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[KX3] Boost Buck 13.8 V Regulator

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Glen Torr-2

[KX3] Boost Buck 13.8 V Regulator

Hi All,

I have a KX3 and am doing some SOTA activations.

I have obtained a 4S LiPo battery which is somewhere north of 16 V with
full charge.

I would like to get a DC-DC regulator as a more elegany solution than
series diodes.

I have searched and searched but no solid outcomes.

Anyone have any input on where to find such a regulator?

Many Thanks,

Glen
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Dom M1KTA

Re: [KX3] Boost Buck 13.8 V Regulator

16V into a KX3 would be terminal to the KX3!

I think you might need to refer to
http://kr7w-sota.blogspot.co.uk/2013/01/qrp-ops-battery-power-fyi.html
that has a few links. (Talking about FT817 but same issue of over voltage).

Or you could just buy a 14.4V LiPo or take one 3.7V cell out of the 4S
pack which will drop it to 13.7V?

72

Dom
M1KTA

p.s. For those not in the know... charging a 4S LiPo battery is not a
case of applying a voltage and leaving it like you would say a SLA you
need a proper LiPo charger. If trying to charge from 13.8V (I assume a
vehicle?) then look for an intelligent charger that will recharge LiPo
'packs'.
You can try and homebrew something but I wouldn't, ebay will usually
bring up plenty of options. Usually you would be able to pick up the
charger/charging electronics at the same time as buying the battery, if
the vendor does not have or cannot advise then be careful what you buy.

On 13/05/13 07:38, Glen Torr wrote:

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Don Nelson

Re: [KX3] Boost Buck 13.8 V Regulator

In reply to this post by Glen Torr-2

Glen,

There a number of down converters from which you could choose to run the
KX3 off of a higher supply voltage - and they are inexpensive. Below is
the ebay listing for one such device. I have this one on order to test.
I have yet to get it and can not validate it yet. Do note that the
output voltage has to be 1.5 volts below the input voltage. Most
important will be the RFI it may generate.

Don, N0YE

http://www.ebay.com/itm/LM2596-DC-DC-Power-Converter-3-2V-40V-to-1-25V-37V-Step-Down-Power-Supply-Module-/230964091763?pt=LH_DefaultDomain_0&hash=item35c6885b73

On 5/13/2013 12:38 AM, Glen Torr wrote:

> Hi All,
>
> I have a KX3 and am doing some SOTA activations.
>
> I have obtained a 4S LiPo battery which is somewhere north of 16 V with
> full charge.
>
> I would like to get a DC-DC regulator as a more elegany solution than
> series diodes.
>
> I have searched and searched but no solid outcomes.
>
> Anyone have any input on where to find such a regulator?
>
> Many Thanks,
>
> Glen
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>
> This list hosted by: http://www.qsl.net
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>

Phil Salas

Re: [KX3] Boost Buck 13.8 V Regulator

I put two 1N5400 diodes in series with each other (these are 3-amp diodes). The diodes are physically side-by-side, with the leads connected in series to keep the assembly small. This all fits nicely between two PowerPole connectors and has a piece of heat-shrink over it. When connected between my 4S2P LiPo battery (16.8VDC fully charged), I get 14.8VDC on receive, and 14.2V with 2.2 amps on transmit at 10 watts. When the receive voltage drops to 13V (as monitored on the KX3), I unplug the diode assembly.

Maybe it is not elegant. But it is cheap, works great, and doesn’t generate any hash.

Phil – AD5X
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David Cutter

Re: [KX3] Boost Buck 13.8 V Regulator

In reply to this post by Don Nelson

I will try a simple low dropout regulator for mine.

