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CP1 Power Handling

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Linden, Mike (BRC-Hes)

CP1 Power Handling

Does anyone know what modifications would need to be made to the CP1
Directional Coupler in order to get it to handle 200W at 20dB
attenuation?

I'd like to use the CP1 as a cost effective means of extending the
useful range of my OHR WM-2 QRP Wattmeter, but 30dB is more attenuation
than I want and the power handling at 20dB is not high enough.

Thanks, Michael N9BDF
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N8LP

Re: CP1 Power Handling

You have a couple options. The flux density is higher, and therefore
heating, with lower number of turns. They also go to a -43 mix (higher
permeability) for the lower turns to keep the shunt reactance of the
voltage xfmr high at 1.8 MHz.

If you don't care about 1.8 MHz, you might be able to get by with 10
turns on the -61 cores... I would have to do the math. The other option
is to stick with the -43 material, but get larger cores. I'm pretty sure
they make the FT50A and FT50B (which are thicker) in -43 material, or
you could go to a FT68 or FT82 if they'll fit. The best bet would
probably be FT50A-43, since we know it would fit physically. I have a
spreadsheet that I use that calculates these things for me... I can plug
these in to see what would work if you like.

73,
Larry N8LP

Linden, Mike (BRC-Hes) wrote:

> Does anyone know what modifications would need to be made to the CP1
> Directional Coupler in order to get it to handle 200W at 20dB
> attenuation?
>
> I'd like to use the CP1 as a cost effective means of extending the
> useful range of my OHR WM-2 QRP Wattmeter, but 30dB is more attenuation
> than I want and the power handling at 20dB is not high enough.
>
> Thanks, Michael N9BDF
> _______________________________________________
> 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
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> Elecraft web page: http://www.elecraft.com
>
>
>
>

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Linden, Mike (BRC-Hes)

RE: CP1 Power Handling

In reply to this post by Linden, Mike (BRC-Hes)

Larry,

If you have the time, I'd certainly appreciate it if you'd run it
through your spreadsheet for me.

Thanks! -Michael

========================================================================
======

You have a couple options. The flux density is higher, and therefore
heating, with lower number of turns. They also go to a -43 mix (higher
permeability) for the lower turns to keep the shunt reactance of the
voltage xfmr high at 1.8 MHz.

If you don't care about 1.8 MHz, you might be able to get by with 10
turns on the -61 cores... I would have to do the math. The other option
is to stick with the -43 material, but get larger cores. I'm pretty sure
they make the FT50A and FT50B (which are thicker) in -43 material, or
you could go to a FT68 or FT82 if they'll fit. The best bet would
probably be FT50A-43, since we know it would fit physically. I have a
spreadsheet that I use that calculates these things for me... I can plug
these in to see what would work if you like.

73,
Larry N8LP

Linden, Mike (BRC-Hes) wrote:
> Does anyone know what modifications would need to be made to the CP1

> Directional Coupler in order to get it to handle 200W at 20dB
> attenuation?
>
> I'd like to use the CP1 as a cost effective means of extending the
> useful range of my OHR WM-2 QRP Wattmeter, but 30dB is more
> attenuation than I want and the power handling at 20dB is not high
enough.
>
> Thanks, Michael N9BDF

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N8LP

Re: CP1 Power Handling

A quick check shows that no small size cores will work for -43 material
with 10T at 1.8 MHz and 200W. However, FT50B cores come close, and are
fine at 3.5 MHz. FT50B is twice the thickness of the FT50A, and would
fit on the board because the thickness would only add height.

73,
Larry N8LP

Linden, Mike (BRC-Hes) wrote:

> Larry,
>
> If you have the time, I'd certainly appreciate it if you'd run it
> through your spreadsheet for me.
>
> Thanks! -Michael
>
> ========================================================================
> ======
>
> You have a couple options. The flux density is higher, and therefore
> heating, with lower number of turns. They also go to a -43 mix (higher
> permeability) for the lower turns to keep the shunt reactance of the
> voltage xfmr high at 1.8 MHz.
>
> If you don't care about 1.8 MHz, you might be able to get by with 10
> turns on the -61 cores... I would have to do the math. The other option
> is to stick with the -43 material, but get larger cores. I'm pretty sure
> they make the FT50A and FT50B (which are thicker) in -43 material, or
> you could go to a FT68 or FT82 if they'll fit. The best bet would
> probably be FT50A-43, since we know it would fit physically. I have a
> spreadsheet that I use that calculates these things for me... I can plug
> these in to see what would work if you like.
>
> 73,
> Larry N8LP
>
>
> Linden, Mike (BRC-Hes) wrote:
>
>> Does anyone know what modifications would need to be made to the CP1
>>
>
>
>> Directional Coupler in order to get it to handle 200W at 20dB
>> attenuation?
>>
>> I'd like to use the CP1 as a cost effective means of extending the
>> useful range of my OHR WM-2 QRP Wattmeter, but 30dB is more
>> attenuation than I want and the power handling at 20dB is not high
>>
> enough.
>
>> Thanks, Michael N9BDF
>>
>
>
>
>
>

Linden, Mike (BRC-Hes)

RE: CP1 Power Handling

In reply to this post by Linden, Mike (BRC-Hes)

Larry,

Thanks! 200W is probably a bit on the high side for my needs (safety
margin), so this looks pretty good.

