I tried honestly to use the HP 50g, and here are a few objections that put me back to the TI-89.
The low resolution (blocky/grainy) HP 50g display detracts from its usefulness as a high-end graphing calculator.
Low resolution limits length of equations and number of equations on the screen.
One of the major reasons for having a high-end calculator is to allow entering long equations on the screen.
That being said, the HP 50g has a dedicated core of aficionados.
HP 50g advocates will present a list of counterpoints–and their arguments have merits.
Given the feature set and the inevitable eventual sunsetting of the 15+ year old TI-89 series, a new user considering what high-end calculator to purchase should look to the TI Nspire CX CAS.
In closing, I will give strong admonition to students.
DO NOT rely heavily on calculators in math courses.
This will only cause suffering in later courses.
Even if the last math class in college will be Calculus I or II, you will never gain the true richness of understanding if constantly using a calculator for homework.
A better approach is to do the problems manually, and on occasion check with the calculator.
Legacy auroral video acquisition has been plagued with several problems including
camera sensitivity
data storage
video time synchronization
software instability
An example of such a system was deployed last winter to Poker Flat Research Range.
The results of this work won “Honorable Mention” at the
CEDAR 2011 Workshop.
A two camera system observed the aurora from Poker Flat Research Range (Chatanika, AK) and Ester, AK.
Notice the hardware synchronization connections on the camera are not being used.
This makes the system reliant on the vagaries of software timing of the OS, which in Windows case can account for order 100 ms.
When one wants 33 ms cadence video, this means such video will be roughly syntonized, but poorly synchronized.
Timing error due to non-hardware synchronization: error for a single frame, the error will accumulate in general due to error bias, quickly leading the cameras to be taking pictures at different times (no video frame overlap in time).
Error source
Description
Error magnitude [s]
camera FPGA
Non-TCXO 100 ppm crystal timebase inside camera
10-6
PC time
NTP error
10-3
software trigger
Start time error due to SDK
10-1
The software trigger error is not predictable and can reach up to 1/2 second.
Aurora has apparent motion of kilometers per second, and so a camera designed for 10..100 m scale width observations needs to have timing error commensurate with the physical phenomenon.
Hopes of a tomographic solution are dashed if the pictures are taken at times distant enough such that the feature of interest changes on timescale less than the error.
imager block diagram
Observational Solution for Auroral Tomography: the ill-conditioned, ill-posed nature of the high-resolution auroral tomography problem dictates attention to detail of all aspects of cross-site registration.
We will have to ensure:
images are accurately registered.
Absolute and relative timing are synchronized to at least 2 orders of magnitude better than the frame cadence (< 1 % timing error)
If the data writing becomes overwhelmed, the system should discard a bit of video and recover rather than stutter the recording.
Plant, G., Semeter, J., Marshall, R., Dahlgren, H., Goenka, C., and Hampton, D. (2011).
A high-speed tomographic imaging system for studying dynamic aurora.
In Instruments or Techniques for Ionospheric or Thermospheric Observation.
CEDAR Workshop, Santa Fe, NM.
ITIT-06.
When you view the aurora, whether by camera or by being outside with your eyes, what you see is a line integral of the line-of-sight brightness of the optically thin aurora.
Mathematically, this is
I = ∫_0 ∞ p(ℓ) dℓ
where:
I is the intensity seen by your eye or camera pixel
p(ℓ) is the volume intensity rate of the aurora at each differential point along ℓ
Volume emission rate of aurora is created when particles (electrons or ions) strike the cold gas of the ionosphere, typically N_2, N_2+ or O.
As altitude increases above a couple hundred kilometers, oxygen starts to become the dominant gas instead of nitrogen.
This affects the color of the aurora, and is part of why aurora appears as green below red.
Unfortunately, many of the images taken of aurora with digital cameras have incorrect white balance, and completely non-physical colors are seen.
Yes, there is purple aurora, but it is quite faint and below the green emissions in altitude.
So a sky full of purple, yellow, and orange is not believable, it’s an artifact of incorrect white balance.
That’s a big part of why it’s good to save auroral photos in RAW format from your camera so you can fix the images in post-processing.
The vacation grounds of upstate New York, particularly the Adirondack area suffer from poor cellular service.
Recent fatal accidents have left the public blaming the lack of cell phone coverage for slow emergency response.
There are a few things professional users (including volunteer emergency services) and prosumers can do to improve in-car cellular service.
Readily available technology yields:
3-watt cell phone automotive/RV/SOHO bidirectional amplifiers (direct or wireless coupling to handset) greatly improve coverage over the internal antenna cell phone
900 MHz long-range cordless phone covers large home / country estate and higher-power units cover campgrounds and remote worksites
outdoor WiFi APs will blanket several acres of worksite/campground with 802.11 2.4 GHz WiFi for modern phones and laptops.
