Hi power HF amplifiers - Page 1
Forum section: electronics / rf-microwave

author: A.Z.
author_rank: Super Contributor
timestamp: August 07, 2021, 09:33:21 am
content: If you seek around you will find a number of very high power HF amplifiers, for examplehttps://www.emtron.com.au/products/dx3sp.phpnow those amplifiers are FAR above whatever legal limit, so I'm really wondering WHO is their market target; for one, I understand that using such an amp at reduced power (at/below legal limit) will put the amplifier under low stress and allow the tubes to last longer, but then I'm not sure that's the reason why some people goes for themSo ... what's your take ?

author: RoV
author_rank: Regular Contributor
timestamp: August 07, 2021, 02:20:42 pm
content: Quote from: A.Z. on August 07, 2021, 09:33:21 amYou will also find a lot of cars capable of running far above any legal speed limit...Probably the reason is similar

author: A.Z.
author_rank: Super Contributor
timestamp: August 07, 2021, 02:27:23 pm
content: Quote from: RoV on August 07, 2021, 02:20:42 pmHm ... but then there aren't all those nice chicks to pick up on the air, and there aren't (at least not that I know) RF speed tracksCome on, my question was serious

author: TimFox
author_rank: Super Contributor
timestamp: August 07, 2021, 02:35:59 pm
content: Of course, with all those digital monitors built into the amplifier panel, the legal operator can keep the output within regulations...Before I looked at the ad, I assumed the "nominal" market for the amplifier was for laboratory purposes, but the wording is obviously aimed at amateur operators.

author: eb4fbz
author_rank: Regular Contributor
timestamp: August 07, 2021, 03:32:23 pm
content: Not everyone sticks to legal limits, and 4kW is at the low side for some of them.Just search for homebuilt amplifiers arround 3CX10000A7...

author: NiHaoMike
author_rank: Super Contributor
timestamp: August 07, 2021, 03:36:49 pm
content: Perhaps there are special licenses that allow use of more than the usual power limit for certain purposes like bouncing a signal off the moon?

author: TimFox
author_rank: Super Contributor
timestamp: August 07, 2021, 04:20:24 pm
content: It's been decades since I was interested in this question.Do the American FCC and its foreign equivalents "type approve" equipment for sale for use on the amateur bands?

author: CJay
author_rank: Super Contributor
timestamp: August 07, 2021, 04:45:47 pm
content: Quote from: A.Z. on August 07, 2021, 09:33:21 amI know you've got the Italian flag in your profile but...Honestly?Italians and Russians.Rules and regulations seem to be pretty much optional for operators in both those countries.I'm pretty sure other countries are similarly lax but they're the two that spring to mind.

author: iMo
author_rank: Super Contributor
timestamp: August 07, 2021, 05:35:28 pm
content: The "ownership" and "operating" are two different things from legal point of view..You may "own" a 10kW transmitter, but you are "not allowed to operate" it (ie. transmit into an antenna).Also in most countries (ie in EU) the local authorities does not care about (does not monitor anymore) the HF bands, thus running ie. 4000 Watts would most probably get unnoticed by them..PS: 4 times more output power adds "1S" only on your S-meter reading..Example: If you transmitted from Paris to New York with 100W output power, and the NY OM gave you a "56" report, with your 6400W he would give you a "59".

author: A.Z.
author_rank: Super Contributor
timestamp: August 07, 2021, 05:46:02 pm
content: Quote from: imo on August 07, 2021, 05:35:28 pmFirst of all anyone (not just EU) could buy those (again, the link was just an example) or build an HF amp going above legal limit, then it isn't just an "italy and russia" thing; if those amplifiers are on the market AND the companies are still in business, I doubt they're just selling to EU people, hence my original question, focus on it, please

author: iMo
author_rank: Super Contributor
timestamp: August 07, 2021, 05:51:02 pm
content: They run it full power.. How would you know they are above the legal limit??

