On Tue, Jun 8, 2010 at 7:32 AM, Steve Barnes <st...@pcswin.com> wrote: > 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. > 300 / frequency in MHz = size in meters
> Steve Barnes > RC-WiFi Wireless Internet Service > > > -----Original Message----- > From: wireless-boun...@wispa.org [mailto:wireless-boun...@wispa.org] 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: wireless-boun...@wispa.org [mailto:wireless-boun...@wispa.org] 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 >> >> m...@aweiowa.com >> >> >> >> _____ >> >> From: wireless-boun...@wispa.org [mailto:wireless-boun...@wispa.org] >> 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: wireless-boun...@wispa.org [mailto:wireless-boun...@wispa.org] >> 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:st...@pcswin.com> <st...@pcswin.com> 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: wireless@wispa.org >> >> Subscribe/Unsubscribe: >> http://lists.wispa.org/mailman/listinfo/wireless >> >> Archives: http://lists.wispa.org/pipermail/wireless/ >> >> >> >> >> >> > ---------------------------------------------------------------------------- >> ---- >> WISPA Wants You! 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