Elecraft

14.9V to KX1?

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Chris Kantarjiev K6DBG

14.9V to KX1?

In my quest to get a lighter/smaller power supply for my KX-1, I
found a wallwart in my junk box. Says 12V, 1A. Actually puts out
14.9V according to the KX-1's 'bat' display.

Specs call for 7-14v. Am I risking damage by exceeding that? It
looks like D2/D3 (1N5817) are prepared to block 20V reverse.

I can keep looking; I'm mostly 'just wondering'. It's kind of
heavy, anyway (I'm sure it's a linear, not switcher, which
is, of course, a mixed blessing.)

Thanks.

73 de chris K6DBG
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Tom Althoff

Re: 14.9V to KX1?

Hi Chris -

My K1 manual says 8.5 to 15.

You should be safe. I am running a Toshiba laptop switching supply which
is rated at 15VDC ouput to run my K1. I see 14.8VDC on my K1's BAT
indicator.

73 de Tom K2TA

----- Original Message -----
From: "Chris Kantarjiev" <[hidden email]>
To: <[hidden email]>
Sent: Tuesday, January 10, 2006 12:34 AM
Subject: [Elecraft] 14.9V to KX1?

> In my quest to get a lighter/smaller power supply for my KX-1, I
> found a wallwart in my junk box. Says 12V, 1A. Actually puts out
> 14.9V according to the KX-1's 'bat' display.
>
> Specs call for 7-14v. Am I risking damage by exceeding that? It
> looks like D2/D3 (1N5817) are prepared to block 20V reverse.
>
> I can keep looking; I'm mostly 'just wondering'. It's kind of
> heavy, anyway (I'm sure it's a linear, not switcher, which
> is, of course, a mixed blessing.)
>
> Thanks.
>
> 73 de chris K6DBG
> _______________________________________________
> Elecraft mailing list
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Tom Althoff

Re: 14.9V to KX1?

X!!!!!!! kX1!!!!!!

As Miss Natatile Latilla used to say....."Never mind".

Sorry....it's 5:45AM and not quite up yet.

----- Original Message -----
From: "Tom Althoff" <[hidden email]>
To: <[hidden email]>
Sent: Tuesday, January 10, 2006 5:40 AM
Subject: Re: [Elecraft] 14.9V to KX1?

> Hi Chris -
>
> My K1 manual says 8.5 to 15.
>
> You should be safe. I am running a Toshiba laptop switching supply which
> is rated at 15VDC ouput to run my K1. I see 14.8VDC on my K1's BAT
> indicator.
>
> 73 de Tom K2TA
>
> ----- Original Message -----
> From: "Chris Kantarjiev" <[hidden email]>
> To: <[hidden email]>
> Sent: Tuesday, January 10, 2006 12:34 AM
> Subject: [Elecraft] 14.9V to KX1?
>
>
> > In my quest to get a lighter/smaller power supply for my KX-1, I
> > found a wallwart in my junk box. Says 12V, 1A. Actually puts out
> > 14.9V according to the KX-1's 'bat' display.
> >
> > Specs call for 7-14v. Am I risking damage by exceeding that? It
> > looks like D2/D3 (1N5817) are prepared to block 20V reverse.
> >
> > I can keep looking; I'm mostly 'just wondering'. It's kind of
> > heavy, anyway (I'm sure it's a linear, not switcher, which
> > is, of course, a mixed blessing.)
> >
> > Thanks.
> >
> > 73 de chris K6DBG
> > _______________________________________________
> > Elecraft mailing list
> > Post to: [hidden email]
> > You must be a subscriber to post to the list.
> > Subscriber Info (Addr. Change, sub, unsub etc.):
> > http://mailman.qth.net/mailman/listinfo/elecraft
> >
> > Help: http://mailman.qth.net/subscribers.htm
> > Elecraft web page: http://www.elecraft.com
>
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Chris Kantarjiev K6DBG

Re: 14.9V to KX1?

In reply to this post by Chris Kantarjiev K6DBG

> Be sure to double-check both the no-load and loaded voltage output...
> it may be much greater a difference than you wish to work with.

Ah, good catch Tom - it drops to under 13V under Tx load. I'll look
for something else. I'd like to find a little laptop supply,
but they tend to be higher current these days - trying to pare
down my weight for the Spartan Sprint :-)

73 de chris K6DBG
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ab4cz

Re: 14.9V to KX1?

In reply to this post by Chris Kantarjiev K6DBG

Chris et al:

I know there is a lot bad said about switching power supply noise, but I've been using little 12V 4A switchers for a couple of years now and have never found noise a problem. Actually, I work in the electronics industry and have collected a number of these from several suppliers and have had no problems with any of them that I can recall. Typically these power supplies are a little bigger than a bar of soap and have an IEC power connector on one end and an output cable on the other. They are all switchers, and as mentioned are rated at 12V 4A output. They work great on the K2 and my SG-2020 running up to 12W or so output, possibly more. Regulation is pretty good ... typically better than 1/2 volt from receive to key-down. The latest batch I got are from Delta Electronics in China and are fully shielded with input and output RFI filtering including a ferrite core on the output cable just before the coaxial connector. These are all "FCC Class B" devices. Several even ha
d exactly the right connector to plug right into the K2. Look around on surplus sites ... you can probably find plenty of these. The coaxial connector you want is 5.5mm outside, 2mm inside. If you buy one and find it noisy, you can bash me on this reflector .... but I've had no problems. If your shack is very near your antenna you may have more problems. My antennas are high (around 60') and my radios are in the basement, so there is good isolation between the power supply and the antennas.

