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Old Feb 21, 2006, 08:11 PM
GordySoar@aol.com
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"He still sees no need for Dial a channel, but I have -- for years"

With my travels it didn't take long to figure out that I was going to be
sitting out while some other pilot sat on a freq all day long, especially on
slopes.

So I bought up all 50 Xtals and carried them along...but the next
realization was that I was over working the sockets...they were never made for the in
and out frequency that I had to do.

However it went beyond that....a couple of times I hadn't brought my xtals
along and I didn't the luxury of having a clear channel at a contest or
slope...and it cost me planes.

When I did the article on the Stylus/Spectra adoptions, I made it clear that
for 90% of the guys flying, guys who seldom travel to contests or fields
where they have not established their 'ownership' and relationship with other
club mates who might share a freq with them...it was a waste of time and money
to do.

The other factor involved IS the dial a crash potential. ALL of the current
synth modules use the tiny dials, with tiny digits. It was why I urged all
recently to invest in the Frequency Checker....by turning on the Freq Checker
BEFORE you turn on your TX after dialing your channel you can quickly verify
that you have indeed chosen 53 instead of 52, or 35...
Unfortunately the thread got lost in trying to use the Freq Checker to check
'others' radios.

So here's what I have seen on the road, around the world's flying sites.
Don't get a Synth module if your intention is just to have a cool gimmick. IF
you don't use it often, you WILL make a mistake. If you don't need to change
frequencies a lot, don't get it.

I use Polk Seeker 11 Synth RX's and the Spectra Module. I get my equipment
tested and tuned every year and sometimes if the friend is equipped I get it
checked more often. I use alcohol, and sometimes for cleaning my antenna

Clear channel is always safest...but that doesn't mean the only way to have
it is to use a Synth Module.
Gordy
Back in the USA! Florida, better have great weather this Saturday!

Old Feb 21, 2006, 10:11 PM
Dan Ahearn
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n/a Posts
Re: "He still sees no need for Dial a channel, but I have -- for years"

"...The other factor involved IS the dial a crash potential. ALL of the
current synth modules use the tiny dials, with tiny digits..."

Not the Evo..... interface via the LCD screen. You have to power off to
change.

DJA

Old Feb 21, 2006, 10:11 PM
Bill's Email
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n/a Posts
Re: "He still sees no need for Dial a channel, but I have-- for years"

Nor the 14MZ. Totally wireless connection. No dials, no nothing. All
electronic.

Dan Ahearn wrote:
> "...The other factor involved IS the dial a crash potential. ALL of the
> current synth modules use the tiny dials, with tiny digits..."
>
> Not the Evo..... interface via the LCD screen. You have to power off to
> change.
>
> DJA

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Old Feb 22, 2006, 12:11 AM
Raschow@aol.com
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Re: "He still sees no need for Dial a channel, but I have -- for years"


In a message dated 2/21/2006 10:54:40 P.M. Eastern Standard Time,
GordySoar@aol.com writes:

The other factor involved IS the dial a crash potential. ALL of the current
synth modules use the tiny dials, with tiny digits. It was why I urged all
recently to invest in the Frequency Checker....by turning on the Freq Checker
BEFORE you turn on your TX after dialing your channel you can quickly verify
that you have indeed chosen 53 instead of 52, or 35...



NO! ALL of them DON"T! Synth module + scanner (at least three such
available) best set-up so far. Good Lift!

Old Feb 22, 2006, 12:11 AM
Martin Usher
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n/a Posts
Re: "He still sees no need for Dial a channel, but I have-- for years"

Those rotary switches on the synth modules are not designed for
continuous use. They're similar to the old circuit board mounted DIP
switches (the ones that you had to flip with the tip of a pencil),
they're great for occasional configuration changes but the contacts and
detents wear out quite fast if you use them repeatedly

Martin Usher

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Old Feb 22, 2006, 06:11 PM
Doug McLaren
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Re: "He still sees no need for Dial a channel, but I have -- for years"

