I remember it well... snow on that (used-to-be) meadow at 7th Street and Northern.
...Jim Thompson
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It\'s what you learn, after you know it all, that counts.
Legal will cost you extra. I usually look for the FCC type certification sticker, but even those are being counterfeited.
Yet anther wireless "extender".
I checked the FCC ID grantee search and found nothing under Wi-Ex or zBoost. Oh-oh.
However, I did find various products made by Digital Antenna that do have FCC ID numbers and are listed on the FCC ID web mess. (Prefix=PZO):
Not really. Unlike buying a monthly service, like POTS, cellular, or VoIP, adding an outside antenna is a one time capital expense, with a rather long service life, and can be amortized over the service life of many cell phones. Think of it as an investment. As for the cordless phone, those are commodity hardware found at any big box store for next to nothing. I don't see the expense. Incidentally, the purpose of my suggestions was to turn the cell phone into a POTS device.
I haven't climbed a tree or phone pole for perhaps 15 years and have no intention of doing so again. (Don't ask about tower climbing and rooftop installs). Anyway, I pay the certified tower climbers and insured tree climbers to risk their lives these days. It takes less time for me to recover from the financial pains, than from a fall.
Like I suggested previously, VoIP is often cheaper.
Speaking of internet connected cell phones, there are also Femto Cellular:
Install a cell site in your house.
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Jeff Liebermann jeffl@cruzio.com
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Passive repeaters like that suck. Let's do the math.
Assumption: Typical PCS cell site at 1900MHz and about 1 watt per carrier. You're at the extreme end of the GSM range (about 25 miles for the older systems) and want to re-radiate the received signal back into your house over a distance of about 100ft.
I'll assume two 15dBi yagi's back to back.
Starting at the cell site end: Tx out: +30dBm Sector antenna gain: +6dBi Path loss: 20 log(FreqMHz) + 20 log(Miles) + 36.6 20 log(1900) + 20 log(25) + 36.6 = -130dB Rx antenna gain: +15dBi (first yagi) ======== Signal at RX in: -79dBm
We now feed that signal into the 2nd yagi and point it into the house:
The GSM standard specifies a minimum receiver sensitivity of -102dBm. Unfortunately, the passive repeater is 20dB lower in signal level. This isn't gonna work.
It's actually much worse in the opposite direction because the typical cell phone only produces perhaps 100mw (+20dBm). Lose another 10dB. The cell site operators try to compensate for this by using crygenically cooled cavities and front ends, but that's fairly rare.
The 0dBi gain of the cell phone antenna is rather optimistic. I would give it about -4dBi or worse, but the official guestimate is commonly
0dBi.
Someone will probably suggest that 25 miles is too far. Fine.... Cut the range in half and you only improve things with 6dB less path loss. That's still 14dB short of minimally functional from the cell site to the phone and up to 24dB short in the other direction.
(Drivel: I hope this makes up for my previously attrocious math in the never ending global warming thread).
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Jeff Liebermann jeffl@cruzio.com
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No, but it sounds like you are. The VA gave up on solving my health problems and put me on 100% non service connected disability. I would rather be working, than struggling to survive on $931 a month. I used to make more than that per week, in overtime.
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It's better than nothing, and if you can get a clear shot at the cell tower with a higher antenna, it can be made to work. Yes, there are losses, but with the right coax, they are minimal. Passive repeaters are not intended to extend the range, but to redirect the signal into a dead spot becasue of obstructions.
An active repeater for pagers was installed at Microdyne, which caused no end of RF spur problems in the engineering department. Since half of the design work was low noise broadband telemetry equipment, most work came to a screeching halt.
Some of the crap was bouncing down the steel hallwauy that connected their building to the production floor, and I could see it on my spectrum analyzer.
They were going crazy trying to figure it out, then got pissed at me when I asked them to turn off the power to the repeater, and their problems all went away.
Instead of a couple dead spots in the complex, the entire 40,000 sq ft building was full of reflections from the 5 watt repeater. The pager company didn't know how to fix it, an had to shut it off. Simply comnnecting the pair of antennas directly solved the problems.
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We had some snow about 30 miles north of Orlando in the late '90s. Needless to say, it didn't last very long.
