We seek to understand and document all radio transmissions, legal and otherwise, as part of the radio listening hobby. We do not encourage any radio operations contrary to regulations. Always consult with the appropriate authorities if you have questions concerning what is permissable in your locale.

Author Topic: Higher power design.  (Read 6455 times)

Offline Stretchyman

  • Sr. Member
  • ****
  • Posts: 338
    • View Profile
Higher power design.
« on: December 09, 2015, 1132 UTC »
Im still musing over a design for much higher power, 200W or 400W carrier which will yield 1KW or 1.5KW on peaks.
Of course this wont be running from 12V and will need DCd mains or inverted from a pair of rather large 12V SLAs.
Please forget any notion of a design like this running from any voltage less than 110V-150V as the currents will be just too high and kill efficiency.
Keeping the volts high means less current (for the same power) and therefore less IR loss.

Three versions; below 2MHz, 3-4MHz & 6-7MHz.

Size wise it should fit in 2U 19 rack and not weigh more than 10LBs or so.

What Im interested in is how many people would be interested in such a design?

Ive had some interest from one notable on here and am willing to put in some effort early next year as my lab will be ready and can give the project some priority.

So, 1 KW O/P min, PWM Mod (obviously), DDS channel selection of user programmable 32Chs, will have to have some kind of protection for over current and high SWR etc.

Ideas please.

Str.
'It's better to give than receive' so why RX when you can TX!

                            Buy one from me, NOW!

Great discounts on ALL my transmitters if purchased via HFUnderground


                                              ;)

Offline Pigmeat

  • DX Legend
  • ******
  • Posts: 3793
    • View Profile
Re: Higher power design.
« Reply #1 on: December 09, 2015, 1755 UTC »
There was a guy who was selling a Class H (?) PWM modulated AM tx kit in the back QRZ about 5 or 6 years ago. I never heard much about it other than the ads and some guys on the AM Window forum wondering about it.

The ad said it would produce a bit more than 500 watts carrier at 120 volts and the kit sold for around 600 dollars.

I'm sure if the price was right, there would be both Pirate and ham interest in your design.

Offline redhat

  • DX Legend
  • ******
  • Posts: 1063
  • "It looks like green bacon in the sky"
    • View Profile
    • Email
Re: Higher power design.
« Reply #2 on: December 10, 2015, 0448 UTC »
The problem with offering something of that scale for sale is that the price point will probably be beyond the reach of most of us, myself included.  I'm working on something similar in my free time, but it will probably be a year before I have something to show for it.  In the mean time, I gotta keep the bills paid ;)

+-RH
Somewhere under the stars...
WinRadio Excalibur/305 w/ a chi-town resonant loop, Kenwood KDC-U356 for mobile listening.
Please send QSL's and reception reports to xfmshortwave [at] gmail [d0t] com

Offline Stretchyman

  • Sr. Member
  • ****
  • Posts: 338
    • View Profile
Re: Higher power design.
« Reply #3 on: December 10, 2015, 0726 UTC »
Indeed, Price could be the problem as I was expecting to sell for 300 which is approx the same and at that price it would have to be a kit, building it would double the price.

How much power do folk really want? is always a question.

Soon as you go above a 10W carrier it means you can forget running from 12V and altho' I can get 25W carrier from a 24V supply even that's pushing it efficiency wise and its 10% better with 45V. So your going to need a mains/inverted supply.

May be able to do a 100W carrier (400W peak) for less? Would that be enough?

I notice folk on here aren't up to building much and while it's time consuming its fun but you do have to know what your doing!

Time is money as they say and I'm happy to recoup time spent designing and laying out PCB's from the sale of kits, building them makes them too expensive unless I do it for nothing, which frankly I'm not prepared to do (much!).

I'd definitely like to get some PCB's done for a higher power design but will only be able to supply kits.

We'll see.

Thanks for your input chaps.

Cheers from Blighty.

Stretchy.
'It's better to give than receive' so why RX when you can TX!

                            Buy one from me, NOW!