On Tue, Feb 21, 2006 at 09:49:41PM -0800, Martin Usher wrote:

| Those rotary switches on the synth modules are not designed for
| continuous use. They're similar to the old circuit board mounted DIP
| switches (the ones that you had to flip with the tip of a pencil),
| they're great for occasional configuration changes but the contacts and
| detents wear out quite fast if you use them repeatedly

Not only that, but the Hitec Spectra module has the switches on the
inside -- so you have to remove the module from the radio for every
change, and it also encourages not actually looking at the dials and
just remembering what channel the radio is on. Which is fine, as long
as your memory is perfect. And the only person I know with a perfect
memory is my wife -- and even then it's only perfect for times when I
screwed up

And every time you remove the module, you risk breaking it, either the
plugs that it goes into, the clips that hold it in, or you could drop
it and break it that way.

At least the Futaba module for the 9C, while almost identical, has the
switches on the outside, so you can change and inspect them easily
without removing it.

And then the rotary switches are TINY. It's very easy to make a
mistake there -- my eyes are reasonably good, and I have to double and
triple check my work there.

Personally, I'd much rather see the synthesized modules built in,
controlled via the computer radio interface itself, ideally with a
scanner. The higher end radios seem to do it just fine, and even the
Polk Tracker radio has it, and for only $200.

The Futaba 14MZ -- doesn't it have some sort of 2.4 GHz setup to tell
the RX what 72 MHz channel to use? (They call it `WFSS'.) Talk about
a Rube-Goldberg machine -- it's like they got half of a spread
spectrum setup going, and then couldn't finish it or something.

I bought a pair of FRS transceivers (i.e. walkie talkies, 460 MHz or
so) recently at Fry's for $10 _for the pair_, with no rebate. These
things each have a TX and a RX, and are fully synthesized and can do
all 14 channels with no crystal swapping. You'd think *all* our R/C
gear would be synthesized by now.

Though what we *really* need is the successor to the Spektrum DX6,
with full range, at least 9 channels, and somewhat more programming
options. (No exponential on the rudder? What were they thinking?)
If they can get that out, it'll be like a license to print money for
them ...

And that's enough random `state of our radio systems' rants for now

--
Doug McLaren, dougmc@frenzy.com
To err is human, but to really foul things up requires a computer.
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Old Feb 23, 2006, 08:11 AM
S Meyer
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n/a Posts
Evolution of RC RF

Since this thread has drifted into the future of RC RF, how about
this scenario.

Eventually all the car guys will graduate to using 2.4G SS, (if not
force them), thus allowing 75Mhz to be utilized for RC spread
spectrum. Then allow the exclusive use to aircraft. If some old non
compliant car radio happens to be in use it will still not cause a crash.

Steve Meyer
SOAR, LSF IV

At 05:41 PM 2/22/2006, Doug McLaren wrote:
>On Tue, Feb 21, 2006 at 09:49:41PM -0800, Martin Usher wrote:
>
>| Those rotary switches on the synth modules are not designed for
>| continuous use. They're similar to the old circuit board mounted DIP
>| switches (the ones that you had to flip with the tip of a pencil),
>| they're great for occasional configuration changes but the contacts and
>| detents wear out quite fast if you use them repeatedly
>
>Not only that, but the Hitec Spectra module has the switches on the
>inside -- so you have to remove the module from the radio for every
>change, and it also encourages not actually looking at the dials and
>just remembering what channel the radio is on. Which is fine, as long
>as your memory is perfect. And the only person I know with a perfect
>memory is my wife -- and even then it's only perfect for times when I
>screwed up
>
>And every time you remove the module, you risk breaking it, either the
>plugs that it goes into, the clips that hold it in, or you could drop
>it and break it that way.
>
>At least the Futaba module for the 9C, while almost identical, has the
>switches on the outside, so you can change and inspect them easily
>without removing it.
>
>And then the rotary switches are TINY. It's very easy to make a
>mistake there -- my eyes are reasonably good, and I have to double and
>triple check my work there.
>
>Personally, I'd much rather see the synthesized modules built in,
>controlled via the computer radio interface itself, ideally with a
>scanner. The higher end radios seem to do it just fine, and even the
>Polk Tracker radio has it, and for only $200.
>
>The Futaba 14MZ -- doesn't it have some sort of 2.4 GHz setup to tell
>the RX what 72 MHz channel to use? (They call it `WFSS'.) Talk about
>a Rube-Goldberg machine -- it's like they got half of a spread
>spectrum setup going, and then couldn't finish it or something.
>
>I bought a pair of FRS transceivers (i.e. walkie talkies, 460 MHz or
>so) recently at Fry's for $10 _for the pair_, with no rebate. These
>things each have a TX and a RX, and are fully synthesized and can do
>all 14 channels with no crystal swapping. You'd think *all* our R/C
>gear would be synthesized by now.
>
>Though what we *really* need is the successor to the Spektrum DX6,
>with full range, at least 9 channels, and somewhat more programming
>options. (No exponential on the rudder? What were they thinking?)
>If they can get that out, it'll be like a license to print money for
>them ...
>
>And that's enough random `state of our radio systems' rants for now
>
>--
>Doug McLaren, dougmc@frenzy.com
>To err is human, but to really foul things up requires a computer.


