Re: [Elecraft] K3 TX Calib Dummy Load Recommendations

[Steve Lawrence via Elecraft]

"What are recommended dummy loads to consider for use when running the K3 TX 
Calibration?"


Thanks to all who've replied both on and especially off list.

The general consensus is that BIRD makes the best dummy loads. Avoiding units 
that incorporate BeO is a consideration.

Others mentioned, in no particular order:

Heath / MFJ Cantenna
Oak Hills Research RFL 100
db Products
Designs that use Caddock film resistors.
MFJs.

TKS & 73 - Steve WB6RSE


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Re: [Elecraft] K3 TX Calib Dummy Load Recommendations

[Drew AF2Z]

I have a db Products 50 watt dummy load which was sold on ebay as 
surplus cellular test equipment. That should mean it's good to a GHz I 
guess. Even though it's only 50 watts I have used it briefly at 100. 
There used to be lots of these on ebay but now all I see are 25 or 30 
watt versions.


73,
Drew
AF2Z



On 08/25/18 19:09, Steve Lawrence via Elecraft wrote:

What are recommended dummy loads to consider for use when running the K3 TX 
Calibration?

Thanks - Steve WB6RSE
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Re: [Elecraft] K3 TX Calib Dummy Load Recommendations

[Don Wilhelm]

Some of the best dummy loads are built from Caddox Thick Film Resistors.
The 50 ohm resistors are non-reactive and flat up through 500 MHz.
They MUST be mounted on a heatsink to achieve their power rating.

Using careful wiring practices (close to zero length leads), you can 
wire 4 of the 25 watt versions in series-parallel for a 100 ohm dummy 
load, but there is a 100 watt version available that will do a better job.


73,
Don W3FPR

On 8/26/2018 8:50 AM, Bill Frantz wrote:
For my KX3, I built a dummy load from three 150 ohm 2 watt resistors and 
a BNC connector. The resistors are in parallel with a lead going to the 
center conductor of the connector. The other leads are folded back over 
the resistors and attached to the ground-side of the connector. The 
whole outside is then covered with a piece of coax braid. It does well 
on the antenna analyser test Bob, K4TAX suggests.



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Re: [Elecraft] K3 TX Calib Dummy Load Recommendations

[Bob McGraw K4TAX]

Try to find carbon resistors as newer film resistors may be reactive.    
Older carbon resistors have a tendency to migrate upwards in value.  Be 
sure to check them with a meter.


73
Bob, K4TAX



On 8/26/2018 7:50 AM, Bill Frantz wrote:
For my KX3, I built a dummy load from three 150 ohm 2 watt resistors 
and a BNC connector. The resistors are in parallel with a lead going 
to the center conductor of the connector. The other leads are folded 
back over the resistors and attached to the ground-side of the 
connector. The whole outside is then covered with a piece of coax 
braid. It does well on the antenna analyser test Bob, K4TAX suggests.


It lives in a pocket of Rose's case and goes where the radio goes.

73 Bill AE6JV

--- 

Bill Frantz    |"After all, if the conventional wisdom was 
working, the
408-356-8506   | rate of systems being compromised would be going 
down,

www.pwpconsult.com | wouldn't it?" -- Marcus Ranum

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Re: [Elecraft] K3 TX Calib Dummy Load Recommendations

[Bill Frantz]

For my KX3, I built a dummy load from three 150 ohm 2 watt 
resistors and a BNC connector. The resistors are in parallel 
with a lead going to the center conductor of the connector. The 
other leads are folded back over the resistors and attached to 
the ground-side of the connector. The whole outside is then 
covered with a piece of coax braid. It does well on the antenna 
analyser test Bob, K4TAX suggests.


It lives in a pocket of Rose's case and goes where the radio goes.

73 Bill AE6JV

---
Bill Frantz|"After all, if the conventional wisdom was 
working, the
408-356-8506   | rate of systems being compromised would be 
going down,

www.pwpconsult.com | wouldn't it?" -- Marcus Ranum

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Re: [Elecraft] K3 TX Calib Dummy Load Recommendations

[Bob McGraw K4TAX]

While one can measure a dummy load with an ohm meter, this is only the 
DC resistance of the resistive element.   It does not assure that it is 
non-reactive as reactance is an AC component related to frequency.   
Dummy loads should appear as 50 ohms at all frequencies within the range 
where they are expected to be used.    A good dummy load will be rated 
at 50 ohms from DC to 500 MHz or higher.


A better way to verify a dummy load is to use an antenna analyzer such 
as a MFJ-259, an Autec, or Comet CAA-500 or RigExpert AA-30, etc.   Do 
connect the dummy load direct to the instrument without a jumper cable 
and sweep the range of frequencies desired.   Any value measured other 
than 50 ohms and with a SWR greater than 1.1:1 is deemed not 
satisfactory for a dummy load.   Another method is to use a return loss 
bridge or a vector network analyzer.


