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K3 + LP100A + Dummy Load

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Phil Hystad-3

K3 + LP100A + Dummy Load

Is this normal or can someone explain? I was looking at the R+iX values reported by the LP100A with my K3 feeding a dummy load. The SWR reported was always small but never super close to 1:1. Most of the SWR in this setup was 1.1:1 up to 1.5:1. The R values ranged from 34 ohms to up to 59 ohms and X was ranging over a number of smallish values < 20 for all the bands.

Is this what most of you would call normal?

Does the K3 output R+iX vary from band to band (I assume so) and is that what I am seeing?

I had thought my dummy load was mostly frequency independent so I am not sure if I am seeing mostly the K3 here or maybe the K3 plus the 6 feet of coax (RG8X) + dummy load.

73, phil, K7PEH

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N5GE

Re: K3 + LP100A + Dummy Load

Phil,

You don't say what type of dummy load you are using, but all of the cantenna
type have about the same SWR curve you witnessed. You will need a precision DL
to get a flat response across a large range. I have two DECIBEL DB4304B 100
watt loads here that are flat up through 2m. I don't think they are made any
more and if they were they would be very expensive. The two I have were bought
at a ham hamfest for $50 each. They are bout 6" x 4" x 4" Most of which is
cooling fins.

Be careful when you buy dummy loads like this at a Hamfest. Take a good
ohm-meter with you. I bought a couple of really well made heavy duty DL's that
were rated at 300w for $100 once and when I measured them at home they were 75
ohm loads, so watch out!

Happy holidays,

73,
Tom
Amateur Radio Operator N5GE
ARRL Lifetime Member
QCWA Lifetime Member

"If somebody has a bad heart, they can plug this jack in at
night as they go to bed and it will monitor their heart
throughout the night. And the next morning, when they wake up
dead, there'll be a record."

--Mark S. Fowler, FCC Chairman,
1981 - 1987

On Thu, 22 Dec 2011 08:37:37 -0800, Phil Hystad <[hidden email]> wrote:

>Is this normal or can someone explain? I was looking at the R+iX values reported by the LP100A with my K3 feeding a dummy load. The SWR reported was always small but never super close to 1:1. Most of the SWR in this setup was 1.1:1 up to 1.5:1. The R values ranged from 34 ohms to up to 59 ohms and X was ranging over a number of smallish values < 20 for all the bands.
>
>Is this what most of you would call normal?
>
>Does the K3 output R+iX vary from band to band (I assume so) and is that what I am seeing?
>
>I had thought my dummy load was mostly frequency independent so I am not sure if I am seeing mostly the K3 here or maybe the K3 plus the 6 feet of coax (RG8X) + dummy load.
>
>73, phil, K7PEH
>

Amateur Radio Operator N5GE

Phil Hystad-3

Re: K3 + LP100A + Dummy Load

The dummy load is the Palstar DL2K, full legal limit handling and I bought it new from Palstar several years ago. None of my operating equipment was purchased at hamfests -- I prefer to be the original owner and pass over any potential difficulties.

peh

On Dec 22, 2011, at 12:20 PM, [hidden email] wrote:

