Re: K3 power supply recommendation

[Edward R Cole]

Wes,

As that may be (it depends on ambient air temp), most hams are not
transmitting key-down for extended time.  In the communication
industry the duty-cycle for Tx to Rx time is assumed to be 10%.  Most
FM equipment is equipped with time out timers that stop continuous
transmission after 3-minutes.  Since I will assume you are not
talking about FM or AM or digital modes like WSJT, the class of
service is ICAS and not CCS.  The Astron 35 will handle 25amps quite
nicely.  25a x 13.8v = 345w.  This is probably way above the typical
100w RF CW/SSB radio dc load.  If the amplifier runs at 60%
efficiency it will draw 167w (about 12amps).  Add the load of the
radio this probably is not more than 17amps.  You can probably add a
VHF radio sitting in Rx and still not exceed 25amps (and that is only
drawn in transmit 10% of the time of use).

If you run any of the modes that are CCS then adding some air cooling
is not a bad idea.  I have fans on my high power VHF and UHF amps to
just have a bit more tolerance to heat.  I do use them for FM
somewhat, and also are used as drivers for WSJT-eme for the 8877
final.  Duty-cycle of WSJT (JT65) is 50% (one minute cycles of
key-down followed by one-minute receive).  This is hard-duty on ham
equipment so lower the RF power if you run these.  I run 55-60w on my
150w amp to drive the 8877 to 1300-1400w.

My station Astron 50M is fused at the distribution panel for 30A so
never exceeds this in any mode.  I have a lot of equipment running at
the same time.

73, Ed - KL7UW

From: "Eugene Balinski" <[hidden email]>
To: Wes Stewart <[hidden email]>,[hidden email],
        [hidden email]
Subject: Re: [Elecraft] K3 power supply recommendations
Message-ID: <[hidden email]>
Content-Type: text/plain; charset="ISO-8859-1"

Another vote for the RM-35. I have had mine for over 30
years.  Not an issue.

Note however that Astron over specs their power supplies.
  They claim that the RS-35 will do 25A continuous.  It will
not.  It gets too darn hot.  Given the heatsink, it should
do about 20 continuous.   This is with static air cooling,
no forced air.

______________________________________________________________
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

[george fritkin]

My shack consists of 20 transceivers.  I think [!!] only 4 run directly on AC power.  The rest run from 12 VDC.  My power supplies range from 35A Astrons to "El Cheapo" switchers.  In the past 8 years the only power supply failure I  had was an Astron. Do not over buy
 
George, W6GF
 

________________________________
 From: Edward R Cole <[hidden email]>
To: [hidden email]
Sent: Wednesday, April 17, 2013 10:19 AM
Subject: Re: [Elecraft] K3 power supply recommendation
 

Wes,

As that may be (it depends on ambient air temp), most hams are not transmitting key-down for extended time.  In the communication industry the duty-cycle for Tx to Rx time is assumed to be 10%.  Most FM equipment is equipped with time out timers that stop continuous transmission after 3-minutes.  Since I will assume you are not talking about FM or AM or digital modes like WSJT, the class of service is ICAS and not CCS.  The Astron 35 will handle 25amps quite nicely.  25a x 13.8v = 345w.  This is probably way above the typical 100w RF CW/SSB radio dc load.  If the amplifier runs at 60% efficiency it will draw 167w (about 12amps).  Add the load of the radio this probably is not more than 17amps.  You can probably add a VHF radio sitting in Rx and still not exceed 25amps (and that is only drawn in transmit 10% of the time of use).

If you run any of the modes that are CCS then adding some air cooling is not a bad idea.  I have fans on my high power VHF and UHF amps to just have a bit more tolerance to heat.  I do use them for FM somewhat, and also are used as drivers for WSJT-eme for the 8877 final.  Duty-cycle of WSJT (JT65) is 50% (one minute cycles of key-down followed by one-minute receive).  This is hard-duty on ham equipment so lower the RF power if you run these.  I run 55-60w on my 150w amp to drive the 8877 to 1300-1400w.

My station Astron 50M is fused at the distribution panel for 30A so never exceeds this in any mode.  I have a lot of equipment running at the same time.

73, Ed - KL7UW

From: "Eugene Balinski" <[hidden email]>
To: Wes Stewart <[hidden email]>,[hidden email],
    [hidden email]
Subject: Re: [Elecraft] K3 power supply recommendations
Message-ID: <[hidden email]>
Content-Type: text/plain; charset="ISO-8859-1"

Another vote for the RM-35. I have had mine for over 30
years.  Not an issue.

Note however that Astron over specs their power supplies.
They claim that the RS-35 will do 25A continuous.  It will
not.  It gets too darn hot.  Given the heatsink, it should
do about 20 continuous.   This is with static air cooling,
no forced air.

______________________________________________________________
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
______________________________________________________________
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

[w0mu]

For a small compact supply the PowerWerx supplies from West Mountain
Radio are great.  They have a cooling fan and will work on 220 or 110.

For my shack supplies I have Astron RM35 and I think a RM50.

On 4/17/2013 11:19 AM, Edward R Cole wrote:

> Wes,
>
> As that may be (it depends on ambient air temp), most hams are not
> transmitting key-down for extended time.  In the communication
> industry the duty-cycle for Tx to Rx time is assumed to be 10%. Most
> FM equipment is equipped with time out timers that stop continuous
> transmission after 3-minutes.  Since I will assume you are not talking
> about FM or AM or digital modes like WSJT, the class of service is
> ICAS and not CCS.  The Astron 35 will handle 25amps quite nicely.  25a
> x 13.8v = 345w.  This is probably way above the typical 100w RF CW/SSB
> radio dc load.  If the amplifier runs at 60% efficiency it will draw
> 167w (about 12amps).  Add the load of the radio this probably is not
> more than 17amps.  You can probably add a VHF radio sitting in Rx and
> still not exceed 25amps (and that is only drawn in transmit 10% of the
> time of use).
>
> If you run any of the modes that are CCS then adding some air cooling
> is not a bad idea.  I have fans on my high power VHF and UHF amps to
> just have a bit more tolerance to heat.  I do use them for FM
> somewhat, and also are used as drivers for WSJT-eme for the 8877
> final.  Duty-cycle of WSJT (JT65) is 50% (one minute cycles of
> key-down followed by one-minute receive).  This is hard-duty on ham
> equipment so lower the RF power if you run these.  I run 55-60w on my
> 150w amp to drive the 8877 to 1300-1400w.
>
> My station Astron 50M is fused at the distribution panel for 30A so
> never exceeds this in any mode.  I have a lot of equipment running at
> the same time.
>
> 73, Ed - KL7UW
>
> From: "Eugene Balinski" <[hidden email]>
> To: Wes Stewart <[hidden email]>,[hidden email],
>     [hidden email]
> Subject: Re: [Elecraft] K3 power supply recommendations
> Message-ID: <[hidden email]>
> Content-Type: text/plain; charset="ISO-8859-1"
>
> Another vote for the RM-35. I have had mine for over 30
> years.  Not an issue.
>
> Note however that Astron over specs their power supplies.
>  They claim that the RS-35 will do 25A continuous.  It will
> not.  It gets too darn hot.  Given the heatsink, it should
> do about 20 continuous.   This is with static air cooling,
> no forced air.
>
> ______________________________________________________________
> 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

______________________________________________________________
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