So with two 2.4 24 dbi Grid with 30" pig tail, what distance of cable would you need in between them for the best match?
Same with 5.8. Reason I ask is I have 2 locations that have no chance of electrical power but need to get around a woods to. Both are very short distances to tower but heavy woods for straight line of site. I actually have some Grids lying around not being used that I could play with. Secondly I am a computer and network expert and I know what a wave is and can measure one on an oscilloscope but have no idea how to convert that to meter/feet/inch. Steve Barnes RC-WiFi Wireless Internet Service -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Mike Sent: Tuesday, June 08, 2010 12:03 AM To: 'WISPA General List' Subject: Re: [WISPA] Repeater You are absolutely right. A quarter wave feed line is an impedance inverter. If my 1/4 wave multiples were even numbered the same effect would be found. (2 x 1/4 wave = half wave) A half wave feed is an impedance repeater. I DO find the idea intriguing, but not so that I will be the one to acid test it. :-) Friendly Regards, Mike -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Greg Ihnen Sent: Monday, June 07, 2010 10:17 PM To: WISPA General List Subject: Re: [WISPA] Repeater My understanding is that a half wavelength long feed line presents zero impedance transformation. See the Smith chart - http://www.scott-inc.com/img/smith.gif The idea being that if you have an impedance of anything other than feed line's impedance ("a perfect match" represented by the point marked 1.0 in the center of the chart) and you plot that impedance it will be a certain distance and direction from 1.0. Then using a compass you measure from 1.0 on the chart out to the plotted input impedance point and swing an arc and draw a circle centered on 1.0 that intersects the plotted input impedance. To calculate the impedance seen at any point along the feed line as you move down the feed line's electrical length (fraction of a wavelength) you move around the Smith chart (actually around the circle you drew) and that will be the impedance seen at that point on the feed line. The scale around the outer diameter of the Smith chart reads in decimal fractions of a wavelength. If you go 1/4 wave down the feed line that represents going .25 wavelength around the Smith chart's outer scale which corresponds to going 180 degrees around the chart (the point opposite of the input impedance on the circle you drew). If you go a half wave down the feed line then you go 360 degrees around the circle that intersects the feed point impedance, in other words you return to where you started. Greg On Jun 7, 2010, at 9:59 PM, Mike wrote: > The whole idea of a passive repeater intrigues me. Two times in many years > I have done just that with limited success. > > > > The first was a metal building I built for Daystar Communications in > SW Florida. It was our NOC and housed our customer support team as > well as the > techs. Cell phone coverage was the pits. What I did was point a Yagi > at a > known cell tower a few miles away. The feed line penetrated the > building and fed a half wave dipole. One of the benefits of that > particular time in > my life is I had access to a very nice network analyzer. The dipole > was cut > very precisely, and the feedline, LMR 600 if I remember correctly, was > cut to a multiple of ¼ wave and acted as an impedance repeater. In > that way any > matching errors to the feedline were negated. It gave cell phones in > the building a couple bars and made usage possible. > > > > The second one was for a customer here in Iowa. They live down in a > bowl and couldn't see my tower 2 miles away. They have a campground. > Cell phones don't work well at all in the bowl. There is a pasture > which has a hill that rises up from the bowl. From that hill you can see my > tower. > They planted a telephone pole and ran electricity to it. We put a > panel pointed at my tower and a second one lower as a repeater which > termed the entire property into a hot spot. It works well. > > > > We took 2 long commercial 800 MHz Yagis and connected them together > with a short feedline measured, with the velocity factor to be a > multiple of ¼ wave > again. One Yagi points at a cell tower, the other points at the campground. > It