Re: [Elecraft] Boost power supplies for RF amps

[Bill Frantz]

On 2/20/17 at 5:35 PM, jackbrin...@me.com (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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(408)356-8506  | internet. I have DSL.| 16345 
Englewood Ave
www.pwpconsult.com |  | Los Gatos, 
CA 95032


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Re: [Elecraft] Boost power supplies for RF amps

[Phil Kane]

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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Re: [Elecraft] Boost power supplies for RF amps

[Phil Kane]

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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Re: [Elecraft] Boost power supplies for RF amps

[Jack Brindle]

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  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, k9...@live.com (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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Re: [Elecraft] Boost power supplies for RF amps

[Bill Frantz]

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, k9...@live.com (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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Re: [Elecraft] Boost power supplies for RF amps

[Bill Johnson]

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:elecraft-boun...@mailman.qth.net] On Behalf Of Ron D'Eau 
Claire
Sent: Monday, February 20, 2017 5:56 PM
To: elecraft@mailman.qth.net
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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Re: [Elecraft] Boost power supplies for RF amps

[Ron D'Eau Claire]

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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Re: [Elecraft] Boost power supplies for RF amps

[Matthew Cook]

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 <
elecraft@mailman.qth.net> 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 <fra...@pwpconsult.com>
>  To: elecraft@mailman.qth.net
>  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, pin...@erols.com (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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Re: [Elecraft] Boost power supplies for RF amps

[David Orman]

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  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, pin...@erols.com (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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Re: [Elecraft] Boost power supplies for RF amps

[Mel Farrer via Elecraft]

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 <fra...@pwpconsult.com>
 To: elecraft@mailman.qth.net 
 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, pin...@erols.com (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] Boost power supplies for RF amps

[Bill Frantz]

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, pin...@erols.com (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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