author: CJay
author_rank: Super Contributor
timestamp: August 07, 2021, 06:06:18 pm
content: Quote from: A.Z. on August 07, 2021, 05:46:02 pmBuying such an amp as the Emtron isn't illegal anywhere that I know of, if people want to buy it then let them, it's up to their conscience how they use it but most of the people I know who have equipment capable of running much higher than legal limit don't boast about breaking the rules if tey do.My experience of nearly 40 years of operating radio is that the stations I hear boasting about using illegal power levels are Italian or Russian and the 'freebanders' too. Then you have the Superbowl AM CB users but they tend to build their own or buy some overvolted, overdriven thing, not a properly designed amp like the Emtron.Personally, I would rather someone were using a well designed and built piece of equipment like the Emtron, that way at least if they do break the rules it's going to cause less interference to legitimiate users.You also need to consider that most if not all ham licenses specify power limits at the feedpoint, so while it's unlikely and a ridiculous waste of power, 4KW might not be hitting the antenna.

author: coppercone2
author_rank: Super Contributor
timestamp: August 07, 2021, 06:16:58 pm
content: you can do overload testing of stuff with iti.e. dummy load characterization for drift, testing power components, etc. A 10x underrating might be one way to make a reliable system.

author: iMo
author_rank: Super Contributor
timestamp: August 07, 2021, 06:24:45 pm
content: Experienced ham radio operators may recognize such stations, but generally it is extremely difficult.Based on a specific actual propagation conditions while doing many QSO's during a short time period in a specific heading first skip you may somehow distinguish when somebody reports much lower output power than actually is using. But that is an extremely rare situation.This year I copied a QSO between an UK and a Norway station at 40m band where the latter added QRP in his call in order to attract the attention of the UK station.They made the QSO and the UK operator added ".. and my dear OM do not tell me you are qrp, you are at least 1kW"..But normally you cannot easily recognize whether a station runs 400W or 2000W or 4000W especially when doing dxes..During an 1 minute long QSO the signal (shown by your S-meter) may fluctuate between S2 and S9 easily (so called QSB) because of the ionosphere fluctuations.That is 9 - 2 = 7 "S" - that is like the transmitter would have changed its output power from 1W to 16kW and back during that QSO..

author: coppercone2
author_rank: Super Contributor
timestamp: August 07, 2021, 07:00:07 pm
content: and that thing would make a hell of a plasma chamber amplifier if you give it a tuner

author: A.Z.
author_rank: Super Contributor
timestamp: August 07, 2021, 07:04:34 pm
content: Thank you all, this is confirming to me the fact that ham hectics has been definitely buried many years ago, and it also makes me feel in peace with all the 6KD6, PL519 and 813 (skipping the Eimac based ones) I've built in years

author: David Hess
author_rank: Super Contributor
timestamp: August 08, 2021, 01:44:10 am
content: There are industrial, military, aerospace, and electromagnetic compliance test applications for that sort of equipment.

author: coppercone2
author_rank: Super Contributor
timestamp: August 08, 2021, 06:24:34 am
content: driving the water soaked hard line conductor with 1500W for an output power of 50W?

author: A.Z.
author_rank: Super Contributor
timestamp: August 08, 2021, 09:32:14 am
content: Quote from: David Hess on August 08, 2021, 01:44:10 amsure, but look at the description of that amplifier I used as an example "QRO", "Bands from 160 to 10 meters" and then more, I don't think they are targeting industrial/aerospace/... AND then, that power is far above legal ham limit

author: A.Z.
author_rank: Super Contributor
timestamp: August 08, 2021, 09:33:29 am
content: Quote from: coppercone2 on August 08, 2021, 06:24:34 amLOL !Well, that's another way to waste moneyBut seriously, what's your take ?

author: TimFox
author_rank: Super Contributor
timestamp: August 08, 2021, 01:39:15 pm
content: Another legitimate use for high-power RF linear amplifiers is MRI, but that usually needs 64 MHz--not a ham band.

