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Chinese ebay amps for KX3

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Richard Lawn

Chinese ebay amps for KX3

Has anyone tried the little inexpensive 45 watt amplifiers out of China
being sold on ebay with their KX3. I built a BPF for an old Palomar amp but
it doesn't seem to work well at all for some reason.
73
Rick W2JAZ
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Hajo Dezelski

Re: Chinese ebay amps for KX3

Hello,

I use this one:
http://pa-11019.blogspot.de/2016/11/diy-kits-70w-ssb-linear-hf-power.html
and it works without any problem.

73 de

Hajo dl1sdz

---
Cela est bien dit, mais il faut cultiver notre jardin.

http://hajos-kontrapunkte.blogspot.de/

Am 20.02.2017 3:46 vorm. schrieb "Richard Lawn" <[hidden email]>:

> Has anyone tried the little inexpensive 45 watt amplifiers out of China
> being sold on ebay with their KX3. I built a BPF for an old Palomar amp but
> it doesn't seem to work well at all for some reason.
> 73
> Rick W2JAZ
> ______________________________________________________________
> 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
> Message delivered to [hidden email]
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Charlie T, K3ICH

Re: Chinese ebay amps for KX3

Very nice amp Hajo

So now, tell me why a mid-sized radio can't have a built in 12 V to say, 50
V converter to drive some HV FETs for cleaner output specs like the Yuge
radios.

73, Charlie k3ICH

-----Original Message-----
From: Elecraft [mailto:[hidden email]] On Behalf Of Hajo
Dezelski
Sent: Monday, February 20, 2017 6:04 AM
To: Richard Lawn <[hidden email]>
Cc: Elecraft Reflector <[hidden email]>
Subject: Re: [Elecraft] Chinese ebay amps for KX3

Hello,

I use this one:
http://pa-11019.blogspot.de/2016/11/diy-kits-70w-ssb-linear-hf-power.html
and it works without any problem.

73 de

Hajo dl1sdz

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Jerry Moore

Re: Chinese ebay amps for KX3

It's not a matter of can't. Why as a customer should I pay for the added
power supply when I'm installing my rig mobile? Or how about if already have
a nice power supply.
Do you want to increase the cost of the radio which will result in a higher
weight and cost for customers that don't want the feature ?
With economies of scale I don't see how they could make profit or even break
even doing anything with a power supply when you look at the market.

-----Original Message-----
From: Elecraft [mailto:[hidden email]] On Behalf Of
Charlie T, K3ICH
Sent: Monday, February 20, 2017 8:48 AM
To: [hidden email]
Subject: Re: [Elecraft] Chinese ebay amps for KX3

Very nice amp Hajo

So now, tell me why a mid-sized radio can't have a built in 12 V to say, 50
V converter to drive some HV FETs for cleaner output specs like the Yuge
radios.

73, Charlie k3ICH

-----Original Message-----
From: Elecraft [mailto:[hidden email]] On Behalf Of Hajo
Dezelski
Sent: Monday, February 20, 2017 6:04 AM
To: Richard Lawn <[hidden email]>
Cc: Elecraft Reflector <[hidden email]>
Subject: Re: [Elecraft] Chinese ebay amps for KX3

Hello,

I use this one:
http://pa-11019.blogspot.de/2016/11/diy-kits-70w-ssb-linear-hf-power.html
and it works without any problem.

73 de

Hajo dl1sdz

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KI4D

Re: Chinese ebay amps for KX3

In reply to this post by Richard Lawn

I have gotten the MX-P50M up and running with my KX3 keying it OK. I was
able to get over 50 watts out of the amp into a dummy load with 6 watts from
my KX-3 on 160 meters. It turns out to be quite simple to configure once I
researched how the amp lead was used for keying with the FT-817 and what the
KX-3 provided for keying. The KX3 provides keying via the ACC2 connector on
the ring terminal on the 2.5mm stereo plug on an adapter cable. The KX3
grounds the key line while transmitting to enable the amplifier to be keyed.
All that was needed was a splice into the red/black lead section intended
for the FT-817 DIN connector with a red/black lead terminated with a 2.5mm
stereo plug. The red lead goes to the ring on the 2.5mm stereo plug. And
that is it. This took more time to figure out than I wanted. Obviously, it
would have taken less time if there was a manual with the amp.