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Old Feb 23, 2006, 10:11 AM
Bill Swingle
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n/a Posts
Re: Evolution of RC RF

Interesting idea Steve. I think I like it. However, SS may require more
bandwidth than is available on 70ish MHz. Don't know... (hey Simon?)

Besides that it would be a radical change and difficult to force down their
throats. ;-)

Bill Swingle
Janesville, CA


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Old Feb 23, 2006, 08:11 PM
Simon Van Leeuwen
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n/a Posts
Re: Evolution of RC RF

Maybe John would care to give us an overview of what to expect from JR
reegarding this very interesting prospect? Or maybe some snippets? :^)

Bill Swingle wrote:
> Interesting idea Steve. I think I like it. However, SS may require more
> bandwidth than is available on 70ish MHz. Don't know... (hey Simon?)
>
> Besides that it would be a radical change and difficult to force down
> their throats. ;-)
>
> Bill Swingle
> Janesville, CA
>
>
> RCSE-List facilities provided by Model Airplane News. Send "subscribe"
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> and AOL are generally NOT in text format
>


--
Simon Van Leeuwen
RADIUS SYSTEMS
PnP SYSTEMS - The E-Harness of Choice
Cogito Ergo Zooom

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Old Feb 23, 2006, 08:11 PM
S Meyer
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n/a Posts
Re: Evolution of RC RF

At 09:33 AM 2/23/2006, Bill Swingle wrote:
>Interesting idea Steve. I think I like it. However, SS may require
>more bandwidth than is available on 70ish MHz. Don't know... (hey Simon?)
>
>Besides that it would be a radical change and difficult to force
>down their throats. ;-)


Narrow band was forced on RC users. And in the end it was a good
thing. I would think most would believe that SS is a good idea. We
need to move towards it.

I did not consider the limitation of the bandwidth, that will be a
hurdle to overcome. But it is clear that we need more power/range
than what current 802.11x can offer. Hence we will need to use
another band and since we are peripheral RF users, being assigned
more bandwidth or a new spectrum from the FCC will not happen.


Steven Meyer
SOAR, LSF IV

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Old Feb 24, 2006, 12:15 AM
Martin Usher
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n/a Posts
Re: Evolution of RC RF

>But it is clear that we need more power/range than what current
802.11x can offer.

Apart from range (limited) the real killer with something like 802.11 is
latency. You probably won't notice it with just one or two people flying
but if you had a contest with a couple of dozen then the transmitters
would share the bandwidth by waiting their turn. (An individual
transmitter could wait quite a long time before getting use of the
medium, in the order of many tens of milliseconds.)(Actually, I've found
that in practice a handful of transmitters get to dominate the medium
and the rest rarely, if ever, get out.)

The present PCM system works extremely well for what it is -- its cheap,
its quite reliable and its economical on spectrum.

