Which PS for K2/100, linear or switcher?

[Darwin, Keith]

My plans to get a K2/100 continue full speed ahead.  Omni V.9 is up on
e-bay and I'm in the process of getting my ducks in a row before I pull
the trigger and commit to a particular rig (new or used is TBD).
 
But what about the PS?  Which one should I get?  Should I go with the
less costly Astron 25 amp switcher or the more traditional Astron 35 amp
linear?
 
Or is there some other power supply I should be looking at?
 
- Keith -
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[hank k8dd-2]

Darwin, Keith wrote:

> My plans to get a K2/100 continue full speed ahead.  Omni V.9 is up on
> e-bay and I'm in the process of getting my ducks in a row before I pull
> the trigger and commit to a particular rig (new or used is TBD).
>  
> But what about the PS?  Which one should I get?  Should I go with the
> less costly Astron 25 amp switcher or the more traditional Astron 35 amp
> linear?
>  
> Or is there some other power supply I should be looking at?
>  
> - Keith -

Keith ....

I'd say if you are going portable a lot, a switching power supply.
If you are going to stay home and never roam, a traditional heavy power
supply.

I have several switching power supplies (Samlex SEC 1223) for travel and
on the
operating desk there is a 50 amp Astron.

72  73    Hank    K8DD

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[Ron D'Eau Claire-2]

A 35 Amp supply is *way* over-kill for a K2/100. A 20 amp supply provides
all the power you need at 100 watts with several amps to spare to run other
things. My K2/100 draws, typically 16 amps "wide open" on the bands
requiring the highest current.  

That's why Elecraft specs a 20 amp supply for the K2/100, and their
specifications are typically quite conservative.

That 20-amp rating on the Astron is for exactly the sort of duty the K2
imposes. It's not "continuous duty" but what we used to call "Intermittent
Commercial and Amateur Service" or ICAS, and which now is simply "ICS"
(guess us Hams don't rate any more <G>). Your K2 will only require full
current -something around 16 amps, typically - when the key is actually down
in CW mode or on individual voice peaks in SSB when running 100 watts.
That's exactly what they mean by ICS even if you're on the air 24/7 with it,
and it's well within the ratings of the 20 amp Astron.

Another decision point for me was to avoid being dependent upon ONE power
supply. I have an 11 amp supply around (which will, incidentally, run the
K2/100 at full output on most bands) and an 8-amp supply on the bench.
Plenty of backup should a supply ever need attention.

My power supplies are all linears because a 20 amp linear isn't all THAT big
or heavy for me and I didn't want to deal with another RFI-generator in the
shack. I'd probably look hard at a very well shielded switcher if I thought
I needed a single supply bigger than 20 amps.

Ron AC7AC



-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Darwin, Keith
Sent: Monday, February 27, 2006 5:54 AM
To: Elecraft Discussion List
Subject: [Elecraft] Which PS for K2/100, linear or switcher?


My plans to get a K2/100 continue full speed ahead.  Omni V.9 is up on e-bay
and I'm in the process of getting my ducks in a row before I pull the
trigger and commit to a particular rig (new or used is TBD).
 
But what about the PS?  Which one should I get?  Should I go with the less
costly Astron 25 amp switcher or the more traditional Astron 35 amp linear?
 
Or is there some other power supply I should be looking at?
 
- Keith -
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[Vic K2VCO]

Ron D'Eau Claire wrote:
> A 35 Amp supply is *way* over-kill for a K2/100. A 20 amp supply provides
> all the power you need at 100 watts with several amps to spare to run other
> things. My K2/100 draws, typically 16 amps "wide open" on the bands
> requiring the highest current.  

Well...actually some K2/100's draw more power.  Mine does take up to 20
amps on some bands.  The 35-amp Astron runs all kinds of things in my
shack and is also usable with another transceiver that I have that does
take more current.