David
G3UNA

----- Original Message -----
From: "Don Nelson" <[hidden email]>
To: <[hidden email]>
Sent: Monday, May 13, 2013 11:56 AM
Subject: Re: [Elecraft] [KX3] Boost Buck 13.8 V Regulator

> Glen,
>
> There a number of down converters from which you could choose to run the
> KX3 off of a higher supply voltage - and they are inexpensive. Below is
> the ebay listing for one such device. I have this one on order to test. I
> have yet to get it and can not validate it yet. Do note that the output
> voltage has to be 1.5 volts below the input voltage. Most important will
> be the RFI it may generate.
>
> Don, N0YE
>
>
>
> http://www.ebay.com/itm/LM2596-DC-DC-Power-Converter-3-2V-40V-to-1-25V-37V-Step-Down-Power-Supply-Module-/230964091763?pt=LH_DefaultDomain_0&hash=item35c6885b73
>
>
> On 5/13/2013 12:38 AM, Glen Torr wrote:
>> Hi All,
>>
>> I have a KX3 and am doing some SOTA activations.
>>
>> I have obtained a 4S LiPo battery which is somewhere north of 16 V with
>> full charge.
>>
>> I would like to get a DC-DC regulator as a more elegany solution than
>> series diodes.
>>
>> I have searched and searched but no solid outcomes.
>>
>> Anyone have any input on where to find such a regulator?
>>
>> Many Thanks,
>>
>> Glen
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>>
>
> ______________________________________________________________
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> Post: mailto:[hidden email]
>
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Mark Goldberg

Re: [KX3] Boost Buck 13.8 V Regulator

In reply to this post by Glen Torr-2

How about using a 4S LiFePO4 battery? From fully charged to 15% charge I
get from about 14 V to 12 V in RX and very little sag on transmit. Pretty
much the ideal battery for this radio in my opinion. They are rated to go
down to 10V or so, but since you don't get that much more and you can
permanently damage the batteries if you go too low, I stop at 12V. The KX3
will run full power throughout this range, too. I use real A123 brand cells
with a balancing charger. These do not have quite as much energy density as
LiPo;, but you do not need anything else. I also keep Eneloops in the KX3.
I have not tested it but I think it will switch over if the external
battery goes below their voltage, somewhere about 10 V. If someone could
confirm that, it would be great. Those NIMH Eneloops run below 11V for most
of the discharge cycle, so only 5 W on those but they hold a charge a long
time so they can be used in a pinch.

73

Mark
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Matt Zilmer

Re: [KX3] Boost Buck 13.8 V Regulator

A workable general purpose solution is shown here:
http://ca.picclick.com/DC-DC-Converter-QS-1212CCBA-80W-Power-Supply-251036051706.html

I'm using it in a mobile setting to isolate the KX3 from the vehicle's
electrical system. Pretty good results, and no hash.

73,
matt W6NIA

On Mon, 13 May 2013 05:55:42 -0700, you wrote:

>How about using a 4S LiFePO4 battery? From fully charged to 15% charge I
>get from about 14 V to 12 V in RX and very little sag on transmit. Pretty
>much the ideal battery for this radio in my opinion. They are rated to go
>down to 10V or so, but since you don't get that much more and you can
>permanently damage the batteries if you go too low, I stop at 12V. The KX3
>will run full power throughout this range, too. I use real A123 brand cells
>with a balancing charger. These do not have quite as much energy density as
>LiPo;, but you do not need anything else. I also keep Eneloops in the KX3.
>I have not tested it but I think it will switch over if the external
>battery goes below their voltage, somewhere about 10 V. If someone could
>confirm that, it would be great. Those NIMH Eneloops run below 11V for most
>of the discharge cycle, so only 5 W on those but they hold a charge a long
>time so they can be used in a pinch.
>
>73
>
>Mark
>______________________________________________________________
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Ignacy

Re: [KX3] Boost Buck 13.8 V Regulator

In reply to this post by Glen Torr-2

DC regulators have limited efficiency, take space and can generates hash. The diodes lose 10% of energy when connected, and 0% when disconnected. The DC-DC converters have stated 80-90% efficiency so they will lose more energy than the diodes. No gains only losses.

The biggest problems with the connector using the diodes is small size, which makes it easy to lose if not careful.

