Re: [Elecraft] Dummy Load with integral digital wattmeter

[Jim Brown]

On 4/30/2021 6:07 PM, j...@kk9a.com wrote:

I use a Telepost LP100A with the sensor connected to a Bird dummy load.


I have a dual-probe LP100A inline with the power amp outs in my SO2R 
station. It auto-switches to the active TX. I have a kW dummy load 
sitting under the operating desk, but it's not part of antenna 
switching, and I haven't used it in years.


73, Jim K9YC
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Re: [Elecraft] Dummy Load with integral digital wattmeter

[john]

I use a Telepost LP100A with the sensor connected to a Bird dummy load.

John KK9A

hawley, charles j jr wrote:

I have one. I like it, but I was thinking more of a test unit.
Dummy load with integral digital meter (digits preferred instead of LEDs)..
To make one out of a W2 would require a W2, that after market KV5J digital
readout or a computer, and the directional coupler. Lots of stuff and wires.
But maybe if I found a stand alone digital wattmeter I could fasten it to a
dummy load...that's a thought.

Chuck Hawley

 Amateur Radio, KE9UW
 aka Jack, BMW Motorcycles

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Re: [Elecraft] Dummy Load with integral digital wattmeter

[hawley, charles j jr]

I have one. I like it, but I was thinking more of a test unit.
Dummy load with integral digital meter (digits preferred instead of LEDs)..
To make one out of a W2 would require a W2, that after market KV5J digital 
readout or a computer, and the directional coupler. Lots of stuff and wires.
But maybe if I found a stand alone digital wattmeter I could fasten it to a 
dummy load...that's a thought.

Chuck Hawley
 c-haw...@illinois.edu

 Amateur Radio, KE9UW
 aka Jack, BMW Motorcycles


From: Jack Brindle 
Sent: Friday, April 30, 2021 3:50 PM
To: hawley, charles j jr 
Cc: elecraft@mailman.qth.net 
Subject: Re: [Elecraft] Dummy Load with integral digital wattmeter

Have you looked at the Elecraft W2?

https://elecraft.com/products/w2<https://urldefense.com/v3/__https://elecraft.com/products/w2__;!!DZ3fjg!qXURJbbL1PqkaGaQGRUvMoMfFuds4479KRvkzFwZGcm4UK5lJ0eexSbFJ813fvOTsn32$>

73!
Jack, W6FB


On Apr 30, 2021, at 1:38 PM, ke9uw 
mailto:c-haw...@illinois.edu>> wrote:

I have recently built a GRPoMeter which has a 16 Watt dummy load with a
digital SWR/Wattmeter in it. It’s great...but only reads up to about 14
Watts.
I would like a similar dummy load meter with a digital meter that reads say
0-10, 0-100, and 0-1000 watts full scale. I like and use the Elecraft 500
watt amp and tuner, so 1000 watts full scale would be perfect..
Too much to ask for. 0-2000 would be acceptable if it had the 3 ranges.
Definitely not  single range analog meters like MFJ and Palstar have
Anyone know of a product like this?

Chuck KE9UW



-
Chuck, KE9UW
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Re: [Elecraft] Dummy Load with integral digital wattmeter

[Jack Brindle via Elecraft]

Have you looked at the Elecraft W2?

https://elecraft.com/products/w2 

73!
Jack, W6FB


> On Apr 30, 2021, at 1:38 PM, ke9uw  wrote:
> 
> I have recently built a GRPoMeter which has a 16 Watt dummy load with a
> digital SWR/Wattmeter in it. It’s great...but only reads up to about 14
> Watts.
> I would like a similar dummy load meter with a digital meter that reads say
> 0-10, 0-100, and 0-1000 watts full scale. I like and use the Elecraft 500
> watt amp and tuner, so 1000 watts full scale would be perfect..
> Too much to ask for. 0-2000 would be acceptable if it had the 3 ranges.
> Definitely not  single range analog meters like MFJ and Palstar have
> Anyone know of a product like this?
> 
> Chuck KE9UW
> 
> 
> 
> -
> Chuck, KE9UW
> --
> Sent from: http://elecraft.365791.n2.nabble.com/
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Re: [Elecraft] Dummy Load recommendation

[CUTTER DAVID via Elecraft]

Don
Thanks for those further notes.  I'm also thinking of the best we can do with 
the most primitive equipment.  Amateurs have been making RF probes forever and 
now we have cheap digital multimeters with >1Mohm input impedance it should be 
even easier to get a good estimate of power using the method you outline but 
without a scope, which itself has to be expensively calibrated and you still 
have to interpret an analogue display.  
I wonder just how good we could make and calibrate an RF probe. 
David G3UNA

> On 31 July 2019 at 16:28 Don Wilhelm  wrote:
> 
> 
> David,
> 
> Your question about "what is good enough" is an informative one.
> When I was doing repair/alignment work for others, it was important to 
> me to have tools that had traceable calibration info.  I had some good 
> 50 ohm dummy loads that were good to 1 GHz, and an LP-100A that was 
> calibrated to NIST standards (which I used as a sanity check for other 
> power measurement instruments).  Having those calibrated tools were 
> important to maintain my customer's trust.
> 
> In amateur practice, such care is not necessarily needed, but the 
> K3/KX2/KX3 TX gain calibration does require a good 50 ohm load up to 50 
> MHz.  That is easily checked by sweeping it with an antenna analyzer.
> 
> As for the power measurement, once you have a good 50 ohm dummy load, it 
> is easy to use a 'scope (with a 10X probe) connected across that dummy 
> load (use a TEE adapter to gain access to the coax center conductor). 
> Then you can measure the RF voltage (peak to peak shown on the 'scope), 
> and use the formula Vp-p squared then divided by 400 to quickly obtain 
> an accurate calculation of the power.  Nothing really expensive except 
> for the 'scope (which can be borrowed in many cases).
> 
> So what you need first is a good 50 ohm dummy load, and secondly, access 
> to a 'scope having reasonable calibration for the vertical deflection at 
> the frequency of interest.
> 
> With that combination, you can check the error in other in-line power 
> measurement equipment.
> 
> In most cases a 10% or 20% error is not going to make a big difference 
> in on-the-air performance - anywhere in the ballpark is usually OK.
> 
> You are correct that we have become complacent because of digital 
> displays.  Take a 4 digit display in an instrument having accuracy of 
> 10% - the difference between a display of 10.41 and 9.37 or 11.45 is 
> meaningless given the 10% accuracy of the instrument itself.  You should 
> round that reading to 10 volts.  Analog readouts automatically do that 
> compensation because you cannot read the meter scale with 4 digit 
> accuracy.  Even my 12 inch slide rule in college was limited to 3 
> significant digits.
> 
> There is a difference between doing it "good enough" and with greater 
> accuracy depends on the purposes of your measurements.
> 
> 73,
> Don W3FPR
> 
> On 7/23/2019 11:38 AM, CUTTER DAVID via Elecraft wrote:
> > I agree with all that has been said and suspect a lot of responders on this 
> > list are or were engineers who are used to using precision equipment.  I 
> > think it can be misleading to look at some instruments built into a 
> > transceiver for instance, but it never seemed to matter, until Elecraft 
> > came along.  I did my calibration with a Bird power meter and a Bird 500W 
> > load but I have no idea when they were last calibrated, so, what value do I 
> > put on the measurements?  Well, it's good enough for me. But calibration is 
> > a special case and I'd never heard of amateurs calibrating for power before 
> > Elecraft.  Accurate power meters are costly to buy and maintain if you are 
> > in business, but for me now I'm retired it doesn't matter so much because 
> > I'm not doing it for a paying customer.  I think we are misled by the easy 
> > precision of the digital multimeter which for a few £ or $ is ten times as 
> > good as what we previously thought were good analogue instruments.  In 
> > short, I think technology can cause us to bite our finger nails 
> > unnecessarily.  10% or 20% power error is hardly noticeable to the guy on 
> > the other side of the world.
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Re: [Elecraft] Dummy Load recommendation

[Don Wilhelm]

David,

Your question about "what is good enough" is an informative one.
When I was doing repair/alignment work for others, it was important to 
me to have tools that had traceable calibration info.  I had some good 
50 ohm dummy loads that were good to 1 GHz, and an LP-100A that was 
calibrated to NIST standards (which I used as a sanity check for other 
power measurement instruments).  Having those calibrated tools were 
important to maintain my customer's trust.


