[TowerTalk] JK Navassa-5

[Jim Lux]

On 11/27/14, 11:30 AM, Ken Garg wrote:
> Joe,
> All data is available at 50ft, 100ft etc. There is not much significant difference thats smoke and mirrors. The reason to show 100ft was taking into account an average ham shack with a coax run. Do you think there will be a significant difference in swr between 100ft and 50ft? Ot do you think that our coax has so much loss that we don’t see swr? Not sure of your point.  If measured swr at the feed point is 1.28:1, then the measured swr at 100ft will be approx 1.2:1 using RG213 as a coax.
> The goal was to show a freespace design vs actual measured for the average ham on a simple page. If someone needs more details, they can always ask in an email through the website.
>
> Thanks,
> Ken
>
> On Nov 27, 2014, at 2:12 PM, Joe Subich, W4TV <lists at subich.com> wrote:
>
>
>> The swr curves for this antenna assembled out of the box at 36ft is
>> presented here .. http://jkantennas.com/navassa-5-data.html
>
> If the antenna is at 36 feet, why are you using 100 feet of coax for
> the measurement?  Why not use 50 feet or calibrate out the losses and
> present true "at the antenna" measurements?
>


You both have valid points.  Maybe the way to do it is to provide "at 
the feedpoint" measurements (calibrating out the coax) for R and X as a 
text file linked somewhere.  Since you compare to the NEC4 model, the 
.nec model file could be published too.

This would be a great trend for ham manufacturers and would go a long 
way towards getting rid of the smoke and mirrors and unrealistic claims 
for the industry as a whole.

These days, there's not much cash value in the electrical design;  what 
a manufacturer is selling is convenience and mechanical design.
After all, the basic antenna design is straightforward:  what really 
differentiates manufacturers is the mechanical details.  Brackets, 
holes, assembly ease, shipping costs.   I'm certainly willing to pay for 
someone else to cut all the aluminum to length, set up a jig to drill 
holes nicely, kit all the assembly hardware and so forth.