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Dummy loads for dummies

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Don Wilhelm

Re: Dummy loads for dummies

Clay,

Unless things have changed since I tested the Caddock Thick Film Power
resistors of other than 50 ohms, I would not parallel 20 1000 ohm
resistors to produce a 50 ohm load. Values other than 50 ohms are not
guaranteed to be non-reactive.

I would put 4 strings of 4 50 ohm resistors in series in parallel. Each
resistor mounted with leads as short as possible.

I don't know about the dissipation characteristics of those resistors
mounted in oil, and I suspect it depends on the heatsinking ability of
the resistor mountings when immersed in the oil.
20 100 watt resistors *should* produce a 2000 watt load, but as I
indicated, it depends on the dissipation of the individual resistors and
how fast they can transfer their heat to the oil. It may be necessary
to attach the resistors to a heat sink and immerse those heat sink
assemblies into the oil.

For all those who are looking for a suitable dummy load for high power,
you usually do not have to be concerned about measurement quality
impedance. Something adequate to provide a suitable load for the
amplifier may be all that is needed. Having a precision 50 ohm load is
a requirement for measurement, but not for routine amplifier tuning and
general operating procedures.

73,
Don W3FPR

73,
Don W3FPR

On 12/27/2016 7:16 PM, Clay Autery wrote:

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Elecraft mailing list

Re: Dummy loads for dummies

In reply to this post by Clay Autery

They make similar resistors up to 800 watt or more, see them on ebay
all the time, they are even made in 25 ohm or 100 ohm so you can
series or parallel them to what you need, easy to make a dummy load that
will handle many KW with just a couple. Large heat sink needed.

> Makes me curious about designing with these TO-220 resistors in the 1000
> Ohm size of appropriate power rating... Parallel 20 of them like folks
> do on the axials that they put in the can type dummy loads with oil.
>
> Options:
>
> 1) 20 in parallel on a finned copper or bare aluminum sink of sufficient
> size and then entire assembly in a oil wetted container.
> 2) Same, but only the finned side of the finned/pinned heat exchanger in
> a coolant bath.
>
> I'd like to have a rugged, high power, key down load built from easily
> obtainable and replaceable parts.
>
> ______________________
> Clay Autery, KY5G
> MONTAC Enterprises
> (318) 518-1389
>
> On 12/27/2016 5:52 PM, Mel Farrer via Elecraft wrote:
>> One thing I might also add in. I use the Film TO-220 style non-inductive resistors with a heat sink in the 200 ohm 1% configuration to test 4:1 baluns at 100 watt level to confirm non saturation on the small QRP baluns I make.
>> Mel, K6KBE
>>
>>
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Jim Brown-10

Re: Dummy loads for dummies

In reply to this post by Paul C

On Tue,12/27/2016 12:22 PM, Paul C wrote:
> It seems tuff to get going in QRP.

Hi Paul,

The only thing "special" about antennas for QRP operation is that
BECAUSE you're QRP, you want the most efficient antennas that you can.
And the simple answer to that is to study the fundamentals in the ARRL
Handbook and the ARRL Antenna Book.

And if you plan to operate portable, you want the most efficient
antennas that are easy to carry, and to rig when you get to your
operating QTH.

There are some tutorials on my website about antennas. They are written
for antennas in general, not just portable antennas.

The best portable antennas are mostly nothing more than wire. The things
you want to BUY are the wire and things that help you rig them. Look for
lightweight, telescoping poles that you can tape a wire to, and ways to
rig it more or less upright. Jackite poles are nice for this use.

Carry more wire to string out as radials. When you can, keep the radials
off the ground a few feet -- for example, string them through scrub
trees and brush. Build dipoles for situations when you can rig two ends
in trees. Find a lightweight method to toss weights tied to fishing line
into trees, tie light weight antenna rope to the line, pull it into the
tree(s), rig the antenna wire to that rope. I used to see a product
called a "wrist rocket" that is essentially a fishing reel attached to a
short rod for launching into a tree. If you're going to use fishing
weights, paint them a bright color so you can find them.

One of my buddies, N6RNO, is awfully good at simply tying a fishing
weight to a fishing line and using his arm as a sort of catapault to
launch wires into trees. He regularly gets our dipoles for CQP
(California QSO Party) county expeditions up 40 ft into trees. When I
first moved to CA 10 years ago, AE6RF did that using a half empty 16 oz
water jug.

Tossing a wire into a tree is also a great way to rig a vertical.

Whatever you do, don't waste a single penny on any commercial antenna
for portable use. Those popular (and expensive) poles antennas with
loading coils are poor antennas -- loading coils are the reason.