There isn’t any fundamental difference in radio waves between two-way radio and cellular.
The ubiquitous handheld cell phones with internal antennas suffer several dB disadvantage vs. older handheld phones with external antennas.
Add several more dB penalty for handheld cell phone used in car or building.
Cellular coverage can be significantly augmented by using bidirectional amplifiers in the home, office or vehicle.
However, terrain in mountainous areas precludes 100% coverage.
Automobile-installed cellular phone repeaters and amplifiers
can yield up to 3 Watts output power from your car back to the tower, just like traditional bag phones.
The bidirectional amplifier costs about $200-$300, the phone adapter another $20, and the install probably $100-$200.
This could be a life-saver or at least a time-saver in remote areas.
The cellular signal is attenuated by more than 10 dB in both directions with a handheld phone in the car compared to an external antenna.
However, in mountainous terrain, oftentimes the problem is simply terrain blockage, so sometimes no amount of hardware will help.
This is where emergency services use their own VHF/UHF repeater towers to fill the cellular gaps via radio.
Burning Man 2007 saw the debut of standalone cellular service via USRP OpenBTS.
OpenBTS can cover remote worksites and campgrounds with cellular, when the provider’s network doesn’t yield coverage.
Bidirectional amplifiers can have 20-80 dB of gain depending on the model.
The lower gain (< 40 dB) models assume the phone is within about 10 meters of the amplifier–and that with a good signal at the donor amplifier.
If the phone already does not have an adequate signal, then a high-gain donor antenna placed up high is required.
To cover outdoor areas with bidirectional amplifier, free-space loss and antenna pattern analysis shows that the isolation distance required is large enough to require fiber optic interconnection to be practical.
This translates to significant expense, probably excessive for a large number of campgrounds and remote outdoor worksites.
Telephone and data coverage to campsites and remote outdoor worksites can consist of two-way radio with interconnect along with outdoor WiFi APs.
Outdoor WiFi AP coverage can be over 100 meters outside when placed at 5-10 meter height.
Two-way radio callboxes are available for < $500, and if a campsite / remote worksite has only one security guard on duty at night on patrol, their walkie-talkie can communicate with the callbox and on the same (or different) channel dial the telephone for half-duplex communications with emergency services over the radio channel.
A callbox per bloc of cabins or periodically throughout the worksite may suffice.
For long-range staff cordless telephones, multiple base stations and dozens of handsets are possible.
It is possible to get over 100 meter range from the base station when it’s placed in a high, clear view location.
The Kenwood TS-2000 has a strong birdie (false signal) at 436.800MHz.
This is the 28th harmonic of X400, the 15.6 MHz TCXO.
Symptoms: the 436.8 MHz TS-2000 birdie interferes with the first third of AO-27 and SO-50 passes, as the 436.795 MHz downlink of these satellites is well within the ± 7.5 kHz bandwidth of the TS-2000 FM receiver.
The maximum 436 MHz Doppler shift for these LEO satellites is about ± 9 kHz.
Thus near AOS of a given pass, AO-27 or SO-50 apparent center frequency is as high as 436.804 MHz.
It’s not until the satellite is reaching maximum elevation that the Doppler shift makes the apparent center frequency low enough (say 463.796 MHz) so that Narrow FM (bandwidth ± 3.75 kHz) and tuning away from the birdie can help greatly.
Aside from hacking the circuitry around X400, the easy fix is simple to use a 436 → 29 MHz downconvertor that completely eliminates the birdie concern.
The effectiveness of SOFTDCD doesn’t match a “real” external TNC–the TNC still relies on the hardware squelch.
This means that the internal TNC may miss packets from mobile/portable devices with fluttering signals common to VHF/UHF.
try “S-meter Squelch (menu #19A)” to enable you to transmit when the received signal is strong and transmits constantly (such as packet satellites like GO-32).
This is ONLY effective when the station you desire to communicate with can receive while transmitting.
You must manually turn up the squelch for an instant, then turn it back down so that the TS-2000 can receive the other station after the TS-2000 sends its data.
The Kenwood TS-2000 with internal TNC is capable of ARISS packet operations.
The performance of the internal TNC can be a little frustrating on receive.
The satellite TRACE feature of the TS-2000 is ONLY useful in conjunction with computer tuning, since it does not account for Doppler shift magnitude increasing relative to frequency.
That is, 1:1 frequency tuning of TRACE is OK for quick adjustments in a satellite linear transponder passband, but computer frequency tracking is necessary to account for Doppler shift during the satellite pass.
For example, a -1.0 kHz Doppler shift on 146 MHz will be about -2.99 kHz on 436 MHz, and so on.
