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Calumet
EVDO Fledgling
Joined: 06 Sep 2007
Posts: 15
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 Posted: Sat Sep 08, 2007 8:41 am Post subject: Are dual band yagis that bad? Same band for 1x as EVDO? |
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| Do 1x and EVDO require different bands? Specifically for Alltel. |
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n6gn
EVDO Junkie
Joined: 22 Aug 2006
Posts: 337
Location: Northern California
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| Posted: Sat Sep 08, 2007 12:37 pm Post subject: Re: Are dual band yagis that bad? Same band for 1x as EVDO? |
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| Calumet wrote: | | Do 1x and EVDO require different bands? Specifically for Alltel. |
1x and DO are protocols rather than frequency ranges. This means that either can potentially be run any where that there is spectrum.
Yagis and most other antennas are frequency selective devices, they tend to be optimium for a particular frequency or range. Yagis in particular tend to be rather narrow band so special effort has to be made to do a good job supporting wide ranges or different frequency ranges in a single design.
In the US, the cellular bands are generally either at "850 MHz" or "1900 MHz" (aka PCS).
In actuality these bands are really ranges of frequencies, e.g. 1900 MHz is really 1850-1910 MHz for the handset to transmit and 1930-1990 for the base to transmit, overall requiring a combination receive/transmit antenna to be able to support 1850-1990 MHz.
Most often, a single service provider uses either 850 or 1900 but not both in a given area. Different providers purchased different spectrum in each area. It isn't uncommon to find Verizon running 1X and EVDO only in the 850 MHz band and Sprint running the same only in the 1900 MHz band.
So, if you are sticking to a single provider, not roaming onto a second or third which would be in different spectrum, a single band antenna may be all that you need.
Back to your original question; dual band yagis for 850 and 1900 are definitely a compromise and never work better, and probably usually not as well, as two separate well-designed single band yagis of the same size. Also, at higher gains, larger size, yagis tend to be difficult to make work as well as is theoretically possible.
OTOH, reflector antennas, like corner reflectors, dishes and co-linear arrays like patch antennas and stacked bow-ties, tend to be more forgiving.
Above ~15 dBi, yagis' theoretical performance is difficult to achieve. Co-linear arrays can often work well up to 20 dB. Much above that and dishes (or large horns) tend to be the only candidates left standing.
Probably more than you wanted to know.
n6gn |
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Calumet
EVDO Fledgling
Joined: 06 Sep 2007
Posts: 15
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| Posted: Sat Sep 08, 2007 1:49 pm Post subject: |
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Thanks, n6gn!
Great information. I have been reading old threads and was hoping that you would contribute to this one.
Is there any way to easily determine which band the tower is using so I will know which yagi to purchase? I have used the tower locator sites and that information isn’t provided. |
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Calumet
EVDO Fledgling
Joined: 06 Sep 2007
Posts: 15
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| Posted: Sat Sep 08, 2007 1:54 pm Post subject: |
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| n6gn: Another question: Do you know of any good sources for the other types of higher gain antennas that you mentioned? |
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n6gn
EVDO Junkie
Joined: 22 Aug 2006
Posts: 337
Location: Northern California
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| Posted: Sat Sep 08, 2007 2:19 pm Post subject: |
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| Calumet wrote: | | n6gn: Another question: Do you know of any good sources for the other types of higher gain antennas that you mentioned? |
If you search my previous postings you should find some measurement and availability information about a dish that I think has has particularly good value for PCS. I don't know of a similar value for 850 MHz, if it turns out that's what you need.
To determine what your current access is, I'd suggest you try to get your phone or modem into ##DEBUG# mode and look to see what it reports. That should give you quite a lot of information, including band, channel, strength, pilot info etc. A link to DEBUG codes for various devices was posted previously on this forum. Again, you'll probably have to search to find it.
n6gn |
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mooch
EVDO User
Joined: 02 Dec 2006
Posts: 40
Location: sunbury, ohio
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| Posted: Sat Sep 08, 2007 6:16 pm Post subject: |
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Ng6n, you've given me some advice in the past regarding antennas for my sprint service and I'm still messing with it. I started out with an omnidirectional Wilson trucker which brought my signal from -100db to about -95db. I've also tried a Wilson Yagi and I get about -92 db with it but my speeds are very close with either antenna (about 500 down and 100kbps up).
