> There is not much significant difference
It depends ... perhaps with quality RG-213 where loss is ~1 dB/100'
at 30 MHz the difference is not significant. However, if you're using
RG58 with nearly 3 dB/100' at 30 MHz even a non-resonant antenna begins
to look good. Your web page does not specify the type of coax and loss
thus "at the feedpoint" measurements are more appropriate.
I do not trust the presented curves in any case - each band shows an
anomalous drop in the last few measurement points. This behavior would
indicate a faulty measurement device, inappropriate date manipulation
(smoothing/averaging), or some potential loss/resonance in the system.
73,
... Joe, W4TV
On 2014-11-27 2:30 PM, 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@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?
73,
... Joe, W4TV
On 2014-11-27 12:34 PM, Ken Garg wrote:
Happy Thanksgiving all !!
A good friend alerted me to a posting by K9OM. His post starts as follows ..”Correct me if
I’m wrong …”. Well, Dick you are WRONG.
The JK Navassa-5 comes pre-drilled, pre-cuts tips from the factory. The user just needs to
assemble the antenna. These antennas are made of the best quality hardware and rated
heavy-duty. There are many other quality manufacturers in the Yagi antenna space and the
Hams are left to some good choices. If you like the JK construction with machined saddles,
and quality hardware, including the “mast plate" all available for $1185
compared to others, then you will buy this antenna. The JK construction and mechanical
robustness speaks for itself and folks that have it will speak to it. The swr curves for
this antenna assembled out of the box at 36ft is presented here ..
http://jkantennas.com/navassa-5-data.html
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