Don't be mislead by the numbers printed on the label.  I have two of the 
"gallon can" oil filled types.  They measure noticeably different values 
than 50 ohms and get quite reactive above 30 MHz.


From this source you will find 100 watt Decibel Product dummy loads 
DB4303B for $50 each. http://www.nm3e.com/loadSampler.htm#LoadSampler



And you will find Bird 100 watt loads, good from DC to 2.4GHz for $85.  
And if you need one for that legal limit amp, they have a Bird 82C being 
a 2500 watt water cooled load for $500.


Everyone should have a dummy load and an antenna bridge for their station.

73

Bob, K4TAX



On 8/25/2018 7:35 PM, Walter Underwood wrote:

I built the Oak Hills Research RFL-100 dummy load kit. It is supposed to be 
good to
144 MHz, so it should be fine at 50. If you’ve never built a kit, this is a 
good one to
start with. The kit is $50. I got the $5 BNC option, since my shack is 100% BNC.

http://www.ohr.com/rfl100.htm

Here are some photos of my build. Mine measured 49.9 Ω, which is within 0.2%.
My Ohmmeter is accurate to +/-0.5%, so I’ll take that as a solid 50 Ω. Because 
the
dummy load is built with 50 resistors, part tolerances will average out.

https://observer.wunderwood.org/2016/12/31/building-a-dummy-load/

wunder
K6WRU
Walter Underwood
CM87wj
http://observer.wunderwood.org/ (my blog)


On Aug 25, 2018, at 4:49 PM, Mark Goldberg  wrote:

A good one that you know is 50 ohms over the range of frequencies and power
you want to use it at. Unfortunately, any particular model may be good or
bad, depending on how it has been used or abused. Is there any way you can
get access to an analyzer to determine if the dummy load is good? I have a
Vector Network Analyzer, but few hams will have one of those.

Also, if you really want to do a real calibration, you should have a
calibrated reference to check against. Lots of devices can be 5-10% off if
not calibrated, worse if abused or damaged. A Bird meter is only specified
to I think 5% of the full scale. So if it is a 200W full scale, it could be
10W off. So 100W might read 110W or 90W.  I've got a calibrated Spectrum
Analyzer and Signal Generator that I use to calibrate all my other stuff
against, but again, few Hams will have similar or spend to keep them in
calibration.

In general, oil filled dummy loads with fins like the Birds shown lower on
this page are going to be good, but expensive:

https://www.birdrf.com/Products/Test%20and%20Measurement/Loads/Coaxial-Terminations.aspx

You can find similar ones used, hopefully not abused and not filled with
PCBs.

I've got a similar one that must be decades old and it works well and is
pretty close to 50 ohms over the HF range. I have not opened it to see what
it is filled with!

73,

Mark
W7MLG


On Sat, Aug 25, 2018 at 4:09 PM, Steve Lawrence via Elecraft <
elecraft@mailman.qth.net> wrote:


What are recommended dummy loads to consider for use when running the K3
TX Calibration?

Thanks - Steve WB6RSE
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Re: [Elecraft] K3 TX Calib Dummy Load Recommendations

[Walter Underwood]

Sorry, that is twenty resistors, not fifty.

wunder
K6WRU
Walter Underwood
CM87wj
http://observer.wunderwood.org/ (my blog)