In amateur practice, such care is not necessarily needed, but the 
K3/KX2/KX3 TX gain calibration does require a good 50 ohm load up to 50 
MHz.  That is easily checked by sweeping it with an antenna analyzer.


As for the power measurement, once you have a good 50 ohm dummy load, it 
is easy to use a 'scope (with a 10X probe) connected across that dummy 
load (use a TEE adapter to gain access to the coax center conductor). 
Then you can measure the RF voltage (peak to peak shown on the 'scope), 
and use the formula Vp-p squared then divided by 400 to quickly obtain 
an accurate calculation of the power.  Nothing really expensive except 
for the 'scope (which can be borrowed in many cases).


So what you need first is a good 50 ohm dummy load, and secondly, access 
to a 'scope having reasonable calibration for the vertical deflection at 
the frequency of interest.


With that combination, you can check the error in other in-line power 
measurement equipment.


In most cases a 10% or 20% error is not going to make a big difference 
in on-the-air performance - anywhere in the ballpark is usually OK.


You are correct that we have become complacent because of digital 
displays.  Take a 4 digit display in an instrument having accuracy of 
10% - the difference between a display of 10.41 and 9.37 or 11.45 is 
meaningless given the 10% accuracy of the instrument itself.  You should 
round that reading to 10 volts.  Analog readouts automatically do that 
compensation because you cannot read the meter scale with 4 digit 
accuracy.  Even my 12 inch slide rule in college was limited to 3 
significant digits.


There is a difference between doing it "good enough" and with greater 
accuracy depends on the purposes of your measurements.


73,
Don W3FPR

On 7/23/2019 11:38 AM, CUTTER DAVID via Elecraft wrote:

I agree with all that has been said and suspect a lot of responders on this 
list are or were engineers who are used to using precision equipment.  I think 
it can be misleading to look at some instruments built into a transceiver for 
instance, but it never seemed to matter, until Elecraft came along.  I did my 
calibration with a Bird power meter and a Bird 500W load but I have no idea 
when they were last calibrated, so, what value do I put on the measurements?  
Well, it's good enough for me. But calibration is a special case and I'd never 
heard of amateurs calibrating for power before Elecraft.  Accurate power meters 
are costly to buy and maintain if you are in business, but for me now I'm 
retired it doesn't matter so much because I'm not doing it for a paying 
customer.  I think we are misled by the easy precision of the digital 
multimeter which for a few £ or $ is ten times as good as what we previously 
thought were good analogue instruments.  In short, I think technology can cause 
us to bite our finger nails unnecessarily.  10% or 20% power error is hardly 
noticeable to the guy on the other side of the world.

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Re: [Elecraft] Dummy Load

[Edward R Cole]

Don-K8MFO and I attended MSU together in the 1960's; old time 
friend.  We visited him at his home in OH a couple years ago and 
found he was in the Christmas tree business (my parents ran a 
Christmas tree farm).  Don has been a long time Dxer and CW buff (has 
a tremendous collection of keys).


Don't recall but I think Don has Elecraft gear in addition to his 
collection of oldies.  Thanks for reminding me of my old friend!


Someday I will load my invert-L to operate 160.

73, Ed - KL7UW ex-K8MWA

From: Jim Danehy 
To: elecraft@mailman.qth.net
Subject: [Elecraft] Dummy Load
Message-ID: <0a44f6bf-177a-43f7-be5b-f3ae9a6e4...@gmail.com>
Content-Type: text/plain;   charset=us-ascii

I worked K8MFO on 160 which is 250 miles from me. Used a Heathkit 
Dummy loaf with oil in the can.



73, Ed - KL7UW
  http://www.kl7uw.com
Dubus-NA Business mail:
  dubus...@gmail.com 


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Re: [Elecraft] Dummy Load

[k2asp kanafi.org]

> On July 23, 2019 at 4:55 PM Jim Danehy  wrote:
> 
> 
> I worked K8MFO on 160 which is 250 miles from me. Used a Heathkit Dummy loaf 
> with oil in the can. 

I am limited in antennas because of the rental apartment rules so I use a 
mag-loop at 15 watts. I've often wondered whether I would have a better signal 
running 100 W into my MFJ dummy load.  Maybe I should try it!

73 de K2ASP
K2/100
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Re: [Elecraft] Dummy Load recommendation

[Fred Jensen]

Recalls to mind Tom Schiller, N6BT, and his "Phased Illuminator."

73,
Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County

On 7/23/2019 1:42 PM, Jim Ragsdale wrote:
I quit using 60 W light bulbs when I worked a station in New Jersey 
from Memphis, Tennessee!

Jim W5LA ex K4QG ex WA4BAC ex WN4BAC


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Re: [Elecraft] Dummy Load

[David Gilbert]

I'd bet a lot of money that something besides the dummy load was doing 
most of the radiating.


Dave   AB7E



On 7/23/2019 1:55 PM, Jim Danehy wrote:

I worked K8MFO on 160 which is 250 miles from me. Used a Heathkit Dummy loaf 
with oil in the can.




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Re: [Elecraft] Dummy Load recommendation

[Jim Ragsdale]

I quit using 60 W light bulbs when I worked a station in New Jersey from 
Memphis, Tennessee!

Jim W5LA ex K4QG ex WA4BAC ex WN4BAC

On 07/23/19 3:03 PM, Grant Youngman wrote:

As a new ham (1958-9) my "dummy load" was a 60 watt light bulb.  Even made a 
few local contacts with it.  Couldn’t afford anything else.  A good pi-network could load 
most anything, anyway .. :-)

Grant NQ5T
K3 #2091 KX3 #8342


But as a new young ham (1960's) I bought a cantenna (paint can filled with 
mineral oil and resistor load immersed) for HF stuff and a Knight-Kit SWR 
meter.  But as I got older and had more cash I got better stuff.


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Re: [Elecraft] Dummy Load recommendation

[Grant Youngman]

As a new ham (1958-9) my "dummy load" was a 60 watt light bulb.  Even made a 
few local contacts with it.  Couldn’t afford anything else.  A good pi-network 
could load most anything, anyway .. :-)

Grant NQ5T
K3 #2091 KX3 #8342

> 
> But as a new young ham (1960's) I bought a cantenna (paint can filled with 
> mineral oil and resistor load immersed) for HF stuff and a Knight-Kit SWR 
> meter.  But as I got older and had more cash I got better stuff.
> 

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Re: [Elecraft] Dummy Load recommendation

[Edward R Cole]

This discussion reminds me that most on this list are HFers and never 
go above 30mcs (MHz).  Or buy all their ham stuff and believe the 
mfrs specs or meters without question.  Probably do not build 
homebrew equipment so never had to measure if such-an-such actually 
is working (and at what level).