>
> Phil,
>
> You don't say what type of dummy load you are using, but all of the cantenna
> type have about the same SWR curve you witnessed. You will need a precision DL
> to get a flat response across a large range. I have two DECIBEL DB4304B 100
> watt loads here that are flat up through 2m. I don't think they are made any
> more and if they were they would be very expensive. The two I have were bought
> at a ham hamfest for $50 each. They are bout 6" x 4" x 4" Most of which is
> cooling fins.
>
> Be careful when you buy dummy loads like this at a Hamfest. Take a good
> ohm-meter with you. I bought a couple of really well made heavy duty DL's that
> were rated at 300w for $100 once and when I measured them at home they were 75
> ohm loads, so watch out!
>
> Happy holidays,
>
> 73,
> Tom
> Amateur Radio Operator N5GE
> ARRL Lifetime Member
> QCWA Lifetime Member
>
> "If somebody has a bad heart, they can plug this jack in at
> night as they go to bed and it will monitor their heart
> throughout the night. And the next morning, when they wake up
> dead, there'll be a record."
>
> --Mark S. Fowler, FCC Chairman,
> 1981 - 1987
>
>
> On Thu, 22 Dec 2011 08:37:37 -0800, Phil Hystad <[hidden email]> wrote:
>
>> Is this normal or can someone explain? I was looking at the R+iX values reported by the LP100A with my K3 feeding a dummy load. The SWR reported was always small but never super close to 1:1. Most of the SWR in this setup was 1.1:1 up to 1.5:1. The R values ranged from 34 ohms to up to 59 ohms and X was ranging over a number of smallish values < 20 for all the bands.
>>
>> Is this what most of you would call normal?
>>
>> Does the K3 output R+iX vary from band to band (I assume so) and is that what I am seeing?
>>
>> I had thought my dummy load was mostly frequency independent so I am not sure if I am seeing mostly the K3 here or maybe the K3 plus the 6 feet of coax (RG8X) + dummy load.
>>
>> 73, phil, K7PEH
>>
>
>
> ______________________________________________________________
> 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

Chester Alderman

Re: K3 + LP100A + Dummy Load

BUT just because you bought it direct from Palstar does not mean it is a
good dummy load! The ONLY way you KNOW it is a good dummy load is for YOU to
measure it with known good test equipment and an ohm-meter is not how it is
done!

73 and Merry Christmas,

Tom - W4BQF

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Phil Hystad
Sent: Thursday, December 22, 2011 3:40 PM
To: [hidden email]
Cc: Elecraft List
Subject: Re: [Elecraft] K3 + LP100A + Dummy Load

The dummy load is the Palstar DL2K, full legal limit handling and I bought
it new from Palstar several years ago. None of my operating equipment was
purchased at hamfests -- I prefer to be the original owner and pass over any
potential difficulties.

peh

On Dec 22, 2011, at 12:20 PM, [hidden email] wrote:

>
> Phil,
>
> You don't say what type of dummy load you are using, but all of the
cantenna
> type have about the same SWR curve you witnessed. You will need a
precision DL
> to get a flat response across a large range. I have two DECIBEL DB4304B
100
> watt loads here that are flat up through 2m. I don't think they are made
any
> more and if they were they would be very expensive. The two I have were
bought
> at a ham hamfest for $50 each. They are bout 6" x 4" x 4" Most of which
is
> cooling fins.
>
> Be careful when you buy dummy loads like this at a Hamfest. Take a good
> ohm-meter with you. I bought a couple of really well made heavy duty DL's
that
> were rated at 300w for $100 once and when I measured them at home they
were 75

> ohm loads, so watch out!
>
> Happy holidays,
>
> 73,
> Tom
> Amateur Radio Operator N5GE
> ARRL Lifetime Member
> QCWA Lifetime Member
>
> "If somebody has a bad heart, they can plug this jack in at
> night as they go to bed and it will monitor their heart
> throughout the night. And the next morning, when they wake up
> dead, there'll be a record."
>
> --Mark S. Fowler, FCC Chairman,
> 1981 - 1987
>
>
> On Thu, 22 Dec 2011 08:37:37 -0800, Phil Hystad <[hidden email]> wrote:
>
>> Is this normal or can someone explain? I was looking at the R+iX values

reported by the LP100A with my K3 feeding a dummy load. The SWR reported
was always small but never super close to 1:1. Most of the SWR in this
setup was 1.1:1 up to 1.5:1. The R values ranged from 34 ohms to up to 59
ohms and X was ranging over a number of smallish values < 20 for all the
bands.
>>
>> Is this what most of you would call normal?
>>
>> Does the K3 output R+iX vary from band to band (I assume so) and is that
what I am seeing?
>>
>> I had thought my dummy load was mostly frequency independent so I am not
sure if I am seeing mostly the K3 here or maybe the K3 plus the 6 feet of
coax (RG8X) + dummy load.