-Michael

-----Original Message-----
From: Larry Phipps [mailto:[hidden email]]
Sent: Tuesday, March 07, 2006 10:29 AM
To: Linden, Mike (BRC-Hes)
Cc: [hidden email]
Subject: Re: [Elecraft] CP1 Power Handling

A quick check shows that no small size cores will work for -43 material
with 10T at 1.8 MHz and 200W. However, FT50B cores come close, and are
fine at 3.5 MHz. FT50B is twice the thickness of the FT50A, and would
fit on the board because the thickness would only add height.

73,
Larry N8LP

Linden, Mike (BRC-Hes) wrote:
> Larry,
>
> If you have the time, I'd certainly appreciate it if you'd run it
> through your spreadsheet for me.
>
> Thanks! -Michael
>

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Robert Friess

Re: CP1 Power Handling

In reply to this post by Linden, Mike (BRC-Hes)

Hi Michael,

I designed the CP1 for Elecraft and in the process I performed many tests to
evaluate the power handling capabilities. The power is limited by heating
of the core and that is primarily a function of flux density and time. The
published specification allows the rated power to be applied for long
periods of time without excessive heating.

The flux density is proportional to the applied voltage, i.e. square root of
power, and inversely proportional to the number of turns, cross sectional
area, and frequency. For a 20 dB coupler the number of turns is fixed at
10. Because of the small turns count type 43 material was chosen to provide
sufficient inductance to maintain performance at the lowest frequency.
Unfortunately, type 43 has a relatively low Curie Temperature, that is, the
temperature at which the magnetic properties of the core disappear. Other
core materials have much higher temperature ratings and lower loss, but they
do not provide sufficient inductance for good performance on 160 meters.

So what does all this mean? I suggest that the easiest thing for you to do
would be to stack three cores together at each position. It will be easier
to wind the cores if you use some sort of adhesive to hold the cores
together. This will provide about 9 times the power handling capability and
meet your power requirement. If you don't hold the key down for 5 minutes
even better. You can order the extra cores from Elecraft.

73,
Bob, N6CM

----- Original Message -----
From: "Linden, Mike (BRC-Hes)" <[hidden email]>
To: <[hidden email]>
Sent: Tuesday, March 07, 2006 6:33 AM
Subject: [Elecraft] CP1 Power Handling

Does anyone know what modifications would need to be made to the CP1
Directional Coupler in order to get it to handle 200W at 20dB
attenuation?

I'd like to use the CP1 as a cost effective means of extending the
useful range of my OHR WM-2 QRP Wattmeter, but 30dB is more attenuation
than I want and the power handling at 20dB is not high enough.

Thanks, Michael N9BDF
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N8LP

Re: CP1 Power Handling

In reply to this post by Linden, Mike (BRC-Hes)

It might also make sense to increase the turns to 14, which would give a
coupling factor of 23 dB, and much more safety margin.

Larry N8LP

Linden, Mike (BRC-Hes) wrote:

> Larry,
>
> Thanks! 200W is probably a bit on the high side for my needs (safety
> margin), so this looks pretty good.
>
> -Michael
>
>
> -----Original Message-----
> From: Larry Phipps [mailto:[hidden email]]
> Sent: Tuesday, March 07, 2006 10:29 AM
> To: Linden, Mike (BRC-Hes)
> Cc: [hidden email]
> Subject: Re: [Elecraft] CP1 Power Handling
>
> A quick check shows that no small size cores will work for -43 material
> with 10T at 1.8 MHz and 200W. However, FT50B cores come close, and are
> fine at 3.5 MHz. FT50B is twice the thickness of the FT50A, and would
> fit on the board because the thickness would only add height.
>
> 73,
> Larry N8LP
>
>
> Linden, Mike (BRC-Hes) wrote:
>
>> Larry,
>>
>> If you have the time, I'd certainly appreciate it if you'd run it
>> through your spreadsheet for me.
>>
>> Thanks! -Michael
>>
>>
>
>
>
>
>

Alan Biocca

Re: CP1 Power Handling

In reply to this post by Linden, Mike (BRC-Hes)

Stacking cores can also help increase power handling capability without taking more pcb space (providing the core is flat on the pcb).

