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Splitter For Two Scanners And One Antenna ?
Hi,
I have two scanners, which I would like them to share a single (Scantenna) antenna in my attic. Only one scanner will ever be on at any time. But, I would like to "permanently" have both scanners attached to the single antenna. What would you recommend as a reasonably low cost splitter for this ? (is Splitter the right term ?) What type of losses would I expect ? Just out of curiosity, would the losses be the same if I was actually to use both scanners at the same time compared to just one of them ? Thanks, Bob |
Splitter For Two Scanners And One Antenna ?
On Sat, 26 May 2007 18:45:36 -0400, "Robert11"
wrote: Hi, I have two scanners, which I would like them to share a single (Scantenna) antenna in my attic. Only one scanner will ever be on at any time. But, I would like to "permanently" have both scanners attached to the single antenna. What would you recommend as a reasonably low cost splitter for this ? (is Splitter the right term ?) Hi Bob, A coax T connector comes to mind. What type of losses would I expect ? 3dB Just out of curiosity, would the losses be the same if I was actually to use both scanners at the same time compared to just one of them ? Through considerable effort you could recover that 3 dB, but I presume your scanners will operate over a considerable expanse of spectrum. This diminishes that effort. Now, if your scanners operate: one is high bands, the other low bands; then you can get more ingenious by building two filters. One would be high pass, and the other low pass, both with roll-offs at the frequency that separates high from low. The antenna feeds them both, and each feeds the appropriate scanner. In essence, this is your splitter (or you can buy one for $50). This would also bring back the 3dB otherwise lost. The T connector could cause one scanner to inject noise into the other one. There is very little isolation of the Local Oscillator from the front end, and you could hear one cycling through the bands on the other scanner (and, of course, vice-versa). Turn one off and that goes away. It's cheap enough to test first before going further. 73's Richard Clark, KB7QHC |
Splitter For Two Scanners And One Antenna ?
"Robert11" wrote in message . .. Hi, I have two scanners, which I would like them to share a single (Scantenna) antenna in my attic. Only one scanner will ever be on at any time. But, I would like to "permanently" have both scanners attached to the single antenna. What would you recommend as a reasonably low cost splitter for this ? (is Splitter the right term ?) What type of losses would I expect ? Just out of curiosity, would the losses be the same if I was actually to use both scanners at the same time compared to just one of them ? Thanks, Bob A cheap CB switcher box would do the job.....lossless... you just switch the feed from one radio to the other !!! Regards... Lee.... |
Splitter For Two Scanners And One Antenna ?
I'd use a splitter designed for television use. You can find one at
almost any store selling TV accessories including discount stores like K-Mart or Wal-Mart. They're very inexpensive. However, they will have type F connectors which you'll have to adapt to BNC or whatever your scanner and antenna use. The adapters will probably cost more than the splitter. If you can't find the adapters where you get the splitter, you can find them at stores like Radio Shack or Fry's. The loss is around 3 dB. This is unavoidable. It won't make a noticeable difference except for weak signals. One of the properties of the splitter, as opposed to just a tee connector, is that the two receivers are isolated from each other. So turning one on or off or disconnecting it should have no effect on the other. Roy Lewallen, W7EL Robert11 wrote: Hi, I have two scanners, which I would like them to share a single (Scantenna) antenna in my attic. Only one scanner will ever be on at any time. But, I would like to "permanently" have both scanners attached to the single antenna. What would you recommend as a reasonably low cost splitter for this ? (is Splitter the right term ?) What type of losses would I expect ? Just out of curiosity, would the losses be the same if I was actually to use both scanners at the same time compared to just one of them ? Thanks, Bob |
Splitter For Two Scanners And One Antenna ?
Robert,
Another thing the splitter does (as opposed to a tee adapter) is maintain the system impedance at all ports. Even though I don't have a brain as big as Roy's, I believe the signal loss in a slight impedance mismatch w/ a 75 ohm splitter would be much less than w/ a tee adapter. Most TV splitters are good up to about 1 GHz; some are rated to 2 GHz. It's good practice to terminate unused port(s) of a splitter (at the splitter or cable end) with a resistor, to maintain the electrical characteristics of the splitter. Also, if you use RG-6 cable instead of RG-58, you can minimize loss in the cable runs, and use adapters only at the antenna and radios. Bryan WA7PRC Roy Lewallen wrote: I'd use a splitter designed for television use. You can find one at almost any store selling TV accessories including discount stores like K-Mart or Wal-Mart. They're very inexpensive. However, they will have type F connectors which you'll have to adapt to BNC or whatever your scanner and antenna use. The adapters will probably cost more than the splitter. If you can't find the adapters where you get the splitter, you can find them at stores like Radio Shack or Fry's. The loss is around 3 dB. This is unavoidable. It won't make a noticeable difference except for weak signals. One of the properties of the splitter, as opposed to just a tee connector, is that the two receivers are isolated from each other. So turning one on or off or disconnecting it should have no effect on the other. Roy Lewallen, W7EL Robert11 wrote: Hi, I have two scanners, which I would like them to share a single (Scantenna) antenna in my attic. Only one scanner will ever be on at any time. But, I would like to "permanently" have both scanners attached to the single antenna. What would you recommend as a reasonably low cost splitter for this ? (is Splitter the right term ?) What type of losses would I expect ? Just out of curiosity, would the losses be the same if I was actually to use both scanners at the same time compared to just one of them ? Thanks, Bob |
Splitter For Two Scanners And One Antenna ?
