 vonsenJust BecausePremium
join:2005-01-06
3 edits | reply to yaman
Re: samsung cordless phone
"samsung" |
Having said all that, I did the 30 second search thing and yes, there are a handful of mainland china companies now manufacturing these radios. Typically, they are operating in the 268.00-269.98 /398.00-399.98mhz range, with a claimed 6W base and 1.5W handheld power and are not meant for use in n. america. A few fall into the unlicensed 900mhz band. On a lark, I called them in china to find out what the wholesale pricing was like and they did indicate a willingness to tweak the mixers and output to move it into the GMRS band, which is probably the case here. That means you will need an $80 license to use this. I don't see that tidbit mentioned anywhere on their webpage. And you really do want the license. With a potential fine of $5K per day for unlicensed use, getting caught without one could be painful.
So in theory you could approach a 30 mile range, but at a guess, I'd say real life might approach 20 miles in rural Iowa under ideal conditions and you'd be lucky to get a tenth of that if you are in a building downtown. Perhaps dgc3154 will keep us up to date on how it actually works, since he has ordered one. Please understand that I am in no way vouching for the online retailer. Only that the equipment does exist. It sure ain't made by samsung though, despite the samsung sgh-n105 phone pictured on the webpage. I couldn't get a clear answer as to whether it is a knockoff or whether they are modifying samsung gsm cells.
Okay, so here's the math. If you are really math phobic, you should stop reading here. I mean it.. last warning, simple, useful, scary math about to pop onto the page...
Signal loss in air can be approximated by..
path loss = 20log(4*π*(r/λ))dB
where our wavelength = 3x10*8/4.62x10*8 = 0.649m
which solves to a loss of -119.4dB for 30 miles.
So our link budget then is
-119.4dB path loss
-0.3dB absorption
-6dB fresnel loss
-10dB for some inevitable minor obstruction
-10dB fade margin
-145.7dB signal loss for 30 mi.
the return link will be the weaker one by far. I have a hard time believing the 1.5W output but I'll use it anyway and we'll be very generous and assume no antenna loss, so
31.8dBm ERP handheld
6dB receiving antenna gain
-2dB cable loss
35.8db link
Leaving us with -145.7dB link - 35.8dB link = -109.9dB NLOS
The base receiver needs a tuner sensitivity of 109.9dB to pick up the signal under these conditions, which is a hot receiver. I'd say that the receiver is really closer to 100dB. But you get the point. Improbable, but not impossible assuming that the specs are what they say they are.
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Helllllllllllllllllllllllllllllp, I think that the broccoli is after me |
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 oroperPatriots Rule
join:2004-06-01
Beverly, MA | said by vonsen: If you are really math phobic, you should stop reading here. I mean it.. last warning, simple, useful, scary math about to pop onto the page... Interesting post.  I didn't listen to you and got lost in the math |
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tj008
join:2004-06-24
Cincinnati, OH | reply to vonsen
Does it say anywhere that these phones are using Digital Spread Spectrum or are they open frequency? I would hate to get a set of these and use them on the GMRS frequencies where everyone can listen to my conversation with the proctologist.  :D
I used to use a nice set of GMRS radios in Cincinnati on a kind person's repeater. Those radios (handheld) had a nice range. and yes, a license is $80 and lasts for five years, and can be used by ones immediate family. Of course, it's been a while since Ive read through the FCC docs.
From the website, it looks as if you need to build yourself a radio station to get the range they say. If you go that far, build yourself a GMRS repeater station for the city in which you live. Then you can offer those interested a nice service. Or get an amateur radio license and use a phone patch. Especially if the samsung phones are not DSS capable.
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vonsenJust BecausePremium
join:2005-01-06 | said by tj008:Does it say anywhere that these phones are using Digital Spread Spectrum or are they open frequency? There isn't any details on that or anything else on the cited webpage. The Chinese models that I found are analog full duplex, not DSS. Ten or 100 frequencies seem to be the norm. So the scanner enthuiasts could listen in. You do realize though that DSS may hide your call from Grandma with a radio shack scanner, but it doesn't stop any decent ham from multiplexing your DSS call and listening in to those too.
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Helllllllllllllllllllllllp, I think that the broccoli is after me |
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tj008
join:2004-06-24
Cincinnati, OH | Thats kind of what I thought too - analog full duplex. Guess I'll dust off that ol' scanner. There are some new cordless phones to listen to now. 
DSS is nice tho - better than talking without it.
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 joakoPremium
join:2000-09-07
/dev/null
kudos:5
 ·Comcast
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said by oroper: said by vonsen: If you are really math phobic, you should stop reading here. I mean it.. last warning, simple, useful, scary math about to pop onto the page... Interesting post. I didn't listen to you and got lost in the math You are the type of person that gives us a bad reputation.
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»www.joako.com |
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| I was wondering if anyone has any new info regarding battery life of these phones.... |
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