Great discounts on ALL my transmitters if purchased via HFUnderground


                                              ;)

Offline redhat

  • DX Legend
  • ******
  • Posts: 1063
  • "It looks like green bacon in the sky"
    • View Profile
    • Email
Re: Higher power design.
« Reply #4 on: December 10, 2015, 1130 UTC »
100W carrier I think would satisfy most ops, particularly if it sounds better than anything they've previously used.  You could probably make the PCB design somewhat universal, so that more/larger fets could be added for more power, with the increased supply voltage of course.  The 100W level is also nice because you can use passive cooling, no fan noise.

And now for the next illusion, make the same box do SSB ;)  It can be done.

+-RH
Somewhere under the stars...
WinRadio Excalibur/305 w/ a chi-town resonant loop, Kenwood KDC-U356 for mobile listening.
Please send QSL's and reception reports to xfmshortwave [at] gmail [d0t] com

Offline Stretchyman

  • Sr. Member
  • ****
  • Posts: 338
    • View Profile
Re: Higher power design.
« Reply #5 on: December 10, 2015, 1311 UTC »
NO, it wont do SSB as it's class E and not linear.

I'm not interested in SSB, fine for comms, crap for tunes!

Sure tho' the design uses parallel FETs, voltage however would be the same, you need lots of volts to keep the losses down.

More FETs = more current = more power however.

The parts are not that expensive, a FET pair can only be $20, it's more the time designing and testing + the meagre amount I will sell (50?) which will drive up the cost.

If someone said 'Build me a 100' that would halve the cost immediately!

Str.
'It's better to give than receive' so why RX when you can TX!

                            Buy one from me, NOW!

Great discounts on ALL my transmitters if purchased via HFUnderground


                                              ;)

Offline Pigmeat

  • DX Legend
  • ******
  • Posts: 3793
    • View Profile
Re: Higher power design.
« Reply #6 on: December 10, 2015, 1407 UTC »
100 watts of good sounding AM has normally been the pirate gold standard. It's why so many guys bust ass and get burns keeping those old Johnson rigs on the air.

Something that you could get 100 watts of good sounding AM out of without getting a hernia, now that's progress!

Offline Stretchyman

  • Sr. Member
  • ****
  • Posts: 338
    • View Profile
Re: Higher power design.
« Reply #7 on: December 10, 2015, 1517 UTC »
Indeed, a notable on here has enquired and I could REALLY not believe he was hauling round a Johnson (Viking?), massive batteries and an invertor to get on the air.

Kind of 'Inspired' me to come up with something more 'Modern'

That stuff is over 50 years old and testament to its design that it's still being used, but really....fine for 'Nostalgic' purposes but otherwise...FFS!

Who Knows having something more portable may make it more popular!

We'll see.

Soon!

Str.
'It's better to give than receive' so why RX when you can TX!

                            Buy one from me, NOW!

Great discounts on ALL my transmitters if purchased via HFUnderground


                                              ;)

Offline John Poet

  • Hero Member
  • *****
  • Posts: 875
  • I survived the Mad Lagomurph
    • View Profile
    • Free Radio Cafe forums
    • Email
Re: Higher power design.
« Reply #8 on: December 10, 2015, 2321 UTC »
That takes a high level of commitment...

... or maybe they should be committed...

something like that, anyway

 ;)




John Poet

"A treasonous voice of dissent"

The Crystal Ship Shortwave
Free Radio Cafe Forums

Offline redhat

  • DX Legend
  • ******
  • Posts: 1063
  • "It looks like green bacon in the sky"
    • View Profile
    • Email
Re: Higher power design.
« Reply #9 on: December 10, 2015, 2327 UTC »
Assuming 400W+ PEP capability, your going to need a supply voltage of at least 65V to deliver the peak power.  I assume this will be a line-powered affair?  I suppose you could use a large boost converter to get 12V up to 65V if battery operation is required.

+-RH
Somewhere under the stars...
WinRadio Excalibur/305 w/ a chi-town resonant loop, Kenwood KDC-U356 for mobile listening.
Please send QSL's and reception reports to xfmshortwave [at] gmail [d0t] com

Offline Stretchyman

  • Sr. Member
  • ****
  • Posts: 338
    • View Profile
Re: Higher power design.
« Reply #10 on: December 11, 2015, 0718 UTC »
100/120V A.C. Dc'd should give 120/150V.