"Roy Lewallen" wrote in message ... I'd use a splitter designed for television use. You can find one at almost any store selling TV accessories including discount stores like K-Mart or Wal-Mart. They're very inexpensive. However, they will have type F connectors which you'll have to adapt to BNC or whatever your scanner and antenna use. The adapters will probably cost more than the splitter. If you can't find the adapters where you get the splitter, you can find them at stores like Radio Shack or Fry's. The loss is around 3 dB. This is unavoidable. It won't make a noticeable difference except for weak signals. One of the properties of the splitter, as opposed to just a tee connector, is that the two receivers are isolated from each other. So turning one on or off or disconnecting it should have no effect on the other. Roy Lewallen, W7EL Robert11 wrote: Hi, I have two scanners, which I would like them to share a single (Scantenna) antenna in my attic. Only one scanner will ever be on at any time. But, I would like to "permanently" have both scanners attached to the single antenna. What would you recommend as a reasonably low cost splitter for this ? (is Splitter the right term ?) What type of losses would I expect ? Just out of curiosity, would the losses be the same if I was actually to use both scanners at the same time compared to just one of them ? Thanks, Bob I was just in BIG LOTS and splitter and adapters could have all been had for less than $5. |
Splitter For Two Scanners And One Antenna ?
In article , Roy Lewallen
wrote: One of the properties of the splitter, as opposed to just a tee connector, is that the two receivers are isolated from each other. So turning one on or off or disconnecting it should have no effect on the other. Roy Lewallen, W7EL Hello, Roy, and all. I would also add that the degree of isolation achieved in an n-way splitter is predicated on how well the port being split n-ways is terminated in the splitter's design characteristic impedance (e.g. 50 or 75 ohms). Sincerely, John Wood (Code 5550) e-mail: Naval Research Laboratory 4555 Overlook Avenue, SW Washington, DC 20375-5337 |
Splitter For Two Scanners And One Antenna ?
J. B. Wood wrote:
In article , Roy Lewallen wrote: One of the properties of the splitter, as opposed to just a tee connector, is that the two receivers are isolated from each other. So turning one on or off or disconnecting it should have no effect on the other. Roy Lewallen, W7EL Hello, Roy, and all. I would also add that the degree of isolation achieved in an n-way splitter is predicated on how well the port being split n-ways is terminated in the splitter's design characteristic impedance (e.g. 50 or 75 ohms). Sincerely, John Wood (Code 5550) e-mail: Naval Research Laboratory 4555 Overlook Avenue, SW Washington, DC 20375-5337 A good point, and one I hadn't considered. The chances of the antenna impedance being 50 ohms over the band of frequencies likely to be used by a scanner is about the same as its being 75 ohms, which is to say about zero. (This is almost certainly true for most TV antennas over the whole TV frequency range also.) Whether the isolation is good enough will have to be determined by experiment. If it isn't, the only solution would be to put a pad at the splitter input to stabilize the impedance. It probably wouldn't take much attenuation to make an appreciable improvement in the isolation. But this application might not require a great deal of isolation anyway. Roy Lewallen, W7EL |
Splitter For Two Scanners And One Antenna ?
In message , Roy Lewallen
writes J. B. Wood wrote: In article , Roy Lewallen wrote: One of the properties of the splitter, as opposed to just a tee connector, is that the two receivers are isolated from each other. So turning one on or off or disconnecting it should have no effect on the other. Roy Lewallen, W7EL Hello, Roy, and all. I would also add that the degree of isolation achieved in an n-way splitter is predicated on how well the port being split n-ways is terminated in the splitter's design characteristic impedance (e.g. 50 or 75 ohms). Sincerely, John Wood (Code 5550) e-mail: Naval Research Laboratory 4555 Overlook Avenue, SW Washington, DC 20375-5337 A good point, and one I hadn't considered. The chances of the antenna impedance being 50 ohms over the band of frequencies likely to be used by a scanner is about the same as its being 75 ohms, which is to say about zero. (This is almost certainly true for most TV antennas over the whole TV frequency range also.) Whether the isolation is good enough will have to be determined by experiment. If it isn't, the only solution would be to put a pad at the splitter input to stabilize the impedance. It probably wouldn't take much attenuation to make an appreciable improvement in the isolation. But this application might not require a great deal of isolation anyway. Roy Lewallen, W7EL Just buy it and try it (a TV splitter will only cost a couple of dollars). It will probably work more than well enough, even if the isolation is well short of the (say) 25 to 30dB you might get under 'ideal' conditions. I wouldn't add any extra attenuation just to ensure that the input port is matched better. You're already going to lose 3dB + just because you are splitting. Ian. -- |
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