[Milsurplus] WTB: Hi Power Resistive (Dummy) Load (sort of OT)

[Dr. William J. Schmidt, II]

I bought my Bird 10kW dummy load off the Broadcast classifieds for $300 
brand new still in the box.  You best try there first, even if you have to 
post an add.  A local station engineer may even lend you one for the 
weekend...

Sincerely,

Dr. William J. Schmidt, II  K9HZ
Trustee of the North American QRO - Central Division Club - K9ZC

Email: bill at wjschmidt.com
WebPage: www.wjschmidt.com

"It's not what you take with you... but what you leave behind that counts. 
Live each day as if it were your last."


----- Original Message ----- 
From: "Peter Gottlieb" <nerd at verizon.net>
To: "Christian R. Fandt" <cfandt at netsync.net>
Cc: <r-390 at mailman.qth.net>; <milsurplus at mailman.qth.net>
Sent: Saturday, March 25, 2006 3:29 PM
Subject: Re: [Milsurplus] WTB: Hi Power Resistive (Dummy) Load (sort of OT)


> Can't you rent one?  The test equipment rental place I used to use up in 
> Massachusetts (in Woburn or Billerica?, was 15 years ago) had stuff like 
> that.  Renting isn't cheap being 10% of list per month typical, but $440 
> for a month of use will get your problem solved.
>
> Peter
>
>
> Christian R. Fandt wrote:
>> Hi folks,
>>
>> I'm looking for a 50 ohm dummy load to repair and maintain an industrial 
>> RF generator used to excite a 1 kW laser cutting system (namely, a Trumph 
>> TLF 1000). I searched the usual suspects (Google, e*ay, etc., including 
>> Fair Radio). Finally found one used equipment outfit in California that 
>> lists several of them being available but doesn't bother to take the time 
>> to reply to my price and delivery requests. I'll try again, but . . .
>>
>> The ideal would be a brand new Bird 8931-115SC13 with an optional 7/16 
>> connector installed (reference: 
>> http://www.bird-electronic.com/products/product.aspx?id=625 ). However, 
>> my friend who owns the shop that uses the laser almost passed out after 
>> hearing the $4400 price. It would be used once to repair the system and 
>> left setting until the next time, whenever that is. He just spent over 
>> $5k to replace the final tube per conclusion of a third-party laser 
>> cutting machine maintenance outfit. They reportedly said that was the 
>> problem causing the too high reflected power (the original problem that 
>> needs to be solved). Uh-huh! And the tech did not even have a dummy load 
>> with him to check the RF generator's performance and tuning after he came 
>> back to install the new tube. He left it back at the shop (~700 miles 
>> away) because "he didn't think he needed it".
>>
>> My task is to isolate the source of the high reflected power between 
>> either the laser "resonator" (which is the laser itself), the RF 
>> generator, or the coax cabling between the units and attack the problem. 
>> Hard to know were to solve the problem without ruling out portions of the 
>> system which are not the cause.
>>
>> Hence, my approach to these two groups for leads. You have been known to 
>> be a wellspring of information over the years.
>>
>> The RF power output is 6.5 kW maximum at 13.56 MHz which means a 7.5 to 
>> 10 kW load is needed. The connector is the 7/16 type (reference: 
>> http://www.amphenolrf.com/products/716.asp ) and I'd need to make an 
>> adaptor of some sort between whatever load I find and the system under 
>> test, if required. I work in a 2-way radio shop for my day job and I 
>> should be able to find components to make that up. We only know of loads 
>> available up to around 2 kW from all our sources; our typical max TX 
>> power we ever get into is 100-125 watts, even for base stations.
>>
>> FYI: The 7/16 connectors are a DIN standard commonly used in Europe for 
>> high power applications.
>> FYI: 13.56 MHz is an unlicensed frequency assigned for use in industrial 
>> applications.
>>
>> Please reply off list as this is not too on-topic.
>>
>> Thanks very much for your help!
>>
>> Regards,  Chris F.
>>
>> NNNN
>>
>> Christian Fandt,    Electronic/Electrical Historian
>> Jamestown, NY  USA      cfandt at netsync.net
>>         Member of Antique Wireless Association
>>         URL: http://www.antiquewireless.org/
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