[amsat-bb] Some concluding thoughts RE: ELK, ARROW, and the full story for the newbie
Mark Lunday, WD4ELG
mlunday at nc.rr.com
Sun Dec 28 20:39:52 PST 2008
As a newbie to AMSAT (but not the hobby) and not the original poster (but an
owner of Arrow and Elk), thanks to ALL who have contributed to this thread.
A discussion with much opportunity for learning for all, especially me.
We can conclude the following as (mostly, but not completely) the full
story, based upon the threads, observations, and data/insight/experience
from several hams with a gallon of experience and technical skills:
1. The Arrow and the Elk antennas "work," both on the repeater and passband
birds. "Work" means the owner can make contacts at various elevations with
power settings 5 watts and below, which is a common configuration of AMSAT
users at this time (handheld HT, handheld antenna, rover). Many hams have
this as their only option, so it will obviously be popular.
2. The Arrow and Elk antennas each have their fans, as shown by this BB and
eham.net. While each person's mileage may vary, and anecdotes indicate that
both work, there are many factors which may impact one operator's
observations over another.
3. The Arrow and Elk antennas are compromise antennas. "Compromise" means
simplicity and portability are optimized at the expense of performance.
"Performance" is defined as optimum design for achieving maximum signal
energy into the satellite AND maximum energy received from the satellite.
It is not debatable that linear antennas will be sub-par to circularly
polarized antennas as a general rule, and in many specific instances as
well. (If twisting the Arrow or Elk is needed to optimize signals
regardless of how easy it is, and if fading is a challenge with these
antennas, then by definition they are not optimum performance antennas).
What is debatable is the satisfaction of the operator based upon his/her
expectations and knowledge of what is happening with the equipment.
Satisfaction will be high for the informed amateur (see next point).
4. The choice of the Arrow or Elk antenna (or some other model) should be
made as an informed decision. The following questions *should* be asked:
For the antenna, is it maximum Portability? Maximum Performance? Minimum
What is the transmitting/receiving equipment? Power amplifier (focus on
this one last), preamp, dual receiver or dual rigs, receiver sensitivity,
equipment type, etc.
What is the objective of the operator? VUCC? WAS? DX? Rag chewing?
Experimental? Other VHF/UHF uses besides satellite?
What are the operator's expectations regarding performance (fading, flutter,
path loss, etc.)
What is the operator's "power budget?" All items must be examined in the
calculation, starting from power out of the rig to losses from connectors
and feedline all the way through duplexers/diplexers/power dividers and then
to the antenna. Also, things like obstructions (trees, leaves, etc) and
factors like metal support masts must be considered. Finally, there is the
satellite and its sensitivity and power output on the downlink. And these
are *theoretical* calculations, there is also the actuality which can be
determined with simple test equipment.
Once these factors are determined, then the operator "should" look at all
the options. But examination of options requires some knowledge regarding
propagation, antenna measurements, actual data (not only from the seller),
and knowledge from those who have the experience. This information and
calculations are available online and in manuals, including ARRL pubs. Does
not require a EE degree, just some curiosity and an open mind.
5. For me, I don't think I will be working Europe with an Arrow or Elk
antenna on AO7. Although I have worked into South America and Caribbean on
AO51, I need to keep my expectations realistic.
6. For me, I will have a lot of fun with these antennas by taking them
portable and demonstrating the hobby to others or tinkering.
7. For me, I would love to have a VUCC Satellite cert on my wall...esp since
sunspots are at a lull right now.
8. For me, I will look further into homebrew antenna design and construction
as well as higher performance antennas for these bands.
The best consumer / ham operator is an informed one.
And this is one of the elements of the Radio Amateur's creed: that the Radio
Amateur is always improving his/her knowledge of the hobby and seeks to be
the best he can be in terms of skill.
Again, thanks to those who took the time to share. It's a great part of
wd4elg at arrl.net
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