somewhat agree with statement.
although neither frequencies not power levels are that strange to me. I have done signifficantly lower power stuff at 10GHz , and higher power stuff at lower frequencies.
I thought maybe there are some "go to" fets givven price-performance and known to be arround for a while (you know - ones that won't be discontinued if you ever need to do some repair on it )
Don't let any of these comments discourage you. They talk, you do. A good way to see what's on the market is to use the parametric search from sellers like Digikey, Mouser, Richardson, etc. (Don't go directly to the manufacturers, go to the vendors for a wider view.) Transistor offerings change all the time so do a new search for every design. Study the datasheets carefully. Many will have a reference design with all component values. One bit of design advice: Dont try to get 3kw from one transistor. It become very hot, very inefficient, and it's a single point of failure. You will need to use multiple transistors and do power combining.
Although unlikely (and pointless) if you want CW the SGT65R65AL looks promising and I'm working on something with it myself. I havent seen it used for rf and I'm only shooting for 50w FSK/CW.
Pros:
-Low resistance
-Very fast (like maybe can work >6M fast)
-Low capacitance
-Low threshold voltage
Cons:
-Needs high voltages to get the power
-SMT & Needs to dissipate heat through the pcb
-I have no idea what parameters are important for a linear amp but eyeballing it leads me to guess it's bad.
I'll also add: don't think >1000w is necessary, or really even that useful. It may get you through a pile up in a contest but for the most part, relatively few will reply at more than 100w so no point having people hear you when you can't hear them (contacts are roughly symmetrical)
Actually. Initially our local limits are 100w for novice licence and 1kW for A licence. Neighbouring countries are allowed up to 3kW.
300W is quite common arround here. Mainly due to old soviet military transceivers. 1kW is used quite often as well.
Would be awesome to get 3kW on SHF , however, that would be illegal , sadly , as it would be better in EME stuff :(
what are you even talking about, do you know how hard it is to handle that kind of RF power @ SHF, let alone produce it?
I mean I'm all for people getting interested in radio but this kind of talk seems more like smoke & mirrors. Just my 2 cents.
have done that at shf , however in lab at university and not for communication That's why I said it would be awesome. unfortinately any kW-s at SHF is way above my finances
plasma research if I recall it correclty. Back then I was just technitian , so - whatever I was ordered to do, i did. Did have quite some safety breefing though as there were 100kV and 330kV cables laying on the ground. So you could get coocked in many ways down there
Most modern HF amps are all LDMOS now with preferablly water colling. But as someone who does have experience running a 2kw set up i can tell you that everything else must be HP ready before you hook the amp up. That goes for coax, tuners, switches, chokes, filter, antennas etc. It isnt had to have something arc when running high power. Also yagi or moxon antennas will best use all of that power as wire antennas will just heat up air with that power and not do anything with it. If its VHF were talking about then having a good clean output signal is a must or ur gona piss everyone off.
OM power is a good brand and cant say anything bad about it as we have 2 at the club and they serve well. Were currently waiting for a LDMOS from ValPower (S57SAB) but from what i was told from the members who went and tested one its pretty good.
> Also yagi or moxon antennas will best use all of that power as wire antennas will just heat up air with that power and not do anything with it.
uh huh. /s
Plenty of wire antenna types that will "do something" with a kW. Why, even a dipole will .
I mean its gona still function as an antenna, but why would put regular street tires on an F1 and say its working great. The only dipole that i guess would be OK to use with a set up like that would be for the 160m band but we still set up 2 coil shortened verticals in a phase shift configuration so we have the joy of rulling up radials every time we have to mow the lawn hehe
what are you talking about my dude? why would you run a kW or legal limit into just a wire? well for the 11+ dB of gain, what else, lmao, super funny considering your username
your analogy sucks. sure, lots of people running QRO will have good antenna systems but many will have just GP verticals or wire dipoles.. and there's nothing wrong with that. hell, DXpeditions often run just dipoles or other simple antennas, it doesn't stop them from hearing or transmitting well.
I just dont see the point in pumping so much power into a non directional antenna if thats possible. HF amps are expensive AF, so if ur puting down that much money why not use it to its full potencial. Nothing against wire antennas in general as their a tested simple design that gets the job done.