The All Electronics CAT# PS-1231 looks like it would work but you will have to change the connector. My point is, don't discount the little switchers. They're cheap, universal input (100 - 264 VAC, work anywhere in the world), small and light. If nothing else, good to have for travel.

regards,

Jim
-------------- Original message ----------------------
From: Chris Kantarjiev <[hidden email]>

> > Be sure to double-check both the no-load and loaded voltage output...
> > it may be much greater a difference than you wish to work with.
>
> Ah, good catch Tom - it drops to under 13V under Tx load. I'll look
> for something else. I'd like to find a little laptop supply,
> but they tend to be higher current these days - trying to pare
> down my weight for the Spartan Sprint :-)
>
> 73 de chris K6DBG
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
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> Subscriber Info (Addr. Change, sub, unsub etc.):
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Vic K2VCO

Re: 14.9V to KX1?

[hidden email] wrote:

> If your shack is very near your antenna you may have more
> problems. My antennas are high (around 60') and my radios are in the
> basement, so there is good isolation between the power supply and the
> antennas.

This is the key point! Your antennas are probably fed with coax with
baluns if needed, or properly installed balanced line. In my opinion,
most problems with switcher noise are caused by the noise energy being
conducted to the 'ground' of the AC line, then flowing along the
feedline in common mode, and then getting picked up by the antenna.
Noise energy can also be radiated by house wiring, etc. Things like
verticals near the house, random wires, etc. are problematic for use
with switchers (or around computers, etc.).
--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
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Martin Gillen

Re: 14.9V to KX1?

In reply to this post by Chris Kantarjiev K6DBG

Hi, Chris.

> Ah, good catch Tom - it drops to under 13V under Tx
load.
> I'll look for something else.

13V is still well within the specified range. As long
as that
13V is developing enough RF does it matter that its 2V
below the
RX voltage?

If it were dropping to 7V on transmit I'd be more
worried :)

- Martin.

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ab4cz

Re: 14.9V to KX1?

In reply to this post by Chris Kantarjiev K6DBG

Martin & Chris,

I think you're giving too little thought to the quality of your power supplies. True, if you're lost in the desert and have no alternative, any power supply that works is good enough ... but you paid nearly a kilobuck for a K2 with accessories and now you're betting your signal will sound good with a $3.00 wall wart. If your voltage is dropping from 14.9 volts to under 13 Volts when you key the transmitter you probably have hum. Everybody gives you a "9" for tone, but do you know what your signal REALLY sounds like? I've heard Cubans get "9" for tone, and they don't have an electrolytic capacitor anywhere on the island! I just did the experiment ... looked in my JUNK box and found a 14V unregulated wall wart. Ran the K2 at 5W and got about 15% 120 Hz modulation on the CW waveform. Changed to one of my switcher bricks and had zero perceptible hum modulation. It's your signal. Kinda like the "swing" in days of old, people will be able to recognize your signal on the ai
r by the hum. To be fair, I think my wall wart is wimpier than yours, as my voltage regulation was worse than you mention ... but you will still have hum. And I'm not promoting switchers, just a REGULATED power supply. Remember, regulation stabilizes the voltage AND REMOVES RIPPLE.

Even if it seems to sound OK, don't you want the best signal your Elecraft rig is capable of? The power supply is often the last thing people think of in designing an electronic system, but it's the only part of the system that touches EVERY circuit ... Your keyed waveform is dependent on power supply dynamic regulation. Even though the PLL runs off a local regulator, every regulator has a Vin / Vout regulation specification. They're not perfect; if the input changes, the output also changes. I know I don't want my callsign associated with a signal that hums, chirps, or drifts.

Sorry if I seem a little passionate about this, but there's places to be cheap and places not to be cheap. It doesn't cost that much to get a decent regulated power supply, even if you have to add a regulator to the output of your wall wart.

For those of you wanting to build some kind of power supply, you may want to look at the Far Circuits catalog. They sell printed circuit boards for QST and ARRL Handbook projects so you can build a decent regulated power supply on a nice quality circuit board. There are a BUNCH of different regulated power supply boards available, several in the $5 price range. Download a copy of the FAR catalog at http://www.farcircuits.net/FAR_CKTS.pdf. I've bought a number of project boards from FAR over the years and have been completely satisfied with the quality of the boards. You have to determine which project board is suitable for your purposes, but the stuff is out there. Or, do a Google search on "electronic kits". There are a number of kit suppliers out there (Ramsey, Rainbow, and others). Nearly any kit supplier has some kind of regulated power supply kit. Build a decent regulated power supply and be confident that your rig is performing at it's peak potential.

Oops, just fell off my soap box. Ouch.

73,

jim

-------------- Original message ----------------------
From: Martin Gillen <[hidden email]>

> Hi, Chris.
>
> > Ah, good catch Tom - it drops to under 13V under Tx
> load.
> > I'll look for something else.
>
> 13V is still well within the specified range. As long
> as that
> 13V is developing enough RF does it matter that its 2V
> below the
> RX voltage?
>
> If it were dropping to 7V on transmit I'd be more
> worried :)
>
> - Martin.
>
>
>
> ___________________________________________________________
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> Security Centre. http://uk.security.yahoo.com
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Chris Kantarjiev K6DBG

Re: 14.9V to KX1?

In reply to this post by Chris Kantarjiev K6DBG

> I think you're giving too little thought to the quality of your power supplies.

Jim,

Not at all - and this kind of comment is exactly why I posted - thanks.

Lower weight is only part of the equation, and I recognize that - I'm
new at this game and still trying to understand all the tradeoffs.
Suffice it to say that I'll be looking for a small regulated
switcher at the local surplus place, because I think that is more
what I want (I'll take my KX-1 along and listen for noise...)

73 de chris K6DBG
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