By now I should have made a few of you angry at my post.   Good!

For most arm-chair operators a Bird and Bird load will be more than 
adequate to determine power and SWR to +/- 5% full scale reading.  It 
was my main antenna meter when working as a professional 
technician.  Rugged, fairly accurate, dependable (don't drop it off the tower).


A good non-inductive 50-ohm resistive load and a scope able to 
measure over 50-MHz will do better.


Next some better directional couplers will give more accurate return 
loss (SWR).


My "standard" is using better than good directional couplers (>20 dB) 
with my HP-432A mw power meter using  up to 10 mw signal 
sources.  This is usable to 18 GHz.  With use of high power coax 
attenuators, I can measure power as high as the rating of the 
attenuator.  I use 50-dB directional couplers on 1296 to measure my 
600w amp (58 dBm).


XG3 is a good 1mw source (0 dBm) up to 200-MHz, though not real 
accurate in frequency (which is not that important for 
power/reflected power).  But harmonic energy exists unless you use a 
filter since the output is a square wave.


I recently bought a used Bird HP 8202 500w load (good to 2500-MHz) 
which I can use with amps up to 1500w (as long as transmission is 
kept short - less than a minute; most tests take only a few 
seconds).  I have a Bird 25w load which I have used up to 150w for 
short measurements.  If it feels hot stop  until cool again.


But as a new young ham (1960's) I bought a cantenna (paint can filled 
with mineral oil and resistor load immersed) for HF stuff and a 
Knight-Kit SWR meter.  But as I got older and had more cash I got better stuff.


A dummy load that you can trust to be SWR 1:1 is good thing to check 
those SWR meters or antenna analyzers with.  Handy when measurements 
seem to be "all over the map".  Use it to test coax cables, for instance.


73, Ed - KL7UW
  http://www.kl7uw.com
Dubus-NA Business mail:
  dubus...@gmail.com 


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Re: [Elecraft] Dummy Load recommendation

[john]

I have a 500 watt and 1000 watt Bird dummy loads and they are well  
made.  These are not toys. I believe that they are rated for average  
continuous power and I do not agree that they need to be rated for 2X+  
the transmitted power, especially for intermittent use like most of us  
do.


John KK9A



Bob McGraw K4TAX wrote:
I agree that Bird dummy loads are some of the best.  Be sure to get  
one rated for at least your maximum power anticipated.  And do allow a  
margin of safety. I use 2x, thus for 100 watts I use a 250 watt rated  
load.


I purchase all of my power measurement equipment from NM3E.COM.

Bob, K4TAX

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Re: [Elecraft] Dummy Load recommendation

[Charlie T]

The secret to using wire-wound resistors for a 50Ω load is to use a lot of them 
in parallel as the inductance divides just as the value does for the number of 
resistors.
Of course, this is only reasonable if you already have a pawful to start with.  
Otherwise, RF rated, big 50Ω non-inductive resistors are available from many 
sources.
I had a lot of 1200 Ω, 10 watt (light blue??) wire-wound resistors, so 24 of 
them between two pieces of G-10 made a decent HF dummy load with a good safety 
factor at 100 watts.

Another handy load, is one that will show 2:1 (100Ω) or 3:1 (150Ω) SWR.  It 
wouldn't have to take much power as you'd only be using it to check an SWR 
readout, etc.
I made a few out of a couple 2W resistors. They'll take reasonable power for a 
very short  (½ second??) check time.

73, Charlie k3ICH



-Original Message-
From: elecraft-boun...@mailman.qth.net  On 
Behalf Of CUTTER DAVID via Elecraft
Sent: Tuesday, July 23, 2019 6:44 AM
To: hawley, charles j jr ; Art Nienhouse 

Cc: Elecraft@mailman.qth.net
Subject: Re: [Elecraft] Dummy Load recommendation)

I often wonder just how useful a precision dummy load really is in the amateur 
service.  I picked up home brew dummy load at the club the other day.  It 
measured 57ohms dc and comprises 4 wire-wound resistors attached in a cluster 
across the end of the coax.  After lots of disparaging remarks I put it on the 
VNA and it didn't look at all bad out to 30MHz: nothing over 1.5:1 and no 
spikes or dips to indicate resonances. I'll have to do it again and make a 
print-out for posterity. 
I've heard that salt water in a bucket works after a fashion.  
So the question is: how good do you need it to be?
David G3UNA 

 

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Re: [Elecraft] Dummy Load recommendation

[CUTTER DAVID via Elecraft]

I agree with all that has been said and suspect a lot of responders on this 
list are or were engineers who are used to using precision equipment.  I think 
it can be misleading to look at some instruments built into a transceiver for 
instance, but it never seemed to matter, until Elecraft came along.  I did my 
calibration with a Bird power meter and a Bird 500W load but I have no idea 
when they were last calibrated, so, what value do I put on the measurements?  
Well, it's good enough for me. But calibration is a special case and I'd never 
heard of amateurs calibrating for power before Elecraft.  Accurate power meters 
are costly to buy and maintain if you are in business, but for me now I'm 
retired it doesn't matter so much because I'm not doing it for a paying 
customer.  I think we are misled by the easy precision of the digital 
multimeter which for a few £ or $ is ten times as good as what we previously 
thought were good analogue instruments.  In short, I think technology can cause 
us to bite our finger nails unnecessarily.  10% or 20% power error is hardly 
noticeable to the guy on the other side of the world.  

David G3UNA


> On 23 July 2019 at 16:16 Bob McGraw K4TAX  wrote:
> 
> 
> Yes a calorimeter is the better way to measure power.   Not inexpensive 
> however. 
> 
> Bob, K4TAX
> 
> 
> Sent from my iPhone
> 
> > On Jul 23, 2019, at 10:07 AM, W2xj  wrote:
> > 
> > If you really want precision, use a water cooled load. Measure the flow 
> > rate and input and output temperature. You can precisely calculate power. 
> > 
> > Sent from my iPad
> > 
> >> On Jul 23, 2019, at 9:38 AM, Bob McGraw K4TAX  wrote:
> >> 
> >> Since power meter systems are calibrated at a known impedance {usually 50 
> >> ohms}, and they are voltage sensing devices, any deviation from the 
> >> calibration value will introduce an error in power indication.  It just 
> >> depends on how precise one prefers to be with power measurements.
> >> 
> >> 100 watts into 50 ohms is 70.71 volts
> >> 
> >> 100 watts into 55 ohms is 74.16 volts
> >> 
> >> 100 watts into 45 ohms is 67.08 volts
> >> 
> >> 73
> >> 
> >> Bob, K4TAX
> >> 
> >> 
> >>> On 7/23/2019 5:43 AM, CUTTER DAVID via Elecraft wrote:
> >>> I often wonder just how useful a precision dummy load really is in the 
> >>> amateur service.  I picked up home brew dummy load at the club the other 
> >>> day.  It measured 57ohms dc and comprises 4 wire-wound resistors attached 
> >>> in a cluster across the end of the coax.  After lots of disparaging 
> >>> remarks I put it on the VNA and it didn't look at all bad out to 30MHz: 
> >>> nothing over 1.5:1 and no spikes or dips to indicate resonances. I'll 
> >>> have to do it again and make a print-out for posterity.
> >>> I've heard that salt water in a bucket works after a fashion.
> >>> So the question is: how good do you need it to be?
> >>> David G3UNA
> >>> 
> >>> 
>  On 22 July 2019 at 23:58 "hawley, charles j jr"  
>  wrote:
>  
>  
>  Used Bird Attenuator is a good deal.
>  
>  https://nm3e.com/AttenuatorSampler.htm
>  
>  Then you’ll have a sample to plug into your counter or scope
>  
>  Chuck Jack Hawley
>  KE9UW
>  
> >>> __
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> >>> Help: http://mailman.qth.net/mmfaq.htm
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> >> 
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Re: [Elecraft] Dummy Load recommendation

[W2xj]

It doesn’t have to be that expensive. I have built several. DIY is as good as 
buying the finished product. 

