[Lowfer] Wm Beacon "Current" Question

[John Andrews]

Neil,

http://www.w1tag.com/RFA.htm

is the correct address. But if you go to http://www.w1tag.com and scroll 
down to "Homemade RF Ammeters", you will get the same thing.

John, W1TAG

On 12/1/2014 9:42 AM, Neil Klagge wrote:
> Hi Mitch. You sent a link that does not work for me.
> You said, " I have had great results
> using the rf ammeters I have built - for various power ( current ) levels
> as shown on John's website, RFAmmeters for LF.  They are very simple to
> build - calibrate very easily and never seem to change. The link is:
> http://www.w1tag.com/RFA.htm/
>
> I am very interested in that article.
> Neil, XSV
>
> w0yse, wg2xsv,now in Vancouver WA
> CN85rq
>
> On Sat, Nov 29, 2014 at 11:41 AM, Mitch Powell <ve3ot.mp at gmail.com> wrote:
>
>> Mike:
>> This may be a repeat of an earlier email - but I have had great results
>> using the rf ammeters I have built - for various power ( current ) levels
>> as shown on John's website, RFAmmeters for LF.  They are very simple to
>> build - calibrate very easily and never seem to change. The link is:
>> http://www.w1tag.com/RFA.htm/
>>
>> Also - first copy of WM this Saturday morning... attached.
>> 73
>> Mitch
>>
>>
>> On Thu, Nov 27, 2014 at 12:18 PM, JD <listread at lwca.org> wrote:
>>
>>> Mike, keep in mind that a current meter for a loop is designed to measure
>>> higher current levels because an electrically small loop offers a very
>> low
>>> resistance if constructed carefully.  A short vertical has inherently
>> high
>>> capacitive reactance, which you neutralize with the loading coil, plus
>>> resistive losses in that coil, the ground system, and nearby
>> environmental
>>> factors.
>>>
>>> Thus, from the P= I^2 * R relationship, we see that for the same power
>>> level, current in a high impedance circuit must be lower than it would be
>>> in
>>> a low impedance circuit.  That's why the meter deisgned for the loop
>> barely
>>> responds in the case of the vertical.
>>>
>>> LowFER vertical antennas vary widely in their resistive component due to
>>> local soil conductivity and coil construction variations.  Most reports
>>> I've
>>> seen on successful beacons indicate measured RF currents typically in the
>>> range of 120-250 mA.  It's hard to get loss factors low enough to exceed
>>> 250
>>> mA for 1 watt.  Much lower than 120 mA, and the beacon may not get out
>> very
>>> well...although nowadays with slow modes like QRSS, that's less of a
>>> problem
>>> than it would have been 15 years ago.
>>>
>>> John
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