The problem is that there are lots of other users contending for band
space who could easily move to modern radio technologies but are
reluctant to give up "their" slice of spectrum. So the public uses like
R/C and wireless networking tend to be crammed into little corners of
the spectrum that nobody else wants (the 2.4GHz band used by most
wireless network equipment is open because its a set of frequencies that
are absorbed by water molecules -- not that good for communication but
excellent for microwave ovens). Now that governments have discovered
that there's a cash cow to be milked auctioning off the spectrum -- one
of the reasons for the move to digital TV is to free up half the old UHF
TV band and the VHF TV bands for sale -- so the chances of us getting a
slice for free is, I'd guess, relatively slim.

I'd love to move to spread spectrum. Just not at microwave frequencies.
If we could get our hands on just one redundant UHF TV channel that
would keep us happy for a very long time.

Martin Usher

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Old Feb 24, 2006, 04:15 AM
Doug McLaren
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n/a Posts
Re: Evolution of RC RF

On Thu, Feb 23, 2006 at 08:42:32PM -0800, Martin Usher wrote:

| >But it is clear that we need more power/range than what current
| >802.11x can offer.

For the record, 802.11x is just one (or a few, to be more accurate)
implementations of spread spectrum. There are many others.

The Spektrum stuff is the only commercial SS recreational R/C
implementation out that there that I'm aware of, and it doesn't use
any of the 802.11x standards. (I'm pretty sure that Futaba already
sells industrial R/C equipment that uses spread spectrum, but I don't
know the specifics.)

As for power/range, the power limit in the 2.4 GHz band is 1 watt in
the US. That is more than enough to get two miles of range,
especially if we use a somewhat directional antenna on the TX. (A
dipole with a screen behind it to shield the operator would be a nice
start, and at 2.4 GHz wouldn't even be too large.)

(The Spektrum DX6 TX only uses 0.1 watt if I recall correctly, and the
antenna provides very little gain.)

| Apart from range (limited) the real killer with something like 802.11 is
| latency. You probably won't notice it with just one or two people flying
| but if you had a contest with a couple of dozen then the transmitters
| would share the bandwidth by waiting their turn.

There are multiple implementations of spread spectrum. Not all
involve `waiting their turn'. Many, including the one used by the
Spektrum DX6 stuff, can transmit all at once and the RX can pick it's
signal out of the resulting mash of noise. And even if we were using
802.11b (the WiFi standard, 11 Mb), the latency would probably be
unnoticible by even the best pilots, even with dozens of planes using
it at once. (As long as people weren't trying to steam video back
from their planes over the same WiFi connections, I guess.)

| The present PCM system works extremely well for what it is -- its cheap,
| its quite reliable and its economical on spectrum.

.... but it can be completely knocked out by another TX on the same
channel. Or a pager 10 signal KHz away could desense your RX so much
that it can't hear yours. It's only reliable if there's no
interference. PCM handles interfence as well as can be expected, via
appropriate use of keep-position and failsafes, but either way, when
there's interfence, *you don't have control*, PPM or PCM.

| The problem is that there are lots of other users contending for band
| space who could easily move to modern radio technologies but are
| reluctant to give up "their" slice of spectrum.

`Easily' is relative. Buying new hardware is expensive. How would
you like it if the FCC said we were losing the 27, 72 and 75 MHz R/C
bands in two years, and we were all to migrate to something else,
probably 2.4 GHz spread spectrum?

And a lot of these places that would give up their spectrum would
migrate to ... cell phones. Which would provide some beneifts over
their current systems, but they'd have to pay per minute to use it.
They're not going to go easily.

| So the public uses like R/C and wireless networking tend to be
| crammed into little corners of the spectrum that nobody else wants

Nobody else wants? You're kidding, right? Spectrum is gold. Some is
more golden than others, but it's all gold. And as for the 2.4 GHz
band, the only reason it's not pure gold is that it's already very
popular, and even if the government outlawed it's use tomorrow, it's
use wouldn't stop.

| (the 2.4GHz band used by most wireless network equipment is open
| because its a set of frequencies that are absorbed by water
| molecules -- not that good for communication but excellent for
| microwave ovens).