Sent from my iPad

> On Jul 23, 2019, at 11:16 AM, Bob McGraw K4TAX  wrote:
> 
> Yes a calorimeter is the better way to measure power.   Not inexpensive 
> however. 
> 
> Bob, K4TAX
> 
> 
> Sent from my iPhone
> 
>> On Jul 23, 2019, at 10:07 AM, W2xj  wrote:
>> 
>> If you really want precision, use a water cooled load. Measure the flow rate 
>> and input and output temperature. You can precisely calculate power. 
>> 
>> Sent from my iPad
>> 
>>> On Jul 23, 2019, at 9:38 AM, Bob McGraw K4TAX  wrote:
>>> 
>>> Since power meter systems are calibrated at a known impedance {usually 50 
>>> ohms}, and they are voltage sensing devices, any deviation from the 
>>> calibration value will introduce an error in power indication.  It just 
>>> depends on how precise one prefers to be with power measurements.
>>> 
>>> 100 watts into 50 ohms is 70.71 volts
>>> 
>>> 100 watts into 55 ohms is 74.16 volts
>>> 
>>> 100 watts into 45 ohms is 67.08 volts
>>> 
>>> 73
>>> 
>>> Bob, K4TAX
>>> 
>>> 
 On 7/23/2019 5:43 AM, CUTTER DAVID via Elecraft wrote:
 I often wonder just how useful a precision dummy load really is in the 
 amateur service.  I picked up home brew dummy load at the club the other 
 day.  It measured 57ohms dc and comprises 4 wire-wound resistors attached 
 in a cluster across the end of the coax.  After lots of disparaging 
 remarks I put it on the VNA and it didn't look at all bad out to 30MHz: 
 nothing over 1.5:1 and no spikes or dips to indicate resonances. I'll have 
 to do it again and make a print-out for posterity.
 I've heard that salt water in a bucket works after a fashion.
 So the question is: how good do you need it to be?
 David G3UNA
 
 
> On 22 July 2019 at 23:58 "hawley, charles j jr"  
> wrote:
> 
> 
> Used Bird Attenuator is a good deal.
> 
> https://nm3e.com/AttenuatorSampler.htm
> 
> Then you’ll have a sample to plug into your counter or scope
> 
> Chuck Jack Hawley
> KE9UW
> 
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>> 
>> 
> 
> 
> 

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Re: [Elecraft] Dummy Load recommendation

[Bob McGraw K4TAX]

Yes a calorimeter is the better way to measure power.   Not inexpensive 
however. 

Bob, K4TAX


Sent from my iPhone

> On Jul 23, 2019, at 10:07 AM, W2xj  wrote:
> 
> If you really want precision, use a water cooled load. Measure the flow rate 
> and input and output temperature. You can precisely calculate power. 
> 
> Sent from my iPad
> 
>> On Jul 23, 2019, at 9:38 AM, Bob McGraw K4TAX  wrote:
>> 
>> Since power meter systems are calibrated at a known impedance {usually 50 
>> ohms}, and they are voltage sensing devices, any deviation from the 
>> calibration value will introduce an error in power indication.  It just 
>> depends on how precise one prefers to be with power measurements.
>> 
>> 100 watts into 50 ohms is 70.71 volts
>> 
>> 100 watts into 55 ohms is 74.16 volts
>> 
>> 100 watts into 45 ohms is 67.08 volts
>> 
>> 73
>> 
>> Bob, K4TAX
>> 
>> 
>>> On 7/23/2019 5:43 AM, CUTTER DAVID via Elecraft wrote:
>>> I often wonder just how useful a precision dummy load really is in the 
>>> amateur service.  I picked up home brew dummy load at the club the other 
>>> day.  It measured 57ohms dc and comprises 4 wire-wound resistors attached 
>>> in a cluster across the end of the coax.  After lots of disparaging remarks 
>>> I put it on the VNA and it didn't look at all bad out to 30MHz: nothing 
>>> over 1.5:1 and no spikes or dips to indicate resonances. I'll have to do it 
>>> again and make a print-out for posterity.
>>> I've heard that salt water in a bucket works after a fashion.
>>> So the question is: how good do you need it to be?
>>> David G3UNA
>>> 
>>> 
 On 22 July 2019 at 23:58 "hawley, charles j jr"  
 wrote:
 
 
 Used Bird Attenuator is a good deal.
 
 https://nm3e.com/AttenuatorSampler.htm
 
 Then you’ll have a sample to plug into your counter or scope
 
 Chuck Jack Hawley
 KE9UW
 
>>> __
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>>> Message delivered to rmcg...@blomand.net
>> 
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Re: [Elecraft] Dummy Load recommendation

[W2xj]

If you really want precision, use a water cooled load. Measure the flow rate 
and input and output temperature. You can precisely calculate power. 

Sent from my iPad

> On Jul 23, 2019, at 9:38 AM, Bob McGraw K4TAX  wrote:
> 
> Since power meter systems are calibrated at a known impedance {usually 50 
> ohms}, and they are voltage sensing devices, any deviation from the 
> calibration value will introduce an error in power indication.  It just 
> depends on how precise one prefers to be with power measurements.
> 
> 100 watts into 50 ohms is 70.71 volts
> 
> 100 watts into 55 ohms is 74.16 volts
> 
> 100 watts into 45 ohms is 67.08 volts
> 
> 73
> 
> Bob, K4TAX
> 
> 
>> On 7/23/2019 5:43 AM, CUTTER DAVID via Elecraft wrote:
>> I often wonder just how useful a precision dummy load really is in the 
>> amateur service.  I picked up home brew dummy load at the club the other 
>> day.  It measured 57ohms dc and comprises 4 wire-wound resistors attached in 
>> a cluster across the end of the coax.  After lots of disparaging remarks I 
>> put it on the VNA and it didn't look at all bad out to 30MHz: nothing over 
>> 1.5:1 and no spikes or dips to indicate resonances. I'll have to do it again 
>> and make a print-out for posterity.
>> I've heard that salt water in a bucket works after a fashion.
>> So the question is: how good do you need it to be?
>> David G3UNA
>> 
>> 
>>> On 22 July 2019 at 23:58 "hawley, charles j jr"  
>>> wrote:
>>> 
>>> 
>>> Used Bird Attenuator is a good deal.
>>> 
>>> https://nm3e.com/AttenuatorSampler.htm
>>> 
>>> Then you’ll have a sample to plug into your counter or scope
>>> 
>>> Chuck Jack Hawley
>>> KE9UW
>>> 
>> __
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Re: [Elecraft] Dummy Load recommendation

[Don Wilhelm]

David,

If your use of the dummy load is only to provide a load to the 
transmitter for things like a quick "does it work" check, then precision 
is not necessary.  Anything that presents an SWR of 1.5 or less would be 
adequate.


