12-channel or 18-channel ?

[royfang]

I am a newbie to geocaching, and am shopping for my first GPS ... I found two models claiming faster response time with 18 channel receiving. Anyone care to provide some insight into the differences? The maker is new to the industry, but make good products in the past with the "cobra" brand.

 

Roy Fang

[+Dave_W6DPS]

I haven't seen these, but it seems frivolous. There are only 24 active GPS Satellites, plus two WAAS birds.

 

It is not too common to get to 12 satellites "in view", and I doubt it would be very likely to get more than 12 often enough to make the additional receiver channels more than a gimmic.

 

It might be better, if you actually have more than 12 birds in view, but I don't think you will see that often enough to make it worth much more money.

 

DO you have a URL for these models? I would like to check them out and be able to make a more informed assessment. (Although, lack of facts is not enough to keep me from commenting, obviously!)

 

Dave_W6DPS

 

My two cents worth, refunds available on request. (US funds only)

[+AmericanSpirit]

I've never even had all 12 channels recieving, so i highly doubt that the 18 would be better/faster. The unit would probably make far more difference then the channels in my opinion, I had an old eagle accunav unit that was 5 channel and worked a lot better than my first 12 channel magellan.

 

There are 10 types of people in the world..those that understand binary and those that don't

[+RobRee]

cobra makes them.

100, 500, 1000 are the numbers. prices will start at 120. windows based menu system (i bail on that one), lots of claims.. read for yourself...

 

cobra electronics

 

robbie

 

A family that Geocaches together... eventually gets wet.

 

required reading

My first bible

Great Orienteering Site!

[royfang]

Yup... also can be found on Google shopping site:

http://froogle.google.com/froogle?q=cobra%20gps%201000&price1=156&price2=299.99&price=between&btnP=Go

 

I called Cobra, there seemed to be some problem with the product family, and they told me that only Cobra 100 is available via Best Buy!

 

Roy Fang

[royfang]

Thanks to all, more discussion sepcifically obout model Cobra 1000:

 

http://www.gpspassion.com/forumsen/topic.asp?TOPIC_ID=1679&SearchTerms=cobra

 

Roy Fang

[+Renegade Knight]

I would avoid Cobra on general principal.

 

=====================

Wherever you go there you are.

[+Dave_W6DPS]

It looks like only the GPS100 is currently available. I may have missed something, but I looked through the manual, quick start card, and reference and found nothing about making a data connection to a computer.

 

The price doesn't seem bad for the features.

 

As for 18 channel receiver vice 12, I still think it is a gimmic more than anything practical. The software is probably where they managed to improve speed.

 

It will be interesting to read some experiences of those who actually buy and use them.

 

I hope I am wrong about no data connection--it would make a GPSr virtually useless to me if I can't connect to a computer. I am looking forward to buying a model with a USB 2.0 connection built in, instead of the antique RS-232 on my Etrex Venture.

 

Dave_W6DPS

 

My two cents worth, refunds available on request. (US funds only)

[+PDOP's]

I agree that 18 channels is probably just a gimick for a recreational GPSr but there must be some valid uses as here's an aviation unit with 24 channels.

 

PDOP's GPS Pages

[+Bilder]

Cobra makes good CB's and FRS radios. Not sure how they would do in the GPS market. I know thier phones had some issues.

 

-------------------------------------------------------------------------------

I have never been lost. Been awful confused for a few days, but never lost!

[+Dave_W6DPS]

quote:

---

Originally posted by PDOP's:

I agree that 18 channels is probably just a gimick for a recreational GPSr but there must be some valid uses as here's an aviation unit with http://www.cmcelectronics.ca/products-services/aviation/CMA-4024GPS.html

 

http://members.shaw.ca/pdops/

---

 

There are reasons for aircraft--they use the channels beyond 12 to recieve SBAS/WAAS and GBAS/LAAS signals. Cobra doesn't mention either of these technologies on the web page for the GSP100. For aviation use there are systems that can provide a lot of signals. Mode L GPS has 24 satellites in 12 hours orbits, evenly space on three main ephemera. Add the two WAAS satellites in geostationary orbits (assuming you are near the west coast and can receive both) it is still unlikely you will actually have more than 12 birds in the aperture of a patch antenna. A patch is almost horizon to horizon, but not quite. With no mountains, buildings, trees, etc., you might get 10 of the standard satellites.

 

I still think the 18 channels are a gimmic. Of course, if they can upgrade the software to use LAAS or some of the other SBAS systems, that would be great.

 

We'll have to see if Magellan and Garmin answer with more than 12 channels in the near future.

 

Personally, I would still prefer that they work on a USB connection. And I still don't see any indication of a computer connection on Cobra's GPS 100. The limited info i can find on the GPS500 doesn't mention it either. The GPS1000 is said to have "capability for PC interface".

 

Dave_W6DPS

 

My two cents worth, refunds available on request. (US funds only)

[+welch]

quote:

---

Originally posted by Renegade Knight:

I would avoid Cobra on general principal.