The advantage of the linear supply is: no electrical noise generation.
Disadvantage: must be at least 2 feet from K2 due to magnetic field.

The advantages of the switchers are:  physically lighter and smaller,
smaller or no magnetic field.  Disadvantage: possible electrical noise
generation.

Many people will tell you that such-and-such a switcher is totally
quiet.  This seems to vary by particular unit.  It also depends on your
antenna and feedline, and the particular frequency.  I personally am
sticking with the linear supply.
--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
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[Ron D'Eau Claire-2]

Vic,K2VCO wrote:

Well...actually some K2/100's draw more power.  Mine does take up to 20
amps on some bands.  The 35-amp Astron runs all kinds of things in my
shack and is also usable with another transceiver that I have that does
take more current.

-----------------------------

Hmmm... Did you increase the 20 amp fast-blow fuse size Elecraft specifies,
Vic?

I just checked mine at full output (>100 watts) on all bands and see the
following:

160M 17 A

80M  17 A

40M  15 A

30M  16 A

20M  15 A

17M  18 A

15M  18 A

12M  16 A

10M  17 A

If you are really drawing 20 amps (or more), that suggests some issues with
your output bandpass filters.

Yes, the K2/100 is a bit more efficient than many rigs. I suspect that's why
a lot of ops got the idea that the 20 amp Astron was too 'light' for it!

Ron AC7AC

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[Craig Rairdin]

> The advantages of the switchers are:  physically lighter and smaller,
> smaller or no magnetic field.  Disadvantage: possible electrical noise
> generation.

> Many people will tell you that such-and-such a switcher is totally
> quiet.  This seems to vary by particular unit.  

My Alinco DM-330MV (32 Amp) switcher sits right next to my K2 and works
fine. Do I just not know what to listen for? What should this ps sound like?
This particular model allows me to adjust the noise frequency to move it out
of the way if necessary. I've twisted that knob from one stop to the other
and I don't hear any difference on the K2.

Craig
NZ0R
K1 #1966
K2/100 #4941

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[Vic K2VCO]

Ron D'Eau Claire wrote:

> Hmmm... Did you increase the 20 amp fast-blow fuse size Elecraft specifies,
> Vic?

I'm using a Rigrunner power strip and I have a 25 amp fuse in the K2's slot.

> If you are really drawing 20 amps (or more), that suggests some issues with
> your output bandpass filters.

I don't recall which band or bands drew 20 amps, but I don't think
there's a problem.  I recall discussing this with Gary at the time and
we decided that 'some of them do this'.  I will check it the next time
I'm in my shack and see which bands.

One other thing to keep in mind is that a slightly reactive load -- even
with a reasonable SWR -- may change the current draw significantly.  I
think this was my issue, actually.  Some band on which the antenna's SWR
was about 1.4:1 nevertheless drew much more current than the dummy load.

> Yes, the K2/100 is a bit more efficient than many rigs. I suspect that's why
> a lot of ops got the idea that the 20 amp Astron was too 'light' for it!

I think the 20 amp Astron would be fine just to run a K2.  In my case I
also have a 2-meter rig (which I used to use for packet and which would
therefore randomly transmit at 45 watts) and a whole bunch of filters,
etc., each of which is good for an amp or so.
--
Best Regards,
Vic Rosenthal
Transparent Software, Inc. -- RAKEFET
559.226.5147
Visit us at <http://www.rakefet.com>
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[Geoffrey Mackenzie-Kennedy-2]

Vic Rosenthal wrote:

> Well...actually some K2/100's draw more power.  Mine does take up to 20
> amps on some bands.

.................................................................................

Hi Vic,

Well I also opted for a 35A 'linear' supply for my K2/100 because I did not
want the power supply to run out of steam on SSB voice peaks in a worst case
situation, thus causing anti-social splatter. I could have bought a 25A
supply but the 35A version cost only a few euros more.