OTOH, if you want to do things like the TX Gain Calibration of the K3 or 
KX2/3, or do measurements with a 'scope (or other measuring device) 
across the dummy load, then better precision is required if one expects 
the results to be meaningful and accurate.


In other words, if your expectation of measurement accuracy is a range 
of +/-50%, then using a load with a 1.5 SWR is acceptable.  If your 
expectation requires an error of less than 10%, then more precision is 
required.  That goes for not only dummy loads, but any other measurement 
instrument.


Parallel non-reactive resistors in a can of mineral oil can be used 
effectively up to 200 watts in a quart can, while up to the legal limit 
can be obtained in a gallon can of oil (Heathkit Cantenna style).  Those 
can be easily homebrewed and the amount of precision depends on the 
resistors used and the care with construction.


73,
Don W3FPR

On 7/23/2019 6:43 AM, CUTTER DAVID via Elecraft wrote:

I often wonder just how useful a precision dummy load really is in the amateur 
service.  I picked up home brew dummy load at the club the other day.  It 
measured 57ohms dc and comprises 4 wire-wound resistors attached in a cluster 
across the end of the coax.  After lots of disparaging remarks I put it on the 
VNA and it didn't look at all bad out to 30MHz: nothing over 1.5:1 and no 
spikes or dips to indicate resonances. I'll have to do it again and make a 
print-out for posterity.

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Re: [Elecraft] Dummy Load recommendation

[Bob McGraw K4TAX]

Since power meter systems are calibrated at a known impedance {usually 
50 ohms}, and they are voltage sensing devices, any deviation from the 
calibration value will introduce an error in power indication.  It just 
depends on how precise one prefers to be with power measurements.


100 watts into 50 ohms is 70.71 volts

100 watts into 55 ohms is 74.16 volts

100 watts into 45 ohms is 67.08 volts

73

Bob, K4TAX


On 7/23/2019 5:43 AM, CUTTER DAVID via Elecraft wrote:

I often wonder just how useful a precision dummy load really is in the amateur 
service.  I picked up home brew dummy load at the club the other day.  It 
measured 57ohms dc and comprises 4 wire-wound resistors attached in a cluster 
across the end of the coax.  After lots of disparaging remarks I put it on the 
VNA and it didn't look at all bad out to 30MHz: nothing over 1.5:1 and no 
spikes or dips to indicate resonances. I'll have to do it again and make a 
print-out for posterity.
I've heard that salt water in a bucket works after a fashion.
So the question is: how good do you need it to be?
David G3UNA



On 22 July 2019 at 23:58 "hawley, charles j jr"  wrote:


Used Bird Attenuator is a good deal.

https://nm3e.com/AttenuatorSampler.htm

Then you’ll have a sample to plug into your counter or scope

Chuck Jack Hawley
KE9UW


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Re: [Elecraft] Dummy Load recommendation

[CUTTER DAVID via Elecraft]

I often wonder just how useful a precision dummy load really is in the amateur 
service.  I picked up home brew dummy load at the club the other day.  It 
measured 57ohms dc and comprises 4 wire-wound resistors attached in a cluster 
across the end of the coax.  After lots of disparaging remarks I put it on the 
VNA and it didn't look at all bad out to 30MHz: nothing over 1.5:1 and no 
spikes or dips to indicate resonances. I'll have to do it again and make a 
print-out for posterity. 
I've heard that salt water in a bucket works after a fashion.  
So the question is: how good do you need it to be?
David G3UNA 


> On 22 July 2019 at 23:58 "hawley, charles j jr"  wrote:
> 
> 
> Used Bird Attenuator is a good deal.
> 
> https://nm3e.com/AttenuatorSampler.htm
> 
> Then you’ll have a sample to plug into your counter or scope
> 
> Chuck Jack Hawley
> KE9UW
>
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Re: [Elecraft] Dummy Load recommendation

[Bob McGraw K4TAX]

I agree that Bird dummy loads are some of the best.  Be sure to get one rated 
for at least your maximum power anticipated.  And do allow a margin of safety. 
I use 2x, thus for 100 watts I use a 250 watt rated load. 

I purchase all of my power measurement equipment from NM3E.COM.  

Bob, K4TAX


Sent from my iPhone

> On Jul 22, 2019, at 5:58 PM, hawley, charles j jr  
> wrote:
> 
> Used Bird Attenuator is a good deal.
> 
> https://nm3e.com/AttenuatorSampler.htm
> 
> Then you’ll have a sample to plug into your counter or scope
> 
> Chuck Jack Hawley
> KE9UW
> 
> Sent from my iPhone, cjack
> 
> On Jul 22, 2019, at 4:59 PM, Art Nienhouse 
> mailto:ka9...@gmail.com>> wrote:
> 
> 
> __
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Re: [Elecraft] Dummy Load recommendation

[Walter Underwood]

If you can solder, or would like to learn, I recommend the RFL-100 kit from Oak 
Hills Research. Simple kit, large parts for easy soldering. It will support 100 
W continuous. I used their BNC/UHF converter so it would have a BNC jack. Nice 
deal for $50.

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

Here are some photos from my RFL-100 build.

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

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

> On Jul 22, 2019, at 3:58 PM, hawley, charles j jr  
> wrote:
> 
> Used Bird Attenuator is a good deal.
> 
> https://nm3e.com/AttenuatorSampler.htm
> 
> Then you’ll have a sample to plug into your counter or scope
> 
> Chuck Jack Hawley
> KE9UW
> 
> Sent from my iPhone, cjack
> 
> On Jul 22, 2019, at 4:59 PM, Art Nienhouse 
> mailto:ka9...@gmail.com>> wrote:
> 
> 
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Re: [Elecraft] Dummy Load recommendation

[hawley, charles j jr]

Used Bird Attenuator is a good deal.

https://nm3e.com/AttenuatorSampler.htm

Then you’ll have a sample to plug into your counter or scope

Chuck Jack Hawley
KE9UW

Sent from my iPhone, cjack

On Jul 22, 2019, at 4:59 PM, Art Nienhouse 
mailto:ka9...@gmail.com>> wrote:


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Re: [Elecraft] Dummy Load recommendation

[Lynn W. Taylor, WB6UUT]

If you had an HTML dummy load, it'd be invisible.

Set your mail client to send E-Mail in plain text, please.

On 7/22/2019 2:58 PM, Art Nienhouse wrote:


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Re: [Elecraft] Dummy load

[Don Wilhelm]

All,

Every ham should have a dummy load capable of the maximum power output 
of the amplifier IMHO.


The "Cantenna" serves well for the purpose of checking the amplifier 
operation and determining if a problem observed is the result of 
"RF-in-the-shack" or an amplifier problem.


A precision 50 ohm load is not required for those purposes.

If you intend to do calibration operations, then the "Cantenna" is 
"iffy" unless you can be certain it is 50 ohms non-reactive (check with 
an antenna analyzer at the frequency of interest).


If you need to do calibrations and make measurements of actual RF 
voltages, then you do need a known 50 ohm non-reative dummy load, and 
the "cantenna" types likely do not 'hack it'.


