[Amps] 2 kW amp project
Peter Frenning [OZ1PIF]
oz1pif at privat.dk
Mon Nov 21 04:42:24 EST 2005
I'm building a 1KW 144MHz amp based on 4xMRF151G and a massive 50V/49A SMPSU
(again surplus telecom). Total weight is less than 18Kg (all components at
hand and factored in), 42x45x18cm excluding handles.
So maybe it's only ~55W/Kg, but more importantly: It's legal max, easily
portable, and robust enough to bring along for DXpeditions!
Same thing with an analog PSU would have been a min. of 15Kgs heavier plus
much more prone to transit damage (because of the very heavy transformer),
this I think is the more pertinent fact.
Of cause if we had easy access to HV SMPSUs a tube amp would be possible
weighing even less....
Vy 73 de OZ1PIF, Peter
********** OZ1PIF **************
Ph. +45 4619 3239
DK-4130 Viby Sj.
----- Original Message -----
From: "PA3DUV" <pa3duv at planet.nl>
To: <g3rzp at g3rzp.wanadoo.co.uk>; <amps at contesting.com>
Sent: Monday, November 21, 2005 10:24 AM
Subject: Re: [Amps] 2 kW amp project
> The weight of an Icom PW1 solid state power amplifier (1 kW out) is 25 kg@
> 1000 watt output (40 watt/kg)
> The weight of an Emtron DX2 twin GU74B tube amp is 27 kG @ 1500 watt
> (56 watt/kg)
> The weight of an Emtron DX4 twin GU84B tube amp with 3 phase PSU is 76 kg
> 6000 watt output. (79 watt/kg)
> The PW1 is equipped with a SMPS, the tube amps with tape wound
> with a FWD
> The tube amp wins hands down when it comes to power/weight ratio.
> Cheers, Dick Knol
> ----- Original Message -----
> From: "Peter Chadwick" <g3rzp at g3rzp.wanadoo.co.uk>
> To: <amps at contesting.com>
> Sent: Monday, November 21, 2005 9:36 AM
> Subject: Re: [Amps] 2 kW amp project
>> The article in QEX was not a simple multi band device, although I suppose
>> it could eventually get to that. It uses a lot of cheap FETs, and goes up
>> to 7 MHz. Going up to 28MHz with cheap FETs may not be on. The output
>> transformer is fearsome, with 1/2 inch copper tubes silver soldered to
>> inch thick copper heatspreaders. Copper is vile stuff to work, too, when
>> it comes to drilling and tapping. Incidentally, it behoves one to be
>> careful when working with sheet copper, since any small cuts that you get
>> from it frequently tend to get infected and take a long time to heal -
>> although not as long as RF burns!
>> The problem with Class E is that it isn't linear, although it modulates
>> well for AM. This suggests that for SSB, either a Cartesian or Polar loop
>> approach is required, which adds considerably to the complexity -
>> a Callum modulator could be used, but that's fairly critical on set up,
>> too. Personally, I need some convincing that at the end of the day, for
>> homebrew ham use, the big SS amp really wins out. From the viewpoint of
>> interesting technical experimentation, there is a lot of fun to had from
>> it, though. One major factor for a linear amplifier is still the
>> heatsinking. Teaching grandmama to suck eggs here, but a larger allowable
>> temperature rise means that the cooling is less critical.
>> Accepting the switching regulator (and high voltage SMPS are available),
>> doubt the tube amp ends up much different in size and weight. There is
>> minor problem of making sure the SMPS is electrically quiet enough, of
>> course. OK, you can switch it off on receive, but if it requires a surge
>> limitation on input current, QSK would be a problem.
>> The tube amp with the 75lb HV transformer isn't likely to get easily
>> knocked off the table, though!
>> Peter G3RZP
>> Message Received: Nov 21 2005, 12:48 AM
>> From: "Bill Turner"
>> To: "wc6w at juno.com" , Amps at contesting.com
>> Subject: Re: [Amps] 2 kW amp project
>> At 09:54 AM 11/20/2005, wc6w at juno.com wrote:
>>> Item #1 is easy. Get a surplus 48V switching power supply from
>>> the telecom world.
>>> My best suggestion for #2 is a dual pi-net. 50 ohms to 500-1000
>>> ohms back to 25-100 ohms. This provides both matching & harmonic
>>> suppression. Two switched coils, 3 (small) vac. variables, plus
>>> some ceramic padders for 80 & 160. Physically about 6" x 7" x 12"
>>> including motor drives for the caps & 10 position bandswitch.
>>>73 & Good morning,
>>> Marv WC6W
>> Sounds good. I almost wish I hadn't started the 8877 project but it's
>> too far along to stop now. :-)
>> Where does one find the surplus telecom supplies? Can you suggest a
>> manufacturer of new ones?
>> 73, Bill W6WRT
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