[HCARC] Loop Questions

[John Canfield]

Did anybody try 160 meters on the field day loop?

John
wb5tht

On 7/2/2015 3:40 PM, Gary J - N5BAA wrote:
> "The frequencies quoted in the last paragraph are obviously MHz not 
> kHz." Without doubt - I just cut and pasted them there without looking 
> at them. Mentally I knew what they were saying.
>
> For Lew King - The loop we used at FD turned out to be approx 562 feet 
> in length.  Working backwards from the formula we should be able to 
> calculate what our resonant points should have approximately been. 
> http://www.n1wpn.net/loop_antennas_and_calculator.htm
>
> 562 feet  gives  160- 1.788 mhz,  80 - 3.576 mhz,  40  -  7.152 mhz,  
> 20 - 14.304 mhz  10 - 28.608 mhz
>
> A few extra feet might have made a big difference:
>
> 565' is comfortably resonant at 1.778 mHz, 3.557 mHz, 7.115 mHz, 
> 14.230 mHz and 28.460 mHz.
> 574' is comfortably resonant at 1.75 mHz, 3.5 mHz, 7.00 mHz, 14.000 
> mHz and 28.000 mHz
>
>
> Gary J
> N5BAA
>
> -----Original Message----- From: Kerry Sandstrom
> Sent: Thursday, July 2, 2015 12:49 PM
> To: Gary J - N5BAA ; HCARC Reflector
> Subject: Re: [HCARC] Loop Questions
>
> Gary,
>
> What counts is the impedance at the transmitter end of the transmission
> line.  The impedance at the transmitter end depends on the impedance at
> the loop feed point, the impedance of the transmission line and the
> length of the transmission line in wavelengths.  It is unlikely that the
> impedance at the transmitter end is 450 Ohm.  The way you figure out the
> impedance is using the complex feed point impedance of the loop and a
> Smith chart.  Since the length of the transmission line in wavelengths
> varies with frequency, the impedance at different frequencies is likely
> to be wildly different.  No matter which balun you use, they will still
> be wildly different and seldom close to 50 Ohm.
>
> The purpose of the copper-clad steel wire is purely for strength. That
> type of wire is typically called "Copperweld" after the manufacturer.
> Solid copper wire is not as strong and will stretch under tension.  If
> you need strength, then you need to use the Copperweld type wire. The
> impedance of the line has very little to do with the material used.  The
> difference between the 400 Ohm line and the 450 Ohm line is because of
> differences in wire size or spacing.  The way Copperweld wire is made is
> by pulling a couple ribbons of copper with a steel wire in the middle
> through a die.  I had a trip to the factory in TN many years ago when I
> was purchasing $100K worth of Copperweld wire and learned quite a bit
> about the process!
>
> The frequencies quoted in the last paragraph are obviously MHz not kHz.
>
>
>
> On 7/2/2015 12:18 PM, Gary J - N5BAA wrote:
>> Lew, Frank, Dale and Gale,
>>
>> Why is it that when using 450 ohm ladder line to feed a loop to the 
>> radio are we are using a 4:1 balun instead of a 9:1 balun??
>>
>> BTW, what type of ladder line is best??  I have seen copper clad 
>> steel at 400 ohms and pure copper from Davis at 450 ohms with the all 
>> copper being cheaper than the copper clad steel – go figure.
>>
>> For Dale, Gale and anyone else who does modeling:  Can you model 
>> Loops at approx 50-60 feet above ground??  It would be nice to know 
>> the best loop length for resonant points in the 160/80/40/20/15 bands 
>> for use at Field Day.  I.e. what length gives us the best choice of 
>> resonant frequencies. The loop skywire website 
>> (http://n1su.com/loop.html) gives the following:
>>
>>    a.. 565' is comfortably resonant at 1.778kHz, 3.557kHz, 7.115kHz, 
>> 14.230kHz and 28.460kHz.
>>    b.. 574' is comfortably resonant at 1.750kHz, 3.5kHz, 7.00kHz, 
>> 14.000kHz and 28.000kHz
>> Is there a longer length that might even do better??  What might 1130 
>> feet look like??  As you can tell – I don’t know squat about loops.
>>
>> Gary J
>> N5BAA
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