73,
Geoff
GM4ESD






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[W4ABW]

I have several Astron power supplies. Always have used them. What are they  ?
Are they switchers are what. I will admit I have never known. I do know they  
are quiet.
 
Al'
W4ABW
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[Phil Kane-3]

On Mon, 27 Feb 2006 08:10:12 -0800, Ron D'Eau Claire wrote:

>A 35 Amp supply is *way* over-kill for a K2/100. A 20 amp supply provides
>all the power you need at 100 watts with several amps to spare to run other
>things. My K2/100 draws, typically 16 amps "wide open" on the bands
>requiring the highest current.

  Hello Elecrafters...... (and Ron - good to see you from the 600M list)

  I'm in the process of joining "the crowd" - ordered my K2/100 on
  line this weekend, at the urging of Robert Crocker, WN7O and with
  the support of Karl N7NLU, two local K2 owners and boosters.

  My two electrons' worth:

  My station power supply is a 12V Group 31 (truck-size) 100AH
  gel-cell battery with a commercial 10A "smart-charger" (which cost
  as much as the battery) backed up with a MFJ 45A switcher (currently
  out for repair, replaced with an Astron 15A linear supply).  The
  computers run on a separate UPS system.

  When we moved here 6 years ago, my wife (who is a utilities engineer
  as was I originally) insisted that the 12V supply be installed to UL
  and USCG standards.  That about doubled the cost but the digital
  meters and the LED circuit-status indicators look so neat in the
  darkened room !!

  At present the supply powers 4 VHF/UHF transceivers, 6 receivers,
  and 4 TNCs, all running 24/7, all on individual circuit breakers.
  The standby current draw is about 5A (if I am to believe the
  ammeters).  There are separate breaker panels for the load bus,
  receivers, and transmitters, and I can run the load from the battery
  and/or the AC supplies depending on which bus breakers are set
  "hot".  I usually set the P/S to be 0.3V lower than the "smart
  charger" (13.8 V float for the gel-cells) so I can leave both
  breakers "hot" and if one supply fails the other takes over. That's
  an old "redundant rectifier" trick that I learned from designing and
  testing communication site power units.

  Well, here I am...waiting for the kit to be delivered.  I'll be
  around.  I'm looking forward to getting on HF again after 40
  years!!!

--
   73 de K2ASP - Phil Kane

   From a Clearing in the Silicon Forest
   Beaverton (Washington County)  Oregon

   Retired and loving every minute of it....
   Work was getting in the way of my hobbies



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[Bob Nielsen]

On Feb 27, 2006, at 8:56 AM, Craig Rairdin wrote:

>> The advantages of the switchers are:  physically lighter and smaller,
>> smaller or no magnetic field.  Disadvantage: possible electrical  
>> noise
>> generation.
>
>> Many people will tell you that such-and-such a switcher is totally
>> quiet.  This seems to vary by particular unit.
>
> My Alinco DM-330MV (32 Amp) switcher sits right next to my K2 and  
> works
> fine. Do I just not know what to listen for? What should this ps  
> sound like?
> This particular model allows me to adjust the noise frequency to  
> move it out
> of the way if necessary. I've twisted that knob from one stop to  
> the other
> and I don't hear any difference on the K2.
>
> Craig
> NZ0R
> K1 #1966
> K2/100 #4941

I have the same model and it really is that quiet.  I bought it to  
replace my Astron RS-20 which wouldn't quite handle the current drawn  
by my TS-570D at full power (the K2/100 draws quite a bit less than  
the Kenwood, however).  Running a comparison with my K2 between a  
linear supply and the Alinco doesn't show any difference in noise,  
birdies, etc., as far as I can tell.