> On Aug 25, 2018, at 5:35 PM, Walter Underwood  wrote:
> 
> I built the Oak Hills Research RFL-100 dummy load kit. It is supposed to be 
> good to
> 144 MHz, so it should be fine at 50. If you’ve never built a kit, this is a 
> good one to
> start with. The kit is $50. I got the $5 BNC option, since my shack is 100% 
> BNC.
> 
> http://www.ohr.com/rfl100.htm
> 
> Here are some photos of my build. Mine measured 49.9 Ω, which is within 0.2%.
> My Ohmmeter is accurate to +/-0.5%, so I’ll take that as a solid 50 Ω. 
> Because the
> dummy load is built with 50 resistors, part tolerances will average out.
> 
> https://observer.wunderwood.org/2016/12/31/building-a-dummy-load/
> 
> wunder
> K6WRU
> Walter Underwood
> CM87wj
> http://observer.wunderwood.org/ (my blog)
> 
>> On Aug 25, 2018, at 4:49 PM, Mark Goldberg  wrote:
>> 
>> A good one that you know is 50 ohms over the range of frequencies and power
>> you want to use it at. Unfortunately, any particular model may be good or
>> bad, depending on how it has been used or abused. Is there any way you can
>> get access to an analyzer to determine if the dummy load is good? I have a
>> Vector Network Analyzer, but few hams will have one of those.
>> 
>> Also, if you really want to do a real calibration, you should have a
>> calibrated reference to check against. Lots of devices can be 5-10% off if
>> not calibrated, worse if abused or damaged. A Bird meter is only specified
>> to I think 5% of the full scale. So if it is a 200W full scale, it could be
>> 10W off. So 100W might read 110W or 90W.  I've got a calibrated Spectrum
>> Analyzer and Signal Generator that I use to calibrate all my other stuff
>> against, but again, few Hams will have similar or spend to keep them in
>> calibration.
>> 
>> In general, oil filled dummy loads with fins like the Birds shown lower on
>> this page are going to be good, but expensive:
>> 
>> https://www.birdrf.com/Products/Test%20and%20Measurement/Loads/Coaxial-Terminations.aspx
>> 
>> You can find similar ones used, hopefully not abused and not filled with
>> PCBs.
>> 
>> I've got a similar one that must be decades old and it works well and is
>> pretty close to 50 ohms over the HF range. I have not opened it to see what
>> it is filled with!
>> 
>> 73,
>> 
>> Mark
>> W7MLG
>> 
>> 
>> On Sat, Aug 25, 2018 at 4:09 PM, Steve Lawrence via Elecraft <
>> elecraft@mailman.qth.net> wrote:
>> 
>>> What are recommended dummy loads to consider for use when running the K3
>>> TX Calibration?
>>> 
>>> Thanks - Steve WB6RSE
>>> __
>>> Elecraft mailing list
>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>>> Help: http://mailman.qth.net/mmfaq.htm
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>>> This list hosted by: http://www.qsl.net
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>>> Message delivered to marklgoldb...@gmail.com
>>> 
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Re: [Elecraft] K3 TX Calib Dummy Load Recommendations

[Gwen Patton]

The QRPGuys QRP tuner kit I built is very nice, but don't go over its 12W
limit, or you'll blow the diode.

Thankfully, I have a pile of them on hand just in case. ;)

Gwen NG3P

On Sat, Aug 25, 2018 at 8:36 PM Walter Underwood 
wrote:

> I built the Oak Hills Research RFL-100 dummy load kit. It is supposed to
> be good to
> 144 MHz, so it should be fine at 50. If you’ve never built a kit, this is
> a good one to
> start with. The kit is $50. I got the $5 BNC option, since my shack is
> 100% BNC.
>
> http://www.ohr.com/rfl100.htm
>
> Here are some photos of my build. Mine measured 49.9 Ω, which is within
> 0.2%.
> My Ohmmeter is accurate to +/-0.5%, so I’ll take that as a solid 50 Ω.
> Because the
> dummy load is built with 50 resistors, part tolerances will average out.
>
> https://observer.wunderwood.org/2016/12/31/building-a-dummy-load/
>
> wunder
> K6WRU
> Walter Underwood
> CM87wj
> http://observer.wunderwood.org/ (my blog)
>
> > On Aug 25, 2018, at 4:49 PM, Mark Goldberg 
> wrote:
> >
> > A good one that you know is 50 ohms over the range of frequencies and
> power
> > you want to use it at. Unfortunately, any particular model may be good or
> > bad, depending on how it has been used or abused. Is there any way you
> can
> > get access to an analyzer to determine if the dummy load is good? I have
> a
> > Vector Network Analyzer, but few hams will have one of those.
> >
> > Also, if you really want to do a real calibration, you should have a
> > calibrated reference to check against. Lots of devices can be 5-10% off
> if
> > not calibrated, worse if abused or damaged. A Bird meter is only
> specified
> > to I think 5% of the full scale. So if it is a 200W full scale, it could
> be
> > 10W off. So 100W might read 110W or 90W.  I've got a calibrated Spectrum
> > Analyzer and Signal Generator that I use to calibrate all my other stuff
> > against, but again, few Hams will have similar or spend to keep them in
> > calibration.
> >
> > In general, oil filled dummy loads with fins like the Birds shown lower
> on
> > this page are going to be good, but expensive:
> >
> >
> https://www.birdrf.com/Products/Test%20and%20Measurement/Loads/Coaxial-Terminations.aspx
> >
> > You can find similar ones used, hopefully not abused and not filled with
> > PCBs.
> >
> > I've got a similar one that must be decades old and it works well and is
> > pretty close to 50 ohms over the HF range. I have not opened it to see
> what
> > it is filled with!
> >
> > 73,
> >
> > Mark
> > W7MLG
> >
> >
> > On Sat, Aug 25, 2018 at 4:09 PM, Steve Lawrence via Elecraft <
> > elecraft@mailman.qth.net> wrote:
> >
> >> What are recommended dummy loads to consider for use when running the K3
> >> TX Calibration?
> >>
> >> Thanks - Steve WB6RSE
> >> __
> >> Elecraft mailing list
> >> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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> >> Message delivered to marklgoldb...@gmail.com
> >>
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Re: [Elecraft] K3 TX Calib Dummy Load Recommendations

