So I've been thinking about trying to build a cellular phone repeater to use inside a home (my girlfriend's basement) because she gets good signal outside, but bad signal inside. I'm thinking its as simple as having a couple good antennas (one for outside, one for inside), band pass filters, and a gain stage or two. The frequencies i need are around 850 Mhz, and possibly the 1900 Mhz range. Has anybody tried this? They sell them for around 500 bucks. I think I have the right idea about this, but am I missing something? Let me know what you guys think.
audioguru2
- Apr 6, 2004
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Hi Ets,
Welcome to our forum. ;D
Save yourself 500 bucks. If the signal is good outside, put an antenna there and wire it with RG-6 satellite coax cable to another antenna inside. If the antennae are proper for the RF frequencies and the cable isn't too long, I think it will work. ;D
Welcome to our forum. ;D
Save yourself 500 bucks. If the signal is good outside, put an antenna there and wire it with RG-6 satellite coax cable to another antenna inside. If the antennae are proper for the RF frequencies and the cable isn't too long, I think it will work. ;D
prateeksikka
- Jun 19, 2004
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hi audioguru!
are these antennas easily available?
at what frequency do they work as i guess mobile phone frequencies in my country may deviate.we generally put signal boosters which are small pin like devices but they certainly pinch on our pocket money ;D
are these antennas easily available?
at what frequency do they work as i guess mobile phone frequencies in my country may deviate.we generally put signal boosters which are small pin like devices but they certainly pinch on our pocket money ;D
Audioguru-
I like your idea, and I think I will start with it. However, I still like the idea of making a repeater, and I don't think it would be very difficult...
I'm gonna need an amplifier (op-amp) that has a very high bandwidth (no attenuation at 850 Mhz). Then I can create a couple active filters to filter out the unwanted frequencies. Any ideas about this?
Thanks.
I like your idea, and I think I will start with it. However, I still like the idea of making a repeater, and I don't think it would be very difficult...
I'm gonna need an amplifier (op-amp) that has a very high bandwidth (no attenuation at 850 Mhz). Then I can create a couple active filters to filter out the unwanted frequencies. Any ideas about this?
Thanks.
A
Alun
- Jan 1, 1970
- 0
It wouldn't cost much to build a simple common emitter amplifier and place it in between the two aerials. However the gain mustn't be too hight and the path loss between the external recieving antenna and internal antenna needs to be high enough to ensure oscilation doesn't occur.audioguru said:
yeah, I was thinking a common emitter amplifier... I was trying to find a good op-amp that'd have the bandwidth, but I probably don't need that much gain...
What about filters? Do you think I need some?
Somebody else recommended RF Circulators to me, but that seems really expensive...
What about filters? Do you think I need some?
Somebody else recommended RF Circulators to me, but that seems really expensive...
audioguru2
- Apr 6, 2004
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To avoid oscillation you don't want any gain. Why use an amplifier?
A
Alun
- Jan 1, 1970
- 0
An audio amplifier has a gain and providing the microphone is kept far enough away from the speaker it won't oscillate.
The same principle applies with the RF repeater, providing the path loss is high enough to attenuate the output to a lower level than the original signal before the amplifier oscillation won't occur. Oscillation only occurs when negative feedback is greater than 1, so in other words the attenuation due to the path loss needs to exceed the gain to avoid oscillation.
ets960,
Have a go with the unamplified option as there's no point in building something when it's not needed. You'll need a pretty good wideband aerial too. I've never seen an op-amp with a high enough gain at this bandwidth for this, the fastest op-amp I've seen has 1GHz unity bandwidth.
The same principle applies with the RF repeater, providing the path loss is high enough to attenuate the output to a lower level than the original signal before the amplifier oscillation won't occur. Oscillation only occurs when negative feedback is greater than 1, so in other words the attenuation due to the path loss needs to exceed the gain to avoid oscillation.
ets960,
Have a go with the unamplified option as there's no point in building something when it's not needed. You'll need a pretty good wideband aerial too. I've never seen an op-amp with a high enough gain at this bandwidth for this, the fastest op-amp I've seen has 1GHz unity bandwidth.
Hi
As Alun Said, There is no op-Amp in such high frequencies. The FT for 741 is 100Khz and if you are lucky
maybe you can find an op-amp which can work at 1.5Mhz. neither CFAs an WTAs can work at these frequecies. this is why you never see an opamp in Transimtters. anyway I am also looking for a transistor working at 1900Mhz,If you find it, please tell me the Part number and where can I buy two or three of them.
And at last, can You tell me that how you understood that your phone is working at 850Mhz? Is it written on the back of it?
ThanX in advance
Shahriar
As Alun Said, There is no op-Amp in such high frequencies. The FT for 741 is 100Khz and if you are lucky
maybe you can find an op-amp which can work at 1.5Mhz. neither CFAs an WTAs can work at these frequecies. this is why you never see an opamp in Transimtters. anyway I am also looking for a transistor working at 1900Mhz,If you find it, please tell me the Part number and where can I buy two or three of them.
And at last, can You tell me that how you understood that your phone is working at 850Mhz? Is it written on the back of it?
ThanX in advance
Shahriar