Don, KI4D
-----Original Message-----
From: Elecraft [mailto:[hidden email]] On Behalf Of
Richard Lawn
Sent: Sunday, February 19, 2017 9:46 PM
To: [hidden email]
Subject: [Elecraft] Chinese ebay amps for KX3

Has anyone tried the little inexpensive 45 watt amplifiers out of China
being sold on ebay with their KX3. I built a BPF for an old Palomar amp but
it doesn't seem to work well at all for some reason.
73
Rick W2JAZ
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len

Re: Chinese ebay amps for KX3

In reply to this post by Hajo Dezelski

Does it work well with all modes? CW/SSB/Digital?

73

Len

-----Original Message-----
Subject: Re: [Elecraft] Chinese ebay amps for KX3

Hello,

I use this one:
http://pa-11019.blogspot.de/2016/11/diy-kits-70w-ssb-linear-hf-power.html
and it works without any problem.

73 de

Hajo dl1sdz

---
Cela est bien dit, mais il faut cultiver notre jardin.

http://hajos-kontrapunkte.blogspot.de/

Am 20.02.2017 3:46 vorm. schrieb "Richard Lawn" <[hidden email]>:

> Has anyone tried the little inexpensive 45 watt amplifiers out of
> China being sold on ebay with their KX3. I built a BPF for an old
> Palomar amp but it doesn't seem to work well at all for some reason.
> 73
> Rick W2JAZ
> ______________________________________________________________
> 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 Message delivered to
> [hidden email]
>

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Richard Fjeld-2

Re: Chinese ebay amps for KX3

In reply to this post by Hajo Dezelski

The way the wire is wound through the tubes in the photo reminds me of
the 100W PA section in the Heathkit HW/SB-104 transceiver.

Dick, n0ce

On 2/20/2017 5:03 AM, Hajo Dezelski wrote:

> Hello,
>
> I use this one:
> http://pa-11019.blogspot.de/2016/11/diy-kits-70w-ssb-linear-hf-power.html
> and it works without any problem.
>
> 73 de
>
> Hajo dl1sdz
>
>

Bill Frantz

Boost power supplies for RF amps

In reply to this post by Charlie T, K3ICH

The short answer is they can. It is only a matter of engineering
time, cost, resulting price, number of customers and competing
projects. In other words, the usual business considerations.

Lets work the idea through for several of the Elecraft RF amplifiers:

The 10-15W K3(s) amp: This amp can have significant IMD at low
voltages as we have discovered with our QRP, all Elecraft, field
day operation. The KX3 seems to do better, so reengineering the
amp may be a better solution. For field day, we try to have
fresh batteries available.

The 100W K3(s) internal amp: This amp also has low voltage IMD
as we found during our 100W California QSO party expeditions.
But, consider the K3(s)'s construction. The front of the radio
is the digital portion, including the DSPs and the front panel
computer. All of this digital noise is isolated from the analog
circuits in the back of the radio. If Elecraft were to include a
boost power supply with the internal amp, that high-current
switcher would be in the analog section, and probably impossible
to quiet. Solution: Get an external boost power supply.

The KXPA100 external amp: This form factor would be an ideal
place to include a boost power supply. The use profile includes
portable battery operation and designing isolation for the power
supply into the package seems straight forward.

The KPA500 external amp: The amp setup procedure sets the
voltage to to 65v to 85v and the specifications call for about
1000 VA of power or about 13A at 75v. That would be nearly 75A
at 13.5 volts assuming 100% efficiency, so it would be a good
idea to put the boost power supply next to the battery and run
75v to the amp. It would make a nice high power mobil rig.