>>
>> 73, phil, K7PEH
>>
>
>
> ______________________________________________________________
> 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

______________________________________________________________
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
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Iain MacDonnell - N6ML-2

Re: K3 + LP100A + Dummy Load

FWIW, the manual for the DL2K specs 56ohms +/- 10%. It's not intended
to be a "calibrated" 50ohm load.

~iain / N6ML

On Thu, Dec 22, 2011 at 12:59 PM, Tommy Alderman
<[hidden email]> wrote:

> BUT just because you bought it direct from Palstar does not mean it is a
> good dummy load! The ONLY way you KNOW it is a good dummy load is for YOU to
> measure it with known good test equipment and an ohm-meter is not how it is
> done!
>
> 73 and Merry Christmas,
>
> Tom - W4BQF
>
>
> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Phil Hystad
> Sent: Thursday, December 22, 2011 3:40 PM
> To: [hidden email]
> Cc: Elecraft List
> Subject: Re: [Elecraft] K3 + LP100A + Dummy Load
>
> The dummy load is the Palstar DL2K, full legal limit handling and I bought
> it new from Palstar several years ago. None of my operating equipment was
> purchased at hamfests -- I prefer to be the original owner and pass over any
> potential difficulties.
>
> peh
>
>
> On Dec 22, 2011, at 12:20 PM, [hidden email] wrote:
>
>>
>> Phil,
>>
>> You don't say what type of dummy load you are using, but all of the
> cantenna
>> type have about the same SWR curve you witnessed. You will need a
> precision DL
>> to get a flat response across a large range. I have two DECIBEL DB4304B
> 100
>> watt loads here that are flat up through 2m. I don't think they are made
> any
>> more and if they were they would be very expensive. The two I have were
> bought
>> at a ham hamfest for $50 each. They are bout 6" x 4" x 4" Most of which
> is
>> cooling fins.
>>
>> Be careful when you buy dummy loads like this at a Hamfest. Take a good
>> ohm-meter with you. I bought a couple of really well made heavy duty DL's
> that
>> were rated at 300w for $100 once and when I measured them at home they
> were 75
>> ohm loads, so watch out!
>>
>> Happy holidays,
>>
>> 73,
>> Tom
>> Amateur Radio Operator N5GE
>> ARRL Lifetime Member
>> QCWA Lifetime Member
>>
>> "If somebody has a bad heart, they can plug this jack in at
>> night as they go to bed and it will monitor their heart
>> throughout the night. And the next morning, when they wake up
>> dead, there'll be a record."
>>
>> --Mark S. Fowler, FCC Chairman,
>> 1981 - 1987
>>
>>
>> On Thu, 22 Dec 2011 08:37:37 -0800, Phil Hystad <[hidden email]> wrote:
>>
>>> Is this normal or can someone explain? I was looking at the R+iX values
> reported by the LP100A with my K3 feeding a dummy load. The SWR reported
> was always small but never super close to 1:1. Most of the SWR in this
> setup was 1.1:1 up to 1.5:1. The R values ranged from 34 ohms to up to 59
> ohms and X was ranging over a number of smallish values < 20 for all the
> bands.
>>>
>>> Is this what most of you would call normal?
>>>
>>> Does the K3 output R+iX vary from band to band (I assume so) and is that
> what I am seeing?
>>>
>>> I had thought my dummy load was mostly frequency independent so I am not
> sure if I am seeing mostly the K3 here or maybe the K3 plus the 6 feet of
> coax (RG8X) + dummy load.
>>>
>>> 73, phil, K7PEH
>>>
>>
>>
>> ______________________________________________________________
>> 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
>
> ______________________________________________________________
> 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

Phil Hystad-3

Re: K3 + LP100A + Dummy Load

In reply to this post by Chester Alderman

Tom,

I agree. Actually, right now I do not trust my dummy load for being close to pure resistive 50 ohms. Indeed, I did not test it at the beginning and this is what motivated me to post the question. I think I have enough to test the DL but won't have time to do it for a week or so.

peh

On Dec 22, 2011, at 12:59 PM, Tommy Alderman wrote:

N5GE

Re: K3 + LP100A + Dummy Load

In reply to this post by Chester Alderman

Naturally you can't test the flatness over a range without test equipment, but
you CAN tell it's a 50 ohm load instead of a 75 ohm load.