-- Alan wb6zqz

-------------- Original message --------------
From: Larry Phipps <[hidden email]>

> A quick check shows that no small size cores will work for -43 material
> with 10T at 1.8 MHz and 200W. However, FT50B cores come close, and are
> fine at 3.5 MHz. FT50B is twice the thickness of the FT50A, and would
> fit on the board because the thickness would only add height.
>
> 73,
> Larry N8LP
>
>
>
> Linden, Mike (BRC-Hes) wrote:
> > Larry,
> >
> > If you have the time, I'd certainly appreciate it if you'd run it
> > through your spreadsheet for me.
> >
> > Thanks! -Michael
> >
> > ========================================================================
> > ======
> >
> > You have a couple options. The flux density is higher, and therefore
> > heating, with lower number of turns. They also go to a -43 mix (higher
> > permeability) for the lower turns to keep the shunt reactance of the
> > voltage xfmr high at 1.8 MHz.
> >
> > If you don't care about 1.8 MHz, you might be able to get by with 10
> > turns on the -61 cores... I would have to do the math. The other option
> > is to stick with the -43 material, but get larger cores. I'm pretty sure
> > they make the FT50A and FT50B (which are thicker) in -43 material, or
> > you could go to a FT68 or FT82 if they'll fit. The best bet would
> > probably be FT50A-43, since we know it would fit physically. I have a
> > spreadsheet that I use that calculates these things for me... I can plug
> > these in to see what would work if you like.
> >
> > 73,
> > Larry N8LP
> >
> >
> > Linden, Mike (BRC-Hes) wrote:
> >
> >> Does anyone know what modifications would need to be made to the CP1
> >>
> >
> >
> >> Directional Coupler in order to get it to handle 200W at 20dB
> >> attenuation?
> >>
> >> I'd like to use the CP1 as a cost effective means of extending the
> >> useful range of my OHR WM-2 QRP Wattmeter, but 30dB is more
> >> attenuation than I want and the power handling at 20dB is not high
> >>
> > enough.
> >
> >> Thanks, Michael N9BDF

N8LP

Re: CP1 Power Handling

In reply to this post by Robert Friess

Bob, have you seen any difference between stacked cores and solid ones
of the same total thickness? In designed my wattmeters, I found more
heating with stacked cores... at least for one combination. The FT50B
core is the same thickness as 2.66 stacked FT50 cores, or 2 FT50A cores.

Larry N8LP

Robert Friess wrote:

> Hi Michael,
>
> I designed the CP1 for Elecraft and in the process I performed many
> tests to evaluate the power handling capabilities. The power is
> limited by heating of the core and that is primarily a function of
> flux density and time. The published specification allows the rated
> power to be applied for long periods of time without excessive heating.
>
> The flux density is proportional to the applied voltage, i.e. square
> root of power, and inversely proportional to the number of turns,
> cross sectional area, and frequency. For a 20 dB coupler the number
> of turns is fixed at 10. Because of the small turns count type 43
> material was chosen to provide sufficient inductance to maintain
> performance at the lowest frequency. Unfortunately, type 43 has a
> relatively low Curie Temperature, that is, the temperature at which
> the magnetic properties of the core disappear. Other core materials
> have much higher temperature ratings and lower loss, but they do not
> provide sufficient inductance for good performance on 160 meters.
>
> So what does all this mean? I suggest that the easiest thing for you
> to do would be to stack three cores together at each position. It
> will be easier to wind the cores if you use some sort of adhesive to
> hold the cores together. This will provide about 9 times the power
> handling capability and meet your power requirement. If you don't
> hold the key down for 5 minutes even better. You can order the extra
> cores from Elecraft.
>
> 73,
> Bob, N6CM
>
> ----- Original Message ----- From: "Linden, Mike (BRC-Hes)"
> <[hidden email]>
> To: <[hidden email]>
> Sent: Tuesday, March 07, 2006 6:33 AM
> Subject: [Elecraft] CP1 Power Handling
>
>
> Does anyone know what modifications would need to be made to the CP1
> Directional Coupler in order to get it to handle 200W at 20dB
> attenuation?
>
> I'd like to use the CP1 as a cost effective means of extending the
> useful range of my OHR WM-2 QRP Wattmeter, but 30dB is more attenuation
> than I want and the power handling at 20dB is not high enough.
>
> Thanks, Michael N9BDF
> _______________________________________________
> 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
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
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> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com
>
>
>

Jim Byers-3

Re: CP1 Power Handling

In reply to this post by Robert Friess

Bob

What combination of core/turns would give up to 40dB and able to
handle 100 watts and what frequency range would it have? Main
interest is HF

73
Jim VE3TTN

On Mar 7, 2006, at 11:46, Robert Friess wrote:

> Hi Michael,
>
> I designed the CP1 for Elecraft and in the process I performed many
> tests to evaluate the power handling capabilities. The power is
> limited by heating of the core and that is primarily a function of
> flux density and time. The published specification allows the
> rated power to be applied for long periods of time without
> excessive heating.