author: A.Z.
author_rank: Super Contributor
timestamp: August 08, 2021, 05:00:21 pm
content: just found a similar discussion herehttps://forums.qrz.com/index.php?threads/illegal-high-power-hf-amplifiers.659044/

author: coppercone2
author_rank: Super Contributor
timestamp: August 08, 2021, 06:08:46 pm
content: I think so long you have output monitoring on the actual signal then having the high power to get a transmission out despite a fault is a good thing, they are supposed to be emergency capable systems.Not a issue for a small time ham but if someone is using it in some kind of capacity in a remote location, perhaps with snow, intense climate, etc. These possibilities will always be somewhat at odds with a neat bureaucratic solution.I read that story before, that there was a ham club with bad heliax soaked with water that was using excessive power levels to transmit very modest signals because of losses. It sounded foolish (more like they did not do maintenance tests) but if this happened during some record snow storm or something, it could be useful. It's one of those things like when you get on the highway if the situation arises you might need to step on it for a little bit of time to avoid an accident, or say passing a semi truck, unblocking a emergency vehical that needs to respond on a narrow road, etc.. the excess speed that is not normally used has its justifiable uses.

author: David Hess
author_rank: Super Contributor
timestamp: August 08, 2021, 07:02:53 pm
content: Quote from: A.Z. on August 08, 2021, 09:32:14 amBut the RF output power meter is calibrated to indicate a limit of 1500 watts. All 1500 watt amplifiers should be able to put out some amount more than 1500 watts for adequate linearity at 1500 watts. This one just appears overbuilt more than most, and should also get better operating life than most.Reading various reviews of the Chinese FU-728F tube makes me think that the power claims are exaggerated.

author: thinkfat
author_rank: Unknown
timestamp: August 12, 2021, 06:33:57 am
content: Isn't the legal limit about power radiated by an imaginary isotropic antenna? What if your feedline is just oh so lossy?

author: A.Z.
author_rank: Super Contributor
timestamp: August 12, 2021, 07:50:05 am
content: Quote from: David Hess on August 08, 2021, 07:02:53 pmDon't know, but reading the comment from W8IDL herehttps://www.eham.net/reviews/view-product?id=11595he states the followingQuoteso apparently the amplifier can really ouput over 4KW but he says he's using it at/below legal limit; fine and as I wrote in the initial post, such a thing would allow the amplifier tubes to have much less stress and last longer, yet I doubt that people "out there" would buy such an amplifier (or a similar one, the one I linked was just as an example) and run it at lower power, also since a (say) 2KW amplifier could be run at 1.5KW or less and allow obtaining the same result (less stress to tubes), so again, what's the purpose for a 5KW Ham HF amplifier ?

author: gargle
author_rank: Newbie
timestamp: August 12, 2021, 01:05:27 pm
content: I may be a little naive but I think there is 2 aims :- less power in lamp which accept much more, so longer life- amp in the "middle" of the band, where it's the most linear, to reduce distortion.But there is also a lot of ham people which consider that amp is life, and don't know the proverb :So much for the ANTENNASo much for the HAM STATION

author: A.Z.
author_rank: Super Contributor
timestamp: August 12, 2021, 01:33:22 pm
content: Quote from: gargle on August 12, 2021, 01:05:27 pmor "90% of a station is the antenna system" (and I'd humbly add the grounding system too,)

author: m3vuv
author_rank: Super Contributor
timestamp: August 20, 2021, 11:09:25 am
content: to make the power gen/utility companys lots of money,i have a homebrew hf amp that will tx about 1700w but never use it when i saw what it draws from the mains,good way for big leccy bills for no real gain as ear as i see it,also being an m3 here a good way to get busted!/nicked.

author: cdev
author_rank: Super Contributor
timestamp: August 27, 2021, 06:55:07 pm
content: Commercial broadcast, military, governments (diplomatic services?) demining, (ground penetrating radar). cooking, baking, soldering? Diathermy?Quote from: NiHaoMike on August 07, 2021, 03:36:49 pm

author: cdev
author_rank: Super Contributor
timestamp: August 27, 2021, 06:59:19 pm
content: Quote from: cdev on August 27, 2021, 06:55:07 pmTo do that one doesn't need the legal limit, just a high gain antenna and a bit of power (enough to exceed the noise level at the receiver which presumably is also using a highly directional antenna).AS I understand it its getting easier and easier to do, affordably and legally. Especially with digital modes.I have some small directional antennas that could be combined with external dishes (As a feed) to give the requisite gain. Wonder if I could receive hams working EME?When I lived elsewhere, at a restaurant equipment shop I found chrome plated steel pot lid thats a perfect parabola (as shown by its ability to focus sunlight into a point with absolute precision. It makes my eyes hurt just to think about it. )Anyway, this does not do much at low microwave frequencies (I suspect for wifi it might deliver ~20 db gain or so.) but the higher you go the more gain you get. This is roughtly an 18 inch dish.. A 1 meter dish is fairly affordable and easy to find. These are popular for direct-TV like services.Hige parabolic dishes are very impractical because of wind loading in storms. But smaller ones would work for EME on higher bands.