 

=====================

Wherever you go there you are.

---

 

Why is that?

 

[+Renegade Knight]

quote:

---

Originally posted by welch:

quote:

---

Originally posted by Renegade Knight:

I would avoid Cobra on general principal.

 

=====================

Wherever you go there you are.

---

 

Why is that?

 

http://brillig.com/geocaching/http://img.Groundspeak.com/user/22008_1700.gif http://www.gpgeocaching.com/

---

 

When I was a kid I had a Sanyo ghetto blaster. It eventually recorded clicks on all my cassettes and that rather pissed me off. Now even if Sanyo get's great ratings I won't buy it.

 

However since that time if I also get a feeling that a company is on a par with the Sanyo of old I won't go near it. Cobra strikes me as cheap junk for no particulary good reason. I've had enough junk break on me to avoid it unless I can't afford better at all.

 

Call it a bias.

 

=====================

Wherever you go there you are.

[+junglehair]

I agree with all above that the 18-channel is just a gimmick. I did want to share the following picture with you though of my GPS using all 12 channels. It was such a rare event that I had to take a picture of it!

 

 

-Junglehair

 

There are 10 kinds of people in this world - those who understand binary and those who don't.

[+Spzzmoose]

18 channel sounds like a waste of cache to me also!

[Kerry.]

18 channels is a little overboard right now and if one could find any mention of GNSS then that might make some sense.

 

But no mention of GNSS (GPS + Glonass) so cross that option of the list.

 

Actually there's been some speculation that receiver channels would increase to 14 or maybe even 16 to account for the "feeling" that WAAS is pinching something useful, which it really isn't anyway.

 

So maybe 18 is just as cheap as 14 or 16 or whatever.

 

In a few year times probably even 24 channel receivers (which have been around for quite a few years) will be outdated if there's a GPS + Galileo + Glonass built. If this milestone is reached then there'll be something like about 80 satellites and even 24 channels will be obsolete.

 

Cheers, Kerry.

 

I never get lost everybody keeps telling me where to go

[royfang]

Hi, thanks to all for the efforts and input.

 

Benefit just as much also from another thread (On a budget - what GPS to buy?) , people here are nice!

 

Roy

 

Roy Fang

[+Searching_ut]

The possibilities of the Cobra's extra channels was discussed awhile back on the Sci.geo.... newsgroup. About the only possibility of the 18 channels being useful that I saw involved autolocating. By being able to search for more sats at the same time, you could possibly speed up the process. Of course if you have a reasonable approximation of your position to begin with, and the time of day of course this wouldn't necessarily make any difference. I'm betting this takes off in a big way with the public however, with many seeing remarkable performance differences. I'm often amazed how much influence the marketing guys have.

[+stu_and_sarah]

I was wondering if this was some sort of specmanship loophole. The screenshots in the manual etc. look like a copy of an eTrex yellow - but to have something to sell it, they need to spec more stuff.

 

For example, the cobra claims an altimeter and compass. However, I don't think the altimeter is barometric, nor is the compass a 'non-moving' one.

 

Looking at the satellite acquisition screen, there are only 10 bars to show signal strength. Now, I don't know if there's another page of them, but if it's 18 channel would there not be 9 bars per page?

 

I'd be wary... and as people have said - how many times do you actually get 12 satellites?

[Kerry.]

quote:

---

Originally posted by Stu & Sarah:

... and as people have said - how many times do you actually get 12 satellites?

---

 

Has a little to do with one's location but in my part of the world, 12 sats 10.6% of the time, can see up to 14 some of the time but that's of academic interest only.

 

No it's not normal or something one should expect and really doesn't mean all that much either but we do have an above normal constellation and if we ever get down do the level the standards are actually based around then some are going to be complaining long and hard but right now they are rather pampered and a little spoilt.

 

If things ever get to the level the standards are based on then that might sort a few out.

 

Cheers, Kerry.

 

I never get lost everybody keeps telling me where to go

[royfang]

Here is the quote from a GPS Watch product review... less channel IS translated into slower reading, or not? Is quick reading in geocaching a critical factor? (as quick draw in a duet ?)

 

http://www.gearreview.com/casiogps.asp

 

"......The GPS watch tracks up to eight satellites at once using eight parallel receivers, or channels. The manufacturer claims that a satellite acquisition will complete in 50 seconds or less, but we found that it took longer than that when there are obstructions. If you are in the same general location and you have previously obtained a reading, satellite acquisition is quicker - about 15 to 20 seconds. We found this to be slower than hand held GPS units as they can track up to 12 satellites at a time instead of Pathfinder's eight. ......."

 

Roy Fang

[+ScottJ]

If you wouldn't buy a food processor made by Honda, or a car made by Sunkist, or a TV made by Frigidaire, why would you buy a GPS made by Cobra?