If the precision is not what you expected you can sell it for what you put into
it. I test the quality over range with an AIM 4170 antenna analyzer.

HNY

73,
Tom
Amateur Radio Operator N5GE
ARRL Lifetime Member
QCWA Lifetime Member

"If somebody has a bad heart, they can plug this jack in at
night as they go to bed and it will monitor their heart
throughout the night. And the next morning, when they wake up
dead, there'll be a record."

--Mark S. Fowler, FCC Chairman,
1981 - 1987

On Thu, 22 Dec 2011 15:59:26 -0500, "Tommy Alderman" <[hidden email]>
wrote:

>BUT just because you bought it direct from Palstar does not mean it is a
>good dummy load! The ONLY way you KNOW it is a good dummy load is for YOU to
>measure it with known good test equipment and an ohm-meter is not how it is
>done!
>
>73 and Merry Christmas,
>
>Tom - W4BQF
>
>
>-----Original Message-----
>From: [hidden email]
>[mailto:[hidden email]] On Behalf Of Phil Hystad
>Sent: Thursday, December 22, 2011 3:40 PM
>To: [hidden email]
>Cc: Elecraft List
>Subject: Re: [Elecraft] K3 + LP100A + Dummy Load
>
>The dummy load is the Palstar DL2K, full legal limit handling and I bought
>it new from Palstar several years ago. None of my operating equipment was
>purchased at hamfests -- I prefer to be the original owner and pass over any
>potential difficulties.
>
>peh
>
>
>On Dec 22, 2011, at 12:20 PM, [hidden email] wrote:
>
>>
>> Phil,
>>
>> You don't say what type of dummy load you are using, but all of the
>cantenna
>> type have about the same SWR curve you witnessed. You will need a
>precision DL
>> to get a flat response across a large range. I have two DECIBEL DB4304B
>100
>> watt loads here that are flat up through 2m. I don't think they are made
>any
>> more and if they were they would be very expensive. The two I have were
>bought
>> at a ham hamfest for $50 each. They are bout 6" x 4" x 4" Most of which
>is
>> cooling fins.
>>
>> Be careful when you buy dummy loads like this at a Hamfest. Take a good
>> ohm-meter with you. I bought a couple of really well made heavy duty DL's
>that
>> were rated at 300w for $100 once and when I measured them at home they
>were 75
>> ohm loads, so watch out!
>>
>> Happy holidays,
>>
>> 73,
>> Tom
>> Amateur Radio Operator N5GE
>> ARRL Lifetime Member
>> QCWA Lifetime Member
>>
>> "If somebody has a bad heart, they can plug this jack in at
>> night as they go to bed and it will monitor their heart
>> throughout the night. And the next morning, when they wake up
>> dead, there'll be a record."
>>
>> --Mark S. Fowler, FCC Chairman,
>> 1981 - 1987
>>
>>
>> On Thu, 22 Dec 2011 08:37:37 -0800, Phil Hystad <[hidden email]> wrote:
>>
>>> Is this normal or can someone explain? I was looking at the R+iX values
>reported by the LP100A with my K3 feeding a dummy load. The SWR reported
>was always small but never super close to 1:1. Most of the SWR in this
>setup was 1.1:1 up to 1.5:1. The R values ranged from 34 ohms to up to 59
>ohms and X was ranging over a number of smallish values < 20 for all the
>bands.
>>>
>>> Is this what most of you would call normal?
>>>
>>> Does the K3 output R+iX vary from band to band (I assume so) and is that
>what I am seeing?
>>>
>>> I had thought my dummy load was mostly frequency independent so I am not
>sure if I am seeing mostly the K3 here or maybe the K3 plus the 6 feet of
>coax (RG8X) + dummy load.
>>>
>>> 73, phil, K7PEH
>>>
>>
>>
>> ______________________________________________________________
>> 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
>
>______________________________________________________________
>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

Amateur Radio Operator N5GE

Don Wilhelm-4

Re: K3 + LP100A + Dummy Load

In reply to this post by Phil Hystad-3

Phil,

All dummy loads are not created equal. Connect yours directly (no coax)
to the LP-100 or an antenna analyzer to determine its characteristics
with frequency (I assume Larry calibrated your LP-100 to NIST
standards). A common ham dummy load is something to tune your amplifier
into and use for general purposes. If you are going to do measurements,
you will need something more like lab quality dummy loads.