Ignacy, NO9E

oe9fwv

Re: [KX3] Boost Buck 13.8 V Regulator

In reply to this post by Mark Goldberg

Mark,

this is exactly what I do. The LiFePO4 has a little more weight, but the cells are robust
and have the correct voltage and probably can do more charge/discharge cycles.
I think the trouble with a voltage regulator is not worth the very little gain in weight.
Regarding the Eneloops in the KX3 I do not know if they take over the supply if the external
power supply drops under 10V, but usually there is a switch in the plug which switches off the
internal battery. I'll have to check this out.

73! de Werner OE9FWV

On 13 May 2013 at 5:55, Mark Goldberg wrote:

> How about using a 4S LiFePO4 battery? From fully charged to 15% charge
> I get from about 14 V to 12 V in RX and very little sag on transmit.
> Pretty much the ideal battery for this radio in my opinion. They are
> rated to go down to 10V or so, but since you don't get that much more
> and you can permanently damage the batteries if you go too low, I stop
> at 12V. The KX3 will run full power throughout this range, too. I use
> real A123 brand cells with a balancing charger. These do not have
> quite as much energy density as LiPo;, but you do not need anything
> else. I also keep Eneloops in the KX3. I have not tested it but I
> think it will switch over if the external battery goes below their
> voltage, somewhere about 10 V. If someone could confirm that, it would
> be great. Those NIMH Eneloops run below 11V for most of the discharge
> cycle, so only 5 W on those but they hold a charge a long time so they
> can be used in a pinch.
>
> 73
>
> Mark
>
>

--
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Albert Einstein (1879 - 1955), Physiker

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Rick Tavan N6XI

Re: [KX3] Boost Buck 13.8 V Regulator

The KX3 draws current from whichever supply (internal batteries or external
source) has the highest voltage.

/Rick

On Mon, May 13, 2013 at 1:25 PM, Dr. Werner Furlan <[hidden email]> wrote:

>
> Regarding the Eneloops in the KX3 I do not know if they take over the
> supply if the external
> power supply drops under 10V, but usually there is a switch in the plug
> which switches off the
> internal battery. I'll have to check this out.
>

--
Rick Tavan N6XI
Truckee, CA
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Rich Heineck

Re: [KX3] Boost Buck 13.8 V Regulator

In reply to this post by Glen Torr-2

An LDO is also a simple option for a higher voltage pack. KX3 RX
current decreases as voltage goes up due to the internal switching
regulators, but minimum TX current at 10W out will likely be somewhere
around 13V. The optimum between the two will probably be around 13.5V,
so that would be a good place to set the LDO output. An LDO with very
low drop is the MIC29502. Typical dropout voltage for 2A will be
about 200mV, and at RX currents will be around 65mV. This low a drop
really isn't necessary here though.

But if the goal is to run the TX at 10W CW, the best power efficiency
will occur with an external supply voltage ~11.8V (or the lowest voltage
before rollback to 5W). So an efficient buck regulator set for about
11.8V ought to give the best battery life. The trade-off will be TX SSB
IMD, where a higher voltage will help.

73,
Rich AC7MA

On 05/12/2013 11:38 PM, Glen Torr wrote:

AC8NS

Re: [KX3] Boost Buck 13.8 V Regulator

In reply to this post by Glen Torr-2

Glen,

I remember seeing an ad for a new Linear Technology device that will do what
you want. See http://cds.linear.com/docs/en/ad/LT8705_Ad_Final(P).pdf

It uses four power MOSFETs and some assembly is required. Here is the
datasheet: http://cds.linear.com/docs/en/datasheet/8705p.pdf

Hop - AC8NS

----- Original Message -----
From: "Glen Torr" <[hidden email]>
To: "Elecraft Reflector" <[hidden email]>
Sent: Monday, May 13, 2013 2:38 AM
Subject: [Elecraft] [KX3] Boost Buck 13.8 V Regulator