73, Jim K9YC

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Paul C

Re: Dummy loads for dummies

Thanks for the ideas, Jim. The tutorial I really want to see (or maybe make someday) is one about the KX1 operations for a complete QRP novice. Such a video would take the ham step by step demonstrating all the features and explain why xyz is important. I write software, and these kind of tutorials are tremendously helpful. It's a great way to encourage others to adopt your product.

It's too bad I won't be able to take my little rig with me on my backpacking trip, but there should be a next time. Thanks for all your good ideas. This is a great hobby.

73,
Paul KG5KXG

-----Original Message-----
From: "Jim Brown" <[hidden email]>
Sent: ‎12/‎27/‎2016 7:13 PM
To: "[hidden email]" <[hidden email]>
Subject: Re: [Elecraft] Dummy loads for dummies

On Tue,12/27/2016 12:22 PM, Paul C wrote:
> It seems tuff to get going in QRP.

Hi Paul,

The only thing "special" about antennas for QRP operation is that
BECAUSE you're QRP, you want the most efficient antennas that you can.
And the simple answer to that is to study the fundamentals in the ARRL
Handbook and the ARRL Antenna Book.

And if you plan to operate portable, you want the most efficient
antennas that are easy to carry, and to rig when you get to your
operating QTH.

There are some tutorials on my website about antennas. They are written
for antennas in general, not just portable antennas.

The best portable antennas are mostly nothing more than wire. The things
you want to BUY are the wire and things that help you rig them. Look for
lightweight, telescoping poles that you can tape a wire to, and ways to
rig it more or less upright. Jackite poles are nice for this use.

Carry more wire to string out as radials. When you can, keep the radials
off the ground a few feet -- for example, string them through scrub
trees and brush. Build dipoles for situations when you can rig two ends
in trees. Find a lightweight method to toss weights tied to fishing line
into trees, tie light weight antenna rope to the line, pull it into the
tree(s), rig the antenna wire to that rope. I used to see a product
called a "wrist rocket" that is essentially a fishing reel attached to a
short rod for launching into a tree. If you're going to use fishing
weights, paint them a bright color so you can find them.

One of my buddies, N6RNO, is awfully good at simply tying a fishing
weight to a fishing line and using his arm as a sort of catapault to
launch wires into trees. He regularly gets our dipoles for CQP
(California QSO Party) county expeditions up 40 ft into trees. When I
first moved to CA 10 years ago, AE6RF did that using a half empty 16 oz
water jug.

Tossing a wire into a tree is also a great way to rig a vertical.

Whatever you do, don't waste a single penny on any commercial antenna
for portable use. Those popular (and expensive) poles antennas with
loading coils are poor antennas -- loading coils are the reason.

73, Jim K9YC

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Wes Stewart-2

Re: Dummy loads for dummies

In reply to this post by Paul C

You might be interested in this: http://k6mhe.com/n7ws/Ladder_Line.pdf

On 12/27/2016 1:22 PM, Paul C wrote:
> Here's another naive idea of mine: I'm planning to use ladder line too. Now I'm waiting for the other shoe to drop, when I realize coax will be my only practical choice.
>
> Paul KG5KXG
>

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Nr4c

Re: Dummy loads for dummies

In reply to this post by Paul C

Carefull. Are they wire-wound power resisters cased in ceramic. If so they are likely inductive and of marginal use as withvRF they will not be just resistive but somewhat inductive and this will skew your results.

Sent from my iPhone
...nr4c. bill

> On Dec 27, 2016, at 9:43 AM, Paul C <[hidden email]> wrote:
>
> I made my own dummy load last night from two 100 ohm resistors wired in parallel. They are rated for 10 watts each and look like little bricks. I measured the resistance at 51 ohms. Do you think this is close enough or should I reduce it to 50?
>
> Paul KG5KXG
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Edward R Cole

Re: Dummy loads for dummies

In reply to this post by Paul C

http://www.kl7uw.com/2M80_inside_1.jpg

In the photo the large black square at bottom of the pc board is a
surface-mount 56-ohm 35w resistor (good at 2m) and available from
Mouser. I believe there were 51-ohm values also. This used in a
23-dB pi-attenuator to take 10w down to 50mw for driving a Toshiba
SAV-36 RF amplifier module in the 80w 2m amp that I build. W6PQL
sells 150w surface mount loads that are good at 1296 MHz. All you
need is a small pcb and a large heat sink.