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Linden, Mike (BRC-Hes)

RE: CP1 Power Handling

In reply to this post by Linden, Mike (BRC-Hes)

Robert,

Thanks for the insight and alternate solution! -Michael

-----Original Message-----
From: Robert Friess [mailto:[hidden email]]
Sent: Tuesday, March 07, 2006 10:46 AM
To: Linden, Mike (BRC-Hes); [hidden email]
Subject: Re: [Elecraft] CP1 Power Handling

Hi Michael,

I designed the CP1 for Elecraft and in the process I performed many
tests to evaluate the power handling capabilities. The power is limited
by heating of the core and that is primarily a function of flux density
and time. The published specification allows the rated power to be
applied for long periods of time without excessive heating.

The flux density is proportional to the applied voltage, i.e. square
root of power, and inversely proportional to the number of turns, cross
sectional area, and frequency. For a 20 dB coupler the number of turns
is fixed at 10. Because of the small turns count type 43 material was
chosen to provide sufficient inductance to maintain performance at the
lowest frequency.
Unfortunately, type 43 has a relatively low Curie Temperature, that is,
the temperature at which the magnetic properties of the core disappear.
Other core materials have much higher temperature ratings and lower
loss, but they do not provide sufficient inductance for good performance
on 160 meters.

So what does all this mean? I suggest that the easiest thing for you to
do would be to stack three cores together at each position. It will be
easier to wind the cores if you use some sort of adhesive to hold the
cores together. This will provide about 9 times the power handling
capability and meet your power requirement. If you don't hold the key
down for 5 minutes even better. You can order the extra cores from
Elecraft.
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N8LP

Re: CP1 Power Handling

In reply to this post by Jim Byers-3

That would not be very practical, because it would be 100 turns. I
suggest using the existing 30dB design, and add external inline BNC
attenuators like the Mini-Circuits HAT-10. That would give you 40 dB total.

Larry N8LP

Jim Byers wrote:

> Bob
>
> What combination of core/turns would give up to 40dB and able to
> handle 100 watts and what frequency range would it have? Main interest
> is HF
>
> 73
> Jim VE3TTN
>
>
>
> On Mar 7, 2006, at 11:46, Robert Friess wrote:
>
>> Hi Michael,
>>
>> I designed the CP1 for Elecraft and in the process I performed many
>> tests to evaluate the power handling capabilities. The power is
>> limited by heating of the core and that is primarily a function of
>> flux density and time. The published specification allows the rated
>> power to be applied for long periods of time without excessive heating.
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
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> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com
>
>
>

Spence Wilhelm

KX1 with 3080 board

In reply to this post by Jim Byers-3

All,

FYI, I just finished upgrading my KX1 to a four band radio! It is now
capable of 20m, 30m, 40m, and 80m. Assembly of the new module for 30 and 80
meters was straightforward and well worth the effort. Ron produced an
excellent instruction manual that greatly simplfied the process. Many
thanks to Wayne and Eric for allowing me to be one of the field testers for
the new module.

I'll be in Folsom CA on a business trip this week and will be on the air in
the evenings near the QRP frequencies on 80m and 40m. Give me a shout!

73,

Spence W7CSW

FYI, I'm not affiliated with Elecraft other than owning a KX1 and a K2 and I
LOVE THEIR PRODUCTS! I recommend the upgrade to anybody wanting more than
three bands on the KX1.

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Don Brown-4

Re: CP1 Power Handling

In reply to this post by Linden, Mike (BRC-Hes)

Hi

I have both the 20 db and 30 db versions of the CP1. Even though the 20 db
is not rated that high I have used it at 100 watts with no problems for
short times. I use them with the OHR WM-2 wattmeter. To get it to go to 200
watts you would at least need to increase the wattage of the terminating
resistors on the CP1 and probably need to increase the core size on the
toroids. Of course I have not done this so I am just guessing.

Don Brown
KD5NDB

----- Original Message -----
From: "Linden, Mike (BRC-Hes)" <[hidden email]>
To: <[hidden email]>
Sent: Tuesday, March 07, 2006 8:33 AM
Subject: [Elecraft] CP1 Power Handling

Does anyone know what modifications would need to be made to the CP1
Directional Coupler in order to get it to handle 200W at 20dB
attenuation?

I'd like to use the CP1 as a cost effective means of extending the
useful range of my OHR WM-2 QRP Wattmeter, but 30dB is more attenuation
than I want and the power handling at 20dB is not high enough.

Thanks, Michael N9BDF
_______________________________________________
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