595U problems / DEBUG / antennas trial / Hopeless (long)

ac439 · EVDO Fledgling Joined: 20 Nov 2007 Posts: 17

Hi all....I'm a sprint PCS EVDO A user and have been reading this forum. I have the sprint/sierra 595U for about 9 months. They didn't sell me the USB720 so I had no choice but to get the 595U.

I live in an area that is a little rural but just within the EVDO A coverage area (according to sprint's map). At first, the setup was a breeze and I had the 595U sitting close to a window and got -92dbm to very weak signal. Signal bar always goes up and down. I got very flaky connections, poor up/down speed and high latency.

The next thing I did was to walk around outside the house with the laptop and been able to pull some nicer signal (around -85db to -88db). I was able to get much better up/down speed. However, the modem needs to be inside, connects to a WinXP box and share connection via ICS. So, being an radio guy, I know the importance of antenna height, low loss coax etc and I ordered some antennas to try. To put a long story short, I put antenna above the roof line and have been able to improve the signal strength (but not much) to -87dbm with reasonable up/down speed. I have been using this setup for 7 months until new problems (of course from sprint) in the past 2 weeks. Signal have been bouncing up and down, kicking from EVDO A to 1xrtt (I have never got EVDOx1 except once yesterday). When it is at 1xrtt, it is slower than a dial up connection with terrible latency. So, thinking I need to redo the external antenna, I got a wilson trucker with build in ground plane. Have it setup a couple of feet away from the first ext antenna. I'm pulling a slightly stronger signal but the up/down speed is getting worse. What stun me is I can have a -82 to -85 dbm displays on SCM, but once I click "GO", the signal bar drops significantly, sometimes to -109 or worse dbm. Once I have made a connection, I opened a browser side by side to SCM. Everytime I click a link to open a new web page (transmitting from modem to tower), the signal bar drops 3-4 bars. So, I thought: "Ok, maybe the battery in the modem is bad and unable to supply higher current to the modem for transmittion". Based on this assumption, I put the modem on different ports of the PC, and used it on another laptop, same problem. I then removed the battery, wired a 4V DC (via a regulated power supply) to the 595U in place of the battery, put a small screwdriver to the microswitch to enable the modem and retry - same thing ! I watched the ammeter on the power supply and it did not show current is being pulled from the modem. To double blind my study, I remove the power supply and battery, enable the microswitch and tested the transmission and the LED ocassionally change to RED, meaning not enough current from USB port and unable to draw any current from the battery (of course, it was disconnected). When I put the battery back and retest, the LED was solid green.

The next day, I did more testing outside the house. I masking taped the 595U on a 10' PVC pipe then I stood it straight it. I got -79 to -82 dbm. Strong signal, reasonable up/down speed. So, I have a crazy idea. I have the 595U on the top of the 10' PVC pipe (approx same height as the Wilson antenna), then I used a ZIPLOG bag to cover it, ran 20' of USB cable inside to connect to the PC. It ran fine for a day. I then went to LOWES and got some PVC electrical conduit box (design for outdoor use), put the modem in and clamped it on the same mask as the Wilson antenna, totally bypassing any external antenna and coax cable. I have been using this setup for about 12 hours now and I'm at -86~-87dbm but it will ocassionally drops to 95 to 98dbm even kicked into 1xrtt until resetting the connection.

I read about the ##DEBUG command and I have played with it a little. Someone here has another thread like "Putting an omni, better signal but worse performance". Someone replied to look at DEBUG to figure out how many towers the modem can see. I have gone through every DEBUG tab and can't figure it out. I'm using SCM 3.04.006, the DEBUG screen has a title bar of Protocol Statistic and I don't see anything refer to the number of towers it can see. On the "network 2" tab, I see a PN Offsets of 105 and Ec/IO of -15dbm.

I think -80 to -90 dbm should not be the issue because I had taken the modem and the laptop to another area (inside city) and I had a -90dbm signal but up/down speed was fantastic.

So, after reading EVDOforums for a while and my testing done, I think my modem can see several towers and maybe I'm located in the middle of them, that has cause the signal fluctuation (due to interference of the same frequency from multiple towers). I have also noticed that external antennas are not adding much signal compare to the modem's internal antenna, usually less than 5 db. Also, I don't believe the internal antenna will be disconnected when the external antenna connector is plugged in, it seems the external antenna is just added to the modem.

Ok, sorry for the long post, but I'm lost. I don't know what I should do next. I don't have much money to spend so buying an amp for $300 is out of the game. I'm thinking about wilson yagi so I can search the right tower. I do have quite a length of Belden 9913 coax if I have to go that route. I'm also thinking about making a cantenna and mount it on the horn of am old sat dish and use this setup to beam the tower.

Can anybody direct me to the link that shows how to interpret the DEBUG screen? Anybody fighting the same thing? Using the same modem? I really need some help and insight here ! Thanks !