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Zero. I got them free from a failed dot com. I started with about 30 boards and used them for various projects. I'm down to 4 which I'll keep for spares and tinkering. Kontron board with a Pentium 166MHz and 512Mbytes ram, which is about right. No fan needed. I wouldn't have used these, except that the price is right. The big headaches are all the adapters and creative wiring necessary to interface the boards to kbd, monitor, serial, ethernet, etc.
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You're not going to solve a 10-20dB shortfall in path loss of a passive repeater by juggling coax cables.
I've tried passive repeater with various 2.4GHz wi-fi setups, with TV reception, and with VHF/UHF commercial installations. None of them worked well enough to justify the effort.
There's also one situation where a passive repeater makes things worse. If there's a weak incident signal coming directly from the cell site, and a roughly equally weak signal coming from the passive repeater, the result will be cancellations and reinforcements spots (dead and hot spots) at various locations. Where one could have obtained tolerable service with a direct shot, the passive repeater turns it into an exercise in position management.
No RF screen rooms? I did all my low level stuff in a home made brass mesh cage. It wasn't perfect, but it was good enough to keep the broadcast, TV, FM, public safety, and commercial junk to tolerable levels. It was kinda difficult to tune a receiver when there was a high power xmitter nearby on the same frequency.
Nice waveguide you have there.
I think that's called rebooting the building.
5 watts shouldn't be much of a problem. The transmitter was probably mistuned, oscillating, or otherwise radiating spurious rubbish. Most of the 5 watt desktop paging systems had an ordinary HT (walkie talkie) inside the box. When I was in the commercial two-way biz, oscillation was a common problem with mismatched or broken antennas. Lots of problems from dissimilar metals creating mixers at high level sites. The solution was to take each installation apart, verify operation with the best test equipment we could borrow or steal, and test every radio in the building. Clean, tune, tweak, or replace. It wasn't unusual to find several xmitters that were spewing rubbish all over the spectrum.
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Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
Sure, but that seems to be a lot of trouble just to get to the performance POTS already had almost a century ago ;-)
Monthly service on POTS is under $20. Our friends who went cell pay $40-50 per month. Except me and my cell which is pre-pay. That's only about $5/mo but not if I'd use it for all the local calls. Those don't cost extra on POTS.
Same here. My back ain't too great anymore. I don't want to get stuck up there and suddenly can't move.
That would require that you are either at a home, in a Starbucks or near a home with unsecured WLAN (which in and of itself is legally iffy).
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You will, it the signal is available at a higher elevation. I have used large passive reflectors, as well. I had a elementary school that couldn't pick up the local educational TV station, even though the signal should have been line of sight. I aimed the antenna at a steel mill's hot strip complex about ten miles further away, and got over 25 dB of gain, as measured on my Sadelco FSM. Working in CATV, just a couple feet of extra height can make the difference between an excellent signal, and no signal at all.
I have had different results than you. I'm not saying that it always works, but I had enough success to try it in other locations. The worst problem I ever had was at 4 GHz, on both earth stations at a TV station in Orange City. ATT built a microwave relay directly over our site, right after it went on the air. The only solution was a double hop microwave relay to the old studio site, and the use of a Monroe dial DTMF remote controller to select the proper transponder, then a 11 GHz CARS relay to the original transmitter site, then a 7 GHZ STL relay to the new transmitter site. The ATT signal was so strong that it could be picked up by the N connector on the end of the 7/8" Andrews Heliax, when disconnected from the LNA. Luckily, it hit the pair of 7 GHz antennas from the side, and didn't overload the receivers, but it did raise the noise floor, by causing about six dB of desense.
Some sites are useless, no matter what you do.
They were at that location for over 20 year s and never needed them, until the pager repeater fiasco. The building was in a notch cut into a hillside, and hidden from all radio, TV, pager & cell phone towers. It was hard to pick up AM or FM radio broadcast in the parking lot. Were would we have found room for almost 50 screened rooms, anyway? We had dozens of the screened rooms at Cincinnati Electronics, for all the good it did. They were so damn hot inside that the test equipment wouldn't stay in calibration, and the techs were soaking wet with sweat most of the year. The only good shielded rooms were the solid aluminum computer rooms, used for their SATE testing. Even then, the Data General computer generated so much noise that some of the PRC-77 radios failed.
Not anymore. L3com bought Microdyne, and closed that plant.
