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Dummy Load recommendation

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Arthur Nienhouse

Dummy Load recommendation

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Lynn W. Taylor, WB6UUT-3

Re: Dummy Load recommendation

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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ke9uw

Re: Dummy Load recommendation

In reply to this post by Arthur Nienhouse

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 <[hidden email]<mailto:[hidden email]>> wrote:

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Chuck, KE9UW

Ken G Kopp

Dummy Load recommendation

I'll second this recommendation ...

73!

Ken Kopp - K0PP

On Mon, Jul 22, 2019, 17:08 Walter Underwood <[hidden email]> wrote:

> 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 <[hidden email]>
> 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 <[hidden email]<mailto:
> [hidden email]>> wrote:
> >
> >
> > ______________________________________________________________
> > 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
> > Message delivered to [hidden email]<mailto:[hidden email]>
> > ______________________________________________________________
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> > Home: http://mailman.qth.net/mailman/listinfo/elecraft
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:[hidden email]
> >
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Bob McGraw - K4TAX

Re: Dummy Load recommendation

In reply to this post by ke9uw

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 <[hidden email]> 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 <[hidden email]<mailto:[hidden email]>> wrote:
>
>
> ______________________________________________________________
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Elecraft mailing list

Re: Dummy Load recommendation

In reply to this post by ke9uw

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" <[hidden email]> 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
>

Charlie T, K3ICH

Re: Dummy Load recommendation

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: [hidden email] <[hidden email]> On Behalf Of CUTTER DAVID via Elecraft
Sent: Tuesday, July 23, 2019 6:44 AM
To: hawley, charles j jr <[hidden email]>; Art Nienhouse <[hidden email]>
Cc: [hidden email]
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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Bob McGraw - K4TAX

Re: Dummy Load recommendation

In reply to this post by Elecraft mailing list

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" <[hidden email]> 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
>>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
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>
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Don Wilhelm

Re: Dummy Load recommendation

In reply to this post by Elecraft mailing list

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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W2xj

Re: Dummy Load recommendation

In reply to this post by Bob McGraw - K4TAX

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 <[hidden email]> 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" <[hidden email]> 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
>>>
>> ______________________________________________________________
>> 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
>> Message delivered to [hidden email]
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
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>
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Bob McGraw - K4TAX

Re: Dummy Load recommendation

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 <[hidden email]> 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 <[hidden email]> 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" <[hidden email]> 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
>>>>
>>> ______________________________________________________________
>>> 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
>>> Message delivered to [hidden email]
>>
>> ______________________________________________________________
>> 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
>> Message delivered to [hidden email]
>
>

W2xj

Re: Dummy Load recommendation

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 <[hidden email]> 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 <[hidden email]> 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 <[hidden email]> 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" <[hidden email]> 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
>>>>>
>>>> ______________________________________________________________
>>>> 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
>>>> Message delivered to [hidden email]
>>>
>>> ______________________________________________________________
>>> 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
>>> Message delivered to [hidden email]
>>
>>
>
>
>

Elecraft mailing list

Re: Dummy Load recommendation

In reply to this post by Bob McGraw - K4TAX

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 <[hidden email]> 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 <[hidden email]> 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 <[hidden email]> 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" <[hidden email]> 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
> >>>>
> >>> ______________________________________________________________
> >>> 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
> >>> Message delivered to [hidden email]
> >>
> >> ______________________________________________________________
> >> 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
> >> Message delivered to [hidden email]
> >
> >
>
>
> ______________________________________________________________
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john@kk9a.com

Re: Dummy Load recommendation

In reply to this post by Arthur Nienhouse

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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Edward R Cole

Re: Dummy Load recommendation

In reply to this post by Arthur Nienhouse

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:
[hidden email]

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Grant Youngman-2

Re: Dummy Load recommendation

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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Jim Ragsdale

Re: Dummy Load recommendation

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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k6dgw

Re: Dummy Load recommendation

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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Don Wilhelm

Re: Dummy Load recommendation

In reply to this post by Elecraft mailing list

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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Elecraft mailing list

Re: Dummy Load recommendation

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 <[hidden email]> 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.