JonKG6VDW

Re: [KX3] Boost Buck 13.8 V Regulator

In reply to this post by Glen Torr-2

Hi Glenn,

I have purchased both of these DC-DC power converters and have been very
happy with them. They both have an adjustable output set voltage and seem
to have very good regulation. The only issue is with RFI that they
generate. The good news is that they are pretty well shielded in aluminum
cases. But their is stil some leakage from the power connections but I
have found that attaching good quality ferrite beads on the power
connectors to pretty much eliminate this as well.

http://www.ebay.com/itm/Low-Ripple-CC-CV-Car-Power-Supply-Module-LED-Driver-DC-DC-8-30V-to-2-16V-80W-/251112762798?pt=LH_DefaultDomain_0&hash=item3a777cadae

http://www.ebay.com/itm/DC-DC-150W-Non-Isolated-Booster-Voltage-Converter-6V-32V-Step-Down-to-0-8V-28V-/260968513486?pt=LH_DefaultDomain_0&hash=item3cc2ef7fce

YMMV and I am sure that their are many other equally fine Regulators out
there....
--
Thanks
Jon
KG6VDW
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Mark Newbold

Re: [KX3] Boost Buck 13.8 V Regulator

Regarding that first regulator, the QSKJ QS-1212CCBA-80W, I have one of those. The IN- and VO-
connections are apparently not wired together internally. You can't look inside because the whole
thing is potted in some solid substance. In the interest of having all my equipment on a common
ground, I wired the IN- and VO- together. Now the red "error" light is lit all the time (even when
those connections are not wired together). And the device shuts down regularly (output voltage drops
to zero until power-cycled). I don't know whether the failure was caused by wiring the connections
together, or whether it's just coincidence.

The thing doesn't make much hash at KX3 receive current levels, but hash increases if you draw more
current from it.

--Mark K7NEW

On 5/15/2013 11:41 AM, Jon Moody wrote:

> Hi Glenn,
>
> I have purchased both of these DC-DC power converters and have been very
> happy with them. They both have an adjustable output set voltage and seem
> to have very good regulation. The only issue is with RFI that they
> generate. The good news is that they are pretty well shielded in aluminum
> cases. But their is stil some leakage from the power connections but I
> have found that attaching good quality ferrite beads on the power
> connectors to pretty much eliminate this as well.
>
> http://www.ebay.com/itm/Low-Ripple-CC-CV-Car-Power-Supply-Module-LED-Driver-DC-DC-8-30V-to-2-16V-80W-/251112762798?pt=LH_DefaultDomain_0&hash=item3a777cadae
>
> http://www.ebay.com/itm/DC-DC-150W-Non-Isolated-Booster-Voltage-Converter-6V-32V-Step-Down-to-0-8V-28V-/260968513486?pt=LH_DefaultDomain_0&hash=item3cc2ef7fce
>
> YMMV and I am sure that their are many other equally fine Regulators out
> there....

--
Mark Newbold K7NEW
Sequim, Washington, USA
http://dogfeathers.com

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picmaster

Re: [KX3] Boost Buck 13.8 V Regulator

In reply to this post by Phil Salas

Hi Phil,

I've seen similar approaches for regulating the heater voltage a vintage Russian military tube receiver. There's a series resistor in the circuit that's connected when the batteries are fresh-charged, and this resistor is bypassed with a switch when the battery voltage falls inside the normal operating range of the tube heater (there's an embedded volt-meter in the tube received for visual check, just like there's such menu in the KX3).

This method is less power efficient than when using a modern SMPS, but it's very "low-tech" and reliable (simpler systems have less and usually more obvious failure modes).

