Trimble R8 Model Differences

We run a model 1 and it has a weak internal antenna (600 foot range), so a repeater is required. Also, no glonass.

If you are looking to purchase used, I know model 3s are the ones to seek out. I don't remember the difference between 2 and 3.

After some internet research, it seems that the hardware is largely the same with the exception of the number of channels:
Model 2 = 72 channels
Model 3 = 220 channels
Model 4 = 440 channels

So I have 2 questions:
(1) the antenna is a parallel receiver not multiplexing or sequential, right?
(2) how many channels do you really need to effectively watch 8 GPS + 8 Glonass satellites (assuming/estimating possible 1/3 of each constellation available at a given moment)?

Scott Bordenet, post: 324075, member: 10097 wrote: After some internet research, it seems that the hardware is largely the same with the exception of the number of channels:

I added to your list...

5800 = Predecessor
R8 Model 1 = 24 channels, GPS Only, Transmit Option (5800 did not have a transmit option)
R8 Model 2 = 72 channels, GPS & GLONASS
R8 Model 3 = 220 channels, GPS, GLONASS, GALILEO
R8 Model 4 = 440 channels, Full GNSS Constellation Support including Triple-Frequency Tracking

Satellite based correction services supported by each varies. These also use channels, depending on what you can pick up.

Answer:
(2) At present, you need 32 channels for your example configuration. 8 x GPS L1, 8 x GPS L2, 8 x GLONASS L1, 8 x GLONASS L2

Thanks for the confirmation...
No if you add in GPS L2C and L5 plus L2P Glonass, that is another 24 channels bringing the total to (32+24=) 56.

Now, will the receiver dedicate channels to ephemeris download? That would temporarily add 16 more channels bringing the total to 72. Is this correct? Then after ephemeris download are these 16 channels left for acquiring new satellites as existing satellites drop from view?

Scott Bordenet, post: 324235, member: 10097 wrote: Thanks for the confirmation...
No if you add in GPS L2C and L5 plus L2P Glonass, that is another 24 channels bringing the total to (32+24=) 56.

Now, will the receiver dedicate channels to ephemeris download? That would temporarily add 16 more channels bringing the total to 72. Is this correct? Then after ephemeris download are these 16 channels left for acquiring new satellites as existing satellites drop from view?

You are correct on your channel math, however their really aren't enough satellites with L5 to take into effect. These are very good questions that I'll look into. I haven't run anything less than Model 3's in years, so 220 channels covers what you need in today's sky.

I guess Trimble can do whatever they want (and they did), however when you go to pick an NGS antenna model, the confusion begins to get real deep, it would of been far better to call these a different model IMO. For R8 models the NGS lists:

TRMR8 NONE

TRMR8-4 NONE

TRMR8_GNSS NONE

TRMR8_GNSS3

Maybe this is more of an NGS issue, BUT if these weren't all named R8 by Trimble then I think the NGS confusion would go away, just something that irks me every time I have to deal with R8 data. I realize most users probably only deal with what they own, BUT I am one of those guys that processes GNSS data daily from a multitude of sources in addition to the Leica receivers I own. Usually I am told it is an R8, OK, now which one do you have and secondly I have to interpret that into what NGS named them, heck we would be way better off if we just used part numbers for ALL manufacturers antennas instead of a model which seems to be a little nebulous at times. Leica isn't immune either , there is a LEIAX1202 and a LEIAX1202A, does the "A" model look different or even have an "A" on it, NO! It has to do with the hardware revision number on the bottom of the antenna which probably very few folks know about since this info was published in a Leica document dated September 2006!

SHG

From what I understand, the NNS picks these names. You'd think they could add the Full Name to their data base. NONE refers to attachments, such as Radomes or Snowdomes... which gets much more confusing (look at the Zephyr Antennas).

SurveyAK said: "I haven't run anything less than Model 3's in years, so 220 channels covers what you need in ** today's ** sky."

The reason why I ask is I am planning to use some Model 2's to drop horizontal and vertical control on sites. I will use one as a rover on the Indiana RTN. I would estimate 4-6 points that I could then use for radial topo. Maybe I would go hit a couple of section corners if I wanted to do a boundary but probably not.

I am trying to asses if and how long Model 2's will be useful. They are very inexpensive now and would save many man-hours of traversing and leveling over the course of a year. Just 10 half days per year = 40 man hours at $125/hr = $5000. If they have a service life of 5 years, then they would have a minimum value of (5 x $5000=) $25,000 at a cost of $5,500.

Does this make sense - does my math work?