I hope I can take some pics within a day or so and post them here so you guys can see my setup.

-AC

Jim_in_VA · Posted: Sat Mar 15, 2008 7:04 pm Post subject:

I don't know if the folks here at evdoforums would object to my posting a link about interpreting the debug screen. I don't want to step on any toes. Alex...any objection?
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Alex · Site Admin Joined: 19 Sep 2006 Posts: 1893

i've seen your debug info jim, feel free to post a link.
if you get in trouble, i get in trouble. Wink

Jim_in_VA · Posted: Sat Mar 15, 2008 8:18 pm Post subject:

hey thanks Alex. Want to be straight with you folks
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Alex · Site Admin Joined: 19 Sep 2006 Posts: 1893

we appreciate your participation, jim.

Jim_in_VA · Posted: Sat Mar 15, 2008 8:34 pm Post subject:

ac439,

I have a post on my blog http://evdotips.blogspot.com describing the various components of the debug screen. This is for a Franklin CDU680 but can easily relate to any other modem that has similar information accessible. I tried not to be too technical in order to keep from boring people to tears. Just ask at the email link there if you need more info.

..thanks Alex
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ac439 · EVDO Fledgling Joined: 20 Nov 2007 Posts: 17

Thanks Jim....I've already been on your site for an hour. First, I was guessing my S/N ratio has been poor. We have new power lines along our house and I'm not sure if this is the cause of the problem. So far, the new power lines have not been causing interference to my amateur radios but I don't have a spectrum analyser so I can't be sure. Second, I went to that link to search for towers within a 4 miles radius. I found 8 towers and most of them unregister and one own by the county. I can't related any of them to Sprint in details. All towers within the 4 miles radius are located at the edge of the circle, i.e. nothing close. The city limit is to the west side of my house (about 4.5 miles) and there are certainly sprint tower for sure but I have a 5 stories high oak tree at the west side of the house also so it is blocking signal between my location and the city. My DEBUG screen looks very different than the picture on your web and I don't see the section for various PN listed. I'm using SCM 3.04.006. What is the SCM I can use to obtain a much similar DEBUG screen to yours ?

One other thing I want to try is the cantenna. At least I can locate the tower I want. Since all the towers are all so far apart, I think a directional antenna should be the best bet. I may need to go up the roof to test it out.

Oh, I just was SCM 1.00.0069.0 (the newer one). Did the DEBUG. The list of PN services is completely empty !!! The PN is 0 !!! Same thing (no PN list) even after connected. Now I'm at 1xRTT. I have noticed that I have a packet error of 8727 in EVDO and Frame error rate of 533748 in 1xRTT section. Subnet color code 220.

Any ideas? Should I just go and try the directional antenna? Thanks

- AC

Jim_in_VA · Posted: Sun Mar 16, 2008 6:10 am Post subject:

If you are using antennasearch.com, in order to get data outside the 4 mile circle you need to enter another address in your search box that is outside the current view but in the general area, also check the "antennas" as well as the towers.

Even a 1xRTT signal has to have a pilot number, so I don't know what the issue is with your debug screen. I don't have a 595U to test it with. Packet Error Rate is usually given in percent so I don't know how the value you stated is relating to that.

The 595U does have an internal battery that must be kept charged to provide good performance. So it is possible you are having a power issue there with your USB port. You can try a Y cable or a powered hub to eliminate that possibility. Inadequate power will degrade the signal reception and connection speed. The 595U is noted for this.

By all means try the home-brew yagi. It performs well and won't cost you anything more than a little construction time and the jitters from drinking all that java first... Smile

You definitely need to try and find the towers even if you have to take your laptop out and "wardrive" your location. It will greatly simplify aiming a directional antenna and knowing just what kind of obstacles you are dealing with, both distance-wise and physically. What is your zip and street? You can IM that if you wish. Maybe I can help you out there. There are other ways to narrow it down.

Jim
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glenozzy · EVDO User Joined: 03 Jan 2007 Posts: 49

1. forget about RSSI the number is meaning less
2. PN and EC\IO is the number that want to be using and closer to 0 on EC is better

the Debug screen has the info you need to make it work correctly.

post a print screen of you debug mode

ac439 · EVDO Fledgling Joined: 20 Nov 2007 Posts: 17

Thanks for replies. I have screen shots from both the original sprint SCM and the newer one I download from their web site as below:-

Here's the first screen from the original SCM after I typed in ##DEBUG

Here's the screen from the same SCM but on Network 2 tab

Here's the screen shot from using the SCM ver 1.00 (the universal one downloaded from sprint web site) - It doesn't give me a list of PNs.

So, I'm not getting the PN info I needed. Is there another connection manager that will display the info? I also went to sierrawireless.com and they don't seem to have a connection manager for download.

