wtp
Member
add up,,,?
Would this splitter work in lieu of a multicoupler?
- Thread starter BinaryMode
- Start date
We were taught in Electronics School everytime you add an adapter cut the cable and put it back together it is .5Db Which does not look bad until you start cobbling together several things.
Ubbe
Member
Adapters have less than 0,1dB attenuation, if there's nothing wrong with them. If you transmit a lot of power the attenuation might go up for a low quality adapter. Put 10 adapters in series and measure their total attenuation from a signal generator and you don't get 5dB but less than 0,1dB, the lowest difference your instrument can measure.
/Ubbe
/Ubbe
wtp
Member
go to your corners !
Ubbe
Member
I'm sorry if I misunderstood, it should had been .05dB per connector? Measure the total loss of 10 connectors in series and it will be 10x0.05= 0.5dB. Yes, that do look like a more logical result, even if my and others measured result are less than 0.1dB, the lowest the instrument could read.
/Ubbe
/Ubbe
BinaryMode
Active Member
Thanks for the input so far. I now have some ideas I will explore.
BinaryMode
Active Member
So, I added a RegaL (UL listed) 3.5 dB loss cable splitter to my two scanners. The results are actually impressive. I can share two scanners with the one antenna and still hear the two 800 MHz band towers I monitor full quieting. I thought for sure due to the 3.5 dB loss I'd lose a bar or two in signal strength but that doesn't seem to be the case. But, I noticed there is interference in the air band. I specifically monitor the guard frequencies of 121.5 and 243.0 and I get interference on both. The common denominator is that both scanners monitor these frequencies and they are AM. I've had to turn off monitoring those frequencies because the scanners will just stop for the max of 1 minute recording nothing but static in ProScan and then scan on. I'm not an expert on this stuff (thus the thread) so my thinking is that there's interference in the splitter. On the other hand, I also monitor certain Mil air band AM frequencies in AM and have not received interference on those. But I monitor those on one scanner. So I'm experimenting here by just monitoring the air guard frequencies on one scanner rather than both and see if that interference comes back. I'm thinking it may be due to IF emissions from both scanners. I don't know. I wonder now if I should switch the IF on one scanner? If my theory is correct, perhaps that will mitigate IF interference in the splitter. I was afraid of this and was hesitant on a standard cable spiltter. One day I'll just buy a proper multicoupler, but not right now.
wtp
Member
i got that 121.5 and 243.0 interference thing from a computer that i had.
it had to warm up for a few minutes and there it was.
it took time to find as i would turn on the computer first, let the dog out and come back.
by then it was warm enough.
it had to warm up for a few minutes and there it was.
it took time to find as i would turn on the computer first, let the dog out and come back.
by then it was warm enough.
BinaryMode
Active Member
I had wondered that very thing. Especially since now I don't get it. Now I'm trying to think how to mitigate any of that if that's what it is. I do believe the computer's power cord (a laptop) has a choke or what ever those are called. Maybe the scanners could benefit from some. I have snap-on chokes on other stuff. I can't remember the darn name now. Choke?
Ubbe
Member
It's the same 12-20dB isolation in a cable splitter as in a Stridsberg multicoupler, or any other splitter/multicoupler/amplifier.
Just power off the other scanner when you get an interference to see if that is the problem. Activating IFX, if the scanner has that option, can then help. In the 200-300MHz range I have all sorts of interferencies that comes from my sat box, the TV, my computer, all sorts of electronics.
Uniden scanners usually have a 4-6dB difference in signal between different signal bars. 1uV are -107dBm and 2uV are 101dBm
The dBm values for a SDS100's signal strength bars, that pretty much equal most other Uniden scanners, are:
1-115
2-110
3-106
4-101
5-96
If you receive a -105dBm signal it will show 3 bars and if you attenuate 2dB to 107dBm it will show 2 bars. If you receive a -100dBm signal it will show 3 bars and if you attenuate 6dB to -106dBm it would still show 3 bars.
/Ubbe