TO-220 form probably more convenient as one can mount them directly
to a heat sink with a tapped hole for a 4-40 machine screw and using
a little heat sink compound. If the heat sink is large enough air
cooling is sufficient.

I have a big old Sierra Electronic 500w coaxial load with heat sink
and built in power meter; weighs about 40-50 lbs; makes a dandy door
stop, too! It is rated to 1000-MHz. Got in trade somewhere? I
would not want to pay retail for one; probably in range of $2/watt.

73, Ed - KL7UW
http://www.kl7uw.com
Dubus-NA Business mail:
[hidden email]

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Jim Brown-10

Re: Dummy loads for dummies

On Wed,12/28/2016 12:26 AM, Edward R Cole wrote:
> I have a big old Sierra Electronic 500w coaxial load with heat sink
> and built in power meter; weighs about 40-50 lbs; makes a dandy door
> stop, too! It is rated to 1000-MHz.

I found a nice oil-cooled dummy load with a big heat sink integral to it
at a hamfest many years ago. It's rated 500W continuous. That was a good
day. Doorstop -- you betcha! :) Measured it with my VNWA and found that
it's good well into UHF. No attached power meter though, but found a
nice Bird with some slugs on another day.

I've also found industrial quality 10W and 100W dummy loads at hamfests
that were salvaged from cell sites. One purchase yielded nearly ten of
them.

This is the sort of stuff I look for at hamfests (some call them flea
markets or swap meets). Also high quality connectors and adapters.

73, Jim K9YC

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David Olean

Re: Dummy loads for dummies

It always pays to keep your eyes open. The local (and only ) surplus
store here has a pile of heat sinks that look just great for a 250 watt
solid state PA. The good part is that they also have a pair of SMA
connectors, PC boards, and associated flanged 50 ohm resistor good for
several hundred watts. I think I paid $15 for one, so I got two DC to
2.4 GHz dummy loads for $7.50 each. It is easy to modify them for what
ever connector you want. Jim is right, but always bring a pocket ohm
meter! heh heh.

Dave K1WHS

On 12/28/2016 8:52 AM, Jim Brown wrote:

> On Wed,12/28/2016 12:26 AM, Edward R Cole wrote:
>> I have a big old Sierra Electronic 500w coaxial load with heat sink
>> and built in power meter; weighs about 40-50 lbs; makes a dandy door
>> stop, too! It is rated to 1000-MHz.
>
> I found a nice oil-cooled dummy load with a big heat sink integral to
> it at a hamfest many years ago. It's rated 500W continuous. That was a
> good day. Doorstop -- you betcha! :) Measured it with my VNWA and
> found that it's good well into UHF. No attached power meter though,
> but found a nice Bird with some slugs on another day.
>
> I've also found industrial quality 10W and 100W dummy loads at
> hamfests that were salvaged from cell sites. One purchase yielded
> nearly ten of them.
>
> This is the sort of stuff I look for at hamfests (some call them flea
> markets or swap meets). Also high quality connectors and adapters.
>
> 73, Jim K9YC
>
> ______________________________________________________________
> 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]
>

Mark Goldberg

Re: Dummy loads for dummies

I also found one of the big oil filled dummy loads at a Hamfest. It handles
500W easily. I bring a phone powered USB powered VNA with me to Hamfests to
check things out. You never know what you will find!

73,
Mark
W7MLG

On Dec 28, 2016 8:25 AM, "David Olean" <[hidden email]> wrote:

> It always pays to keep your eyes open. The local (and only ) surplus
> store here has a pile of heat sinks that look just great for a 250 watt
> solid state PA. The good part is that they also have a pair of SMA
> connectors, PC boards, and associated flanged 50 ohm resistor good for
> several hundred watts. I think I paid $15 for one, so I got two DC to 2.4
> GHz dummy loads for $7.50 each. It is easy to modify them for what ever
> connector you want. Jim is right, but always bring a pocket ohm meter! heh
> heh.
>
>
> Dave K1WHS
>
>
> On 12/28/2016 8:52 AM, Jim Brown wrote:
>
>> On Wed,12/28/2016 12:26 AM, Edward R Cole wrote:
>>
>>> I have a big old Sierra Electronic 500w coaxial load with heat sink and
>>> built in power meter; weighs about 40-50 lbs; makes a dandy door stop,
>>> too! It is rated to 1000-MHz.
>>>
>>
>> I found a nice oil-cooled dummy load with a big heat sink integral to it
>> at a hamfest many years ago. It's rated 500W continuous. That was a good
>> day. Doorstop -- you betcha! :) Measured it with my VNWA and found that
>> it's good well into UHF. No attached power meter though, but found a nice
>> Bird with some slugs on another day.
>>
>> I've also found industrial quality 10W and 100W dummy loads at hamfests
>> that were salvaged from cell sites. One purchase yielded nearly ten of them.
>>
>> This is the sort of stuff I look for at hamfests (some call them flea
>> markets or swap meets). Also high quality connectors and adapters.
>>
>> 73, Jim K9YC
>>
>> ______________________________________________________________
>> 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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ng7m

