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Author Topic: What makes this dummy load so expensive  (Read 9060 times)
M6YDB
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Posts: 47




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« on: September 30, 2013, 09:18:24 AM »

I needed a dummy load to tune my TS-830S with so bought one off ebay that looked suitable, second hand for around £17 ($25).

When looking for some further details on it I managed to track down the datasheet etc from here:

http://uk.rs-online.com/web/p/rf-dummy-loads/0613690/

Why on earth do they cost the best part of £500 new ($750).  Surely there can't be anything about them that causes them to be that expensive?

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NO2A
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« Reply #1 on: September 30, 2013, 09:59:34 AM »

Maybe cause it uses Beryllium Oxide and goes up to 2ghz? I really don`t know. A good old Cantenna can handle about 1kw,and is all most hams would ever need. If you`re using a dry dummy load they can get awfully hot,even at 100 watts. I have a built in one in my MFJ 989C. It works fine,but I would never run more than 100 watts to it,regardless of what they say. MFJ actually claims it can handle a kw for 10 seconds. Not from my amp it won`t! Btw: the ARRL lab tested that tuner years ago and said it was a 90 watt dummy load!
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G3RZP
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« Reply #2 on: September 30, 2013, 10:09:22 AM »

RS have always been expensive: the BeO won't help keep the price down.

Note it is only rated to take the output of the TS830 for 2 minutes.
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M6YDB
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« Reply #3 on: September 30, 2013, 10:20:30 AM »

Thanks for the responses.

I had seen the power chart - I just use it for tuning the valves.  Send for a few seconds to tune and off again, on again for another few seconds and off.

Doesn't get remotely warm and I use the 'Tune' function also.

Am building up to making the dummy load Ken K4EAA has on his hyrbid pages but needed something in the meantime.
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KA5IPF
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« Reply #4 on: September 30, 2013, 10:37:23 AM »

I needed a dummy load to tune my TS-830S with so bought one off ebay that looked suitable, second hand for around £17 ($25).

When looking for some further details on it I managed to track down the datasheet etc from here:

http://uk.rs-online.com/web/p/rf-dummy-loads/0613690/

Why on earth do they cost the best part of £500 new ($750).  Surely there can't be anything about them that causes them to be that expensive?



That's the difference between a commercial grade accurate dummy load good to 2 gHz and a ham grade sorta accurate and good maybe thru the HF bands.
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M6YDB
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Posts: 47




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« Reply #5 on: September 30, 2013, 11:37:07 AM »

Same seller has another one listed if anyone is interested...

http://www.ebay.co.uk/itm/50-ohm-Professional-Dummy-Load-50WCW-ex-equipment-N-Connector-/181224114694?pt=UK_Mobile_Phones_Communication_Ham_Radio_Receivers_Transceivers&hash=item2a31cc8a06

Does say it came from a commercial set up...
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M6GOM
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Posts: 914




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« Reply #6 on: September 30, 2013, 11:39:26 AM »

It is quite hard to maintain a constant impedance over a wide frequency range. Your average 50 Ohm resistor starts going well out of spec long before 150MHz.
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G3RZP
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« Reply #7 on: September 30, 2013, 01:21:34 PM »

Suspend the load in a gallon can of cold water - keeping the connector dry. that will extend the time you can dissipate 100 watts. Such a can could be a used paint tin, although any house decorating here is done either by the XYL or a professional.

My rule after my mother asked me to do some painting and then complained about the quality.....we didn't speak for 6 months after that!
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TANAKASAN
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« Reply #8 on: October 01, 2013, 03:39:16 AM »

G3RZP, I feel your pain but it is possible to go too far the other way. Most people when painting will sand, undercoat, maybe sand again then put on a top coat of gloss. My grandfather would sand, undercoat, sand, undercoat, sand, gloss, sand, gloss and once he had finished you could use the finished piece as a shaving mirror.

As for the dummy load, it's expensive because it's from RS Components, I've seen these bandits charge four times the price for a standard part that was available over the counter from Electrovalue (now no longer around). I always purchase stuff like this from hamfests or make my own.

Tanakasan
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G3RZP
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« Reply #9 on: October 01, 2013, 08:16:21 AM »

Tanakasan,

Often Farnell are cheaper. RS and Farnell do so well because they have stuff in stock, you can get it the next day, and it's convenient for engineers and buyers - but it costs. Like you, I buy at hamfests or from component suppliers who don't rip you off - and there are some specialising in selling to amateurs.
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G7MRV
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« Reply #10 on: October 09, 2013, 02:38:44 PM »

Both RS and Farnell/CPC are expensive as they hold massive stocks available for next day courier delivery. If your job cannot wait for parts, and most professionals cant due to very tight contract service level agreements, then you pay a premium for the availability.

Excellent surplus loads can be found on the auction sites these days, especially here in the UK, with the demise of analogue TV. Look for loads by Bird or AFL (Aerial Facilities Ltd) These are UHF and higher broadcast quality, and can be had for a fraction of the cost of new
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WN2C
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Posts: 453




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« Reply #11 on: October 13, 2013, 09:02:44 AM »

Anybody who pays the 'new' price for that dummy load for use in ham radio is a DUMMY!
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