Strange behaviour with wireless N adapter and corner reflector antenna

Bought a Mini 150Mbps USB WiFi Wireless Adapter 150M USB LAN Card 802.11n/g/b with 2 dBI Antenna.

This uses the Realtek RT5370 chipset.

I already was using an RT8187L USB with antenna in the back room and I swapped over to the new USB adapter to see how it performed in comparison.

I must say the performance was very impressive, equal to or even slightly more sensitive than the previous Realtek.

So I then played around trying various antennas on the new adapter - dipol, yagi, biquad, patch etc and all performed as per expectations until I attached my corner reflector (dipole based).

Performance was shot to pieces. Signal strength was excellent but quality was almost zero.

I double checked the connection. It's using "G" as I don't have an "N" router.

Is this some sort of modulation issue ?

Any idea Why the huge drop in performance ?

Rob

Ps here's the unit, which at $5 AU is amazing value. Quite well made too.

http://www.ebay.com.au/itm/ws/eBayIS...:AU:1123#rpdId

Dr Who wrote:

> Bought a Mini 150Mbps USB WiFi Wireless Adapter 150M USB LAN Card 802.11n/g/b with 2 dBI Antenna.
>
> This uses the Realtek RT5370 chipset.
>
> I already was using an RT8187L USB with antenna in the back room and I swapped over to the new USB adapter to see how it performed in comparison.
>
> I must say the performance was very impressive, equal to or even slightly more sensitive than the previous Realtek.
>
> So I then played around trying various antennas on the new adapter - dipol, yagi, biquad, patch etc and all performed as per expectations until I attached my corner reflector (dipole based).
>
> Performance was shot to pieces. Signal strength was excellent but quality was almost zero.
>
> I double checked the connection. It's using "G" as I don't have an "N" router.
>
> Is this some sort of modulation issue ?
>
> Any idea Why the huge drop in performance ?
>
> Rob
>
> Ps here's the unit, which at $5 AU is amazing value. Quite well made too.
>
> http://www.ebay.com.au/itm/ws/eBayIS...:AU:1123#rpdId

OOOps I just realized I put the readings back to front for the corner reflector.

The link quality is excellent at 95%, but the signal strength is terrible.

Changed the connector but still unusable.

All the other antennas work excellently with the adapter.

On 13 Jan 2012 08:54:53 +1000, "Dr Who"
<dead_letter_office@hotmail.com> wrote:

(snip)
>So I then played around trying various antennas on the new adapter - dipol, yagi, biquad, patch etc and all performed as per expectations until I attached my corner reflector (dipole based).
>
>Performance was shot to pieces. Signal strength was excellent but quality was almost zero.
>
>I double checked the connection. It's using "G" as I don't have an "N" router.
>
>Is this some sort of modulation issue ?
>
>Any idea Why the huge drop in performance ?

Faulty antenna - design or fabrication.

On 13 Jan 2012 08:54:53 +1000, "Dr Who"
<dead_letter_office@hotmail.com> wrote:

>Bought a Mini 150Mbps USB WiFi Wireless Adapter 150M
>USB LAN Card 802.11n/g/b with 2 dBI Antenna.

Tiny little thing. Impressive.

>This uses the Realtek RT5370 chipset.
>
>Signal strength was excellent but quality was almost zero.

I think you mean signal strength was lousy while link quality
was high. The way it works is that link quality is really
a measure of the bit error rate. If there's little data moving,
the link quality tends to be a rather high number.

Also, some drivers and chipsets seem to have problems reporting the
signal strength and quality. I'm not sure of the issue, but I have a
USB dongle (chipset unknown) which reports zero signal strength at all
times. However, it works just fine.

>I double checked the connection. It's using "G" as I don't have an "N" router.

Good. That makes troublshooting less complicated. However, if your
driver allows you to turn OFF the "N" features, I would try that just
to see if it helps.

Tell me about the corner reflector. How is the antenna positioned?
What is the antenna orientation relative to the reflector?
What OS are you using?
What program are you using to display the signal strength and quality?
Duz it work normally without the corner reflector?

Want me to recycle my previous rant on why using an omni to illuminate
a dish (or corner reflector) results in plenty of receive gain, and
miserable transmit gain?

>Is this some sort of modulation issue ?

Probably not.

>Any idea Why the huge drop in performance ?

Nope, not enough info. (Hint: Numbers please).

>Ps here's the unit, which at $5 AU is amazing value. Quite well made too.
>http://www.ebay.com.au/itm/ws/eBayIS...:AU:1123#rpdId

I'm tempted to buy one just to play with it. Looks nice on paper.


--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com jeffl@cruzio.com
# http://www.LearnByDestroying.com AE6KS

The RT5370 is a RAlink part, not realtek. Different companies.

http://www.ralinktech.com/en/index.php
http://www.realtek.com/

Both companies have their fans. However, I can tell you the RT8187 is
totally kick ***. The Rokland Tube/U version is worth checking out,
unless you are looking for uber cheap parts.

This is the high speed alfa I have
> http://inchi1.ez-show.com/in/front/b...ategory=105483

The website indicates Ralink RT2770 RT2750. I don't recall which chip
set it uses. I can tell you the 2.4Ghz performance is no comparison to
the RT8187, though it is fine for home use. Just don't expect to do any
long distance links with the Ralink part.