author: geggi1
author_rank: Frequent Contributor
timestamp: August 28, 2021, 09:42:24 am
content: Remember that this rating is on CW and SSB. If the linear is used on AM the maximum power output to not damage the valves is probably 30%-40% of the maximum rating (1200W - 1600W) that is very close to legal limit in the US, Australia and probably plenty of other countries.

author: bd139
author_rank: Super Contributor
timestamp: August 28, 2021, 09:52:26 am
content: Another legal reason is using compromised antennas or feeds. For example your ERP might be within the legal limit but the power you stick up the feed might be considerably higher. If you have a massive beam antenna remotely located then that is perfectly reasonable.But mostly it's these retards I expectNot that I do it now but I kept my shit under 10W apart from a surprisingly successful IRF530 based amp which ran a whole 40W on CW.

author: cdev
author_rank: Super Contributor
timestamp: August 28, 2021, 10:46:14 pm
content: I didn't realize people got credit for cable loss and got to make it up. If that is what you are proposing.Are you sure?Also, how are directional antennas handled. I could see this getting kind of complicated quickly and where regulatory matters go, sometimes simpler is better. Also, the law shouldn't discourage or penalize people for good practices considerate of the resource. People should use the least power and the antenna, seems preferably a directional antenna - not wasting signal where its not going to help...whatever is necessary to make the link work, IMHO.

author: cdev
author_rank: Super Contributor
timestamp: August 28, 2021, 10:57:09 pm
content: Thats an illegal CB amplifier. His voice makes me think he's from the southern US.Do those peoples signals make it to the EU? I bet some of them do.

author: bd139
author_rank: Super Contributor
timestamp: August 28, 2021, 11:07:18 pm
content: Regarding feed loss, that is one thing yes. But directional antennas on low frequencies are quite large. Even a 40m yagi is impractical for most. So you have to put up with somewhat inefficient radiators potentially.On longer wavelength bands things get interesting though. For example on 2200m expect to throw 170 watts down the feedline and get 0.4W EIRP. To hit the limit of 5W EIRP in some regions, you'd have to throw 2125 watts down that feed line.Also on top of that some of the modulations are not very bandwidth efficient. AM for example is terrible. SSB is marginal. CW and FT8 etc are excellent. To get a better SnR you have to throw much more power down the line on AM or SSB to reach the same distance.CW is my favourite though. I managed to hit Tasmania from the UK on 2 watts thanks to some glorious propagation conditions once!

author: cdev
author_rank: Super Contributor
timestamp: August 29, 2021, 01:11:09 am
content: Transistors that work at LF frequencies would be quite affordable, most here likely already have em..For antenna, make a mag loop out of several turns of copper pipe or maybe coax (for the braid and coax connectors) , and a big homemade capacitor, maybe?It seems as if it makes sense to use a magnetic loop antenna or similar so you wont need radials.. Cuts down on ground losses, I would guess..Look at helical magnetic loops.. They look like a good approach.

author: bd139
author_rank: Super Contributor
timestamp: August 29, 2021, 08:07:00 am
content: IRF530 MOSFETs seem to be the workhorse for this stuff. Slightly explodey but cheap as anything.Google for some 630m and 2200m loading coils. That’s what people seem to be doing. The mag loops would still be too big.

author: tkamiya
author_rank: Super Contributor
timestamp: August 31, 2021, 05:11:20 am
content: In my day's in Japan, it was possible to purchase Henry 8K. A remote capable unit produces 10KW at 100% duty cycle. Of course I neither had a budget or desire to buy such a monster.Some serious contesters have have quite a few of way over legal limit amplifiers. Somewhere on Internet, there is a 40KW amp someone designed as part of dare.My max is 100 watts. I never needed anything more.