73,
Don W3FPR

On 5/1/2019 2:32 PM, Bob McGraw K4TAX wrote:
Those gallon bucket dummy loads, often referred to as "Cantenna" loads, 
are inexpensive and generally work OK to a limit.  They do have specific 
power limitations vs. time such as 1 minute at 1KW.   Also, they may not 
be 50 ohms.   Yes, the label says 50 ohms, but is it?   All 3 of mine 
measure differently.  One as high as 68 ohms.   And they change 
impedance as they heat.   I've purchased all of mine new and two are now 
quite old.  The 3rd one is 3 years old and has migrated up a few 
ohms.    Beware of hamfest bargains unless you know what you are buying.


On the other hand and for many more , the loads made by Bird and 
Celwave and other commercial loads are more reliable and accurate.  They 
also cost a lot more money.   And even with these, beware of hamfest 
bargains unless you know what you are buying.


Here is a link to the company I've dealt with for Bird products. 
https://www.nm3e.com/loadSampler.htm#LoadSampler



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Re: [Elecraft] Dummy load

[Bob McGraw K4TAX]

Those gallon bucket dummy loads, often referred to as "Cantenna" loads, 
are inexpensive and generally work OK to a limit.  They do have specific 
power limitations vs. time such as 1 minute at 1KW.   Also, they may not 
be 50 ohms.   Yes, the label says 50 ohms, but is it?   All 3 of mine 
measure differently.  One as high as 68 ohms.   And they change 
impedance as they heat.   I've purchased all of mine new and two are now 
quite old.  The 3rd one is 3 years old and has migrated up a few 
ohms.    Beware of hamfest bargains unless you know what you are buying.


On the other hand and for many more , the loads made by Bird and 
Celwave and other commercial loads are more reliable and accurate.  They 
also cost a lot more money.   And even with these, beware of hamfest 
bargains unless you know what you are buying.


Here is a link to the company I've dealt with for Bird products. 
https://www.nm3e.com/loadSampler.htm#LoadSampler


Accurate and known value loads are necessary when measuring power.   
Most power meters and measurements are accurate at 50 ohms.  Use a 
different impedance load or one that has changed value and the power 
meter will become one of questionable accuracy.


73

Bob, K4TAX


On 5/1/2019 7:40 AM, Mark Goldberg wrote:

How much do you want to spend?

One of these Bird Termaline series, or similar is the top of the line, but
will cost you:

https://www.birdrf.com/Products/Test%20and%20Measurement/Loads/Coaxial-Terminations/500-watts/8201_500-Watt-Oil-Cooled-Terminations.aspx

I was lucky to find a DA412B/U military surplus 600W dummy (similar to Bird
8401) load at a hamfest for cheap.The good ones have N or better connectors
and Hams tend to avoid them. Adapters are not expensive if you want to
connect to PL259s, but I actually use Ns in most of my station. It will
take a continuous key down from my KPA500 with no problem.

73,

Mark


On Wed, May 1, 2019 at 5:04 AM richard gilley 
wrote:


Hi,
Would like a recommendation for a 500 watt dummy load.

Thank you all
Richard  AD1G
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Re: [Elecraft] Dummy load

[Mark Goldberg]

How much do you want to spend?

One of these Bird Termaline series, or similar is the top of the line, but
will cost you:

https://www.birdrf.com/Products/Test%20and%20Measurement/Loads/Coaxial-Terminations/500-watts/8201_500-Watt-Oil-Cooled-Terminations.aspx

I was lucky to find a DA412B/U military surplus 600W dummy (similar to Bird
8401) load at a hamfest for cheap.The good ones have N or better connectors
and Hams tend to avoid them. Adapters are not expensive if you want to
connect to PL259s, but I actually use Ns in most of my station. It will
take a continuous key down from my KPA500 with no problem.

73,

Mark


On Wed, May 1, 2019 at 5:04 AM richard gilley 
wrote:

> Hi,
> Would like a recommendation for a 500 watt dummy load.
>
> Thank you all
> Richard  AD1G
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Re: [Elecraft] Dummy load

[Ariel Jacala]

Are you a radio amateur?  I don't see a call sign.

Ariel

Sent from my iPad

On Aug 19, 2013, at 2:21 PM, Rick Bleda rbled...@gmail.com wrote:

 I feel like the dummy, but I just bought and put together the DL-1 from
 Elecraft, and I have no clue how to use it. Can someone help? I need step
 by step instructions: ( lol
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Re: [Elecraft] Dummy load

[Don Wilhelm]

Rick,

A dummy load is something that you connect to a transmitter which you 
want to test without using an antenna.
It provides a good 50 ohm resistive load to the transmitter whereas an 
antenna feedline impedance can vary all over the place (transmitters are 
designed to operate into a 50 ohm resistive load).


When the transmitter is not in use, it is wise to connect the antenna 
output to a dummy load - the transmitter will be better protected from 
static surges coming in on the antenna feedline - those surges can 
damage the transmitter or receiver.


Do not exceed the power rating of the dummy load.

The Elecraft DL1 has a diode detector that allows you to use your DMM to 
measure the recified DC voltage and compute the actual power using the 
formula in the instruction manual.


Another use of a dummy load is on ATUs that have more than one antenna 
port - connect the dummy load to any unused port just in case that ANT 
is accidentally selected.  You transmitter will be loaded with the 
proper load rather than transmitting into an open circuit (that can 
damage the transmitter)


73,
Don W3FPR

On 8/19/2013 2:21 PM, Rick Bleda wrote:

I feel like the dummy, but I just bought and put together the DL-1 from
Elecraft, and I have no clue how to use it. Can someone help? I need step
by step instructions: ( lol



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Re: [Elecraft] Dummy load

[Mike WA8BXN]

I guess the first step is deciding what you want to do with it. They are
generally connected to the output of a transmitter in place of an antenna.
Then you can test the transmitter without causing interference to others. As
described in the manual, you can use a volt meter with it to determine the
amount of power coming out of the transmitter. 

 

73 - 

Mike WA8BXN 

 

 

 

 

 

---Original Message--- 

 

From: Rick Bleda 

Date: 8/19/2013 2:21:54 PM 

To: Elecraft@mailman.qth.net 

Subject: [Elecraft] Dummy load 

 

I feel like the dummy, but I just bought and put together the DL-1 from 

Elecraft, and I have no clue how to use it. Can someone help? I need step 

by step instructions: ( lol
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Re: [Elecraft] Dummy load

[Mike K2MK]

Hi Rick,

Connect your transmitter output to the BNC input of the DL-1. A dummy load
allows you to test your transmitter without sending your transmitted RF
signal into an antenna where it can cause unintentional interference to
others. The DL-1 has a 20 watt limit. You can also attach a voltmeter to the
test points for a voltage measurement that translates to watts of output per
the chart in the manual.

73,
Mike K2MK


Rick Bleda wrote
 I feel like the dummy, but I just bought and put together the DL-1 from
 Elecraft, and I have no clue how to use it. Can someone help? I need step
 by step instructions: ( lol





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View this message in context: 
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Re: [Elecraft] Dummy load

[Dick Dievendorff]

Hi, Rick!

You connect the Dummy load to the antenna connector of your transmitter
using a short jumper coax connector (or a dual-male BNC adapter, if
appropriate).  Now the transmitter sees a very nice antenna, approximately
50 ohm resistive impedance.  You can transmit (within the power limits of
your dummy load) and the transmitter should see more or less a 1:1 SWR load.

I use dual plug BNC adapter to connect my DL-1 to the K3 KXV3 transverter
output connector during the milliwatt Tx gain calibration. 