Re: Dummy loads for dummies

In reply to this post by Jim Brown-10

I guess I'll chime in on the dummy load discussion (pictures below). Over
the last few months, I have picked up a couple Bird Termaline Coaxial
Resistor dummy loads (these may be the models K9YC is referring to). I got
tired of the crappy cantenna style QRO loads that are typical of the
current Ham Radio market. The capillary motion of the oil getting all over
the top of the can... attracting dirt, bugs etc... these usually get
relegated to the garage sooner than later. (or dumpster) I have never seen
any leaking from the following Bird oil filled dummy loads. Nor have I had
to replace any of the gaskets.

This thread is a bit off topic at this point, but In my humble opinion, I
would consider the following Bird dummy loads to be ones to consider for
your shack. If you are patient on fleaBay, you will find some really good
deals, especially if you are willing to clean them up and have been filled
with the proper dielectric oil. I don't think anyone would buy one new...
over $800 for the Bird 8401 listed below for example. But at surplus /
used prices, if you can find one from $50 to $250, it will be the last QRO
dummy load you will ever buy. They all use Bird QC connectors like you
would find on a Bird 43 watt meter. If you make it through this email,
I'll admit I got a little obsessed with buying and cleaning up several Bird
dummy loads! I'm guilty as accused... ;)

*Bird 8401* (the perfect ham shack dummy load IMHO, still in production
<http://www.birdrf.com/Products/Terminations_Loads/Coaxial-Terminations/600-watts/8401_600-Watt-Oil-Cooled-Terminations.aspx>)
Over
$800 new???. I was very lucky to find a new / old stock one of these with
the cardboard still wrapped around it for $250 shipped. $250 for a dummy
load you ask??? Well for a commercial piece of Bird equipment that will
handle 600 watts continuous and is good from DC to 3ghz. De-rated, this
load will handle 1.5kw for 10 minutes easily and more if you put a fan on
it. This is more dummy load than I'll ever need in the shack and the one I
will never sell.

Here are pictures of my *Bird 8401*:
http://www.nc7j.com/downloads/ng7m/Bird8401DummyLoad/ (new old stock, no
cleanup required)

*Bird 8404* (identical to the 8401 except that it has an N connector gender
bender with mount on the front). I picked up one of these in rough shape
shipped for $52 shipped and restored it for my good buddy W7CT Jim. We
added new Shell dielectric transformer oil and the total cost was $82.

Here are pictures of W7CT's $82 *Bird 8404* (before and after cleanup with
new oil):
http://www.nc7j.com/downloads/W7CT/Bird%208404%20Coaxial%20Resistor%20Termaline/

*Bird 8201* Most common Bird 500 watt dummy load you will find on
fleaBay. Still
in production
<http://www.birdrf.com/Products/Terminations_Loads/Coaxial-Terminations/500-watts/8201_500-Watt-Oil-Cooled-Terminations.aspx>.
I picked up one of these in great shape shipped for ~$150. This will be
the easiest model to find and probably the best value. Rated from DC to
1ghz, it's probably the best bargain in a Bird QRO dummy load that is still
in production. Again, de-rated, this will handle 1.5kw for many minutes...
and more with a fan.

Before and after clean up pictures of my *Bird 8201 *(like new condition):
http://www.nc7j.com/downloads/ng7m/Bird8201DummyLoad/

*Bird 8135* Little brother dummy load to the 8401 / 8201, still in
production
<http://www.birdrf.com/Products/Terminations_Loads/Coaxial-Terminations/150-watts/8135_150-Watt-Oil-Cooled-Terminations.aspx>.
150 watts continuous. These are easily found on fleaBay in the $60 to $150
price range. 150 watts continuous. Good from DC to 4ghz with a bit higher
VSWR along the way. The one I found was like new and looks like the
current production pictures on the Bird website. A cool little oil filled
dummy load to pair up with your K3 line, or match with an 8201/8401.