No, it's called logical troubleshooting. Turn it off, and the problems went away. Turn it back on, and it's back.
I have no idea what was inside the pager repeater. It, and one antenna were mounted above the drop tile ceiling in engineering, and not our property. Anyway, the last repeater I built was in the late '60s, and it used a transmitter strip from a GE preprog, and a receiver strip from a Motorola Twin-V. It was on 146.01/146.61 MHz and was usable over
50 miles in some directions. A homebrew diplexer was built out of copper pipe, the COR was built with salvaged germanium transistors, and the timers were surplus unijunction transistors from Poly Paks. The mores code ID generator was a mix of Poly paks RTL ICs and silicon diodes. It was still in daily use 20 years later.
I did jury rig another two meter repeater from an old 75 W Fairchild VHF high band base station, but only used it a couple hours into a cantenna to test some radios.
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No, it won't. Please re-read my assumption and calcs. I assumed line-o-sight for 25 miles between the cell tower and the passive repeater. That's a non-obstructive, no junk in the way, no Fresnel Zone issues, straight line. Going higher is not going to increase the received signal strength at the passive repeater. I even left out the coax and connector losses to make it look good. Despite that, it was
10-20dB short of barely usable.
Same problem as back to back antennas (passive repeater) with no antenna gain. Same with periscope antennas, flyswatters, and billboards. They have a small capture area (aperture) and therefore do not reflect much of the received signal. Most of the RF just keeps going past the reflector. Besides, to make a passive reflector work, the user would need to attach a directional antenna to the cell phone, and point it at the reflector. That doesn't solve the original problem (decent home cellular coverage without going outdoors).
Various repeaters I've built and maintained over the years: (Circa 1960's) (1999's) (2008) The bigger the mess and the uglier the box, the better it works.
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Hi Jeorge, Well, we went for the 'all in one' plan, that includes all you want domestic long distance on the line. Easier to budget that way. Plus, we have a second line on Vonage that includes our 877 number. Since we got off cable modem and went to DSL, the Vonage line has been fine!
BTW, IIRC you HAVE to designate a long distance carrier. It just doesn't HAVE to be ATT...
The problems that I had with my cable modem and VoIP turned out to be the cable company. While at one particular moment or another you got high speed throughput (10Mbs+) it would periodically just pause... for about a second... and this just wrecked hell on Vonage. It is hard to deal with 500 to 1000ms of dead air during your conversation, esp. when it comes in the middle of a word!
Now, the cable company says that it has fixed this little glitch in their infrastructure, but it is too late. I went to land line and DSL, and haven't been happier. I also switched to sattelite TV!
Nope, don't have to. I just cancelled long distance for this here phone. Had to call two different (!) AT&T companies, one to cancel LD and the other to cancel the plans we had. No idea why they don't talk to each other.
They charged a fee of $3.98 for the privilege to cancel!! Does anyone monitor monopolies these days?
Anyhow, now we will be using a 10-10 number for LD. About 2c/minute to places like Europe. Why on earth can nobody offer that just as a designated long distance provider so you don't have to pre-dial a 10-190 number? If the 10-10 guys can that means there must be enough bandwidth available at the matching wholesale price level.
BTW, one guy at AT&T asked me if I was unhappy. I said yes, because of being slapped a min charge but that this ain't the main reason. "Oh, and do you have another opportunity to call long distance?" ... "Yes" ... "Well, we could offer you a better rate at xx/min plus x Dollars monthly, can I interest you in this" ... "Thanks, but not right now, we pay no monthly fee and $0.02 to Europe" ..... *THUD*. That really floored him.
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The reflector I used was over 100 feet high, and over a mile long. It was the metal siding of a hot strip steel mill, and had less interference than the original path that had worked for several years. The metal wall was about 60 feet higher than the antenna on the school's roof. They started school that year, and the ETV channel from Dayton was missing from the system. It was full of gosting, and severe fading. All the other channels in that direction still worked, but weren't downconvertd, or fed to the class rooms. Apparently, a new shopping center was built in just the right spot and angle to destry the path. I was on the third story slate roof and saw the hot strip in the disatance. I swung the antenna about 120 degrees and got a clean signal that was stronger than the original. I had to pad the antenna 10 dB to keep from overloading the UHF to VHV downconverter.