The adapter looks something like this:

http://www.mouser.com/ProductDetail/Amphenol-RF/31-218-RFX/?qs=sGAEpiMZZMvKc
Ua6gL0RXDfubrP3pdc2hl1EOgQvgOU%3d

73 de Dick, K6KR


-Original Message-
From: elecraft-boun...@mailman.qth.net
[mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Rick Bleda
Sent: Monday, August 19, 2013 11:22 AM
To: Elecraft@mailman.qth.net
Subject: [Elecraft] Dummy load

I feel like the dummy, but I just bought and put together the DL-1 from
Elecraft, and I have no clue how to use it. Can someone help? I need step by
step instructions: ( lol
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Re: [Elecraft] Dummy Load

[Ron D'Eau Claire]

James, today a dummy load is a highly-recommended and inexpensive tool in
any modern ham shack. Any of the popular brands are fine for aligning your
K3. You do NOT need an expensive precision laboratory load.

If you are a dedicated QRP operator, a low powered load is fine. Keep in
mind that the fastest way to destroy a dummy load is to overload it. Having
a dummy load rated for substantially more than the power you plan to run is
a wise investment, especially when you realize that most dummy loads are
rated for only short transmissions lasting several seconds at their rated
power. It's all a matter of being to dissipate the heat. 

On line, www.rfparts.com  offers a wide variety of dummy loads - many used
and tested - for power ranges of a few watts up to hundreds of watts and at
good prices. For up to 100 watts they are under $100. 

Elecraft offers a nice QRP dummy load, the DL-1, in kit form that also
allows you to do power measurements using a common DMM. See
http://www.elecraft.com/mini_module_kits/mini_modules.htm (scroll down the
page) 

If you want to do a little soldering, the Tom, N0SS (SK) web site has
excellent plans for rolling your own loads at a very low cost:

http://www.n0ss.net/dl_30w_hf-uhf.pdf

Personally, I have an MFJ 1.5 kW dummy load that has done excellent service
for decades: http://www.mfjenterprises.com/Product.php?productid=MFJ-264

There are a number of other dummy loads at various prices and power ranges
on the MFJ web site. 

73, Ron AC7AC

-Original Message-
From: elecraft-boun...@mailman.qth.net
[mailto:elecraft-boun...@mailman.qth.net] On Behalf Of James
Sent: Friday, July 20, 2012 11:15 AM
To: Elecraft@mailman.qth.net
Subject: [Elecraft] Dummy Load

What is the recommended solution to the requirement of a 5w dummy load
during assembly of the K3?


 73  James / K1SD / Rhode Island

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Re: [Elecraft] Dummy Load

[Jim Wiley]

Any 50-ohm non-inductive load will do, as long as it will handle the 
power.  You can use any one of a number of commercial products, or 
Elecraft has the DL-1 kit that will do.  Just make sure the load is of 
good quality.  A light bulb does not meet this requirement.  It is very 
possible to make a suitable load using one of the Caddock 50-watt 50-ohm 
chip resistors and a heat-sink.


- Jim, KL7CC

James wrote:
 What is the recommended solution to the requirement of a 5w dummy load
 during assembly of the K3?


  73  James / K1SD / Rhode Island



 -Original Message-
 From: elecraft-boun...@mailman.qth.net
 [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Art Nienhouse
 Sent: Friday, July 20, 2012 1:17 PM
 To: Elecraft@mailman.qth.net
 Subject: [Elecraft] K3 with the w2ihy audio gear

 Scott
 I have been using Julius 8 band box since he first came out with it and
 still have it driving K3.
 The main reason is the noise gate is better than the gate in the K3, the
 gate in the K3 needs to have more canceling on the back ground noise I can
 literally watch tv with the volume low four foot from the mic and talk on
 the radio with out the tv audio coming in over my voice, and its easier /
 faster to turn off the audio effects or change the gate as well.
 It will surly killed the amplifier fan noise as well used to chase grids on
 144 mHz the Command II fan was very noisy the Julius box gate fixed that
 problem.

 I use the ATR 30 which I bought for $22  a few years ago and it came with a
 16 ft cable XLR to 1/4 in plug , I have a GOLDLINE PRO as well the only
 difference is the PRICE.


 Regards
 Art
 ka9zap
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Re: [Elecraft] Dummy Load

[Bob]

Hi James,

 Very good quality used ones, and pretty cheap too, here:

https://www.ridgeequipment.com/store/dummyloads.html

Nice additions to the tool box for the future for $12 (75W)  or $7.5 (15w).  
Pick up any adapters you may need too.

NFI but a satisfied customer.

73,
Bob
K2TK  ex KN2TKR (1956)  K2TKR

On 7/20/2012 2:15 PM, James wrote:
 What is the recommended solution to the requirement of a 5w dummy load
 during assembly of the K3?


   73  James / K1SD / Rhode Island



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Re: [Elecraft] Dummy Load

[N5GE]

Good afternoon James,

You are not restricted to a 5w dummy load, you can use any dummy load of 5w or
greater.

If you don't have a dummy load, Elecraft has a 20w dummy load kit:
DL1 Wideband 20W Dummy Load

You can find it at: http://www.elecraft.com/mini_module_kits/mini_modules.htm

Enjoy your K3!

Amateur Radio Operator N5GE
ARRL Lifetime Member
QCWA Lifetime Member


On Fri, 20 Jul 2012 14:15:12 -0400, James jms_k...@verizon.net wrote:

What is the recommended solution to the requirement of a 5w dummy load
during assembly of the K3?


 73  James / K1SD / Rhode Island

[snip]

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Re: [Elecraft] Dummy Load

[Don Wilhelm]

James, there are many possibilities, but if you want a quality dummy 
load at a reasonable price that is also flat (is a constant 50 ohms 
non-reactive) to above 500 MHz, take a look at the 75 watt dummy load 
offered by Ridge Equipment 
https://www.ridgeequipment.com/store/index.html.  It is $12, but you 
will likely want to buy an adapter to the N connector if you don't have 
one already.

Caution, this dummy load is rated at 75 watts, but I would not try to 
push it to 100, even for a short time - those elements are touchy.

73,
Don W3FPR

On 7/20/2012 2:15 PM, James wrote:
 What is the recommended solution to the requirement of a 5w dummy load
 during assembly of the K3?


   73  James / K1SD / Rhode Island



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Re: [Elecraft] Dummy Load

[ab2tc]

Hi,

I highly recommend this dummy load. I have 3 of them and I routinely expose
them to 100+ watts for short periods. My IC-7200 typically puts out 120W on
a 14V supply. I do not think these dummy loads are touchy at all. They are
probably mostly thermally limited although it's likely that something will
fuse if really high power is applied. 100+ watts, no problem IMHO.

AB2TC - Knut

PS: NFI here, too, but a very satisfied customer.




Don Wilhelm-4 wrote
 
 James, there are many possibilities, but if you want a quality dummy 
 load at a reasonable price that is also flat (is a constant 50 ohms 
 non-reactive) to above 500 MHz, take a look at the 75 watt dummy load 
 offered by Ridge Equipment 
 https://www.ridgeequipment.com/store/index.html.  It is $12, but you 
 will likely want to buy an adapter to the N connector if you don't have 
 one already.
 
 Caution, this dummy load is rated at 75 watts, but I would not try to 
 push it to 100, even for a short time - those elements are touchy.
 
 73,
 Don W3FPR
 
 snip




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Re: [Elecraft] Dummy Load

[Ron D'Eau Claire]

The danger of applying too much power to a dummy load is overheating the
element. That will change the resistance of the element so it will no longer
be a 50-ohm dummy load. One can drive the resistance of the load far from 50
ohms - typically to a much higher resistance - before it opens or fuses
completely. 

