Scanner Antenna Question

[Blacksmith]

I bought the wife a new scanner for Valentines Day this year. It is a BCT 15X. She really likes it.

She wants a larger antenna to scan more areas as opposed to just the whip. I was thinking about running the lead through coaxial cable that was used by an old satellite system. This goes to nearly all the rooms in the house including the shelter area. This way we could run it into different areas of the house by moving the scanner around and connecting a bridge to the cable. I think the longest run would be about 200'.

- Is this too long to run a scanner antenna lead?

- Are there any problems with running the antenna through coaxial?

- Is there a better way of doing this? I don't want wires strung everywhere.

[TacAir]

You migh run into issue cause by an impedance mis-match - TV cable is usually 75 ohms Z, radios, 50.

Old coax cable may be high loss as well.

Buy some RG-8x and an outside antenna, make a new/fresh run and know its 'righ't from the get--go..

[Blacksmith]

I already have the antenna. I bought it when I bought her the scanner. That is how far behind I am on certain tasks.

[crypto]

Check your old satellite cable and make sure its 75-ohm (it should be).

As long as thats the case, yeah it should work fine.

[gary in ohio]

Ignore any issue with 50ohm vs 75ohm.. Its a scanner you will not see any noticeable issue. 200ft is a bit long but if its quality RG6 then you should be ok.

[Radio guy]

What kind of satellite system did you have? If the cables run to all rooms in the house there would be a "multiswitch" for Directv or Dish that will cause problems with scanner reception and some are only rated for 950-1450MHz. If you replace it with a splitter you will loose at least half of the signal every time you divide the signal. A 2-way TV splitter will have at least 3.5dB loss and a 4-way will have at least 7dB loss and so on.

Reception will also be affected depending on the frequencies you are trying to receive. VHF lo band and Hi band is not so bad with a 200ft run of RG6 at 800MHz your looking at an additional 12dB loss on top of whatever your splitter losses are. 12dB loss would leave you with about 1/17th of the signal you started with.

You can get an active "multicoupler" designed for scanner use and that will split the signals without any loss except for your long cable loss. Active splitters for cable TV use are not a good choice due to higher noise figures.
Radio Guy

[Blacksmith]

What kind of satellite system did you have? If the cables run to all rooms in the house there would be a "multiswitch" for Directv or Dish that will cause problems with scanner reception and some are only rated for 950-1450MHz. If you replace it with a splitter you will loose at least half of the signal every time you divide the signal. A 2-way TV splitter will have at least 3.5dB loss and a 4-way will have at least 7dB loss and so on.

Reception will also be affected depending on the frequencies you are trying to receive. VHF lo band and Hi band is not so bad with a 200ft run of RG6 at 800MHz your looking at an additional 12dB loss on top of whatever your splitter losses are. 12dB loss would leave you with about 1/17th of the signal you started with.

You can get an active "multicoupler" designed for scanner use and that will split the signals without any loss except for your long cable loss. Active splitters for cable TV use are not a good choice due to higher noise figures.
Radio Guy

Ok thanks RG, that is what I was wondering.

I do not know what kind of system was there when the previous owner had it installed. He did run it to nearly every room. Outside there is a four way splitter so I figure there have to more splitters than that as there are 11 connections inside. The cable is RG6. It does NOT say Direct TV and they do advertise on their cable (at least the new cable run says it).

Most of what we are monitoring is VHF (obviously non-digital). If there are tornado warnings we will be in the basement like we were earlier this spring. I think the weather alerts are in the 162 Mhz range?

Do you have an example of a proper scanner multicoupler?

[Radio guy]

Any satellite system has to send voltage up the coax to the LNB and or have switching capability for different polarities/orbital slots and that doesn't work through a regular splitter. Check the make, model and frequency range of the splitter thingee to see if that's what it really is or if its a multiswitch.

Some satellite splitters are only rated for 950-1450MHz which is not very useful for most scanner freqs but some satellite and TV splitters are rated for 40-2150MHz and some will cover 5-2150MHz. A normal TV/cable splitter should cover 40-800MHz ok.

