
---------------------- 
NOTES FROM THE BIKELAB 
Issue #10 -- 5/28/91
by Steven K. Roberts
----------------------

Copyright (C) 1991 by Steven K. Roberts.  All Rights Reserved.
(Intact reposting and free distribution is OK with permission; 
personal forwarding is OK without.)

	IN THIS ISSUE:
		The Antenna Farm
		Nifty Regulators

	"Daddy toys!"
		-- concise assessment by Julia Selfridge, age 2,
		upon being introduced to BEHEMOTH for the first time.

	Well, there are now 49 days to departure, and I'm in the D
	phase of the PFD phenomenon that most concisely describes my
	work habits (Procrastination Followed by Despair).  It is clear
	now that the machine will indeed roll.  It has gears, brakes,
	lights, a Cateye, and a radio... all working.  There's pack
	space, and most areas are waterproofed.  Many subsystems are
	nailed down on the bike and have been tested on umbilici, but
	now await cabling or software to become useful.  The primary
	task is to complete as many "lab" tasks as possible in the next
	7 weeks...  for after that, I will no longer have the milling
	machine, hardware inventory, high-speed scope, huge work area,
	or all those wonderful new daddy-toys still shrink-wrapped on
	the bench.

	Good thing this is a passion, eh?

	Actually, the project is moving faster than ever -- I have new
	help.  Answering my recent call, Martin Rowland has moved up
	from San Diego to be the techno-gofer and general assistant
	between here and departure.  This helps a lot, greatly reducing
	the time spent moving my body around Silly Valley in order to
	acquire objects.  David K. Z. Harris of Telebit is donating
	some time to bring up the ham gear and related components, Bill
	Muench and Mike Perry are helping get the FORTH code started,
	Steve desJardins is building the pneumatically actuated landing
	gear, Bob Lockhart is doing the PCB CAD work on the audio
	crosspoint network, and the various people I've credited before
	are still helping with various projects... collectively making
	it likely that BEHEMOTH will indeed raise a quizzical eyelid
	and utter "hello, world" just in time for RAGBRAI.

	Incidentally, if you've been reading this alias for a while and
	still harbor a quite reasonable suspicion that it's all twisted
	technoid fiction, there will be some current photos in the
	media during the next couple of months.  Sometimes editorial
	schedules slip, but I've been told of the following:

     *	5 page spread in the July DISCOVER, with detailed captions
     *	3 pager in the August BICYCLING, including stunning photos
     *	interview with pix in the next MONDO 2000
     *	article in the 5/28 SF EXAMINER, and CHRONICLE later this week
     *	a reprint in the next issue of ComputorEdge from San Diego
     *	technical article with photos in NOMADNESS #10

	Or come to Iowa during the last week in July and join 10,000
	cyclists in a mad, drunken 430-mile ride from Missouri Valley
	to Bellevue...

	On with the technical news!

The Antenna Farm
----------------

	BEHEMOTH is bristling with a veritable thicket of skyhooks,
	some of which have already received mention in this series.
	Now that they're all mounted, however, it's a good time for a
	summary.

	Technically speaking, the bike carries 18 separate antennae,
	not including all the unintended ones (cables, LCD panels,
	spokes, and probably my nose).  This all makes me wish for some
	magical phased array that could do it all... for every one of
	these has to be packaged, cabled, waterproofed, positioned
	optimally relative to the others, dragged through the viscous
	medium known as air, and hauled up hills.  But, boy, can I ever
	communicate!

	Let's cruise up the electromegnatic spectrum from 150 kHz to 14
	GHz and look at all the bike parts that radiate, resonate,
	ionize the atmosphere, or pluck whispers from the ether...

Active SWL whip (150 kHz - 30 MHz and 78-108 MHz)

	This is seldom deployed while riding, but is the 46" amplified
	whip that came with Sony's new ICF-SW1 miniature digital
	shortwave receiver.  Clever box -- the radio has its own local
	whip, or you can plug in an RF amplifier module connected by
	micro-coax on a little reel to the big one.

HF mobile dipole (3-28 MHz)
	
	Featured in issue #1 of this series, this is proving to be a
	dramatic alternative to the traditional mobile vertical for HF
	ham operation (I use an Icom 725 transceiver).  The basic
	problem with HF verticals is that they use the vehicle as a
	counterpoise -- the bike is not only too small (hah) for
	effective use on low frequencies, but there is a very real
	danger of RF hot spots in this mode.  The solution is a
	balanced antenna such as a dipole, and this one is constructed
	of two Outbacker Jr 7-band verticals (75-40-20-17-15-12-10
	meters).  They are normally stowed against the telescoping
	fiberglass mast (BYP, or Big Yellow Pole) on the back of the
	trailer, but can be flipped up to either a horizontal or
	vertical dipole configuration (also V or inverted-V, actually,
	though I haven't tried it) and locked with knobs.  The entire
	assembly while mobile is about 7 feet off the ground, extending
	to 13 feet when I'm camped.  The BYP is hinged, and has a
	breakaway mechanism designed by Steve desJardins to protect the
	trailer body if I do something stupid like ride under a low
	tree limb.

