_rank: Frequent Contributor
timestamp: August 14, 2024, 12:03:25 am
content: Quote from: radiolistener on August 13, 2024, 10:36:07 amNone of those big mega stations are using anything remotely modern. They are on tubes because that same transmitter cabinet has been in use for over 40 years. When radio Australia shut down, they only had 1 spare tube and new tubes for it had not existed in years. The problem they all have is spare parts. Mate of mine is a tech for a large AM/FM radio chain here, all their TX sites are solid state, with hot swap able amp modules making up the transmitter rack.

author: CaptDon
author_rank: Super Contributor
timestamp: August 14, 2024, 02:27:38 pm
content: Those hot-swap module units are common. The output is usually one or two loops around a ferrite core which isolates the R.F. output voltage from the module power supply voltages. The R.F. output links are in a large series chain and there is a bridging switch so that when the module is pulled out the series R.F. link remains completed. The D.C. power to the modules can all be parallel due to the isolation of the R.F. output transformer. We ran a solid state Gates/Harris to replace the old Gates/Harris MW-5 which was a PWM modulated 5KW (6100 actual) AM transmitter. The MW-5 was more finicky about mis-match due to icing/etc. than the old tube type RCA BTA-5 and the solid state Harris was more finicky than the MW-5. The solid state unit would roll back the output power if the mis-match was above around 1.3:1

author: A.Z.
author_rank: Super Contributor
timestamp: August 14, 2024, 02:44:16 pm
content: Quote from: CaptDon on August 14, 2024, 02:27:38 pmAll fine, but then... move to Ham HF bands, there we haven't the luxury of transmitting on a single "fixed" frequency, we may (and probably will) change frequency/band, now imagine what this means for a Ham using a linear like the one in subject when it comes to match the antenna...also since, at that power levels, we will want an almost perfect match, otherwise we may just decide to move to US (if we aren't already there) and only power on the linear on 4th July

author: Bud
author_rank: Super Contributor
timestamp: August 14, 2024, 11:40:47 pm
content: With a digital amp you'd be spitting stuff all over the spectrum. You'd need good filtering on the output to meet out-of-band emission specs.

author: CaptDon
author_rank: Super Contributor
timestamp: August 15, 2024, 01:27:01 am
content: Single fixed frequency??? Those hot swap modules are as broadband as a barn door!!!! They aren't tuned, they are transformer output. I am looking at some old LW/MW Harris designs and I believe the exact same modules were used from 200KHz to at least 1.8MHz, almost a decade span. My material is from around 1998 when competition for the solid state dollar was big and everyone was pushing 'reliability' and 'ease of repair' because us tube dinosaurs never thought solid state could survive lightning strikes and plasma ball lightning rolling out of the phasor cabinets. We all kept a tube type around for a backup for many years until solid state could prove itself worthy. Modules back then ranged from around 250W to 500W each. I've been away from the line of work for many years but I bet modules are easily pushing 1KW each today. My old workplace has a 10KW solid state FM unit now. I was gone by the time they installed that one. I guess power reduction at 1.3:1 VSWR is how they bought 'reliability'. A decent antenna farm shouldn't shift that far but 6 inches of rime ice covering most of a 4 tower directional array is going to do some weird things, Including totalling cars and demolishing antenna dog houses!!! 50 to 100 pounds falling 250 feet makes a mark!!

author: iMo
author_rank: Super Contributor
timestamp: August 15, 2024, 10:29:40 am
content: 2000kW midwave TX with solid state PA..https://en.wikipedia.org/wiki/Transmitter_Solthttps://youtu.be/LWyIwCoA8l4

author: Phil1977
author_rank: Frequent Contributor
timestamp: August 15, 2024, 10:41:32 am
content: Quote from: Bud on August 14, 2024, 11:40:47 pmI suppose blocking the PWM frequency of a class-D amp is easier and more efficient then blocking harmonics of an only slightly clipping class-A or class-B.The times are over that SMPS and digital amplifiers are generally noisy.