Thanks. - AC

brigca · EVDO User Joined: 26 Jun 2007 Posts: 26

had many of the problems you've got and I finally resolved them and have been rock solid for the last week, first time ever. Assuming you're running windows.

1) download the newer sprint connection manager, 1.10.23, from www.sprint.com/downloads for supporting all the EDVO devices include Sierra/etc. It has some nice features too.

2) check firmware "tools->mobile info" and if you're not running p201002, the latest, then upgrade your firmware using the SCM "tools->check for new update". The interface is screwy, you have to click in the window, tab to get focus on the "start" button and then hit "enter". the mouse wont do it. you'll know you did it correctly when blue progress bars display otherwise keep hacking to get it started.

3) (0ptional) call sprint tech support and have them perform a ##RTN, not sure exactly what this does but I'm guessing it's a reinitalization of the modem, they had me do it. (must be disconnected)

4) change "tools->setting->mobile->mode" to "CDMA EVDO" to keep it from changing down to r1xtt. (must be disconneced)

5) change "tools->setting->mobile->connection type" to "NDIS" which allows windows to auto reconnect transparently which is a nice feature. (must be disconnect)
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ac439 · EVDO Fledgling Joined: 20 Nov 2007 Posts: 17

With the help of Jim, I have found the problem and been able to apply a fix (cheap). I'd like to express my sincere thanks to him. Jim, you are great !!!!

Here what I did:-

Without getting any PN info from the DEBUG screen, I decided to try out the cantenna. I don't have the exact coffee can as in Jim's site so I went to Lowes and got a brand new 1 gallon paint can. I also went to the local RatShack trying to get some female N connector panel mount or BNC panel mount to no avail. I wanted to try thing out fast so I didn't drill any holes but to masking tape everything inside the paint can. I found a 1.75" thick small plastic lunch box and taped the 595U over it, then I taped the whole thing inside the paint can (see pic below). I just let the USB cable coming out from the front. Then I started to aim towers.

First, I aimed to the one that is most likely a sprint tower. Signal improved a little bit but not much (The Ec/Io was still around 10dbm). I then aimed to the WNW side (towards the city, but no clear line of sight to tower and have trees blocking). The signal improved to around -81dbm and the Ec/Io came down to -6dbm. I have 5 signal bars and a very stable connection. Speedtest.net shows consistently 800k down and 250k up. My kids went on and play online games for a couple of hours and it was absolutely rock solid, not a single disconnection. I have also noted the signal bar has been very stable and don't see the dropping of signal anymore.

This morning, my up/down speed is even better. I have one test shows 1400k down and 250k up overall averaging above 1.2M down and 250k up.

My next step is to figure out the best way to put those things permanently and mount it. But now I have taped everything on the ladder. My wife thinks the cantenna is ugly, but I like homebrew. I would still like to get the modem inside and run a coax to the can instead (a typical cantenna design). Worse case, I have to get a yagi (to please my wife's eyes).

Here's some pics:-

Original omni antennas (left is Wilson trucker, right is Ebay dual band mount on home brew ground plane):

Cantenna based on Jim's idea:

Again, thanks Jim so much for your help !!!!

- AC

Jim_in_VA · Posted: Mon Mar 17, 2008 7:50 am Post subject:

lol...glad that worked out...now you can reclaim some roof space Laughing

...and use that Omni when you are mobile
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ac439 · EVDO Fledgling Joined: 20 Nov 2007 Posts: 17

I just want to post follow up that with the cantenna, I am having rock solid connection. I still have not have a chance to figure out permanent mounting yet. The speed has been great although there were a couple of days that the signal strength and the Ec/Io were not as good (about -89dbm and -10db). Now I'm always connects at Evdo Rev A (never connects at 1xrtt again since using cantenna). I found that the speed has an inverse relationship with the Ec/Io number. Usually, if my Ec/Io is less than 5db, the internet speed is always great. When this number rose to about 9db or 10db, the speed slowed down to about 300-400 k download (as the traffic on the tower got busy). So, I can conclude that signal strength is not a good indicator of connecting speed but the Ec/Io is.

I've a few new ideas now on the antenna including corner reflector and wire mesh parabolic reflector. I'm going to so some experiments and post result here.

ac439 · EVDO Fledgling Joined: 20 Nov 2007 Posts: 17

Nothing beats the USB modem inside the paint can ! I tried corner reflector, I can get 5 bars good signals but the down/up speed is not as good. I have also relocated the "modem-cantenna" inside the house and hung it over a window pointing to the west side; I have good signals bars and great down/up speed but for some reasons the connections paused a few times (even the SCM said connected). I have also tried putting the "modem-cantenna" at the same location as my Ebay antenna (above the roof) - great signal ! But I'm not comfortable with the modem under direct sunlight over there.

My conclusion is if the direct placement of the modem inside the paint can is the best, it completely eliminated the RF cable loss. The downside is leaving a piece of equipment outdoor that may expose to extreme heat.
- AC