HF wire dipole pack (7-28 MHz)

	Experience has shown that there's no substitute for full-size
	wire dipoles, so there's a little nylon bag stuffed in the
	satellite basement under the WASU subflooring.  Inside is a 50'
	hank of RG-58 coax, some nylon rope, and simple dipoles for
	40/15, 20, and 10 meters, each with an SO-239 connector at the
	center insulator.  I'll carry this until I have a chance to A-B
	it against the Outbackers under a variety of conditions, and
	will toss it with pleasure if the difference turns out to be
	minor.  Stringing dipoles between trees can be an amusing
	ritual, but it does get old after a while -- and is seldom
	worth the bother for a short layover.  (Actually, I just made a
	tough decision yesterday to remove the MFJ tuner and artificial
	ground currently built into the communications bay.  The plan
	was to carry a military surplus longwire and load it up
	whenever I'm stopped, but it's just too much of a pain.  I've
	never been happy with anything requiring a tuner, and the
	danger of high RF voltages from pilot error with grounding is
	too great.  Besides, I need the commbay real estate.)

Pager/CB helical duck (27 MHz)

	There are three whip antennas on the trailer, evenly spaced
	along the centerline of the solar panels.  Their mounting
	platforms are electronically bonded to the aluminum substrates
	of the panels, making them an excellent ground plane.  (Someone
	pointed out that the giant semicrystalline silicon rectifiers
	atop this ground plane may detect transmitted RF and impose
	noise on the battery bus -- any RF wizards out there want to
	comment on this?)  The most forward of these antennas is the CB
	helical duck from Larsen, and it is switched through a couple
	of BNCs in the coax patch panel between the default security
	pager and the culturally useless but occasionally handy CB
	rig in the trailer.

2-meter halfwave (144-148 MHz)

	The classic workhorse antenna for bicycle-mobile 2-meter
	operation is the Larsen halfwave whip.  I've used this for
	years with excellent results:  it has a wide radiation angle
	and accepts a seat-back mounting 15 degrees off vertical
	without loss of gain fore-aft; it needs no ground plane; it's
	thin and discreet.  If you operate bicycle mobile, forget the
	1/4 and 5/8 wave units and get one of these.  (A J-pole is a
	higher-gain option, but is generally much more delicate.) This
	unit, on an NMO mount bolted to a plug TIG-welded into the seat
	back, is kept from flailing uncontrollably by a sliding
	coupling to the fiberglass flagpole plugged into the seat
	tube.  A coax cable runs directly to the console 2-meter rig --
	a hacked Icom u2AT, repackaged and powered via a 9-volt Power
	Trends switcher.  Although there is a dual-bander on the
	trailer, using it along with the requisite coax patch panel,
	duplexer, and disconnect headers would require 6 coax connector
	pairs... a bit excessive for a micropower transceiver!

(2) wireless intercom helical whips (169-186 MHz)

	One of the interesting features of BEHEMOTH's security system
	is the ability to open a bidirectional audio link between bike
	and manpack, letting me find out when the beeper sounds if the
	situation justifies further action (often, a level-2 violation
	is just someone harmlessly touching the machine out of
	curiosity).  I once tried this via 2 meters, but the very first
	test under real conditions yielded some brain-dead bozo
	muttering:  "what the **** is this piece of ****?"  I panicked,
	imagining the reaction of the FCC and the amateur radio
	community, and immediately disconnected the circuit.  This
	time, it's a license-free low-power wireless intercom good for
	a few hundred feet, and the antennas, again from Larsen, are
	custom helical rubber ducks -- one on the RUMP and the other on
	the manpack.

VHF-UHF dual-bander with duplexer (144-148 and 440-450 MHz)

	This Larsen whip (guess you're starting to notice that I like
	Larsen antennas -- you can get more info on them by calling the
	company at 800-426-1656) is a shunt-fed grounded coil
	dual-bander, which is 5/8-wave at 2 meters and 1/2 over 1/2
	colinear at 440.  Nice unit.  It holds the coveted center spot
	on the solar ground plane, and is cabled to Larsen's AD 2/70
	duplexer.  This presents two spigots, one for each band, and
	these are normally cabled to the Yaesu 290 and 790 multimode
	transceivers (my big guns for VHF and UHF).  In case I haven't
	mentioned them earlier in this series, these are excellent
	radios:  very low battery drain, FM-CW-USB-LSB modes, plug-on
	modules for 25-watt amplifiers or battery packs, and pleasant
	user interface.  I have used the pair, aided by a pair of ARR
	preamps and a KLM satellite antenna, to work OSCAR 13 with good
	results, and on the bike they will be used for the microsats,
	packet, and long-range terrestrial operation.  Incidentally,
	this antenna tends to flail around if unsupported -- I made a
	guying collar that slips over the top element onto the center
	coil, and attached four thin guy lines down to the solar
	surface.