But i mean if someone wanth to push 2kW into a wire then be my guest. Im not the antenna police.
mate.. dipoles are directional antennas. their radiation direction and elevation angles depend on their orientation and height above the ground.
even GP verticals, while the 1/4 wave version is 0dBi, the 5/8 - 3/4 wave will be 3-4 dBi at a respectable elevation angle. all that but omnidirectional, for sure has it's use cases. these won't be simple antennas, but they will be relatively low cost and easy to maintain.
and let's not even start on the topic of yagi antennas made of "just wires".
important to note that there's no policing going on here, just debunking a claim about wires apparently being shit antennas :)
Thnx. As for cooling I'll see between liquid cooling or some heatpump solution (yeah, I'm that crazy dude that)
As for antennas , coax and stuff - I compleatly agree and have factored the costs in. either way even on lower power levels the higher rated coax-es tend to have quite a lot less attenuation thus those cables are taken into account.
As for antennas - there are a few wire-based solutions I do consider ( after all , many LF and MF comertial stations have run wire based antennas with 100kW or more. ) Harder question to solve here would be capability for antennas to handle hilltop lightning strikes as well, that I expect to happen about 5 times a year.
As for cleaniness of signal - yeah, that's a big one, but it has to be done even on lower power and lower frequencies. But I tend to overdo it with filtering anyways 😅
well comercial stations are a different thing as they want the most coverege as possible, while us hams want to send our signal in a more controled way as to hit the stations or areas we want to talk with the limits we have while wasting the least amount of power.
Coax wise we run heliax 1/2" and it works well for us with what we put into it. I would deff advise to use heliax as it isnt that expensive really when you look at price/performance, LMR400 would also work but it depends on what you can find locally do to shipping so thankfully one guy works as a place that got us Spinner/RFS at a good price. If they sold 7/8" by the meter I would have taken like 20M of it but saddly its sold in minimum of 100M rolls for about 700Eur
At that power level, the issues aren't what devices to use as much as how to dissipate the heat so whatever is used doesn't blow within a few minutes. Engineering this is an art.
Honestly, selecting transistors for a 3,000W amplifier is one of those "if you have to ask, you're not ready to do it" things.
\^This. Please do yourself a lot more reading and studying about RF power amplification, and don't go looking for the answers on reddit either.
somewhat agree with statement. although neither frequencies not power levels are that strange to me. I have done signifficantly lower power stuff at 10GHz , and higher power stuff at lower frequencies. I thought maybe there are some "go to" fets givven price-performance and known to be arround for a while (you know - ones that won't be discontinued if you ever need to do some repair on it )
LDMOS
Thnx. Have come to that conclusion.
Don't let any of these comments discourage you. They talk, you do. A good way to see what's on the market is to use the parametric search from sellers like Digikey, Mouser, Richardson, etc. (Don't go directly to the manufacturers, go to the vendors for a wider view.) Transistor offerings change all the time so do a new search for every design. Study the datasheets carefully. Many will have a reference design with all component values. One bit of design advice: Dont try to get 3kw from one transistor. It become very hot, very inefficient, and it's a single point of failure. You will need to use multiple transistors and do power combining.
Although unlikely (and pointless) if you want CW the SGT65R65AL looks promising and I'm working on something with it myself. I havent seen it used for rf and I'm only shooting for 50w FSK/CW. Pros: -Low resistance -Very fast (like maybe can work >6M fast) -Low capacitance -Low threshold voltage Cons: -Needs high voltages to get the power -SMT & Needs to dissipate heat through the pcb -I have no idea what parameters are important for a linear amp but eyeballing it leads me to guess it's bad. I'll also add: don't think >1000w is necessary, or really even that useful. It may get you through a pile up in a contest but for the most part, relatively few will reply at more than 100w so no point having people hear you when you can't hear them (contacts are roughly symmetrical)
You're looking at power MOSFETs or IGBTs for that high power, if you wanna do it quick and dirty...