73 Bill AE6JV

In thread "Re: [Elecraft] Chinese ebay amps for KX3", on 2/20/17
at 5:47 AM, [hidden email] (Charlie T, K3ICH) wrote:

>So now, tell me why a mid-sized radio can't have a built in 12 V to say, 50
>V converter to drive some HV FETs for cleaner output specs like the Yuge
>radios.
-----------------------------------------------------------------------
Bill Frantz |The nice thing about standards| Periwinkle
(408)356-8506 |is there are so many to choose| 16345
Englewood Ave
www.pwpconsult.com |from. - Andrew Tanenbaum | Los Gatos,
CA 95032

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Elecraft mailing list

Re: Boost power supplies for RF amps

I have long wondered why some manufacture did not think of it. That is a amp with built in 12 VDC boost PS. With all of the new switching tech, it should be a KISS solution and make the amp SOUND GREAT all of the time....
Just my opinion hi.
Mel, K6KBE

From: Bill Frantz <[hidden email]>
To: [hidden email]
Sent: Monday, February 20, 2017 2:08 PM
Subject: [Elecraft] Boost power supplies for RF amps

The short answer is they can. It is only a matter of engineering
time, cost, resulting price, number of customers and competing
projects. In other words, the usual business considerations.

Lets work the idea through for several of the Elecraft RF amplifiers:

The 10-15W K3(s) amp: This amp can have significant IMD at low
voltages as we have discovered with our QRP, all Elecraft, field
day operation. The KX3 seems to do better, so reengineering the
amp may be a better solution. For field day, we try to have
fresh batteries available.

The 100W K3(s) internal amp: This amp also has low voltage IMD
as we found during our 100W California QSO party expeditions.
But, consider the K3(s)'s construction. The front of the radio
is the digital portion, including the DSPs and the front panel
computer. All of this digital noise is isolated from the analog
circuits in the back of the radio. If Elecraft were to include a
boost power supply with the internal amp, that high-current
switcher would be in the analog section, and probably impossible
to quiet. Solution: Get an external boost power supply.

The KXPA100 external amp: This form factor would be an ideal
place to include a boost power supply. The use profile includes
portable battery operation and designing isolation for the power
supply into the package seems straight forward.

The KPA500 external amp: The amp setup procedure sets the
voltage to to 65v to 85v and the specifications call for about
1000 VA of power or about 13A at 75v. That would be nearly 75A
at 13.5 volts assuming 100% efficiency, so it would be a good
idea to put the boost power supply next to the battery and run
75v to the amp. It would make a nice high power mobil rig.

73 Bill AE6JV

In thread "Re: [Elecraft] Chinese ebay amps for KX3", on 2/20/17
at 5:47 AM, [hidden email] (Charlie T, K3ICH) wrote:

>So now, tell me why a mid-sized radio can't have a built in 12 V to say, 50
>V converter to drive some HV FETs for cleaner output specs like the Yuge
>radios.
-----------------------------------------------------------------------
Bill Frantz |The nice thing about standards| Periwinkle
(408)356-8506 |is there are so many to choose| 16345
Englewood Ave
www.pwpconsult.com |from. - Andrew Tanenbaum | Los Gatos,
CA 95032

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David Orman

Re: Boost power supplies for RF amps

In reply to this post by Bill Frantz

I believe the new Anan-8000DLE does exactly this, and steps up the voltage
to 50V. No idea if there's any noise related to these boost converters.
Seems like a neat idea, just not sure how it will work in practice.

On Mon, Feb 20, 2017 at 4:08 PM, Bill Frantz <[hidden email]> wrote:

