| Author |
Message |
    
Sinker
Member
Username: Sinker
Post Number: 91
Registered: 8-2005
| | Posted on Thursday, September 22, 2005 - 10:10 am: | 
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I have seen from many posts that it is good to have a dummy load. Why is this???
Will one of these let me know if my meters are accurate???
What should I look for in a Dummy Load???
I will use it with the following system:
Base: Texas Ranger 696F SSB Base
Antenna: Maco V-5000
Amp: KLV-1000
Meter: Workman 3 face 5000
Think Copper has one that would meet my needs???
Or I guess more importantly do I even need one???
Just a dummy asking about dummy loads.
Thanks guys,
Tim
CEF-634 |
Hotwire
Advanced Member
Username: Hotwire
Post Number: 578
Registered: 1-2005
| | Posted on Thursday, September 22, 2005 - 12:55 pm: |
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A dummy load allows you to work on a radio and test it without an antenna. I believe doing things such as setting peak wattage a dummy load is needed instead of an antenna for technical reasons above my head. |
Bruce
Senior Member
Username: Bruce
Post Number: 3131
Registered: 9-2003
| | Posted on Thursday, September 22, 2005 - 1:34 pm: |
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It's also the law Testing must be done off the air except for short transmissions. HEATHKIT for many years marketed a 1 gallon can with oil inside of it and a 50 ohm resistor ..... The CANTENNA was a great simple way to comply....... and lasted decades. |
Moderator1516
Moderator
Username: Moderator1516
Post Number: 43
Registered: 8-2005
| | Posted on Thursday, September 22, 2005 - 6:49 pm: |
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i wonder how one of these could be made,how would you connect the coax
moderator1516
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Allagator
Advanced Member
Username: Allagator
Post Number: 688
Registered: 9-2002
| | Posted on Thursday, September 22, 2005 - 7:21 pm: |
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i made 2 useing a old mason jars but one was was only rated at 10 watts max but i do have one i made that will take 100 watts ! ill look for the info and post it !
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Kid_vicious
Advanced Member
Username: Kid_vicious
Post Number: 680
Registered: 9-2004
| | Posted on Thursday, September 22, 2005 - 7:25 pm: |
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if you wanted to make your own "cantenna" you would need some high wattage reated resistors, (carbon composition so they are non-inductive) that equal 50ohms when placed in parallel.
it would go like this:
(3)150ohm resistors=50ohms.
(6)300ohm resistors=50ohms.
(20)1,000ohm resistors=50ohms
if you used 1 watt resistors the power handling capability would be:
3 watts
6 watts
20 watts.
to make one out of a paint can; drill a hole in the lid big enough for an SO-239 to fit through.
mount the SO-239 in the lid with the coax side facing out. twist together all of the ends of your resistors so it looks like one big ugly resistor, and solder the ends.
solder one side to the center terminal of the SO-239 and put a bolt through the can near the bottom; solder the other end of your big resistor
to a spade connector and then to the bolt.
if the can has no oil in it, then it will handle the rating of the resistors.
im not sure how much more power it will handle if you fill it with oil, (use type F transmission fluid) but someone else on here might know.
sinker, go to the place that you got your guy rope from and see if they have a dummy load that will handle 1,000 watts.
that's how much you'll need to use it with your KLV-1000.
you'll use it to tune up the amp on the freq. you are on and then switch to your antenna.
this will keep you from annoying others while you tune up.
matt |
Patzerozero
Senior Member
Username: Patzerozero
Post Number: 1532
Registered: 7-2004
| | Posted on Saturday, September 24, 2005 - 6:42 pm: |
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i know this dummy-load up the street...if i could just wrap his mic cord around his neck once... |
Tech291
Moderator
Username: Tech291
Post Number: 238
Registered: 11-2004
| | Posted on Saturday, September 24, 2005 - 8:57 pm: |
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Sinker,
A dummy antenna load will allow you to work on a radio or tune your amature amplifier without transmitting interference over the airwaves.the online auction services are a good source of the larger ones you would need to use with an amp the size of the klv-1000.I obtained mine from such a place.it was mil surplus n.i.b. for $35.00 + shipping.While I havnt found its exact rating it will handle a klv-1000 and hardley get warm.it is one of the air cooled,cast aluminum types and originally had a giant bnc type connector which I changed to a flange type so-239.
tech291
cef#291
kc8zpj
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Xlaxx
Intermediate Member
Username: Xlaxx
Post Number: 289
Registered: 4-2002
| | Posted on Monday, September 26, 2005 - 11:49 pm: |
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It is a good practice to test off-the-air. Especially tuning an amplifier for SSB.
A dummy load is a wise investment.
Decide what your wattage needs are and get a decent load to handle it.
Bird makes fine dummy loads.
...check internet auction sites,... but beware!
73
XLAXX
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Therealporkchop
Intermediate Member
Username: Therealporkchop
Post Number: 448
Registered: 11-2002
| | Posted on Friday, November 04, 2005 - 5:09 pm: |
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True statements so far...
My two cents about dummy loads...ever been listening to the radio and heard some bozo whistling and the classic "audio" being said, over and over and over and over. Well, a dummy load would cure that problem cause they wouldn't be on the air.
Another useful purpose is with co-phased antennas, you hook it to one side of your line, that way you fool the SWR meter into thinking you have a perfect match on that side. Then you adjust the remaining antenna. Then you change it out for the dummy load and put the antenna back on the side you first had your load hooked to. Then you can adjust it as well, and if all goes well you'll end up with a system that is correctly adjusted.
On the bench, the dummy load serves the purpose of removing the antenna to do away with interferrence but also gives a more true reading of what the transmitter is doing. It can also be helpful to eliminate capacitance which is what an antenna has, giving a more correct deadkey and swing reading on a meter. Sometimes you'll see less when using the dummy load, so if you like to see bigger numbers I'd test on the antenna!
Also when used on either a base or mobile setup, it helps to eliminate the antenna as a problem, so you can decide if it's radio or coax that is causing the problems... |
Hollowpoint445
Advanced Member
Username: Hollowpoint445
Post Number: 884
Registered: 6-2004
| | Posted on Friday, November 04, 2005 - 7:45 pm: |
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Just something to consider - if you connect a dummy load to an antenna switch, and there's an antenna connected to to the switch, unless the switch has very high isolation you'll be transmitting a little on the antenna when switched to the dummy load.
A friend of mine used his dummy load that way and didn't believe me when I told him I could hear his testing. I repeated every word he said into his dummy load and then he believed me. He bought a better switch that's marketed as having very high isolation and the problem went away. |