 

Don't get me wrong, it might be a fine GPS ... but it'll take a lot of fine points to overcome the fact that it was made by a CB radio manufacturer who's never built one before.

 

--

Scott Johnson (ScottJ)

[+Cachetrotters]

For those not interested in or reading regularly about astronomy, the high-end telescopes now provide positioning for alignment using built-in GPSr in the forks. Some advertise in excess of 12 channels so you REALLY know where your telescope is, so therefore polar-alignment is better than the competitors model.

 

Sheesh.

 

PS- Can't wait to hear all the crying from those who couldn't find the cache with 18 channels--more than enough of that now with only 12...

[Jeremy]

At Groundspeak we try and pick up at least one of each model so we know how all the GPS units work.

 

I almost picked the Cobra at Best Buy but after being skunked with the low end Geko with a lack of a cable connector, I checked the low-end Cobra and it has the same problem. I'll wait for the next version to come out with the cable before I make a decision on their models.

 

The 18 channel claim reminded me of the movie Spinal Tap quote "It goes to 11" - I actually called up the PR folks for Cobra to get more info on their product and they indicated that it gets a faster signal lock since each channel can roam to lock on satellites faster. Obviously if there are only so many birds within view there won't be an improvement on accuracy, but from a cold start it *should* lock into the satellites faster.

 

I'm apprehensive as to the quality of the GPS receiver, but since I don't have a first-hand account of the interface and hardware, I can't give an informed option. It is, however, good to know that there is another possible leader in GPS unit design.

 

At this point I would Garmin or Magellan over a Cobra Unit, and ignore 18 channels as a deciding factor in your GPS purchase.

 

Jeremy Irish

Groundspeak - The Language of Location

[+Bloencustoms]

Here in southeast LA, I have had a lock on all twelve channel at onec many times. I'm onlyable to see one of the WAAS sats, but even with WAAS disabled and the 12th channel open, it still gets a lock. It's not uncommon for me to see EPE's of 15 feet or less with WAAS enabled. It does take a few moments to get a lock on the sats, but so long as to be a problem.

 

"The fertilizer has hit the ventilator"

[lomd]

quote:

---

Originally posted by Roy Fang:

Here is the quote from a GPS Watch product review... less channel IS translated into slower reading, or not? Is quick reading in geocaching a critical factor? (as quick draw in a duet ?)

 

http://www.gearreview.com/casiogps.asp

 

"......The GPS watch tracks up to eight satellites at once using eight parallel receivers, or channels. The manufacturer claims that a satellite acquisition will complete in 50 seconds or less, but we found that it took longer than that when there are obstructions. If you are in the same general location and you have previously obtained a reading, satellite acquisition is quicker - about 15 to 20 seconds. We found this to be slower than hand held GPS units as they can track up to 12 satellites at a time instead of Pathfinder's eight. ......."

 

Roy Fang

---

 

That is accurate, but far less significant

than it might appear to be. The main advantages

of any additional channels after the eighth

are reduced cold-start acquisition time (which

may well be a noncritical factor, especially for

geocaching) and a _bit_ more ease in dealing with

movement and tree (or mountain, bulding, etc)

cover.

 

In real practive, tree (or mountain) cover,

exactly how many satellites are actually visible

at a given time (it is rare enough to have ten,

let alone 12 or 18) and the relative positions

of said satellites are far more important

factors. It is especially important to realize

that as long as you maintain a reliable signal

from three satellites (four if you want altitude

info), each additional satellite helps mainly

in keeping the lock (since satellites wander out

of sight continuously), but has very little

effect on accuracy. It has been said, and it

is probably true, that an unit with five parallel

channels is more accurate than a multisequential

eight- , twelve- or eighteen-channels unit.

 

There are systems that allow one to get much

improved accuracy with GPS receivers - mainly

DGPS and WAAS - but they are considerably more

complex than just having additional, essentially

idle channels.

[royfang]

OK... damage is done... , just got my etrex this morning from Circuit City for $99 (reg. 119)

 

Aiming to get the Earthmate for my tablet PC, that way I get in-car navigation with 14" color screen plus an off-road piece for a total of less than $230 (i.e. on top of the sunk investment on a tablet PC)!

 

Roy Fang

[+Searching_ut]

quote:

---

Roy Fang said:

 

Aiming to get the Earthmate for my tablet PC, that way I get in-car navigation with 14" color screen plus an off-road piece for a total of less than $230 (i.e. on top of the sunk investment on a tablet PC)!

---

 

If your tablet PC has a serial port, or if you have a serial to USB adapter, you might find your eTrex to be as good an option if not better for use with your tablet PC. It outputs NMEA data, which means you can use it with most GPS enabled mapping software. I use my GPS units with my pocket PC for road navigation. If you're caching, you use the PC software to navigate on the roads by, then simply disconnect the cable and head out the door when you find the best parking spot.

[royfang]

wow ... there's a potential for a huge saving.. $70 less the cost of a a cable!!

 

Thanx!

 

Roy Fang