> The short answer is they can. It is only a matter of engineering time,
> cost, resulting price, number of customers and competing projects. In other
> words, the usual business considerations.
>
> Lets work the idea through for several of the Elecraft RF amplifiers:
>
> The 10-15W K3(s) amp: This amp can have significant IMD at low voltages as
> we have discovered with our QRP, all Elecraft, field day operation. The KX3
> seems to do better, so reengineering the amp may be a better solution. For
> field day, we try to have fresh batteries available.
>
> The 100W K3(s) internal amp: This amp also has low voltage IMD as we found
> during our 100W California QSO party expeditions. But, consider the K3(s)'s
> construction. The front of the radio is the digital portion, including the
> DSPs and the front panel computer. All of this digital noise is isolated
> from the analog circuits in the back of the radio. If Elecraft were to
> include a boost power supply with the internal amp, that high-current
> switcher would be in the analog section, and probably impossible to quiet.
> Solution: Get an external boost power supply.
>
> The KXPA100 external amp: This form factor would be an ideal place to
> include a boost power supply. The use profile includes portable battery
> operation and designing isolation for the power supply into the package
> seems straight forward.
>
> The KPA500 external amp: The amp setup procedure sets the voltage to to
> 65v to 85v and the specifications call for about 1000 VA of power or about
> 13A at 75v. That would be nearly 75A at 13.5 volts assuming 100%
> efficiency, so it would be a good idea to put the boost power supply next
> to the battery and run 75v to the amp. It would make a nice high power
> mobil rig.
>
> 73 Bill AE6JV
>
> In thread "Re: [Elecraft] Chinese ebay amps for KX3", on 2/20/17 at 5:47
> AM, [hidden email] (Charlie T, K3ICH) wrote:
>
> So now, tell me why a mid-sized radio can't have a built in 12 V to say, 50
>> V converter to drive some HV FETs for cleaner output specs like the Yuge
>> radios.
>>
> -----------------------------------------------------------------------
> Bill Frantz |The nice thing about standards| Periwinkle
> (408)356-8506 |is there are so many to choose| 16345 Englewood Ave
> www.pwpconsult.com |from. - Andrew Tanenbaum | Los Gatos, CA 95032
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

Matthew Cook

Re: Boost power supplies for RF amps

In reply to this post by Elecraft mailing list

I have a Codan 6924 lunch box radio that does just this.

(
http://www.hfradiosales.com.au/codan_%20barrett_hf_radio_information/RADIOS/files/6924%20MK2-2.jpg
)

It takes in 10-15V and boosts it to 28V to feed a 25W PA, it does so only
on TX. This radio was designed in 1969 and released to market in 1971, I
got mine given to me in 1979. So this concept is not new. Way back when
the 28V RF transistors of the day did not operate well with low collector
voltages at 12V, IMD was way too high. For reference the 6924 IMD is
better than -40dB PEP for a 38 yr old radio.

I believe we will see a return of the 50V MOSFET PA's in commercial
equipment again, especially with the explosion of LDMOS devices and the
ever decreasing availability of 16-18V bi-polar RF transistors.

73

Matthew
VK5ZM

On 21 February 2017 at 09:10, Mel Farrer via Elecraft <
[hidden email]> wrote:

