Extending USB cable with CAT5 cable adapters

You can also get "active" extension leads which require no seperate power supply. One I looked at allows 3 x active leads plus a standard lead at 5metres each. So up to 20m or 60 odd feet.

That would have been my suggestion, as well.

Hadn't seen those before.

They certainly look the way to go.

Thanks guys.

Rob

I used an active USB extender for my set up at one time and it worked fine for me. Although now I have about 20 ft of good coax (can't remember the #) to get into the my boat, because it is easier to waterproof. Ok Rob, you got me wondering now, I'm on a boat, using a 15dbi flat panel antenna receiving a signal 300 ft to 400 ft away. Sometimes the signal is excellent and other times barely usable. I understand this is a two way signal, and I would think the usual bottleneck would be the receive signal strength. So having a 500mw transmit signal would probably not help the situation. Is there a way to see whether the transmit or receive signal is the weak link? Mike

But this is mostly a guess on my part

My understanding is that antenna gain is bi-directional and signal strength ties in accordingly.

Check out this pdf document on the subject.

Best laymans read I've seen.

There are obviously a number of things that can cause changes to existing signal strength - which appear to be primarily related to external interference.

Cheers

Rob

Just to elaborate on the previous post.

The difference between the cheap Ebay Realtek adapter and the Belkin PCI card using the same 12 dbi biquad is a 10 - 15 % improvement in signal to noise with the Realtek - according to my wifi sniffer chart.

The Realtek driver works OK under XP but its lousy under Ubuntu (Linux) and the Belkin is much better there = so the driver for the application makes a big difference.

Also although the S/N is a lot better, I'm not totally convinced that the stability is as good as the Belkin, even though the signal quality is shown to be better.

The upshot is that when the system is under load and the Apple Air next door is being used (the guy is home) you can see the device drop back to 48 and even 36 G at times.

Move the antenna away from the suspected problem area and the issue goes away - back to 54G, so it's definitely interference in my case.

Cheers again

Rob

My understanding is that there is no such thing as good coax. Well of course some is better that others, however it *all* has significant losses. A USB extension cable has exactly zero loss in all cases.

Maybe Jeff or another will be along in a minute to explain the details, or you could search previous posts.

I agree about reciprocity of the antenna, my comment was about the Realtek with it boast of 500mw output.

I'll check it out. Being on a boat is a challenge, If you have a very high gain antenna (very directional) you can get a strong signal but when the wind blows the boat shifts and misses the target. I also have a tidal range of 2 ft per day and as much as 3.5 ft over the year. Mike

I'm guessing I used 9913 with 7.5 db loss per 100 ft. With 20 ft of cable I calculate 1.5 db loss, throw in maybe another

1.5db loss for the connectors and we get 3 db loss. Ya that's a loss. Some may call that significant, I'll call it moderate loss. If I get energetic I'll go back to the USB wifi adapter connected to the antenna with a active USB extender into the boat. and see if it helps. Mike

Mike, you would appreciate that an over-water path - or any path at low angles over a reflective surface - is going to present all sorts of signal cancellation possibilities. (In microwave path engineering, the reflections off seemingly innocuous stuff like cereal crops is plenty high enough to cause a problem). While polarisation selection can minimise the problem - and circular or elliptical can help greatly - once you get onto high gain (aka directional) antennae you need to be particularly attentive to this. The microwave point-to-point solutions (space/frequency diversity) are a little difficult to engineer into domestic WiFi :-(

As a quick check, while you are monitoring signal strength on your coax-fed antenna try changing the positioning - height, polarisation etc - and see what effect that shows. Also try placing a reflective horizontal surface several inches below the expected signal path and play with that a bit.

Right now my software says I have a -60dbm signal strength, this is plenty of signal for my surfing. It does bounce a little from -58dbm to -68dbm. But mostly -60dbm. It also says my link speed is TX 54Mbps RX 48Mbps. This is all Good. I've using this for about two years a most of the time it is fine, just on a few days here and there I have trouble. My link is mostly across a concrete parking lot. Mike

It's my understanding usb cables do have length limitations maxing out at around 5 metres before the beginnings or significant loss so you might need either a repeater and a quick google ?

What adapter/card are you using Mike?

Rob

Hi Rob, I'm using a TL-WN321G made by TL-Link

I modified it by putting a female N connector on it. A little bit of a trick, but it's not to difficult. It was cheap on ebay (new), I paid $12 for it. Looks like they're $15 now with free shipping. Mike

The transmit power on mine is supposedly 22 (+/- 1) dBm.

54G Receive sensitivity -79 dBm

The claims made are a bit extreme, but it certainly does a good job of dragging in weak signals with the 150 x 150 mm biquad (home made) attached.

Cheers

Rob

I just did a speed test at;

results are Download 5698KBit/s Upload 377 KBit/s Connections 2486 and Ping 22 ms I don't know what it all means. I'm using the TP-link TL-WN321G with a 15 dbi flat panel antenna, at 300 to 400ft. Mike

a panel (and yagi) has a wider area horizontally than vertically, boats tend to rock (waves,wind, tide, moving around etc), for a cheap/easy/quick test, mount/rotate the panel 90 degrees so horizontal is vertical and v is h.... free and worth a shot....

Interesting thought, I'll see if I can find the pattern for my antenna. Thanks, Mike

Depending on the polarisation of the *source* signal, that may yield something entirely different from what the user's antenna pattern might suggest.