73,
Nikolay // LZ1NRD

----- Цитат от Phil & Debbie Salas ([hidden email]), на 13.05.2013 в 14:45 -----

> I put two 1N5400 diodes in series with each other (these are 3-amp diodes). The diodes are physically side-by-side, with the leads connected in series to keep the assembly small. This all fits nicely between two PowerPole connectors and has a piece of heat-shrink over it. When connected between my 4S2P LiPo battery (16.8VDC fully charged), I get 14.8VDC on receive, and 14.2V with 2.2 amps on transmit at 10 watts. When the receive voltage drops to 13V (as monitored on the KX3), I unplug the diode assembly.
>
> Maybe it is not elegant. But it is cheap, works great, and doesn’t generate any hash.
>
> Phil – AD5X

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Stephen M. Shearer

Re: [KX3] Boost Buck 13.8 V Regulator

In reply to this post by JonKG6VDW

Another source
http://www.goodluckbuy.com/-dc-dc-converter-qs-1212ccba-80w-power-supply-aut
o-boost-buck-80w-cc-cv-charger.html
Cheaper,
Shipping is from Shenzhen, China {free} but took about 3 weeks.
It should be very useful to boost a 12V battery to 13.8V to charge my KX3 or
as a regulator for my solar panel to do the same..
73, Steve WB3LGC
-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Jon Moody
Sent: 15 May, 2013 2:41 PM
To: [hidden email]
Subject: Re: [Elecraft] [KX3] Boost Buck 13.8 V Regulator

Hi Glenn,

I have purchased both of these DC-DC power converters and have been very
happy with them. They both have an adjustable output set voltage and seem
to have very good regulation. The only issue is with RFI that they
generate. The good news is that they are pretty well shielded in aluminum
cases. But their is stil some leakage from the power connections but I
have found that attaching good quality ferrite beads on the power connectors
to pretty much eliminate this as well.

http://www.ebay.com/itm/Low-Ripple-CC-CV-Car-Power-Supply-Module-LED-Driver-
DC-DC-8-30V-to-2-16V-80W-/251112762798?pt=LH_DefaultDomain_0&hash=item3a777c
adae

http://www.ebay.com/itm/DC-DC-150W-Non-Isolated-Booster-Voltage-Converter-6V
-32V-Step-Down-to-0-8V-28V-/260968513486?pt=LH_DefaultDomain_0&hash=item3cc2
ef7fce

YMMV and I am sure that their are many other equally fine Regulators out
there....
--
Thanks
Jon
KG6VDW
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Mark Goldberg

Re: [KX3] Boost Buck 13.8 V Regulator

I've been following this discussion for a while now and want to add my $.02.

I used my KX3 as a panadapter, with I and Q out to a good quality 24
Bit 192 kHz sound card on Field Day.

Every switching regulator / charge controller / DC-DC converter
generates hash on the bands, some much worse
than others. We had lots of examples, from laptop supplies to MPPT
charge controllers to inverters and they all
generated something. The best only generate spectral spikes at
specific places in the bands so you can avoid
the hash by not operating on those frequencies. Some are so bad they
produce noise everywhere, so loud that
you effectively can't operate. I was able to quiet some of them down
with ferrite cores. The cheaper ones seemed
to be the worst as they have no attempt at filtering.

I work in the avionics field and the equipment is required to meet
stringent radiated (through the air) and conducted
(power line) emissions standards. There is extensive filtering and
even a filter cap value or a ground trace or a hole in
the case can make a difference of night and day. Most consumer
equipment does not even attempt to meet similar
requirements and it is very difficult to quiet something down from the
outside sometimes. The military will sometimes
box something up in a shielded box and put expensive feed-through caps
and big series inductors on all the lines.
That is fine if weight is no object.

Not only does the radiated stuff cause problems but the conducted
stuff on the power can reek havoc even if you
have the antenna terminated. The KX3 is pretty good at rejecting it,
but the sound card no so much. You can tell
because the noise spectrum is symmetrical about the zero frequency
line for power line noise, and does not move
when you tune the radio.

Dropping voltage with diodes or resistors does not generate hash, but
it wastes precious power. If you drop
20% of the voltage, that is just thrown away. You need a bigger,
heavier battery to compensate, or you operate
for less time.

I really like LiFePO4 batteries. They stay between 14 and 12 volts for
virtually their entire discharge curve
and they are less likely to explode than other LI batteries. I've only
used matched, balanced A123 packs so far.
Those packs connected directly to the KX3 have worked really well for
me. I can hear everyone, them hearing
me with QRP power, not so much.

That is my $.02

Mark
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