> I have long wondered why some manufacture did not think of it. That is a
> amp with built in 12 VDC boost PS. With all of the new switching tech, it
> should be a KISS solution and make the amp SOUND GREAT all of the time....
> Just my opinion hi.
> Mel, K6KBE
>
> From: Bill Frantz <[hidden email]>
> To: [hidden email]
> Sent: Monday, February 20, 2017 2:08 PM
> Subject: [Elecraft] Boost power supplies for RF amps
>
> The short answer is they can. It is only a matter of engineering
> time, cost, resulting price, number of customers and competing
> projects. In other words, the usual business considerations.
>
> Lets work the idea through for several of the Elecraft RF amplifiers:
>
> The 10-15W K3(s) amp: This amp can have significant IMD at low
> voltages as we have discovered with our QRP, all Elecraft, field
> day operation. The KX3 seems to do better, so reengineering the
> amp may be a better solution. For field day, we try to have
> fresh batteries available.
>
> The 100W K3(s) internal amp: This amp also has low voltage IMD
> as we found during our 100W California QSO party expeditions.
> But, consider the K3(s)'s construction. The front of the radio
> is the digital portion, including the DSPs and the front panel
> computer. All of this digital noise is isolated from the analog
> circuits in the back of the radio. If Elecraft were to include a
> boost power supply with the internal amp, that high-current
> switcher would be in the analog section, and probably impossible
> to quiet. Solution: Get an external boost power supply.
>
> The KXPA100 external amp: This form factor would be an ideal
> place to include a boost power supply. The use profile includes
> portable battery operation and designing isolation for the power
> supply into the package seems straight forward.
>
> The KPA500 external amp: The amp setup procedure sets the
> voltage to to 65v to 85v and the specifications call for about
> 1000 VA of power or about 13A at 75v. That would be nearly 75A
> at 13.5 volts assuming 100% efficiency, so it would be a good
> idea to put the boost power supply next to the battery and run
> 75v to the amp. It would make a nice high power mobil rig.
>
> 73 Bill AE6JV
>
> In thread "Re: [Elecraft] Chinese ebay amps for KX3", on 2/20/17
> at 5:47 AM, [hidden email] (Charlie T, K3ICH) wrote:
>
> >So now, tell me why a mid-sized radio can't have a built in 12 V to say,
> 50
> >V converter to drive some HV FETs for cleaner output specs like the Yuge
> >radios.
> -----------------------------------------------------------------------
> Bill Frantz |The nice thing about standards| Periwinkle
> (408)356-8506 |is there are so many to choose| 16345
> Englewood Ave
> www.pwpconsult.com |from. - Andrew Tanenbaum | Los Gatos,
> CA 95032
>
> ______________________________________________________________
> 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
> Message delivered to [hidden email]
>
>
>
> ______________________________________________________________
> Elecraft mailing list
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>
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> Message delivered to [hidden email]
>

Bill K9YEQ

Re: Boost power supplies for RF amps

In reply to this post by Bill Frantz

And there is little difference in signal strength, might actually be stronger as copy is better and less signal wasted by eliminating IMD, etc.

73,
Bill
K9YEQ

-----Original Message-----
From: Elecraft [mailto:[hidden email]] On Behalf Of Ron D'Eau Claire
Sent: Monday, February 20, 2017 5:56 PM
To: [hidden email]
Subject: Re: [Elecraft] Boost power supplies for RF amps

For the rigs running off of 12 (13.8) Vdc, how about simply not running the rig "all knobs full right"?

Reducing the power by 25% will improve IMD performance at lower voltages, yet that power difference is virtually impossible to detect on the H.F.
bands.

73, Ron AC7AC

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Bill Frantz

Re: Boost power supplies for RF amps

I'm trying to reconcile this advice with our experience running
QRP field day. We frequently have two or 3 K3s on a single band
(CW, SSB, Digital/GOTA). We use batteries and solar cells since
our site does not permit generators. When the radios are being
fed from a charged battery or a battery being charged from the
solar cells, we don't have a significant problem with
interference between stations. (Antenna placement helps a lot
too.) When the voltage drops, the complaints increase.

Of course, our 5 watts is quite a bit below the full power of
the low power RF amp in the K3.

73 Bill AE6JV

On 2/21/17 at 4:05 PM, [hidden email] (Bill Johnson) wrote:

>Reducing the power by 25% will improve IMD performance at lower
>voltages, yet that power difference is virtually impossible to
>detect on the H.F.
>bands.
-----------------------------------------------------------------------
Bill Frantz | Truth and love must prevail | Periwinkle
(408)356-8506 | over lies and hate. | 16345
Englewood Ave
www.pwpconsult.com | - Vaclav Havel | Los Gatos,
CA 95032

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Jack Brindle-2

Re: Boost power supplies for RF amps

Bill;

To be fair, we have had one instance of the problem, and that station was running the battery critically low. In fact the battery failed at that voltage (something like 10 volts) and had to be permanently removed from service. Perhaps the answer is to take the battery manufacturer’s advice and not to run the batteries below 11.5 volts. I believe the K3 has a low-voltage alarm that can be applied to the problem so that it gives a warning at the critical voltage and won’t continue until the power is corrected.

In general, we have found the K3 to be an excellent performer when running off battery at 12 to 13.8 volts, whether charging or not. Anyone wishing to hear us, just listed for K6EI in Field Day. And for those who wonder, having great antennas 500 or so feet above San Francisco Bay gives us great signals, even at 5 watts.