73, Ron AC7AC

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Re: [Elecraft] Dummy Load

[Bill Frantz]

I built my own using 3 150 ohm 2 watt resistors from Fry's 
Electronics. I put them in parallel with the wires on one side 
soldered to the center connector of a coax connector. I bent the 
other wires back over the resistors and soldered them, along 
with some coax braid to the connector shell. Testing the result 
with a MFJ antenna analyzer showed 1.0:1 through the HF bands 
and about 1.3:1 on 2 meters. Result: a 6 watt dummy load.

For more power, I probably would by a commercial dummy load, but 
this solution involved the least travel and elapsed time.

Cheers - Bill, AE6JV

On 7/20/12 at 11:15, jms_k...@verizon.net (James) wrote:

What is the recommended solution to the requirement of a 5w dummy load
during assembly of the K3?
---
Bill Frantz| I don't have high-speed  | Periwinkle
(408)356-8506  | internet. I have DSL.| 16345 
Englewood Ave
www.pwpconsult.com |  | Los Gatos, 
CA 95032

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Re: [Elecraft] Dummy load for KPA3?

[Bob]

I'd buy this:

https://www.ridgeequipment.com/store/dummyloads.html

75 watts and $12.   I've been happy with mine bought a couple of years ago.

73,
Bob
K2TK  ex KN2TKR (1956)  K2TKR


On 2/7/2012 10:11 AM, Jim Miller wrote:
 I'm considering adding the amp to my k3/10. I see a 50w dummy load is reqd
 for setup. Any recommendations? Should I get a 100w one instead?

 Build vs buy?

 73

 jim ab3cv



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Re: [Elecraft] Dummy load for KPA3?

[Ron D'Eau Claire]

Jim, dummy loads are invariably rated for limited periods of time before
they must be allowed to cool off. So a larger dummy load allows you to feed
it power longer. For example, I have a 1.5 KW dummy load that will handle
1.5 kW, but for less than 10 seconds between cool-down periods. It'll handle
100 watts for ten minutes before needing to cool down. 

A practical dummy load for Ham use is not a highly-precise load. Such loads
are available at a price for lab work, but not needed to check a transmitter
output in the real world. That said, be careful when buying a used load.
Since they require cool-down periods, many loads are sold used after they
have been overheated and the resistance element has been damaged.  

There are many built units available. I picked up an MFJ-264 years ago. It's
rated at 1.5 KW, 1-650 MHz and still available new for under $80. 

You can roll your own these days too. Resistive elements are readily
available. The biggest part of the project is providing a suitable heat
sink. Tom, N0SS (SK) has notes and design suggestions for building a dummy
load on his web site which is still active:

http://www.n0ss.net/index_general.html

Ron AC7AC

-Original Message-
From: elecraft-boun...@mailman.qth.net
[mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Jim Miller
Sent: Tuesday, February 07, 2012 7:11 AM
To: Elecraft Reflector
Subject: [Elecraft] Dummy load for KPA3?

I'm considering adding the amp to my k3/10. I see a 50w dummy load is reqd
for setup. Any recommendations? Should I get a 100w one instead?

Build vs buy?

73

jim ab3cv

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Re: [Elecraft] Dummy load for KPA3?

[Dick Dievendorff]

I have acquired a number of dummy loads over the years.

A lot depends on your ultimate needs.  If you buy the minimum now, you might
end up buying something larger later.

For the purposes of K3/100 Tx Gain Calibration, you'll need a dummy load
that can dissipate 50 watts for short periods.  Tx Gain calibration holds
the key down on each of 6 frequencies at the 5 and 50 watt power levels for
about 4-10 seconds at a time.  

If you're careful, that can be handled by something as small as an MFJ-261
that is rated for 30 watts or 100 watts peak.  I burned mine up while
testing Tx Gain Calibration when I stepped through the code with a debugger
and left the transmitter on for too long.  I didn't replace it. It's a very
convenient size.

I recently bought a pair of 75 watt dummy loads from Ridge Equipment. I'm
using them for an antenna tuner project where I want the load to be really
just resistive on all interesting frequencies. They come with N connectors,
so you might need an SO-239 adapter that Ridge Equipment also sells.  I like
these very much.  They are like new, and present an SWR  1.02 up to about
700 MHz.  At 3 GHz they get all the way up to 1.12.
https://www.ridgeequipment.com/store/dummyloads.html

If you eventually expect to use an amplifier, perhaps a higher power dummy
load would be a good investment.  

A dry dummy load like an AEA-1500 or Palstar DL-1500 can handle 100 watts
for extended periods (10 minutes or so) or 1500 watts for a few (10)
seconds.

If you need to support key down at full 1500 watt power for a few minutes,
you might want a can filled with mineral oil, such as the old Heath Cantenna
or Ameritron ADL-2500 or MFJ -2500.

If you're testing high power amplifiers for extended periods, you might need
to invest in something with a fan, such as the Palstar DL2K, DL5K, Ameritron
ADL-2500 or MFJ-265.  The high end of these is the Alpha 2100, which
reportedly handles 1500 watts indefinitely.  It is what RF Concepts calls a
legacy product, however.

I normally think of a dummy load as something I'd use primarily in testing
and calibration, but I've recently thought of a good use for it in a contest
multi-radio antenna switching project when I need an antenna to switch an
exciter to during band transitions.  I don't want to leave the antenna
connection open or shorted while I switch a radio to a band where another
nearby radio could be transmitting, so a low power dummy load is just a
perfect antenna for this. The receiver is somewhat protected from same
band transmitters, and if the exciter is keyed it won't see a load that
exercises the transceiver's protection circuitry.  

73 de Dick, K6KR






-Original Message-
From: elecraft-boun...@mailman.qth.net
[mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Jim Miller
Sent: Tuesday, February 07, 2012 7:11 AM
To: Elecraft Reflector
Subject: [Elecraft] Dummy load for KPA3?

I'm considering adding the amp to my k3/10. I see a 50w dummy load is reqd
for setup. Any recommendations? Should I get a 100w one instead?

Build vs buy?

73

jim ab3cv
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Re: [Elecraft] Dummy load for KPA3?

[Don Wilhelm]

That Ridge Equipment dummy load is very good - I would recommend it 
highly for any measurement or calibration work.  I would not exceed 75 
watts with it.
If you want a dummy load to leave connected to your K3 when not in use 
and general all-around the shack work, you might want to consider 
building one in a quart paint filled with mineral oil - see: 
http://www.k4eaa.com/dummy.html - I have two similar dummy loads here in 
quart cans and a larger one in a gallon can that have served well for 
many, many years.

73,
Don W3FPR

On 2/7/2012 11:17 AM, Bob wrote:
 I'd buy this:

 https://www.ridgeequipment.com/store/dummyloads.html

 75 watts and $12.   I've been happy with mine bought a couple of years ago.

 73,
 Bob
 K2TK  ex KN2TKR (1956)  K2TKR


 On 2/7/2012 10:11 AM, Jim Miller wrote:
 I'm considering adding the amp to my k3/10. I see a 50w dummy load is reqd
 for setup. Any recommendations? Should I get a 100w one instead?

 Build vs buy?

 73

 jim ab3cv

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Re: [Elecraft] Dummy load for KPA3?

[Jim Miller]

thanks all. went with the ridge eqp suggestion.

73

jim ab3cv
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