Bob, N7XY
K2 #3273


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[Rick Dettinger-2]

Craig - I had that supply.  On 80 M I could hear hash every 25khz or so.
There was a knob to alter the switching supply frequency.  It worked but was
something else to keep in mind while operating.  When I am pounding brass
with someone, I like my rig to be as transparent as possible.  Thats why I
like simple analog rigs that are intuitive to operate.  I currently use a
30AH marine gel cell to power my QRP rigs , thru a rig runner.    Rick -
K7MW
----- Original Message -----
From: "Craig Rairdin" <[hidden email]>
To: <[hidden email]>
Sent: Monday, February 27, 2006 8:56 AM
Subject: RE: [Elecraft] Which PS for K2/100, linear or switcher?


> The advantages of the switchers are:  physically lighter and smaller,
> smaller or no magnetic field.  Disadvantage: possible electrical noise
> generation.

> Many people will tell you that such-and-such a switcher is totally
> quiet.  This seems to vary by particular unit.

My Alinco DM-330MV (32 Amp) switcher sits right next to my K2 and works
fine. Do I just not know what to listen for? What should this ps sound like?
This particular model allows me to adjust the noise frequency to move it out
of the way if necessary. I've twisted that knob from one stop to the other
and I don't hear any difference on the K2.

Craig
NZ0R
K1 #1966
K2/100 #4941

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[Earl W Cunningham]

The noise from a switching power supply comes in via the antenna, so if
the antenna is located suitably distant, the P.S. can be located next to
the rig and you won't hear the noise.  

All switchers generate noise to some degree.  For those that say their
switcher dosen't, they should locate their P.S. near to their antenna and
then they'll change their mind.

73, de Earl, K6SE
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[Ron D'Eau Claire-2]

Vic wrote:
One other thing to keep in mind is that a slightly reactive load -- even
with a reasonable SWR -- may change the current draw significantly.  I
think this was my issue, actually.  Some band on which the antenna's SWR
was about 1.4:1 nevertheless drew much more current than the dummy load.

--------------

Absolutely! That's why I suggested that for anyone with a "chronic"
over-current problem it might be a problem with an output LPF network since
it can cause exactly that symptom even when feeding a 50 ohm non-reactive
load.

Of course the Astron 20A can deliver considerably more than 20A on peaks
without trouble, but that should NEVER happen in normal operation since
tune-up should always be done at greatly-reduced power (typically 20 watts
or so). So the only real issue should be that of running full power into a
somewhat reactive load.

You raised an interesting question so I tried a little experiment with
reactive loads on my K2/100. On 80 meters where mine draws 16 Amps at just
100 watts into an SWR of 1.0:1, the current demand increases to 18 Amps when
the SWR is increased to 2.0:1 with excess inductive reactance and actually
drops to 15 A when the SWR is increased to 2.0:1 with excess capacitive
reactance in the load (I have a center fed doublet with a manual balanced
ATU so it's easy to tinker with the SWR). If yours is hitting 20 amps, that
would be less than a 10% difference. I'd not be surprised to see that sort
of variation in rigs.

My point was only that a 35 amp supply for the K2/100 was "overkill" and
that the 20A supply Elecraft recommends is plenty to supply a K2/100 with
full transmit current at 100 watts. I've never had the 20 amp "fast blow"
fuse in my power supply line open under any operating conditions.

Some rigs may demand closer to 20 Amps than others, but there should not be
enough difference to be of concern or to justify using a bigger supply for
that reason alone. One point to keep in mind is that Astron rates their
supplies conservatively. Not all manufacturers are as careful as Elecraft
and Astron with their ratings.

I've seen some posts here on the reflector saying that since Astron rates
the 20A supply at 16 Amps continuous duty it is being pushed hard by the
K2/100 which might draw closer to 20 Amps at times. That's simply not
correct. The 20A ICS rating that Astron gives for the supply is precisely
for the sort of load the K2/100 imposes on it at full power in normal
Amateur service. Even if someone was going to run their K2/100 key-down 24/7
as a beacon or something, they'd have to reduce the RF power significantly
below 100 watts to avoid damaging the K2/100. That would greatly reduce the
current demand on the power supply.

Ron AC7AC

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