- Jack, W6FB

> On Feb 20, 2017, at 4:57 PM, Bill Frantz <[hidden email]> wrote:
>
> I'm trying to reconcile this advice with our experience running QRP field day. We frequently have two or 3 K3s on a single band (CW, SSB, Digital/GOTA). We use batteries and solar cells since our site does not permit generators. When the radios are being fed from a charged battery or a battery being charged from the solar cells, we don't have a significant problem with interference between stations. (Antenna placement helps a lot too.) When the voltage drops, the complaints increase.
>
> Of course, our 5 watts is quite a bit below the full power of the low power RF amp in the K3.
>
> 73 Bill AE6JV
>
> On 2/21/17 at 4:05 PM, [hidden email] (Bill Johnson) wrote:
>
>> Reducing the power by 25% will improve IMD performance at lower voltages, yet that power difference is virtually impossible to detect on the H.F.
>> bands.
> -----------------------------------------------------------------------
> Bill Frantz | Truth and love must prevail | Periwinkle
> (408)356-8506 | over lies and hate. | 16345 Englewood Ave
> www.pwpconsult.com | - Vaclav Havel | Los Gatos, CA 95032
>
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Phil Kane-2

Re: Boost power supplies for RF amps

In reply to this post by Bill Frantz

At my home station I run my transmitters on a "boosted" 14+ V bus using
a TG Electronics Boost Regulator - and "the knobs" at about "3 o'clock".
The station battery can go as low as 11.5 V but the 14V bus stays there.

On 2/20/2017 3:56 PM, Ron D'Eau Claire wrote:
> For the rigs running off of 12 (13.8) Vdc, how about simply not running the
> rig "all knobs full right"?
>
> Reducing the power by 25% will improve IMD performance at lower voltages,
> yet that power difference is virtually impossible to detect on the H.F.
> bands.

73 de K2ASP - Phil Kane
Elecraft K2/100 s/n 5402

From a Clearing in the Silicon Forest
Beaverton (Washington County) Oregon
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Phil Kane-2

Re: Boost power supplies for RF amps

In reply to this post by Matthew Cook

On 2/20/2017 3:11 PM, Matthew Cook wrote:

> I believe we will see a return of the 50V MOSFET PA's in commercial
> equipment again, especially with the explosion of LDMOS devices and the
> ever decreasing availability of 16-18V bi-polar RF transistors.

Modern commercial communication sites have all gone to 48V "Bell
Telephone Standard - positive ground" with corresponding radio
equipment. Inverters for 120V AC and 12/24V DC where needed. It's a
whole new world for us "old timers".

73 de K2ASP - Phil Kane
Elecraft K2/100 s/n 5402

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

VP - General Counsel & Engineering Manager
CSI Telecommunications, Inc. - Consulting Engineers
San Francisco, CA - Beaverton, OR
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Bill Frantz

Re: Boost power supplies for RF amps

In reply to this post by Jack Brindle-2

On 2/20/17 at 5:35 PM, [hidden email] (Jack Brindle) wrote:

>To be fair, we have had one instance of the problem, and that
>station was running the battery critically low. In fact the
>battery failed at that voltage (something like 10 volts) and
>had to be permanently removed from service. Perhaps the answer
>is to take the battery manufacturer’s advice and not to run
>the batteries below 11.5 volts. I believe the K3 has a
>low-voltage alarm that can be applied to the problem so that it
>gives a warning at the critical voltage and won’t continue
>until the power is corrected.

Thanks for reminding me of the details. The 100W CQP incidents
and the 5W FD ones get blurred in my mind.

Yes, the K3 has a low voltage warning. The level is controlled
by the "BAT MIN" CONFIG menu setting with a default of 11V. It
sends out a beep tone and flashes BAT LOW on the display. If you
use a boost regulator like the TG Electronics Boost Regulator,
note that these may introduce a junction voltage drop which will
cause the warning to sound at a higher voltage.

73 Bill AE6JV

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