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Difference in dummy loads

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NJMike

Difference in dummy loads

I need to purchase a dummy load for use with my K2/100. What's the
difference between a dry dummy load and an air cooled dummy load? Which is
better?

Thanks,
Mike NJ2OM

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NJMike

Re: Difference in dummy loads

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Eric Norris-2

Re: Difference in dummy loads

In reply to this post by NJMike

Basically the same thing. I suggest the Vectronics DL-650 (dx engineering)
or a commercial pull from Ridge Equipment. For serious testing, I fire up
my 2GHz, 6kW water-cooled dummy load--louder than 10 KPA-1500s on PCP.

Always get more capacity than you need. --because you'll need it later. If
you get an amp, a high power dummy load is essential for tracking down
possible RFI. I keep a 50-watt dummy load on ANT2 of the K3S for a quick
TXGN CAL, and a DL-2500 on ANT2 of the KPA1500. But then, I love the smell
of a hot dummy load in the morning. It smells like...radio.

73 Eric WD6DBM

On Wed, Jul 1, 2020, 2:44 PM NJMike <[hidden email]> wrote:

> I need to purchase a dummy load for use with my K2/100. What's the
> difference between a dry dummy load and an air cooled dummy load? Which is
> better?
>
> Thanks,
> Mike NJ2OM
>
>
>
> --
> Sent from: http://elecraft.365791.n2.nabble.com/
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Don Wilhelm

Re: Difference in dummy loads

A dry dummy load is good for up to its power rating - but do not exceed
that rating. The air cooled dummy loads not only require power for the
fan, but may be over-rated for their power spec.

I prefer dry or oil immersed dummy loads.

A good dummy load should present a 1.0 SWR for all the bands of
interest. Check with an antenna analyzer. If you have access to a
vector analyzer, it should show 50 ohms resistive and zero reactance at
all frequencies of interest.

Those home-built with resistors can usually be OK up through 30 MHz, but
may fail at 50 MHz and above - and that includes the 'cantenna' types
(oil immersed resistors). careful construction is required to reduce
the inductance involved in the mounting and assembly.

I have 3 'cantenna' type dummy loads, two for 150 watts In quart cans
and one for 1000 watts in a gallon can. They are OK up through 30 MHz,
but not above that level.
They are good for loads on the transmitter, but are not sufficient for
precise measurement.

I also have 2 precision dummy loads that are good up into the GHz
region. Those are the ones that I use for measurements (up to 100
watts) And for the K3 TX Gain calibration. I have another that I rate
at 50 watts (using a 100 watt Caddock thick film resistor on a heatsink)
that is a good load up through 220 MHz.

None of mine are air cooled.

73,
Don W3FPR

On 7/1/2020 7:45 PM, Eric Norris wrote:

> Basically the same thing. I suggest the Vectronics DL-650 (dx engineering)
> or a commercial pull from Ridge Equipment. For serious testing, I fire up
> my 2GHz, 6kW water-cooled dummy load--louder than 10 KPA-1500s on PCP.
>
> Always get more capacity than you need. --because you'll need it later. If
> you get an amp, a high power dummy load is essential for tracking down
> possible RFI. I keep a 50-watt dummy load on ANT2 of the K3S for a quick
> TXGN CAL, and a DL-2500 on ANT2 of the KPA1500. But then, I love the smell
> of a hot dummy load in the morning. It smells like...radio.
>
> 73 Eric WD6DBM
>
> On Wed, Jul 1, 2020, 2:44 PM NJMike <[hidden email]> wrote:
>
>> I need to purchase a dummy load for use with my K2/100. What's the
>> difference between a dry dummy load and an air cooled dummy load? Which is
>> better?

KEN-3

Re: Difference in dummy loads

In reply to this post by NJMike

The difference between a "dry" and an "air cooled"? I think they are the
same. The difference is with "oil cooled". Heathkit used to sell a
"Cantenna" which was a dummy load in a gallon paint can. Add your own
transformer oil. IIRC it was rated for a KW for a short period.

Ken WA8JXM

On Wed, Jul 1, 2020 at 5:45 PM NJMike <[hidden email]> wrote:

Bill Frantz

Re: Difference in dummy loads

I have a MFJ-264 which is rated for 100W more or less
continuously and 1500W for 10 seconds. It seems to work within
its specs. I've used it at up to 1KW or so.

I assume it is like most MFJ equipment, it does what it is
specified to do, but don't push it even a little bit beyond.

73 Bill AE6JV

-----------------------------------------------------------------------
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(408)348-7900 | as a design you haven't | 150 Rivermead
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NH 03458

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NW0M

Re: Difference in dummy loads

In reply to this post by NJMike

Hi Mike,

Don't over-think this one. For 98% of us hams the MFJ dummy loads will work
fine.

The MFJ-260C is rated at 300 watts and sells for $50.

The MFJ-264 is rated for 1500 watts (an Ohio vendor sells it for $80) if you
think an amplifier is in your future plans.

73, Mitch

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NJMike

Re: Difference in dummy loads

I ordered the MFJ-260C. Thanks for all the replies!

Thanks,
Mike NJ2OM

> On Jul 2, 2020, at 6:44 AM, NW0M <[hidden email]> wrote:
>
> Hi Mike,
>
> Don't over-think this one. For 98% of us hams the MFJ dummy loads will work
> fine.
>
> The MFJ-260C is rated at 300 watts and sells for $50.
>
> The MFJ-264 is rated for 1500 watts (an Ohio vendor sells it for $80) if you
> think an amplifier is in your future plans.
>
> 73, Mitch
>
>
>
> --
> Sent from: http://elecraft.365791.n2.nabble.com/
> ______________________________________________________________
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Edward R Cole

Re: Difference in dummy loads

In reply to this post by NJMike

I bought an air-cooled Bird 8201 rated 500w to 3-GHz from e-bay for
$300. It can handle 1500w for short transmissions.

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

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Elecraft mailing list

Re: Difference in dummy loads

Buyer beware.
I bought a superb, almost new, almost unused Bird 8141, in its original box and it failed after a short while. Taking it apart it was obvious that it had been well and truly cooked. It must have been hammered. The main connection had corroded and separated from the element. I have photos. The solution was exceedingly cheap and easy: separate the parts from the body, wash with IPA etc, sit contact parts in tomato ketchup for a couple of hours, clean up and re-assemble.

David G3UNA/G6CP

> On 02 July 2020 at 18:16 Edward R Cole <[hidden email]> wrote:
>
>
> I bought an air-cooled Bird 8201 rated 500w to 3-GHz from e-bay for
> $300. It can handle 1500w for short transmissions.
>
> 73, Ed - KL7UW
> http://www.kl7uw.com
> Dubus-NA Business mail:
> [hidden email]
>
> ______________________________________________________________
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