*Bird 8166* Dry 150 watt continuous dummy load, good from DC to 2.5ghz with
a bit higher VSWR (no longer in production
<http://www.birdrf.com/~/media/Bird/Files/PDF/discontinued-manuals/920-8000S_coaxial-load-resistor.ashx>).
You can find these used for around $65 to $150.

Anyway, this is more information than most wanted to see in dummy loads!!
There are many other Bird models out there. I got over my Bird dummy load
obsession, but I'm happy with what I found and they all make a great
addition to the shack. There are certainly models from Bird that will
handle much more power, but I'm still of the opinion that the 84/82 line
are the perfect size for use in the shack.

Off my dummy load soap box.

Max NG7M

On Wed, Dec 28, 2016 at 1:52 AM, Jim Brown <[hidden email]>
wrote:

> On Wed,12/28/2016 12:26 AM, Edward R Cole wrote:
>
>> I have a big old Sierra Electronic 500w coaxial load with heat sink and
>> built in power meter; weighs about 40-50 lbs; makes a dandy door stop,
>> too! It is rated to 1000-MHz.
>>
>
> I found a nice oil-cooled dummy load with a big heat sink integral to it
> at a hamfest many years ago. It's rated 500W continuous. That was a good
> day. Doorstop -- you betcha! :) Measured it with my VNWA and found that
> it's good well into UHF. No attached power meter though, but found a nice
> Bird with some slugs on another day.
>
> I've also found industrial quality 10W and 100W dummy loads at hamfests
> that were salvaged from cell sites. One purchase yielded nearly ten of them.
>
> This is the sort of stuff I look for at hamfests (some call them flea
> markets or swap meets). Also high quality connectors and adapters.
>
> 73, Jim K9YC
>
>
> ______________________________________________________________
> 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]
>

--
M. George
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Richard Fjeld-2

Re: Dummy loads for dummies

In reply to this post by Wes Stewart-2

FWIW, comments to consider about open wire feedline from my experience:

Window line has shattered in the cold winter winds. Frost, snow, and ice
easily accumulates. It catches the wind easily.
On the plus side, window line conductors do not fold over on each other.
Conductors stay evenly spaced.

Ladder line does require measures to keep conductors from twisting and
folding over on each other. As Ron mentions, tension is necessary.
Ladder line has less problems in inclement weather. Ladder line is much
better in the wind.

I designed my loop and ladder line so that I can melt ice off it. That
would be more difficult to do with window line.

Dick, n0ce

On 12/28/2016 12:01 PM, Ron D'Eau Claire wrote:

> Wes makes an excellent point: "window" line and open wire line are not the
> same. Both the resistive losses in the relatively tiny wires in the window
> line and the webs of insulation impact its performance as described in his
> paper.
>
> My open wire line is homebrew, using #10 or #12 copper wire spaced with
> common "dog bone" insulators sold for end insulators. They hold the wires
> about 3 inches apart. Typically, one spacer every 3 or 4 feet is quite
> adequate to maintain the spacing with the lines under tension.
>
> 73, Ron AC7AC
>
>

Bill K9YEQ

Re: Dummy loads for dummies

And you can add a slight twist to reduce wind whipping, etc. I don't like
it, though. PITA for me.

73,
Bill
K9YEQ

-----Original Message-----
From: Elecraft [mailto:[hidden email]] On Behalf Of
Richard Fjeld
Sent: Wednesday, December 28, 2016 10:07 PM
To: [hidden email]
Subject: Re: [Elecraft] Dummy loads for dummies

FWIW, comments to consider about open wire feedline from my experience:

Window line has shattered in the cold winter winds. Frost, snow, and ice
easily accumulates. It catches the wind easily.
On the plus side, window line conductors do not fold over on each other.
Conductors stay evenly spaced.

Ladder line does require measures to keep conductors from twisting and
folding over on each other. As Ron mentions, tension is necessary.
Ladder line has less problems in inclement weather. Ladder line is much
better in the wind.

I designed my loop and ladder line so that I can melt ice off it. That would
be more difficult to do with window line.

Dick, n0ce

On 12/28/2016 12:01 PM, Ron D'Eau Claire wrote:
> Wes makes an excellent point: "window" line and open wire line are not
> the same. Both the resistive losses in the relatively tiny wires in
> the window line and the webs of insulation impact its performance as
> described in his paper.
>
> My open wire line is homebrew, using #10 or #12 copper wire spaced
> with common "dog bone" insulators sold for end insulators. They hold
> the wires about 3 inches apart. Typically, one spacer every 3 or 4
> feet is quite adequate to maintain the spacing with the lines under
tension.
>
> 73, Ron AC7AC
>
>
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