The RT8187 has a virtual router option in the windows driver. Very nice.

miso wrote:

>
>
> The RT5370 is a RAlink part, not realtek. Different companies.
>
> http://www.ralinktech.com/en/index.php
> http://www.realtek.com/
>
> Both companies have their fans. However, I can tell you the RT8187 is totally kick ***. The Rokland Tube/U version is worth checking out, unless you are looking for uber cheap parts.
>
> This is the high speed alfa I have
> > http://inchi1.ez-show.com/in/front/b...ategory=105483
>
> The website indicates Ralink RT2770 RT2750. I don't recall which chip set it uses. I can tell you the 2.4Ghz performance is no comparison to the RT8187, though it is fine for home use. Just don't expect to do any long distance links with the Ralink part.
>
> The RT8187 has a virtual router option in the windows driver. Very nice.


Yes, I've use the 8187L chipset for many years and I'm well aware of how good a performer it is.

This RT5370 chip is no slouch either and it's low power use as well, which is a good thing given the 8187L pulls full USB power and drains the battery quicker than most.

I think Jeff may be on the money that it's not reporting correctly. Same thing happens with Realek adapters in Linux where they look bad but are actually going OK.

For $5 - 6 it's an ammazingly good little dongle.

I will try a few file transfers and clock it to see what happens.

If you read the reports from Rokland, Data Alliance, etc. the RL8187 is
an exceptional chipset. Both advise that you get the RL81817 if you
don't want 5GHZ. I have them both and can tell you the Realtek runs
rings around the RAlink.

http://www.data-alliance.net/Page.bo...late=alfa-wifi
Basically if you need N, get the 036NH, otherwise get the 036H.

My experience isn't simply with reporting, but rather with actual long
distance use. Based on simply the number of WAPs seen, the 8187 is the
winner as well.

Sure it is fine for the price. Search for "300Mbps USB Wireless Adapter
WiFi Lan Network Card". Three bucks more, but the realtek chipset.

I prefer the realtek driver over ralink.

miso wrote:

>
>
> If you read the reports from Rokland, Data Alliance, etc. the RL8187 is an exceptional chipset. Both advise that you get the RL81817 if you don't want 5GHZ. I have them both and can tell you the Realtek runs rings around the RAlink.
>
> http://www.data-alliance.net/Page.bo...late=alfa-wifi
> Basically if you need N, get the 036NH, otherwise get the 036H.
>
> My experience isn't simply with reporting, but rather with actual long distance use. Based on simply the number of WAPs seen, the 8187 is the winner as well.
>
> Sure it is fine for the price. Search for "300Mbps USB Wireless Adapter WiFi Lan Network Card". Three bucks more, but the realtek chipset.
>
> I prefer the realtek driver over ralink.


Interesting stuff miso.

I've long been a fan/user of the 8187L and yes it is top of the 54G heap - and the current long distance heap I suppose.

I just ran some basic tests to compare throughput and sensitivity of the 8187L v the cheap RT5370.

Sent a 9 MB file between my DLink DSl-2642B router (standard dipole) and my old 1.6 Athlon test rig several rooms away. Distance about 30 feet, three red brick walls between antennas.

15 element beam yagi - 8187L - 6.2 secs, 5370 - same
10 DBI Biquad - same results as above.

So no variation in throughput.

1.45 MB/sec is pretty good in that situation.

Ran Network Stumbler and used beam yagi to pick up weak signal with 8187L more than 100 metres away - 77 dBm

Hooked up the 5370 to yagi, wasn't in the same ball park for signal strength, way down near 95 dBm

So 8187L is king on sensitivity.

BUT, the interesting thing was that whereas the 8187L picked up 6 ssids, the 5370 found 7.

The yagi was not moved between testing.

While the 8187L is clearly the better chipset, for $6 the 5370 is pretty amazing value for in house use.

Rob

Dr Who wrote:

> miso wrote:
>
> >
> >
> > If you read the reports from Rokland, Data Alliance, etc. the RL8187 is an exceptional chipset. Both advise that you get the RL81817 if you don't want 5GHZ. I have them both and can tell you the Realtek runs rings around the RAlink.
> >
> > http://www.data-alliance.net/Page.bo...late=alfa-wifi
> > Basically if you need N, get the 036NH, otherwise get the 036H.
> >
> > My experience isn't simply with reporting, but rather with actual long distance use. Based on simply the number of WAPs seen, the 8187 is the winner as well.
> >
> > Sure it is fine for the price. Search for "300Mbps USB Wireless Adapter WiFi Lan Network Card". Three bucks more, but the realtek chipset.
> >
> > I prefer the realtek driver over ralink.
>
>
> Interesting stuff miso.
>
> I've long been a fan/user of the 8187L and yes it is top of the 54G heap - and the current long distance heap I suppose.
>
> I just ran some basic tests to compare throughput and sensitivity of the 8187L v the cheap RT5370.
>
> Sent a 9 MB file between my DLink DSl-2642B router (standard dipole) and my old 1.6 Athlon test rig several rooms away. Distance about 30 feet, three red brick walls between antennas.
>
> 15 element beam yagi - 8187L - 6.2 secs, 5370 - same
> 10 DBI Biquad - same results as above.
>
> So no variation in throughput.
>
> 1.45 MB/sec is pretty good in that situation.
>
> Ran Network Stumbler and used beam yagi to pick up weak signal with 8187L more than 100 metres away - 77 dBm
>
> Hooked up the 5370 to yagi, wasn't in the same ball park for signal strength, way down near 95 dBm
>
> So 8187L is king on sensitivity.
>
> BUT, the interesting thing was that whereas the 8187L picked up 6 ssids, the 5370 found 7.
>
> The yagi was not moved between testing.
>
> While the 8187L is clearly the better chipset, for $6 the 5370 is pretty amazing value for in house use.
>
> Rob

Oh forgot to say, looks like my corner reflector is on the blink/ Must be a bad connection somewhere - was working great but now not.

So it's nothing to do with the adapters.

Interesting stuff though.

Rob