VHF-UHF dual-band helical whip (144-148 and 440-450 MHz)

	Though not mounted on the bike itself, this one counts in our
	antenna chautauqua -- it's the rubber duckie attached to the
	Icom IC-24 dual-band handheld transceiver.  Amazing device.
	Word on the street is that the antenna that comes with the Icom
	is not so hot, but I think they changed it in more recent
	deliveries.  I have both the original Icom and a Larsen of
	similar dimensions, and will experiment with the 15" Diamond
	dual-bander before packing up for departure.

(2) UHF packet link helical whips (457.525 and 457.575 MHz)

	The bike-to-manpack data link consists of a pair of Motorola
	Radius RNET transceivers, and Larsen quarter-wave UHF ducks cut
	to my licensed itinerant and cargo frequencies are mounted on
	the RUMP at shoulder level and on a flip-up coax elbow on the
	Zero manpack.  The coax patch panel in the trailer and a Lemo
	waterproof connector on the RUMP allow the bike's data radio to
	be patched to the much more efficient dual-bander for
	long-range use.

VHF-UHF television whip (55-211 MHz and 471-801 MHz)

	This is just the whip antenna on the Sony Watchman TV set.

UNGO security remote (300 MHz)

	Inside the RUMP, the UNGO box security system is mounted on the
	forward fiberglass wall -- watching for movement via a blob of
	mercury inside a 40 kHz field.  This has proven in past
	machines to be highly reliable, and is the basic "Yikes!
	Someone is touching me!" sensor.  Like most car alarms these
	days, it has a pocket remote control, and this little antenna
	picks up the digitally encoded 300 MHz signal.

Cellular elevated feed whip (821-896 MHz)

	The rear spot on the solar lid belongs to the cellular whip, an
	elevated feed unit from Larsen with 3db gain.  This has
	slightly better than normal cellular performance due to the
	extra height, but is nothing like the next item...

Cellular 6-element yagi (824-868 MHz)

	You know how frustrating it is to be just outside cellular
	service range, watching your NO SERVICE light flash in the
	middle of a conversation?  This fixes that problem dramatically
	-- it's a 6-element beam with 10db gain, cut for the cellular
	mobile unit's transmit frequency range.  I've tested this to
	about 100 miles on my Oki 491 with good results, and it is ONLY
	for use when unmoving and outside a normal service area since
	the radiation pattern can confuse the cell sites and frustrate
	normal channel-management operations.  (A more typical use is
	to provide a cellular alternative to stringing wires for remote
	home sites.)

GPS receiver (1.575 GHz)

	Mounted in a little nacelle molded into the new fiberglass
	fairing is an impressive bit of RF black magic, about 4"
	square.  This is the antenna for the Trimble TANS GPS
	navigation receiver, receiving spread spectrum time code data
	from a constellation of 24 satellites in circular orbit (about
	17 are now in place).  The antenna contains a 50db preamp
	powered via the coax feedline, and the actual element is a
	piece of thick glass-epoxy circuit board with a ground plane on
	one side and a rectangle on the other... fed with a single pin
	about a third of the way in from a corner.  Something about
	standing waves and circular polarization... like I said, black
	magic!  I call it my "here and now" box:  when powered on, it
	puts out a continuous feed of latitude, longitude, and
	elevation (to about 100 feet); speed to .1 mph; and time to 1
	microsecond.

Microwave security unit (10 GHz)

	Moving up rapidly in the spectrum, we find a peak at 10 GHz --
	belonging to the AM Sensors (formerly Alpha Industries)
	microwave doppler motion sensor, the first level of security
	monitoring.  The feedhorn is mounted vertically, penetrating
	the top of the RUMP and firing into what appears to be a fat
	mounting base for the 7" yellow flasher.  Inside is the hack:
	a copper 90-degree cone with its apex at the exit aperture of
	the antenna, resulting in a 360-degree radiation pattern around
	the bike with a 48 degree spread from the horizontal.
	Sensitivity is set to trigger a response when a person moves
	within 10-15 feet (not necessarily an alarm condition, but good
	to know).

