| Author |
Message |
snsriram79
Joined: 08 May 2001
Posts: 75
|
 10 Mar 2003 6:39 tv amplifier |
|
|
|
hi there
i bought a tv tuner card and connected it to my pc
i found certain channels are damn good and certain channel r pathetic. when i asked my service provider he said computer reuiires 80 db signal whereas tv 60 db is enough thats y the picture is bad
i asked to put booster near my house and he said it is not possible as it will cost him more
can any1 provide me a solution for this. can any1 give me a low cost tv amplifier circuit to be constructed with 10$ and the tv amplifier must meet PAL standards
10q
|
|
| Back to top |
|
 |
flatulent
Joined: 19 Jul 2002
Posts: 4849
Helped: 289
Location: Middle Earth
|
| 10 Mar 2003 6:51 minicircuits |
|
|
|
Minicircuits company sells broad band amplifiers and will deal with the public by credit card. http://www.minicircuits.com/dg03-172.pdf is a page of their low noise ones. Note that the MAN series cost about $20 and require you to wire to the pins.
You might try a local store that sells televisions to see if they also sell amplifiers.
Another option is antenna gain and an outdoor antenna.
|
|
| Back to top |
|
|
klug
Joined: 04 Jul 2002
Posts: 740
Helped: 5
|
| 10 Mar 2003 23:31 |
|
|
|
Hi,
I have designed a lot of TV cable systems, some were up to 20000 subscribers.
Let see some significant TV levels in subscruiber point:
40 dB/mkV is noisy, but enough to make good syncro.
50 dB is good enough for Black/White.
57 dB - old standard for B/W.
66 dB - minimum standard for color SECAM. I think PAL is little bit better - (64 is equivalent for PAL)
And you have to get 47 dB signal/noice ratio.
Also you need to have not more than 4 dB difference between channels in the same band. No more then 6 dB in different bands. If you have large difference then you will have some intermodulation on amplifier on cable network.
Last multibands tuners (modules) (UHF, VHF and HiperBand) are not so good at all. I think you need to add 3-4 dB for them. So, you need to have at least 70 dB in your card input. But also pay attention for some intermodulation - the upper level is near 88 - 90 dB.
You need to define what is a picture of bad channel, if it has some "snow" then you have weak signal, but if you have some thin horizontal lines on picture then maybe you have too big signal on that channel. Also you can find some floating image of neighbor channel - it is intermodulation for big difference or big level.
Maybe it is fault of your cable provider. You need to make this test: apply signal directly to some good TV-set. Look at bad channels. If they are not good at all - apply to your provider to make his service better. He must make good picture on your TV.
One solution to increase levels is to change splitter from cable system to you. As a rule they use 16-20 dB splitters, you can ask to change it to 12 (or even 10) dB splitter. So you will increase level on 6-10 dB. But maybe you have additional rf-splitter at your home, look to your cables - you can replace it or even move if second feed is not using.
Also look at your antenna socket on the wall near TV, as a rule they are using some universal socket for TV and FM signals, open your wall panel and look to the board, you will find some RCL filters there. If you will delete this circuit you will add some 6 - 10 dB too.
Good Luck! klug.
|
|
| Back to top |
|
|
Hishamsaleh
Joined: 06 Jan 2003
Posts: 100
|
| 11 Mar 2003 17:16 |
|
|
|
have a look on this... I didn't check what exactly is this but may help! I donno!!!
http://perso.wanadoo.fr/f6itv/p2011001.htm
http://www.mitedu.freeserve.co.uk/Circuits/RF/uhfamp.gif
http://www.mitedu.freeserve.co.uk/Circuits/RF/uhfpreamp.htm
|
|
| Back to top |
|
|
FANT
Joined: 27 Feb 2002
Posts: 332
Helped: 9
|
| 11 Mar 2003 22:41 |
|
|
|
I have had the same problem with my PC TV card and checking for the level at the input signal I have discovered that on the home TV and on the card the levels were about the same, but the picture at the card was much worst.
Asked to the supplier of the PC board they told me that for them is not wise to try to increase to the maximum the sensibility due the high level of noise inside the PC.
For this reason the PC card is desensibilized and I have solved the situation in this way:
1) waited 1 year to expire the warranty ( LOL )
2) modified the board to add a 12 V out in the central pin of the antenna connector, limited at about 100 mA ( to avoid that a short will destroy card and PC )
3) bought from a local store a 15 dB 40 - 860 MHz amplifier ( about 10 Euro ) and connected about two meters away from the PC, in between the wall socket and the board antenna connector.
4) Switch On the PC and tuned the card on many brilliant channels ( no noise )
Mandi
|
|
| Back to top |
|
|
Borber
Joined: 01 Jan 1970
Posts: 1461
Helped: 109
|
| 13 Mar 2003 8:08 ANT AMPLIFIER |
|
|
|
you can try this amplifier. It has 15dB of gaain and frequency responce from 30MHz up to 1GHz.
|
|
| Back to top |
|
|
snsriram79
Joined: 08 May 2001
Posts: 75
|
| 13 Mar 2003 9:48 |
|
|
|
thank you border but how to open the file
it is in sum WMF format
bye
thank u
|
|
| Back to top |
|
|
shashag
Joined: 24 Mar 2003
Posts: 5
|
| 24 Mar 2003 20:42 |
|
|
|
| well, it is depend about it
|
|
| Back to top |
|
|
flatulent
Joined: 19 Jul 2002
Posts: 4849
Helped: 289
Location: Middle Earth
|
| 24 Mar 2003 21:40 double click it |
|
|
|
| I double clicked the icon and the file opened in a window with a schematic. One thing to add to the circuit is bypass capacitors at the B+ leads to each stage.
|
|
| Back to top |
|
|
Borber
Joined: 01 Jan 1970
Posts: 1461
Helped: 109
|
| 25 Mar 2003 7:05 tv amp |
|
|
|
OK. Circuit was actually copy of simulation ckt from M(at)cap. My intention was just to give an idea.
You must also ommit generator, generator resistor and load from circuit.
Power supply can be placed within the amplifier housing or the amplifier can be powered through the cable, input or output...
|
|
| Back to top |
|
|
nostrada
Joined: 04 May 2001
Posts: 40
|
| 25 Mar 2003 17:31 |
|
|
|
good info...
but with the diagram, what kind of capacitor can we use for the best results?
|
|
| Back to top |
|
|
Borber
Joined: 01 Jan 1970
Posts: 1461
Helped: 109
|
| 26 Mar 2003 6:43 more details |
|
|
|
| Design of TV AMP is not problematic. You can use ordinary disc ceramic capacitors and 1/8W resistors. PCB can be simple one layer providing wide ground. You can use SMD components with BFR92 transistors. Amplifier can be placed in metal or even into plastic housing. The important thing is that ground connection between input and output connector should be made massive.
|
|
| Back to top |
|
|