author: knapik
author_rank: Regular Contributor
timestamp: September 01, 2021, 02:25:40 am
content: We have an SPE 2 kW HF amplifier at work (more than the legal limit for amateur radio over here) because we calibrate in line power meters, so all of that energy is being dumped right into a termination anyways. Even with 2kW we still have to turn down a lot of power meters because they're rated at a maximum of 10 kW.

author: thinkfat
author_rank: Unknown
timestamp: September 01, 2021, 05:16:31 pm
content: I do remember a story of a US ham operator who saved a satellite by overpowering a leaking oscillator in one of its transponders that clogged the command channel, from his ground station. He sent a command to disable the transponder, saving the satellite. His signal was "louder" than the leak from the LO. I don't quite remember, but it was one of the AMSAT vehicles.

author: bd139
author_rank: Super Contributor
timestamp: September 01, 2021, 05:20:14 pm
content: Probably followed immediately by the FCC turning up

author: rfclown
author_rank: Frequent Contributor
timestamp: September 15, 2021, 04:58:15 pm
content: I worked at Sunair for a short time. Our HF transceiver had an output of 125W, but the external amplifiers were 500W, 5kW and 10kW. Their market wasn't amateur radio.

author: thinkfat
author_rank: Unknown
timestamp: September 15, 2021, 08:57:45 pm
content: Quote from: thinkfat on September 01, 2021, 05:16:31 pmI finally found a reference of this:http://om6bb.bab.sk/files/HAM%20kniznica/Magaziny/QST/09%20September%202000%20QST.pdfThe HAM in question is David Blaschke, W5UN, and the satellite was DOVE-OSCAR 17.Not easy to find stuff that predates Y2K, on the internet.

author: Jr460
author_rank: Regular Contributor
timestamp: September 15, 2021, 09:27:01 pm
content: Market for HF high power......Sure, long ago when I was a kid went on a tour of the VOA site about 5 miles from me. Rather than a normal tour, it was a bunch of HAMs and most of the operations people at the VOA site were Hams. We saw all the cool stuff and got shown things that most people had no idea what it was.They did crazy things like 500KW, yes half a million, HF band into a curtain antenna to beam a double side band suppressed carrier with a different program in each sideband to somewhere in Africa. And that was just one of the transmitters.In the winter the building was heated from steam from the cooling water around the tubes. The audio transformer of an AM transmitter, B+ for RF output tubes it runthru it, was as tall as I was at the time. You could hear what was broadcast if you were in the right room because the steel laminations were not perfectly tight and and so large that they produced some sound.Now the VOA site with all the towers supporting the antennas and feed lines are gone, now a park. The operations/transmitter building remains for history.

author: M0HZH
author_rank: Regular Contributor
timestamp: December 16, 2021, 09:59:46 am
content: 1. There are 194 more countries besides the US and they all have different legal limits for amateur radio; Canada has 2.25kW for example, others allow special experimental licenses with higher limits (UK can allow up to 2kW) etc.2. Many amplifiers are rated for amateur radio typical duty cycle, which is quite low and not really standardised; solid amplifiers are rated for the ICAS (Intermittent Commercial and Amateur Service) standard, which is 50% duty cycle (5 minutes on / 5 minutes off) but tested in a dummy load. In a contest you might exceed 50%, continuously for 48+ hours, in a antenna system that doesn't have perfect SWR across the entire band, in a room that might get too hot; you need an amplifier "normally" rated much higher than the legal limit to be able to do that many weekends a year, for many years, without failing.3. People like to have more power available if needed for that special DX pileup, even if they break the limits.

