[amsat-bb] best tripod for the arrow II handheld antenna

Tue Aug 15 14:26:00 UTC 2017

One way to quantify RF exposure is with a tool published by VK3UM mostly
for the EME community where radio power levels are higher than what is used
for low earth orbit satellites:

http://www.vk3um.com/emr%20calculator.html

--
73 de JoAnne K9JKM
k9jkm at amsat.org

On Tue, Aug 15, 2017 at 9:08 AM, Mike Diehl <diehl.mike.a at gmail.com> wrote:

> Julian,
>
> No apologies necessary, there's absolutely nothing wrong with asking
> questions.
>
> As far as research goes, I'm not aware of what studies have been done.
> This is probably because it has been of little concern to me based on what
> I know about RF and the design of Yagi-Uda antennas.
>
> RF is non-ionizing meaning it is incapable of causing any changes at a
> molecular level. RF only has the ability to cause heating of objects in its
> vicinity. That said, I'm not sure it's even possible to feed an arrow with
> enough power to cause any real heating without damaging the antenna first.
>
> We can look at why antennas like this are used in the first place. These
> antennas have a good front to back ratio that directs the RF away from the
> handle. If we compare the radiation pattern of an arrow to that of a
> standard rubber duck antenna you'll see that much less energy is directed
> at the user. Personally, if I was concerned with exposure I would worry
> more about a 1/4 wave whip than a Yagi. Of course that assumes I don't have
> the Yagi pointed at myself. :)
>
> If you would like more on the topic this page may be a good starting point
> https://www.fcc.gov/engineering-technology/electromagnetic-compatibility-
> division/radio-frequency-safety/faq/rf-safety
>
> Others in the group may know of studies done on the subject, I'm sure
> they'll share if they do.
>
> 73,
>
> Mike Diehl
> AI6GS
>
> > On Aug 14, 2017, at 11:40 PM, Julian Horn (Clara) <
> julianhorn at clara.co.uk> wrote:
> >
> > Apologies if this is a dumb question, but it is from a relative newcomer
> to this field . . . :)
> > Has any research been carried out on the (medical) safety of hand-held
> antennas such as the Arrow whilst transmitting?
> > I understand the power is relatively low, but unlike say a mobile (cell)
> phone, average power I imagine will be much higher?
> > Are there any measurements of field strength this close to the driven
> element and any assessments of the risks?
> >
> > 73, Julian M0NUX
> >
> >
> >
> >> On 15 Aug 2017, at 01:14, Mike Diehl <diehl.mike.a at gmail.com> wrote:
> >>
> >> On a more serious note there are advantages to hand holding the Arrow
> even if it feels like you need to be an octopus to pull it off. There's a
> certain hand ear coordination that seems to come naturally when matching
> polarity by simply twisting your wrist. This advantage alone can be
> significant over fixed polarity or polarity matching by some mechanical
> means. The only time I would recommend a tripod is if there is some
> physical reason for not being able to hold it.
> >>
> >> Often times people go the tripod route because it seems like too many
> things are going on at once. One common pitfall is trying to log while a
> pass is in progress, usually on paper. A better solution is to record the
> audio for playback later. A simple voice recorder or even a smartphone
> works great. If using a voice recorder be sure to set the clock to UTC,
> timestamps will make logging a lot easier.
> >>
> >> Another way to free up a hand is to use a boom mic headset with a foot
> switch for PTT. By doing this you free up your hand to operate the VFO(s).
> >>
> >> Like Bryan pointed out, it can seem counterintuitive that holding the
> antenna can make things easier but when you evaluate the rest of your
> station you may find other ways to free yourself to aim.
> >>
> >> If you find that there's just simply no way to operate without a tripod
> then maybe you can describe the difficulties you face. I've seen many
> clever designs, each with their own advantages and disadvantages making
> them each suitable to a different crowd. Let us know what you're looking to
> get out of a tripod setup, I'm sure there are plenty of people willing to
> share their solutions.
> >>
> >> 73,
> >>
> >> Mike Diehl
> >> AI6GS
> >>
> >>> On Aug 14, 2017, at 4:33 PM, Bryan KL7CN <bryan at kl7cn.net> wrote:
> >>>
> >>> Mike's being funny. :)
> >>>
> >>> I used to use a $10 tripod I got from the Goodwill. The main thing I
> appreciated about it was its ability to do axial rotation -- think: camera
> on its side. When the Arrow was attached, I would us that feature to rotate
> the Arrow along its axis.
> >>>
> >>> Nowadays I do what Mike does: I hold the Arrow in my hand. It takes
> some time to become comfortable with holding the antenna correctly while
> adjusting for Doppler and pressing the mic button, but after some practice
> I found it to be the most efficient way. It's counterintuitive, but using
> your hand to orient the antenna is very fast and flexible.
> >>>
> >>> -- bag
> >>>
> >>> Bryan KL7CN/W6
> >>> Location: CM98, usually
> >>> E-Mail: bryan at KL7CN.net
> >>> Telephone/SMS: 408-836-7279
> >>>
> >>>> On Aug 14, 2017, at 16:23, Mike Diehl <diehl.mike.a at gmail.com> wrote:
> >>>>
> >>>> I find a biped to work best with an arrow antenna. Works great for
> aiming and polarity matching.
> >>>>
> >>>> 73,
> >>>>
> >>>> Mike Diehl
> >>>> AI6GS
> >>>>
> >>>>> On Aug 14, 2017, at 1:55 PM, Laura Tunnell <drlnt at cox.net> wrote:
> >>>>>
> >>>>> What is best tripod for the arrow II handheld antenna ?
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
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> >> _______________________________________________
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> >> to all interested persons worldwide without requiring membership.
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> of AMSAT-NA.
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> >
> _______________________________________________
> Sent via AMSAT-BB at amsat.org. AMSAT-NA makes this open forum available
> to all interested persons worldwide without requiring membership. Opinions
> expressed
> are solely those of the author, and do not reflect the official views of
> AMSAT-NA.
> Not an AMSAT-NA member? Join now to support the amateur satellite program!
> Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
>