Qualcomm satellite terminal (14 GHz)

	Finally, up in the rarified ether of the Ku band, there is the
	OmniTRACS terminal.  More than any other single bike system,
	this expresses the theme of this whole adventure:  maximum
	connectivity under all conditions, rendering my physical
	location irrelevant via the magic of technology.  (This system
	is described a little more fully in Issue #8.)  Inside the 12"
	diameter white dome is a stepper-motor-driven feedhorn, curved
	and shaped to yield a 5-degree wide by 40-degree high beam,
	centered at 40 degrees above the horizon.  This is driven in
	azimuth by the controller, which monitors the signal from the
	GTE GSTAR satellite for feedback.  Occasionally it glances over
	at a "tracker" bird to triangulate its own location within
	about 1000 feet, automatically location-stamping all my
	outgoing email.  1 GHz IF and REF lines connect the antenna to
	the OmniTRACS main unit under the trailer's forward Thermoclear
	subfloor.  The net effect?  24-hour-a-day email connectivity,
	hacked into internet via the Qualcomm hub in San Diego and a
	Sun 3/260 that rewrites mail headers and otherwise manages tha
	network hooks.

	Phew.  There.  The only thing that scares me about all this
	(other than the usual problem of hauling it up hills and the
	potential for frying myself with some exotic blend of radiated
	energy), is the effect on certain non-technical functionaries
	who hold accept-reject power (and worse) at national borders.
	Bernard Magnouloux, circumnavigating the globe the hard way via
	bicycle (the length of Africa, the Length of South America,
	across China, etc), was harrassed at some obscure African
	border for being a spy.  It was the high-tech equipment that
	got him in trouble... a pocket shortwave radio like any of us
	could put on the Visa card for about sixty bucks.  I may have
	problems with that someday...

	"What is this?"

	"Oh, just my satellite link.  For email."  I smile disarmingly,
	hoping the guard will stop aiming his service revolver at my
	chest.

	"And this?"

	"Ah, that.  A high-speed packet data link for file transfers
	between the bike and this little aluminum briefcase here...."

	"I see.  You will follow me.  Keep your hands where I can see
	them."

	Considering that I was harrassed for over an hour when bringing
	the bike into Port Angeles, WA from its display at Expo in
	Vancouver, this is not at all farfetched.  Next version... the
	stealth model...

	Arthur C. Clarke observed quite accurately that "any
	sufficiently advanced technology is indistinguishable from
	magic."  Where governments are involved, replace "magic" with
	"national security risk."  In a philosophical sense, of course,
	that's quite true... is there anything that shows LESS respect
	for artificial national borders than radio waves?

Nifty Regulators
----------------

	This issue is getting long, but there is one more thing I
	really have to tell you about.  You know those ubiquitous
	3-terminal regulators that have been around since the early
	1970's -- the 340 series and its various cousins?  They're
	handy but horrendously inefficient, burning away the difference
	between input voltage and output voltage in the form of heat,
	linearly related to the load current.  Obviously useless for an
	application such as this where power is a scarce resource.

	Switching regulators have been around for years, of course, but
	have a well-deserved reputation for being difficult to
	design.   Chips from Maxim and Linear Technologies go a long
	way toward making life easier (and are still the best approach
	for really fine-tuning and cost-optimizing a low-power switcher
	design).  But haven't you just ACHED for something quick and
	easy, like a drop-in 3-terminal regulator replacement that
	doesn't require you to think about inductors and catch diodes?
	Ah, I thought so.

	Well, now there is one.  The 78SR series from Power Trends is
	just that -- slick little 1.5 amp 3-terminal modules that make
	efficient power supply design about as easy as GROSS power
	supply design was back when we didn't know any better.  They're
	available in 5, 9, and 12 volt models, are short-circuit
	protected, draw about 6 mA quiescent, accept up to 30 volts in,
	and run at about 90% efficiency with loads above 100 mA or so.
	Implementation is trivial -- an input electrolytic to slow the
	rise time of a fast power switch, an output cap to reduce 650
	kHz ripple (seems pretty optional -- I don't even notice the
	effects when running radio gear), and in some applications a
	zener to clamp the output in situations when the input voltage
	rise time is extremely short.  That's it.  They work
	beautifully, and are being scattered all over the bike to
	produce regulated voltages from the 12-volt battery bus.

	Check 'em out... the company is Power Trends in Batavia, IL
	(contact Don Mattheisen at 708-406-0900).

 Cheers from the Bikelab!

		Steven K. Roberts 
		Nomadic Research Labs 
		P.O. Box 2185 
		El Segundo, CA 90245-2185

		wordy@bikelab.Sun.com (primary internet)
		GEnie, MCI, or AOL:  wordy

