[Lowfer] Re:RF Milliammeter - Great Info. !!!

[Andy - KU4XR]

Thanks Todd:  

That's some good information to save, and bookmark. 
I appreciate all the suggestions and info I have
gotten since I put the beacon on the air. Many operators
have offered me their wisdom and experiences. I'll continue
trying ways to improve the signal.

73, and have a good day;  Andy " XR " 





> Hi Andy,
> Like Charlie W5COV mentioned the clamp-on RF ammeter by
> Kyle K0LR
> is supposed to be a good one that you can build.
>  
> Thermocouple RF milliammeters are pretty rare these days.
> The one I used is  
> the RF Ammeter from the ART-13 transmitter. It shows a
> scale of 0-5 Amps  but 
> the actual meter movement is around .075 A or 75 milliamps
> I think but  don't 
> remember exactly. It has a self-contained thermocouple. The
> ART-13 RF  ammeter 
> is still available from Fair Radio Sales for $25 each. 
>  
> I built a test setup to calibrate the meter by using a
> variac and two  6.3vac 
> small filament transformers in series, the 6.3v secondary
> of one  going to 
> the primary of the second one to double step down the input
> to a  very low AC 
> voltage. This is safe enough to connect directly across the
>  ART-13 meter if you 
> make sure to start at zero voltage first and slowly  bring
> up the variac.  I 
> calibrated the one I have by running the very low  level
> 60Hz AC thru it with 
> a Fluke DVM in series set to a low AC amps scale and 
> varying the voltage thru 
> it with the variac and calibrating the scale with  the
> Fluke DVM.  60Hz AC 
> will calibrate an RF
> ammeter nicely as the thermocouple reading will change very
> little when  
> reading 
> 60Hz to LF frequencies. This setup can be used to calibrate
> other low-scale  
> reading RF milliammeters.
>  
>  A good one-watt Lowfer setup should easily put more than
> 100  milliamps of 
> RF current into the antenna/ground system. But starting out
> with a  less than 
> optimum setup you will probably be well under 100 milliamps
> RF. You  can always 
> put a shunt resistor across the RF milliammeter to increase
> the  full-scale 
> reading to your liking.
>  
> John W1TAG has a good article on RF Ammeters for LF use :
>  
> _http://www.w1tag.com/RFA.htm_
> (http://www.w1tag.com/RFA.htm) 
>  
>  
> 73 Todd WD4NGG
>  
>  
> 
> 
> 
> **************Looking for simple solutions to your
> real-life financial 
> challenges?  Check out WalletPop for the latest news and
> information, tips and 
> calculators.     
> (http://www.walletpop.com/?NCID=emlcntuswall00000001)
> _______________________________________________
> >From the Lowfer mailing list
> Send messages to: Lowfer at mailman.qth.net
> To sub/unsub visit:
> http://mailman.qth.net/mailman/listinfo/lowfer