Both your dummy load and the 6 feet of RG8X will show a frequency
dependency since you do not have a precision 50 ohm dummy load. A
transmission line that is not terminated in its characteristic impedance
acts like an impedance transformer, and that transformation ratio is
frequency dependent.

If you want a dummy load that is flat WRT frequency and suitable for
instrumentation use, take a look at the Caddock 50 ohm Thick Film
Resistors - they are available up to 100 watt rating. You must use them
on a heat sink, and keep the leads as short as possible, and you will
have a precision dummy load. Caution - even with the heat sink, do not
exceed their power ratings, they will go open circuit in an instant.
I use several of those as instrumentation precision loads.

Other sources of precision dummy loads is Ridge Equipment -
https://www.ridgeequipment.com/store/dummyloads.html. They have one
rated at 75 watts for $12 and one rated at 15 watts for $7.50 - those
are quite good for instrumentation purposes.

73,
Don W3FPR

On 12/22/2011 11:37 AM, Phil Hystad wrote:

> Is this normal or can someone explain? I was looking at the R+iX values reported by the LP100A with my K3 feeding a dummy load. The SWR reported was always small but never super close to 1:1. Most of the SWR in this setup was 1.1:1 up to 1.5:1. The R values ranged from 34 ohms to up to 59 ohms and X was ranging over a number of smallish values< 20 for all the bands.
>
> Is this what most of you would call normal?
>
> Does the K3 output R+iX vary from band to band (I assume so) and is that what I am seeing?
>
> I had thought my dummy load was mostly frequency independent so I am not sure if I am seeing mostly the K3 here or maybe the K3 plus the 6 feet of coax (RG8X) + dummy load.
>
> 73, phil, K7PEH
>

ab2tc

Re: K3 + LP100A + Dummy Load

Hi,

I highly recommend the 75W dummy load from Ridge Equipment. I have one permanently connected in my system. I believe it is a military surplus piece of equipment with absolutely superior characteristics like an SWR at 500MHz of 1.05 or less. It has no problem with 100W for a minute or less for sure.

AB2TC - Knut

<quote author="Don Wilhelm-4">
Phil,

All dummy loads are not created equal. Connect yours directly (no coax)
to the LP-100 or an antenna analyzer to determine its characteristics
with frequency (I assume Larry calibrated your LP-100 to NIST
standards). A common ham dummy load is something to tune your amplifier
into and use for general purposes. If you are going to do measurements,
you will need something more like lab quality dummy loads.

Both your dummy load and the 6 feet of RG8X will show a frequency
dependency since you do not have a precision 50 ohm dummy load. A
transmission line that is not terminated in its characteristic impedance
acts like an impedance transformer, and that transformation ratio is
frequency dependent.

If you want a dummy load that is flat WRT frequency and suitable for
instrumentation use, take a look at the Caddock 50 ohm Thick Film
Resistors - they are available up to 100 watt rating. You must use them
on a heat sink, and keep the leads as short as possible, and you will
have a precision dummy load. Caution - even with the heat sink, do not
exceed their power ratings, they will go open circuit in an instant.
I use several of those as instrumentation precision loads.

Other sources of precision dummy loads is Ridge Equipment -
https://www.ridgeequipment.com/store/dummyloads.html. They have one
rated at 75 watts for $12 and one rated at 15 watts for $7.50 - those
are quite good for instrumentation purposes.