At one one point you had recommended that I try the grid antenna in the link below. My question at this point is that the grid antenna in the link is shown to be for 2.4 ghz and I was curious if anything would have to be done to this antenna to get it to work properly with Sprint EVDO REV A. Thanks!
http://www.hyperlinktech.com/web/hg2424g.php |
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n6gn
EVDO Junkie
Joined: 22 Aug 2006
Posts: 337
Location: Northern California
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| Posted: Sat Sep 08, 2007 8:21 pm Post subject: |
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| mooch wrote: |
At one one point you had recommended that I try the grid antenna in the link below. My question at this point is that the grid antenna in the link is shown to be for 2.4 ghz and I was curious if anything would have to be done to this antenna to get it to work properly with Sprint EVDO REV A. Thanks!
http://www.hyperlinktech.com/web/hg2424g.php |
Check the threads about those. Somewhere I reported my gain and SWR measurements of these antennas operating at 1.9 GHz. Bottom line is that they happen to work quite well for PCS.
n6gn |
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Calumet
EVDO Fledgling
Joined: 06 Sep 2007
Posts: 15
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| Posted: Sun Sep 09, 2007 9:38 am Post subject: |
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mooch
Tried to copy link to post n6gn referred but spam allert got me so here is the content:
[I just measured a pair of the WiFi dishes I referenced previously, with a microwave vector network analyzer on an outdoor range. They actually do even better than the claimed 24 dBi at 2.4 GHz.
The interesting (and useful) thing is that even though the matching impedance isn't great, about 2:1 VSWR, they work quite well at 1.9 GHz -- 23.5 dBi so they should make Sprint PCS work pretty well. The slight mismatch causes only ~.5 dB extra loss and is probably no worse than many PCS antennas as they are actually used. Furthermore, a little bit of cable loss rapidly improves the match that the phone sees. My opinion is that this is nothing to worry about.
These probably have at least 10 dB and maybe 15 dB more gain than any yagi you are likely to find.
You have to make sure to point them carefully though! I'd suggest pointing them with a compass and level rather than trying to use the RSSI reading from a phone or card. Be sure you mount them with the feed and ribbing running vertically. LMR400 makes a good feed line choice.
]
n6gn:
Hyperlinktech now has a 900mh parabolic grid listed at 15db gain. Do you think this will dip down into the 800s to cover CDMA?
I followed your suggestion of using the debug feature of my phone but was unable to determine the frequency. Signal strength was reported as 90MN / A. According to a tech bulletin from Wilson Electronics, the upper case “A” indicates 1900MHz on other phones so perhaps this is the case with my Motorola e815.
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n6gn
EVDO Junkie
Joined: 22 Aug 2006
Posts: 337
Location: Northern California
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| Posted: Sun Sep 09, 2007 1:48 pm Post subject: |
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| Calumet wrote: |
Hyperlinktech now has a 900mh parabolic grid listed at 15db gain. Do you think this will dip down into the 800s to cover CDMA?
I followed your suggestion of using the debug feature of my phone but was unable to determine the frequency. Signal strength was reported as 90MN / A. According to a tech bulletin from Wilson Electronics, the upper case “A” indicates 1900MHz on other phones so perhaps this is the case with my Motorola e815.
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I did just recently notice that they advertise the 900 MHz grid antenna. I suspect that it will work very well even between 800-850 MHz where a cell handset may transmit. One of the nice things about reflector antennas is that the feeds are generally simpler and tend to be broadband. Even if the SWR is slightly worse than the optimum, away from design center, I doubt that it will cause a problem or significant degradation down to the bottom of the US 850 MHz cell band. I'd have to measure one to know for sure but I'd tend not to worry about it. I'd think one would very much be worth trying if you know for sure that what you want is an 850MHz-only antenna with a lot of gain.
I'd also be interested to know if anyone has more information about the "A" suffix in the DEBUG report. It could mean you're seeing an "A" block of PCS [1850-1865 MHz and 1930-1945 MHz] which is very common, if not the most common PCS allocation.
n6gn |
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Atanasoff7
EVDO Newbie
Joined: 18 Sep 2007
Posts: 3
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| Posted: Wed Sep 19, 2007 3:01 pm Post subject: |
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| Is there a way to combine the output of one 800 and one 1900 antenna to provide a signal containing both? |
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n6gn
EVDO Junkie
Joined: 22 Aug 2006
Posts: 337
Location: Northern California
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| Posted: Wed Sep 19, 2007 10:33 pm Post subject: |
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| Atanasoff7 wrote: | | Is there a way to combine the output of one 800 and one 1900 antenna to provide a signal containing both? |
Yes, the device is called a diplexer and for bands separated as far as 850/1900 it is actually a fairly simple device, most cell phones have at least one of them built into them. They are actually very inexpensive.However, getting something with connectors on it for the use you are suggesting might cause the price to go up.