Limey builders use 110V tranny's on building sites and you lot have 120V

So one design can be powered direct from mains or inverted from 12/24V batteries to the higher voltage.

Covered in my first post  ;)

Oh and..... Yes JP, Definitely Committed!

 :)
'It's better to give than receive' so why RX when you can TX!

                            Buy one from me, NOW!

Great discounts on ALL my transmitters if purchased via HFUnderground


                                              ;)

Offline redhat

  • DX Legend
  • ******
  • Posts: 1063
  • "It looks like green bacon in the sky"
    • View Profile
    • Email
Re: Higher power design.
« Reply #11 on: December 11, 2015, 0745 UTC »
I personally wouldn't bother with rectified mains until you get to the 500W carrier level or so, simply from a safety and cost standpoint.  Switching supplies are so cheap, you can string 3 of them together to get 150VDC, quite enough for 500W CW.  Also above that power level, power factor correction becomes compulsory for efficiency.  It also helps reduce mains hum in the audio, unless your mod has humbucking.

 BTW 'inverting' over here means running a power inverter to get 120VAC from 12VDC, hence why I asked about mains power.

+-RH
« Last Edit: December 11, 2015, 0748 UTC by redhat »
Somewhere under the stars...
WinRadio Excalibur/305 w/ a chi-town resonant loop, Kenwood KDC-U356 for mobile listening.
Please send QSL's and reception reports to xfmshortwave [at] gmail [d0t] com

Offline Stretchyman

  • Sr. Member
  • ****
  • Posts: 338
    • View Profile
Re: Higher power design.
« Reply #12 on: December 11, 2015, 0902 UTC »
Inverting is same here, not sure what we're not saying to each other!!

Whether the amp is plugged directly into (U.S.) mains or run from a (110V) isolation transformer or from an inverted supply will ALL lead to the same voltage.

120V A.C. (or 110 or whatever)

This will be rectified and smoothed inside the amp to 120/150V D.C.

Cost is a bridge rectifier and a smoothing cap.

3 PSU's are way to big as the amp is not even as big as one of them!

Choice can be up to the end user.

The 110V isolation trannies are very cheap and safe enough and that would be my recommendation.

Str.

 :)
'It's better to give than receive' so why RX when you can TX!

                            Buy one from me, NOW!

Great discounts on ALL my transmitters if purchased via HFUnderground


                                              ;)

Offline redhat

  • DX Legend
  • ******
  • Posts: 1063
  • "It looks like green bacon in the sky"
    • View Profile
    • Email
Re: Higher power design.
« Reply #13 on: January 13, 2016, 0847 UTC »
The problem with that is you still have the weight problem to contend with.  I like rack mount stuff, there's just something 'official' looking about it.  A relatively shallow 3U chassis could contain up to 1KW, and weigh less than 25 pounds.  At the 1KW level even considering modest efficiency, you still need around 1600W during 100% modulation, and that takes a rather heavy transformer.  Build a PFC boost circuit to get 250VDC, isolate the drive, and there you go.  I'd call that progress.  Leave the iron to the scrappers ;)

+-RH
Somewhere under the stars...
WinRadio Excalibur/305 w/ a chi-town resonant loop, Kenwood KDC-U356 for mobile listening.
Please send QSL's and reception reports to xfmshortwave [at] gmail [d0t] com

Offline Stretchyman

  • Sr. Member
  • ****
  • Posts: 338
    • View Profile
Re: Higher power design.
« Reply #14 on: January 13, 2016, 1158 UTC »
If it's in a rack it's in the house and you may as well use SMPSU's

I'm looking at 'Portable' use, hence the 110V from a genni or inverted from 12/24/48V D.C.

The PSU can be left up to the user anyway, I'm just designing the amp and PWM!

 ;D
'It's better to give than receive' so why RX when you can TX!

                            Buy one from me, NOW!

Great discounts on ALL my transmitters if purchased via HFUnderground


                                              ;)