73,
Don W3FPR

<snip
</quote>

N8LP

Re: K3 + LP100A + Dummy Load

In reply to this post by Phil Hystad-3

I have been recommending the dummy loads and power attenuators from
Ridge Equipment for years. They usually have a good selection, excellent
quality and great prices. They will also provide a VNA plot for 10 bucks
more as I recall. Remember that these loads usually have N connectors,
so you may need an adapter.

73,
Larry N8LP

On 12/23/2011 6:48 AM, [hidden email] wrote:

> Date: Thu, 22 Dec 2011 14:29:14 -0800 (PST)
> From: ab2tc<[hidden email]>
> Subject: Re: [Elecraft] K3 + LP100A + Dummy Load
> To:[hidden email]
> Message-ID:<[hidden email]>
> Content-Type: text/plain; charset=us-ascii
>
> Hi,
>
> I highly recommend the 75W dummy load from Ridge Equipment. I have one
> permanently connected in my system. I believe it is a military surplus piece
> of equipment with absolutely superior characteristics like an SWR at 500MHz
> of 1.05 or less. It has no problem with 100W for a minute or less for sure.
>
> AB2TC - Knut
>
>
> Phil,
>
> All dummy loads are not created equal. Connect yours directly (no coax)
> to the LP-100 or an antenna analyzer to determine its characteristics
> with frequency (I assume Larry calibrated your LP-100 to NIST
> standards). A common ham dummy load is something to tune your amplifier
> into and use for general purposes. If you are going to do measurements,
> you will need something more like lab quality dummy loads.
>
> Both your dummy load and the 6 feet of RG8X will show a frequency
> dependency since you do not have a precision 50 ohm dummy load. A
> transmission line that is not terminated in its characteristic impedance
> acts like an impedance transformer, and that transformation ratio is
> frequency dependent.
>
> If you want a dummy load that is flat WRT frequency and suitable for
> instrumentation use, take a look at the Caddock 50 ohm Thick Film
> Resistors - they are available up to 100 watt rating. You must use them
> on a heat sink, and keep the leads as short as possible, and you will
> have a precision dummy load. Caution - even with the heat sink, do not
> exceed their power ratings, they will go open circuit in an instant.
> I use several of those as instrumentation precision loads.
>
> Other sources of precision dummy loads is Ridge Equipment -
> https://www.ridgeequipment.com/store/dummyloads.html. They have one
> rated at 75 watts for $12 and one rated at 15 watts for $7.50 - those
> are quite good for instrumentation purposes.
>
> 73,
> Don W3FPR
>
> <snip
> </quote>

Edward R Cole

Re: K3 + LP100A + Dummy Load

In reply to this post by Phil Hystad-3

Just a comment on dummy loads:

I do a lot of ham radio work at VHF and higher (up to 10-GHz), so
making good power measurements involves having a good 50-ohm
termination (load). For most of my testing I have several coaxial
loads: A 25w Termaline (Bird) is used a lot in the shack as it tests
Z=51 + j0 on my MFJ-269B antenna analyzer and shows zero reflected on
a Bird43 power meter. Some of the other loads show 52 or even 54
ohms on the MFJ, and not quite resistive (I marked all them so I
would know). In all cases resistance measurement with an ohmmeter
agrees with the R parameter in the complex impedance equation.

I even have a 500w Sierra termination (door stop load) which has a
integral power meter, but it is not exactly 50-ohms and the meter is
not in agreement with the Bird43, so I use it as a safe load for high
power but not for high accuracy measurements. I have seen coax loads
shift way off 50-ohms due to overheating from too much or too long a
transmission.

I bought some of the Cadsoft 100w surface-mount attenuators to use in
a 900-MHz amplifier to permit driving with 10w exciter. They were in
the $12 range from Mouser.

One can make very fine 50-ohm loads using them on a proper heat sink
at a fraction of the cost of coaxial loads.

73, Ed - KL7UW, WD2XSH/45
======================================
BP40IQ 500 KHz - 10-GHz www.kl7uw.com
EME: 50-1.1kw?, 144-1.4kw, 432-QRT, 1296-?, 3400-?
DUBUS Magazine USA Rep [hidden email]
======================================

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