Most of the RF just keeps
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Nice, if you happen to have a handy steel mill. Your original suggestion was two back to back yagi antennas as a GSM cellular passive repeater, not passive reflector. I cranked out the necessary calculations to demonstrate that even under ideal conditions, a passive repeater won't work.
As for your passive reflector (not repeater), I had a 900MHz STL (analog audio) link that was bounced off a large steel garage wall. It worked just fine except early mornings, when I was getting a nasty low frequency hum or buzz in the audio. I eventually found that the building was rather flimsy and that starting a big diesel tractor near the reflector wall would cause it to vibrate. The vibrations modulated the FM signal, which appeared as a low frequency buzz. When I beat on the wall with a 2x4, I also could hear the banging in the audio. We later extended the antenna pole on one end of the link sufficiently to use a different building as a reflector.
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I had a Marti 900 MHz STl transmitter in storage. I don't know if it's still in one of over 500 banana boxes of parts in my old shop. Most of the STL I've worked with is 6 or 11 GHz TV equipment.
Do you remember the old '60s vintage vacuum tube Heathkit IG-102 AM signal generator? Another tech swore it couldn't be used for FM. I put my hands around the vent holes and yelled into them. He about fell off his bench stool when it came blaring out of the speaker of the radio he was working on. ;-)
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Oh yes. I used one of those at one time in high skool. Totally unstable, no calibration, non-linear AM modulation, but cheap.
Rolling forward to about 1973, I complained to HP about their HP 606B signal generator:
showing two nasty 120Hz sidebands on the spectrum analyzer. HP claimed that since it was an AM only generator, having two FM sidebands was perfectly acceptable. I was trying to use it for FCC certification testing and the sidebands messed up the results and photos[1]. Never mind that the spec sheet said something like "spurious rubbish = -60dB" HP interpreted that to mean AM only spurs, while I decided it meant all forms of spurs, no matter the origin. The end result was a change to the specification sheet for what as almost an end of life product, and an application note explaining how to recognize the difference between AM and FM modulation rubbish on a spectrum analyzer.
The 606 was too massive to respond to yelling into the case, but I could hear FM modulation if I banged on the case. I'll spare you my stories about early synthesized radios and microphonics. Far too many of my VCO's ended up suspended on rubber shock absorbers or embalmed in RTV.
[1] I was using the HP606B because I transmitted into the HP8640B signal generator and blew up something.
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I added a 1/8" aluminum plate between the chassis and front panel, then zener regulated the B+. It made a huge difference. :)
The first synthesized business radio I worked with was the Pace Landmaster series. It worked surprisingly well for the price, and beat Motorola to market by a few months.
I am trying to remember the model number of the crappy Logimeterics signal generator with the nixie tube frequency displays we had at Cincinnati Electronics. Saying they drifted was being polite. :(
This might be it:
What is left of my test equipment is listed on this web page:
I really miss the HP 3325B and Tektronix 2465B I had at Microdyne. :( I don't need the network analyzer or Fireberd BER test set anymore, but if I spent more time at my bench I would like to have another 8660C. I never was crazy about the 8640. I never used one that didn't have problems. i troubleshot some of the 8660B & C models for the old guy who ran the cal lab. I would love to find a good meter for my HP 332 distortion analyzer. The shop roof leaked, and water destroyed the movement a couple years ago, during the hurricanes. Every time I see a meter, they want three to ten times what I paid for the analyzer working, and calibrated.
My Polarard 10 MHz to 44 GHz spectrum analyzer isn't on that list. The tag said it needed a new BWO, but a large part of the power supply wiring was unsoldered and tied in a knot. There are so many parts missing that I will part it out fore the aluminum, some day. At least the 260 MHZ display nit works, so I might build my own with the leftover microwave RF parts on hand. :)
Another item not on the list is a C band signal generator Microdyne built and used in house when they were in the Sat TV business for Broadcast and CATV equipment. It may be the only one in existence, and there was no documentation in the file room, so they were probably built by the engineering department when the company was based in Maryland. they made the mistake of telling the employees that they were closing that plant, and moving engineering to Florida. The came in the next day to find all documentation destroyed. They had a couple complete units that hadn't been shipped, and had to reverse engineer their whole product line.
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