Yes, microwave ovens use 2.45 GHz, and yes, water will absorb
radiation at this wavelength. However, this does not mean that 2.4
GHz is not that good for communication, unless you're trying to
communicate to a submarine (and they use megawatts and ELF signals for
that -- 76 Hz or so. Not KHz, not MHz, but Hz.) Attenuation due to
the atmosphere at 2.4 GHz is *negligible* -- about 0.01 dB/mile.
(Citation?
http://www.syngress.com/book_catalog...WAN/sample.pdf.) Even in
heavy rain (4 inches/hour), the attenuation is only 0.08 dB/mile --
utterly insignifigant to us, and how often do you fly in heavy rain
anyways?

In fact, 2.45 GHz was chosen because it's *not* the frequency where
water absorbs the most of the signal. This is a benefit because you
want your food cooked all the way through, not just at the surface.
(Citation: http://www.lsbu.ac.uk/water/microwave.html.)

| TV band and the VHF TV bands for sale -- so the chances of us getting a
| slice for free is, I'd guess, relatively slim.

True, on both accounts. Big bucks.

| I'd love to move to spread spectrum. Just not at microwave
frequencies.

Microwave frequencies would be great. 3.25 cm antennas? What's not
to love? At that size, you could even have a RX that has multiple
antennas, and it just uses the one with the best signal at any
instant. Yes, getting the antenna out of a carbon fiber boom might be
tricky, but that's easily solved by moving the first RF stage out of
the boom entirely -- a little button you mount on the outside if your
plane, and the antenna (or two) comes out of that.

It also lets you easily have a directional antenna on your TX, giving
you better range and/or using less power. (Granted, you don't want a
very high gain antenna, as it won't be aimed carefully at your plane,
but 6 dBi of gain would probably be just fine.)

The path loss is larger at this frequency (due to the smaller
receiving antenna and it intercepting less of the signal) but this is
easily compensated for with more sensitive receivers. Any external
interfernce is reduced by a similar figure, so it's not really a big
deal.

| If we could get our hands on just one redundant UHF TV channel that
| would keep us happy for a very long time.

Yes it would. And since our data rates are relatively low, we don't
even need that much bandwidth, even for 100+ simultaneously flying
airplanes in the same place. But 6 MHz of bandwidth could easily be
worth over a *billion* dollars. (Reference:
http://www.njtelecomupdate.com/lenya...879481137.html
-- 60 Mhz of spectrum worth $28 billion, so 10% of that should easily
be worth over a billion.)

That would be way cool if the AMA could buy us 6 MHz of spectrum in an
upcoming auction, but that would make even the new headquarters in
Muncie seem awfully cheap.

I'd love to see us get 1 MHz of bandwidth dedicated to SS R/C use (and
being SS, there's no need to break it up to air and ground
frequencies.) But I just don't see it happening.

--
Doug McLaren, dougmc@frenzy.com
-- Never do tomorrow what you can do the day after tomorrow --
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Old Feb 24, 2006, 08:16 AM
Bill's Email
Guest
n/a Posts
Re: Evolution of RC RF



Doug McLaren wrote:
> (I'm pretty sure that Futaba already
> sells industrial R/C equipment that uses spread spectrum, but I don't
> know the specifics.)



Indeed they do:

http://www.futaba.com/products/irc/i...tion/index.asp

There is no magic to this stuff and it is certainly not like the
Spektrum radio folks "invented" this technology. They were simply the
first to implement it for model use. I suspect that any radio company
that cares to can fairly easily implement their own version. But as is
being said in this thread there are a couple of hurdles that need to be
cleared before it can be fully brought to th model market.

Another little factoid about SS is that if you ever go out of range,
your link is toast. Once it is broken your TX and RX cannot reacquire
it. That would be bad. Definitely want to stay within range. Although
the current stated range is getting close to what my eyes can see!!


WEM

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