Question about 2 Scanners to 1 antenna

[mike36507]

Currently I have a Uniden BCD996XT and a RS Pro-163 connected to a RS discone with just a standard spitter that I bought from Wal Mart. My RS scanner will not pick up most VHF frequencies, but my Uniden will. The RS scanner picks up UHF and 800 MHz pretty good though.
My question is will this multicoupler work better?
Stridsberg MC202 Passive Multicoupler, 10 MHz - 1 GHz, 2 ports.


I have just noticed on my RS scanner that if I push the ATT button it will pick it up, which really does not make any sense to me.

 

[kb2vxa]

The answer is a $70 no, it has the same 3dB input to output loss as the Wal Mart TV signal splitter. To explain a passive device, it splits the signal in half (the -3dB loss) so you get half at each output from what you put in.

What you need is an amplified coupler with unity gain that compensates for the loss, that way you get out exactly what you put in. I'd avoid one with +dB gain because they tend to overload the receiver front end causing intermod and other problems.

 

[mike36507]

Thanks. Any idea on what is going on with this RS scanner with having to attenuate certain VHF frequencies?

 

[n5ims]

Thanks. Any idea on what is going on with this RS scanner with having to attenuate certain VHF frequencies?

You're experiencing overload (too much signal) on that scanner. The attenuator reduces the signal strength (by about 20 dB) to help eliminate the overload condition. What may be causing the overload is a very strong signal nearby (it doesn't have to be on the same frequency, just close to the same band). It may be from a powerful NOAA Weather Radio transmitter, one or more paging transmitters, FM broadcast transmitter, TV broadcast transmitter (most are on UHF, but some are still on the VHF frequencies), or various other types. Do you have any towers nearby that might help you clue in on what may be causing the overload?

Since you already have an overload condition on your scanner, any "improvements" to your antenna system probably won't help (and probably will make things worse). There are filters you can use to help filter out the strong signal(s) that may help your situation though. The attenuator is an easy, cheap fix if it works for you though.

 

[mike36507]

I do have towers about 2 miles from me, but another question is why doesn't my Uniden have that problem, or is that mainly a RS/GRE problem. This is my first RS scanner I have ever owned, I have been tempted to get rid of it and get me a BCT15XT.

 

[n5ims]

The RS/GRE scanners generally have a more sensitive front end on their scanners to help them pick up weak signals, but this tends to cause them to overload more easily. To help them work well both with weak signals and near strong ones, they added the attenuator to use when needed to block the strong signals. Most newer versions allow the attenuator to be used either globally (on or off for everything) or per channel (so you can use it when only on the channels you need it).

 

[mike36507]

Oh ok...makes sense. Thanks

 

[jackj]

I would almost bet that your problem is the type of splitter you are using. If you hook the RS scanner direct to the antenna does it still have receive problems? If not then the problem is that the Uniden scanner is putting out trash that is blocking the RS scanner. You will need a splitter, probably an active splitter, with good port-to-port isolation (>15 db).

 

[mike36507]

No even with the RS scanner connected directly to the antenna it still has receiving problems. On VHF at least, UHF and 800 it does a little better than the Uniden.

 

[W2NJS]

What you would probably do best with is a decent diplexer, such as the 416/4160 line from Comet, which is designed for receive and transmit functions. The insertion losses are nowhere near the figures you were quoted above, and the cost is about same as the SWL junk that passes for multi-radio and/or multi-antenna diplexers.

 

[datainmotion]

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Mike,
In my opinion, based on years of experience with GRE-based scanners, n5ims is right on the money, in your case.

Mike

 

[kruser]

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Mike,
In my opinion, based on years of experience with GRE-based scanners, n5ims is right on the money, in your case.

Mike

I agree 100%. GRE made radios almost act like they have a preamp running at all times which is a no no in an area with lots of RF activity.
FM radio stations seem to be the culprit for many users but in my case, it was several VHF paging systems very near me that make the GRE's useless for VHF monitoring unless I install PAR notch filters to notch out the paging signals.
IMO, the Unidens have much better front ends and maybe much better selectivity to help filter out the out of band signals that seemt to kill the GRE's.

The GRE's do have the upper hand when scanning UHF from 700 and higher though when compared to the Unidens.