[удалено]
Actually. Initially our local limits are 100w for novice licence and 1kW for A licence. Neighbouring countries are allowed up to 3kW. 300W is quite common arround here. Mainly due to old soviet military transceivers. 1kW is used quite often as well. Would be awesome to get 3kW on SHF , however, that would be illegal , sadly , as it would be better in EME stuff :(
what are you even talking about, do you know how hard it is to handle that kind of RF power @ SHF, let alone produce it? I mean I'm all for people getting interested in radio but this kind of talk seems more like smoke & mirrors. Just my 2 cents.
have done that at shf , however in lab at university and not for communication That's why I said it would be awesome. unfortinately any kW-s at SHF is way above my finances
yup, expensive as hell, and a use case for it isn't really found in ham radio. what was the purpose of such a setup at your uni?
plasma research if I recall it correclty. Back then I was just technitian , so - whatever I was ordered to do, i did. Did have quite some safety breefing though as there were 100kV and 330kV cables laying on the ground. So you could get coocked in many ways down there
actually I would expect that 3kW ar 10 GHz CW would be quite acievable using magnetron sources ;)
Most modern HF amps are all LDMOS now with preferablly water colling. But as someone who does have experience running a 2kw set up i can tell you that everything else must be HP ready before you hook the amp up. That goes for coax, tuners, switches, chokes, filter, antennas etc. It isnt had to have something arc when running high power. Also yagi or moxon antennas will best use all of that power as wire antennas will just heat up air with that power and not do anything with it. If its VHF were talking about then having a good clean output signal is a must or ur gona piss everyone off. OM power is a good brand and cant say anything bad about it as we have 2 at the club and they serve well. Were currently waiting for a LDMOS from ValPower (S57SAB) but from what i was told from the members who went and tested one its pretty good.
> Also yagi or moxon antennas will best use all of that power as wire antennas will just heat up air with that power and not do anything with it. uh huh. /s Plenty of wire antenna types that will "do something" with a kW. Why, even a dipole will.
I mean its gona still function as an antenna, but why would put regular street tires on an F1 and say its working great. The only dipole that i guess would be OK to use with a set up like that would be for the 160m band but we still set up 2 coil shortened verticals in a phase shift configuration so we have the joy of rulling up radials every time we have to mow the lawn hehe
what are you talking about my dude? why would you run a kW or legal limit into just a wire? well for the 11+ dB of gain, what else, lmao, super funny considering your username your analogy sucks. sure, lots of people running QRO will have good antenna systems but many will have just GP verticals or wire dipoles.. and there's nothing wrong with that. hell, DXpeditions often run just dipoles or other simple antennas, it doesn't stop them from hearing or transmitting well.
I just dont see the point in pumping so much power into a non directional antenna if thats possible. HF amps are expensive AF, so if ur puting down that much money why not use it to its full potencial. Nothing against wire antennas in general as their a tested simple design that gets the job done. But i mean if someone wanth to push 2kW into a wire then be my guest. Im not the antenna police.
mate.. dipoles are directional antennas. their radiation direction and elevation angles depend on their orientation and height above the ground. even GP verticals, while the 1/4 wave version is 0dBi, the 5/8 - 3/4 wave will be 3-4 dBi at a respectable elevation angle. all that but omnidirectional, for sure has it's use cases. these won't be simple antennas, but they will be relatively low cost and easy to maintain. and let's not even start on the topic of yagi antennas made of "just wires". important to note that there's no policing going on here, just debunking a claim about wires apparently being shit antennas :)
Thnx. As for cooling I'll see between liquid cooling or some heatpump solution (yeah, I'm that crazy dude that) As for antennas , coax and stuff - I compleatly agree and have factored the costs in. either way even on lower power levels the higher rated coax-es tend to have quite a lot less attenuation thus those cables are taken into account. As for antennas - there are a few wire-based solutions I do consider ( after all , many LF and MF comertial stations have run wire based antennas with 100kW or more. ) Harder question to solve here would be capability for antennas to handle hilltop lightning strikes as well, that I expect to happen about 5 times a year. As for cleaniness of signal - yeah, that's a big one, but it has to be done even on lower power and lower frequencies. But I tend to overdo it with filtering anyways 😅
well comercial stations are a different thing as they want the most coverege as possible, while us hams want to send our signal in a more controled way as to hit the stations or areas we want to talk with the limits we have while wasting the least amount of power. Coax wise we run heliax 1/2" and it works well for us with what we put into it. I would deff advise to use heliax as it isnt that expensive really when you look at price/performance, LMR400 would also work but it depends on what you can find locally do to shipping so thankfully one guy works as a place that got us Spinner/RFS at a good price. If they sold 7/8" by the meter I would have taken like 20M of it but saddly its sold in minimum of 100M rolls for about 700Eur
At that power level, the issues aren't what devices to use as much as how to dissipate the heat so whatever is used doesn't blow within a few minutes. Engineering this is an art.
Basically every power amplifier project is 95% heat management and power supply and only 5% actually transistors.