Also check what frequencies you need to receive and if its VHF hi band or lower it might work out. Otherwise you can have so much loss in the cable and splitters that the stock rubber duck antenna on the scanner might work better than a roof mount antenna.
Radio Guy

[crypto]

you know, what if he just reversed the polarity on the BNC connector going into the scanner, so he used the braid on the entire old cable system as an antenna?

Since its a DX only antenna, the net effect should be much better than using the center conductor.

[Radio guy]

That may work ok for HF reception but for VHF/UHF scanner not so good. Even using the braid for HF reception you would probably pick up lots of extra noise from every switching power supply in the house.
The OP didn't really mention connecting a good VHF/UHF scanner antenna outside to feed the lossy distribution system. Without a decent antenna up high all you have is a bunch of coax to each room with nothing feeding it.
Radio Guy

[Blacksmith]

The OP didn't really mention connecting a good VHF/UHF scanner antenna outside to feed the lossy distribution system.

I put it belatedly in post 3. I have the recommended outdoor antenna for the scanner. It has a coax connector on it which got me going down this road.

I was going to go take a picture of the connector outside and then I realized that that the contractor for our service had hooked up his connection to it and is using it for our subscription. Turns out the cable runs I want to use or not connected to any splitters. The original owners ran independent lines to each room from the splitter outside that I don't need.

I just went and traced the three we plan to use the most. One is much longer than I thought though. It runs the length of the house twice inside and out as well as weaving around the attic (this guys was not interested in conserving cable). It looks to be closer to 300'.

Some of the frequencies are in the UHF range (450) but most are VHF (150s)

[Blacksmith]

I finally got around to hooking the whole mess up. Mrs. Blacksmith is pleased as punch. Sounds great and we can hear the whole county (and more) clear as a bell now. I can disconnect two wires and reconnect another wire to have it go to the shelter in the basement. Once I get a splitter on there it will just be one wire and moving the scanner to the basement. That will only take a minute now that the cables are marked. No more static channels. No need to drill more holes. Smiles all around.

Coax adapter in the back of scanner. Running into the unused SATV wire in the kitchen. No you can't have my cookies.



Antenna run off the roof of the garage at the back of the house.



So the answer is Yes, you can use your CATV/ SATV wiring to run an antenna line for your scanner with certain freq ranges.

[Radio guy]

To make the cable system an antenna you would connect the center pin of the BNC on the scanner to the braid of the cable system and not connect anything to the ground of the receiver. If you reverse the center and braid and they are both connected it will not work because even though the outside of the coax is now going to the input of the receiver, the center of the coax connected to the radio chassis would still make the cable system a transmission line and it would not receive or radiate like an antenna. Or at least not very well.

Whenever you have two parallel wires carrying AC current or radio signals (same thing) there will be little or no radiation or pickup from the parallel wires. Disconnect one of the wires at one end and you still have a transmission line. Disconnect one wire at both ends and now you potentially have an antenna.

you know, what if he just reversed the polarity on the BNC connector going into the scanner, so he used the braid on the entire old cable system as an antenna?

Since its a DX only antenna, the net effect should be much better than using the center conductor.

[Blacksmith]

An interesting idea to be sure but since I already had the antenna it was not needed. Also I have other plans for the rest of the coax. The guy that built the place had cable lines run to every single room. He either really loved TV or really loved having cable run.

Just realized I have to climb back up there to zip tie the cable to the mast to keep it from blowing around.

[KJ4VOV]

An interesting idea to be sure but since I already had the antenna it was not needed. Also I have other plans for the rest of the coax. The guy that built the place had cable lines run to every single room. He either really loved TV or really loved having cable run.

Just realized I have to climb back up there to zip tie the cable to the mast to keep it from blowing around.

When a friend built her house back in '03 I did all the communications wiring. Every room in the house (including bathrooms) had cable, network and phone jacks, with multiple jacks in her office and in the living room and master bedroom. I ran more than 1,500 feet of RG-6 quad and 2,000 feet of CAT 6 in that house (three stories with the kitchen and living room on the top). She now has a 36" LCD widescreen in the master bath, easily viewable from her jacuzzi and a secure home network with a media server and 8tb of movies.