1500W for up to 20 seconds according to their web site
73, Jim VE7FO
----- Original Message -----
From: "Jim Lux" <jimlux@earthlink.net>
To: towertalk@contesting.com
Sent: Friday, August 7, 2015 7:40:08 AM
Subject: Re: [TowerTalk] Phase Vertical Dummy Load
On 8/7/15 7:10 AM, David Robbins wrote:
> I use a vectronics DL-650m. Yes, it is overkill as it is rated at 1500w,
> but it is small enough to fit in an upside down coffee can for protection
> from the weather.
that small implies that it isn't rated for 100% duty cycle: I'll bet it
gets mighty hot, mighty quick at that power.
A smaller one would probably be ok most of the time as
> dump power normally should be 100w or less if you are well balanced... BUT
> (yes, the BIG BUT) if something happens to one of the verticals and you
> don't notice it right away a 100w or even 250w dummy load would fry pretty
> quickly.
The small air cooled load like the DL-650M will fry in a minute at that
kind of power
The MFJ_264 is quite similar in design, and they give a power vs time
chart (with a very non linear horizontal scale, which doesn't give me
much confidence in it). 1250W at 10 seconds, 250W at 50 seconds, 100W
indefinitely.
(which makes sense.. physically, it's the size of a big 100W power
resistor, but not a kilowatt power resistor)
So it really depends on how long "not notice it right away" is (e.g.
"what's that hot resistor smell?")
Actually, though, what is the maximum power that goes into the dump port
on one of those passive phasing units? Say one of the antennas is
shorted/open?
On a microwave 90 degree hybrid (like a Lange coupler), with all ports
except one properly terminated, the power into the load is down 6 dB
from the input power (3 dB because the input power is split between the
two output ports, another 3dB because the reflected power from the "bad"
port is split between the load and the input port).
On typical 4 square systems, the power division among elements isn't
equal (they're designed for equal element currents, and the feed point Z
isn't the same for all elements)
>
> David Robbins K1TTT
> e-mail: mailto:k1ttt@arrl.net
> web: http://wiki.k1ttt.net
> AR-Cluster node: 145.69MHz or telnet://k1ttt.net
>
>
> -----Original Message-----
> From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of
> john@kk9a.com
> Sent: Friday, August 07, 2015 13:44
> To: towertalk@contesting.com
> Subject: [TowerTalk] Phase Vertical Dummy Load
>
>
>
> I am curious what people are using for the dummy load used on phased
> vertical controllers and how they are mounted. I do NOT wish to have the
> dummy load in the shack. My plan is to have something that will be outside
> and work in a variety of temperatures. I can mount it in an enclosure
> however heat is a concern. Is air cooled better than the oil type outdoors?
> Who makes a quality dummy load that will work in this environment? What is
> the typical percentage of dump power across 80m?
> Any suggestions and pictures are welcome.
>
> 73,
> John
>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|