gives cell phones a couple bars where they didn't work most of the > time before. > > > > If you used a couple high gain, efficient dishes and separated them > with minimum feedline or hardline, it should work in a similar way. I > would be curious to see the results as I haven't done it with > frequencies over 800 MHz. I wouldn't look for any magic results but > reasonable results if your engineering is sound. > > > > Friendly Regards, > > > > Mike > > > > Mike Gilchrist > > Disruptive Technologist > > Advanced Wireless Express > > P.O. Box 255 > > Toledo, IA 52342 > > Mike's > <http://www.tamatoledonews.com/page/category.detail/nav/5001/Local-Columns.h > tml> Weekly Column > > 239.770.6203 > > [email protected] > > > > _____ > > From: [email protected] [mailto:[email protected]] > On Behalf Of Jack Unger > Sent: Monday, June 07, 2010 5:21 PM > To: WISPA General List > Subject: Re: [WISPA] Repeater > > > > For this to work, one end needs to be very short. In a typical mountain-top > repeat situation, the combined free-space path loss from BOTH paths is more > than enough to prevent the link from working. > > Greg Ihnen wrote: > > Actually I've done this on ships where the deck department needed to > communicate with the engine room and personnel down in compartments > where winches for line handling were located. We're talking very short > distances (less than the length of the ship - around a 1000 ft) and > short cable runs. > But it did let enough RF leak into the below deck areas to facilitate > communications. > > Greg > > On Jun 7, 2010, at 4:34 PM, Bob Moldashel wrote: > > > > Garbage...... > > Let's say optimum consideration here... > > Present RSL -68 db ....Subtract cable loss -2 dB = -70 Add +24 db > for the Grid = -46 > > Free Space Loss at 1/10th of a mile is -84 db > > Soooooo... > > If you take the -46 dB level out and add the FSL of -84 dB that will > give you a -130 dB. > > I don't think that will work...... > > Get a repeater or get a stronger receive signal at your receive > antenna. Like -20dB > > -B- > > > > > Steve Barnes wrote: > > > Ok I have never even thought about doing this. Does it actually work? This > sounds WAY to simple. > > A 29Db Grid on a Grain Leg pointed at the AP that has a -68 signal plugged > into a 24 DB Grid Pointed to the house 1/4 mile away. What kind of > signal would you have on the back side at the house? > > Steve Barnes > RC-WiFi Wireless Internet Service > > > -----Original Message----- > From: [email protected] [mailto:[email protected]] > On Behalf Of Rubens Kuhl > Sent: Monday, June 07, 2010 4:20 PM > To: WISPA General List > Subject: Re: [WISPA] Repeater > > One option to consider is a passive repeater. Wire a coax cable > between the > two dishes and you are done... no electronics to fail, no power to > supply on > a remote location. > > (haven't tested this trick with dual polarity, though) > > > Rubens > > > On Mon, Jun 7, 2010 at 11:00 AM, Steve Barnes > <mailto:[email protected]> <[email protected]> wrote: > > > > I have avoided repeaters like the plague but I have a situation where > I have > one and I am looking for a better option. When I started my wisp I > was 100% > Tranzeo. At this one location I setup a CPE connected to a TR-6000 > that has > 2 Ethernet ports that pass through POE. I ran 1 Ethernet up the tower with > a POE at the bottom, and a crossover in between. > > I would like a similar layout for other locations. Issue I see is that not > many other units, UBNT or MT have a 2nd Ethernet that pass through POE? > > How does everyone you get around this? > > Trying to stay cheaper than a RB433, 2 radios, and 2- antennas, box, > pigtails, 2 LMR cables. > > Steve Barnes > RC-WiFi Wireless Internet Service > > > ---------------------------------------------------------------------- > ---------- > WISPA Wants You! Join today! > http://signup.wispa.org/ > ---------------------------------------------------------------------- > ---------- > > WISPA Wireless List: [email protected] > > Subscribe/Unsubscribe: > http://lists.wispa.org/mailman/listinfo/wireless > > Archives: http://lists.wispa.org/pipermail/wireless/ > > > > > > ---------------------------------------------------------------------------- > ---- > WISPA Wants You! 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