Maybe someone on here knows of an economical source of connectored/packaged ones.
n6gn |
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Jayson
EVDO Heavy User
Joined: 17 Feb 2007
Posts: 101
Location: ohio , in the sticks
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| Posted: Fri Oct 26, 2007 9:49 am Post subject: |
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hey n6g9 i was wondering if this antenna would work the same as the hyperlink
WIFI Grid style directional Antenna, 2.4Ghz with an advertised 24 dBi gain.
Electrical Specifications:
Frequency 2400-2500 MHz Gain 24 dBi -3 dBi Beam Width 8 degrees Cross Polarization Rejection 26 dBi Front to Back Ratio 24 dB Sidelobe -20dB Max Impedance 50 Ohm Max. Input Power 50 Watts VSWR < 1.5:1 avg. Lightning Protection: DC Short
Mechanical Specifications:
Weight 8 lbs. (3.62 kg) Grid Dimensions 39.5 in (100 cm) x 23.5 in (60 cm) Mounting 1.25 in. thru 2 in. (31.8 - 50.8 mm) diameter mast max. Elevation Angle 0 to +10 degrees
RoHS Compliant. Operating Temperature -40° C to to 85° C (-40° F to 185° F)
thanks!!!!! |
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n6gn
EVDO Junkie
Joined: 22 Aug 2006
Posts: 337
Location: Northern California
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| Posted: Fri Oct 26, 2007 10:47 am Post subject: |
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| Jayson wrote: | hey n6g9 i was wondering if this antenna would work the same as the hyperlink
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Well, what you're wondering is if the out-of-design-band performance of one antenna will be the same as that of another. Generally the answer is no but I can't tell you for sure without measuring it.
The hyperlink antenna I measured and reported is a parabolic reflector. The reflector part of these antennas almost always operate well over a very large frequency range. The grid (non-solid) reflector has a limitation as to highest frequency at which it works well. Essentially above some frequency the spacing becomes to great and signal starts penetrating rather than reflecting from it.
The frequency selective portion of these antennas is in the feed, the part that sticks out in front of the reflector. Normally these are relatively simple antennas, often just a dipole and a reflector, which have relatively broad bandwidth (frequency coverage). However 1.9 GHz is quite a ways from 2.4 GHz - about 20 %. Even for a dipole feed this is starting to be rather far to expect good performance.
When I measured the Hyperlink, I found that the impedance match degraded below 2.4 GHz but actually got better again around PCS - being around 2:1 VSWR. Mismatch in itself isn't necessarily a big deal. It means that without extra effort, not all of the power is transferred from one place (the coaxial cable or handset) and another (the antenna). But even for moderate mismatches the loss may not be terribly significant. That was the case for the hyperlink, it wasn't quite as well matched at PCS as at 2.4 but the grid reflector actually works a bit better at PCS and the bottom line is that the antenna as a whole works very well.
So, this overly long answer is just to say " I don't know" but that there's a reasonable chance that a different WiFi antenna will still work pretty well. 
n6gn |
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xrayman
EVDO Junkie
Joined: 23 Feb 2007
Posts: 253
Location: Kansas City
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| Posted: Fri Oct 26, 2007 2:10 pm Post subject: |
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| n6gn since we on the topic of the hyperlink 2.4 GHz antenna you tested at 1.9 GHz, what do you think about using this same antenna at 2.5GHz? |
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n6gn
EVDO Junkie
Joined: 22 Aug 2006
Posts: 337
Location: Northern California
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| Posted: Fri Oct 26, 2007 2:53 pm Post subject: |
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| xrayman wrote: | | n6gn since we on the topic of the hyperlink 2.4 GHz antenna you tested at 1.9 GHz, what do you think about using this same antenna at 2.5GHz? |
I don't think I noticed when I measured it. But if you mean 2.50 GHz, I think it will be fine. Even at 2.59 GHz it's probably in good shape but I suspect that by the time you get to 3 GHz, even if you were to retune the feed, that there would be some degradation. It appears to me that the grid spacing is about all that can be tolerated for good performance up to a 2.4-2.5 GHz upper limit.
n6gn |
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