Follow up from week 1. The design my Antenna was based on https://www.youtube.com/watch?v=RcO5WAiksNI.
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Follow up from week 1. The design my Antenna was based on https://www.youtube.com/watch?v=RcO5WAiksNI.
5:26 ”SWR meter for testing aerials”
While it is common practice to use SWR meters to evaluate in some way
whether or not an antenna is good or bad it is a very risky exercise that
can lead a person into making false conclusions.
SWR meters simply will tell you if the meter see’s a 50 Ohm match.
New Hams (and many not so new Hams) are very pleased when they see a low
SWR reading , however this reading is in no way a judgment on how well an
antenna works.
Take this example , , , , say our antenna is really screwed up for some
reason and it has a 10 Ohm impedance.
Consider too that our coaxial cable connectors are badly soldered and they
now add 40 Ohms extra resistive impedance.
This settup is going to really SUCK and you would be lucky if anyone hears
you at all……however the SWR meters says , ¨Everythings fine buddy , we
have a 1-1 SWR¨ – while the meter says it see’s a 50 Ohm match , the
antenna is still garbage.
SWR meters have very limited use in Ham shacks and are very often
unrelaible source of usefull information , yet for some reason , every Ham
has two or three of them hanging around somewhere., and some will even pay
big dollars for a meter that very accurately tells him nothing much at all.
———–
6:18 ”Ime hoping that won’t matter much” (hot melt glue)
The glue can only affect the way the antena works if it affected by RF
radiation.
To ckeck if it is , get a hot melt glue stick and put it in the microwave
oven for a few miniutes on high power.
If it melts or gets hot thats not good.
But if it stays cold and hard then it is not affected by RF radiation —
that’s good.
The same thing applies to your other plastic parts.
While I haven’t tested hot melt glue in the microwave before I have checked
PVC pipes and they are usually good.
Thumbs UP buddy :-)
Dan, yes of course.
My Ham Shack, what I meant to say was an antenna analyser rather than a swr
meeter. As I understand an analyser can also measure the impedance as well
as the swr.
I also have had some success in ‘hacking’ my psu. So will do a video on
that soon.
Hi Ben. fab video. Can you bring your antenna to class next week ? It will
be a perfect prop for our class. and I will be able to show you the SWR of
your antenna quite accurately !