[Walter Underwood]

I built the Oak Hills Research RFL-100 dummy load kit. It is supposed to be 
good to
144 MHz, so it should be fine at 50. If you’ve never built a kit, this is a 
good one to
start with. The kit is $50. I got the $5 BNC option, since my shack is 100% BNC.

http://www.ohr.com/rfl100.htm

Here are some photos of my build. Mine measured 49.9 Ω, which is within 0.2%.
My Ohmmeter is accurate to +/-0.5%, so I’ll take that as a solid 50 Ω. Because 
the
dummy load is built with 50 resistors, part tolerances will average out.

https://observer.wunderwood.org/2016/12/31/building-a-dummy-load/

wunder
K6WRU
Walter Underwood
CM87wj
http://observer.wunderwood.org/ (my blog)

> On Aug 25, 2018, at 4:49 PM, Mark Goldberg  wrote:
> 
> A good one that you know is 50 ohms over the range of frequencies and power
> you want to use it at. Unfortunately, any particular model may be good or
> bad, depending on how it has been used or abused. Is there any way you can
> get access to an analyzer to determine if the dummy load is good? I have a
> Vector Network Analyzer, but few hams will have one of those.
> 
> Also, if you really want to do a real calibration, you should have a
> calibrated reference to check against. Lots of devices can be 5-10% off if
> not calibrated, worse if abused or damaged. A Bird meter is only specified
> to I think 5% of the full scale. So if it is a 200W full scale, it could be
> 10W off. So 100W might read 110W or 90W.  I've got a calibrated Spectrum
> Analyzer and Signal Generator that I use to calibrate all my other stuff
> against, but again, few Hams will have similar or spend to keep them in
> calibration.
> 
> In general, oil filled dummy loads with fins like the Birds shown lower on
> this page are going to be good, but expensive:
> 
> https://www.birdrf.com/Products/Test%20and%20Measurement/Loads/Coaxial-Terminations.aspx
> 
> You can find similar ones used, hopefully not abused and not filled with
> PCBs.
> 
> I've got a similar one that must be decades old and it works well and is
> pretty close to 50 ohms over the HF range. I have not opened it to see what
> it is filled with!
> 
> 73,
> 
> Mark
> W7MLG
> 
> 
> On Sat, Aug 25, 2018 at 4:09 PM, Steve Lawrence via Elecraft <
> elecraft@mailman.qth.net> wrote:
> 
>> What are recommended dummy loads to consider for use when running the K3
>> TX Calibration?
>> 
>> Thanks - Steve WB6RSE
>> __
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>> Please help support this email list: http://www.qsl.net/donate.html
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>> 
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Re: [Elecraft] K3 TX Calib Dummy Load Recommendations

[Grant Youngman]

Any decent commercial nominally 50 ohm 100W+ DL ought to work fine, as long as 
it isn’t a piece of junk that falls apart at 50 MHz.  It doesn’t need to be 
NIST traceable :-)

Grant NQ5T
K3 #2091 KX3 #8342

> On Aug 25, 2018, at 7:09 PM, Steve Lawrence via Elecraft 
>  wrote:
> 
> What are recommended dummy loads to consider for use when running the K3 TX 
> Calibration?
> 

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Re: [Elecraft] K3 TX Calib Dummy Load Recommendations

[Mark Goldberg]

A good one that you know is 50 ohms over the range of frequencies and power
you want to use it at. Unfortunately, any particular model may be good or
bad, depending on how it has been used or abused. Is there any way you can
get access to an analyzer to determine if the dummy load is good? I have a
Vector Network Analyzer, but few hams will have one of those.

Also, if you really want to do a real calibration, you should have a
calibrated reference to check against. Lots of devices can be 5-10% off if
not calibrated, worse if abused or damaged. A Bird meter is only specified
to I think 5% of the full scale. So if it is a 200W full scale, it could be
10W off. So 100W might read 110W or 90W.  I've got a calibrated Spectrum
Analyzer and Signal Generator that I use to calibrate all my other stuff
against, but again, few Hams will have similar or spend to keep them in
calibration.

In general, oil filled dummy loads with fins like the Birds shown lower on
this page are going to be good, but expensive:

https://www.birdrf.com/Products/Test%20and%20Measurement/Loads/Coaxial-Terminations.aspx

You can find similar ones used, hopefully not abused and not filled with
PCBs.

I've got a similar one that must be decades old and it works well and is
pretty close to 50 ohms over the HF range. I have not opened it to see what
it is filled with!

73,

Mark
W7MLG


On Sat, Aug 25, 2018 at 4:09 PM, Steve Lawrence via Elecraft <
elecraft@mailman.qth.net> wrote:

> What are recommended dummy loads to consider for use when running the K3
> TX Calibration?
>
> Thanks - Steve WB6RSE
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