author: A.Z.
author_rank: Super Contributor
timestamp: December 16, 2021, 10:14:14 am
content: Quote from: M0HZH on December 16, 2021, 09:59:46 amAll good points, but then one sees stuff like thesehttp://www.dc9dz.de/en/tsunami.htmlhttp://www.dc9dz.de/en/tsunami100k.htmland starts wondering if that's just "to have more power available if needed"

author: M0HZH
author_rank: Regular Contributor
timestamp: December 16, 2021, 11:58:32 am
content: I see DC9DZ's projects more like engineering achievements, but there are some in the wild; of course there are people running them ilegally.Also, the numbers are very misleading; "100kW" RF output with a 30kVA power supply, that's probably 15kW real output with the tube massively outside spec (rated for 11kV anode voltage, absolute max limit 13kV, ran at 17kV here). A realistic safe-ish number is probably 10kW for RF output.

author: mag_therm
author_rank: Frequent Contributor
timestamp: December 16, 2021, 04:04:44 pm
content: 20m ft8 is getting spoiled by appliances in USA day time with their wick turned up too high.FT8 reception can't use conventional AGC.Yesterday there were transmissions coming in here in Michigan, more than S9 +20dBIf wsjr-x gets a signal over its +80dB level, it will stop decoding.Also the computer sound card can clip.Yesterday I turned the receiver IF down by about 20dB in the day, and then progressively turned it up overnight.I am thinking about a very slow AGC based on out of band noise level.

author: cdev
author_rank: Super Contributor
timestamp: December 23, 2021, 07:46:38 pm
content: A better antenna seems to me to almost always make more sense than more power. Unless people like a one way monologue over a conversation!

author: Bud
author_rank: Super Contributor
timestamp: December 24, 2021, 06:20:37 pm
content: Quote from: cdev on August 28, 2021, 10:46:14 pmIn Canada at least we do not get credit for cable loss, the output is measured across a matched dummy load. And with this method, directionality of the antenna is irrelevant for the purpose of RF power legal limit.

author: Bud
author_rank: Super Contributor
timestamp: December 26, 2021, 02:41:56 am
content: Worked many QSOs with Americas, Europe and Russia on 20M with this mobile setup with an all-band 100W Icom and top loaded stick. The most interesting one was mobile-to-marine mobile with a guy on a cargo ship in the ocean somewhere near Florida, lol.

author: M0HZH
author_rank: Regular Contributor
timestamp: January 02, 2022, 08:04:34 am
content: I don't necessarily agree. On HF, once you have a decent setup antenna gain is generally more expensive than power gain, especially below 20m. For example, if you have a wire dipole in a tree at a good height, you will need a tower & 3-el Yagi to gain almost 3dB, on 7MHz that is a US$3000-4000 job; increasing power from 100 to 600W (almost 8dB) costs half that.And receive capability is not about antenna gain but about S/N ratio, so increasing antenna gain does not directly translate to better receive (it receives more signal but also more noise).

author: David Hess
author_rank: Super Contributor
timestamp: January 02, 2022, 10:19:25 am
content: Quote from: M0HZH on January 02, 2022, 08:04:34 amDirectivity has a major influence on S/N, and improving directivity can be a major cost.

author: A.Z.
author_rank: Super Contributor
timestamp: January 02, 2022, 10:26:00 am
content: Quote from: David Hess on January 02, 2022, 10:19:25 amwell, I agree on diirectivity, but it isn't the only factor, as an example this antennahttp://www.kk5jy.net/LoG/will give surprisingly good reception, but isn't so directive and is really cheap

author: Theboel
author_rank: Frequent Contributor
timestamp: January 02, 2022, 02:41:39 pm
content: I disagree with You about directivity try to build one if You want to see what I mean.back to over legal limit I think I can Understand if legal limit is 1500w some one use 2500w amplifier to overcome cable loss etc but for people who use 5kw or more with legal limit only 1500w I think that is wrong thing to do.

author: coppercone2
author_rank: Super Contributor
timestamp: January 03, 2022, 06:08:26 am
content: always keep in mind that some people have crazy transmission losses from say snow. Never would hurt to have extra power on hand for whatever reason in a critical situation, so long ERP is monitored.

author: thinkfat
author_rank: Unknown
timestamp: January 03, 2022, 11:14:46 am
content: Quote from: M0HZH on January 02, 2022, 08:04:34 amEver worked your way through a pile-up in CQWW? I've operated DL0TD for two or three years in CQWW SSB, I can attest to the value of antenna directivityPS: do you know what a "crocodile" is?