Signal loss using a line splitter?

[KAPcsg]

I have a Diamond D130 discone antenna mounted to the roof that uses a 100 foot low-loss cable into the house. Right now I can only mount it to one radio at a time, but I would like to run a three-way splitter on it and simultaneously use it for my scanner, CB and Ham radios.
My concern is loosing signal strength, either via the splitter, or by connecting three receivers to it at once. Also, would there be a preferred connector, i.e,. BNC, SMA, etc. to limit signal loss?
I'm not currently using a signal amplifier.
Thanks.

 

[mule1075]

I have a Diamond D130 discone antenna mounted to the roof that uses a 100 foot low-loss cable into the house. Right now I can only mount it to one radio at a time, but I would like to run a three-way splitter on it and simultaneously use it for my scanner, CB and Ham radios.
My concern is loosing signal strength, either via the splitter, or by connecting three receivers to it at once. Also, would there be a preferred connector, i.e,. BNC, SMA, etc. to limit signal loss?
I'm not currently using a signal amplifier.
Thanks.

If you plan on transmitting on the ham and cb radios you are going to need another solution.

 

[ko6jw_2]

You seem to be referring to the type of signal splitter used with TV antennas or cable TV as opposed to a duplexer or triplexer used in ham radio. The first type splits a signal for reception while the later provides insolation needed for transmitters to share a single antenna. Both have insertion losses. For example, I use a triplexer to split a triband antenna between 2 meter, 220 and 440 radios. The 2 meter output technically passes signals from 0 to 150 Mhz. The 220 output is a band pass filter and the 440 covers about 400 to 500. This is fine for the three transceivers, but would not work well with a scanner. Insertion losses would be in the neighborhood of 3db.

The Diamond D130, in spite of its claims to cover 25 to 1000 Mhz, will be useless on CB. It can transmit on 6 meters, but not at 27 Mhz. The resonance can be lowered somewhat by using a longer whip, but not as low as CB. The stock configuration would have a very high SWR at 27 Mhz.

As regard to connectors, the preferred one would be type N. Low loss and constant impedance. Most duplexer and triplexers use SO239 or PL259 unfortunately.

Using multiple ham radios is very practical. Adding CB and scanners into the mix will be difficult or impossible.

 

[KAPcsg]

I would be using this for receiving only. The discone antenna that I have does include the top element for 25-50 MHz, and picks up CB currently.

 

[JoshuaHufford]

These are high quality power dividers, 10-1000MHz, if you need something out of that range might have to look for something else, from everything I've read this is the best way to split your signal.

power divider

Then you could add this preamp ahead of the power divider to make up for the insertion loss.

p broadband vhf/uhf

If you really want to improve things you could put the preamp at your antenna then use this to feed power to it.

dcinj

 

[ko6jw_2]

I have one of these antennas and it may pick up CB, but it won't do it well. The top mounted whip and loading coil have noting to do with the discone part. They are useful, but intended to allow 6 meter operation with a low SWR. The receive efficiency at 27 Mhz is very poor.

Since you are not transmitting, a TV type splitter will work with an insertion loss. They are usually specified on the splitter.

 

[wtp]

NEVER hook up a transmitter to a receiver.
how about two antennas ?
one for the scanner and one for the transmitters.

 

[mule1075]

NEVER hook up a transmitter to a receiver.
how about two antennas ?
one for the scanner and one for the transmitters.

Take off the microphones and it should not be a problem.

 

[Ubbe]

You'll need someting like this: https://www.amazon.co.uk/MFJ-1707-Transmit-Receive-RF-Switch/dp/B01KXTYSPA
Put that close to the antenna and there's probably enough room inside to put a good low noise 20dB amplifier there for RX to overcome coax and splitter losses. Ultra Low Noise Amplifier PGA-103+ 2 GHz Gain>20dB by GPIO Labs on Tindie

/Ubbe

 

[JoshuaHufford]

I thought he said this was receive only?

 

[jim202]

Not to confuse you with what has already been said, let me re state the losses. If you have a 2 way splitter, you will only get half the signal strength at each of the ports from the antenna. If you use a 3 way splitter, you will only get 1/3 of the signal at each of the ports that the antenna is picking up.

Without an amplifier in line your not going to be happy with just putting a splitter in series with the coax cable coming from the antenna.

A word of caution in just picking up a low cost in line amplifier. You have to take into account the possibility of a near by strong signal causing an overload issue and killing your ability to hear anything while that signal is present. Going to a low cost amp is more problems that it resolves. Spend some time looking at a decent in line amp that has the multi ports built into it. Yes it will be down in the radio room and you will have to live with the line loss of the coax cable between the antenna and the amp.

Look around where you live for towers. Is it a cellular tower? Is it a tower that may have a paging transmitter on it? Is it a public safety tower that will be having chatter based on the incident activity in your area? The only way to really find out what is around you is to drive around with a scanner and see what you hear with little to no antenna on it.

You can also do some homework and look up your local license information from information that you can cull from the database right here on RadioReference for at least the public safety portion of your homework.

Good luck on your efforts. Hope the information you have got from reading this thread helps you.

 

[KAPcsg]

I had no idea that a splitter will actually split the signal strength. I assumed that if you were receiving signals from four different bands, i.e., scanner, cb, ham, gmrs, etc., that the splitter would be akin to using four separate antennas.

 

[JoshuaHufford]

That is why you need a preamp to overcome the loss. Ideally the preamp is placed as close to the antenna as possible so the coax loss is also overcome, but ahead of the splitter is the next best option.

 

[Ubbe]

All splitters degrade the signal level as it has to supply each output with a signal. If you where to use a diplexer, or triplexer, and each output would only contain part of the frequency band, one port for 350MHz and higher and one for 100-200Mhz and a third for 70Mhz and lower, they would hardly attenuate the signal at all, less than 1dB. Moonraker has a couple of those as well as other amatuer radio suppliers.

If you want to split the signal equally you should look at a $40 low-noise high signal capable amplifier, like the one I refered to, that can handle signals at +30dBm, you'll never see those signal levels if you don't transmit with an antenna just a fot away, without loosing performance and have that at the antenna and then the splitter down at the scanners.

/Ubbe

 

[W5RGP]

I would be using this for receiving only. The discone antenna that I have does include the top element for 25-50 MHz, and picks up CB currently.

I have the same antenna going into an 8 port stridesburg multi coupler my antenna is 50 feet up I don’t have any problems with signal loss

Matter fact I bought a yagi to try to get a little better reception in one direction and the diamond pulls in a better signal then the yagi pointed straight at the tower some 40 miles away



Sent from my iPhone using Tapatalk

 

[Ubbe]

50 feet up are pretty high. My 4-port Stridsberg don't like strong signals, it adds noise as soon as the signal level goes a bit high. Stridsberg modified a multicoupler for a RR member here, reducing the gain, so it wouldn't get compromised at the members location. As soon as you deal with external antennas I recommend to always use a variable attenuator to check what happens when you gradually add attenuation. There's often a certain level, sometimes a narrow one, where you get a maximum signal strenght that doesn't de-sense an active multicoupler or your scanners.

/Ubbe

 

[KAPcsg]

I have the same antenna going into an 8 port stridesburg multi coupler my antenna is 50 feet up I don’t have any problems with signal loss

Matter fact I bought a yagi to try to get a little better reception in one direction and the diamond pulls in a better signal then the yagi pointed straight at the tower some 40 miles away



Sent from my iPhone using Tapatalk

I had a similar experience back in the late 90's. I bought a Grove Scanner Beam from Grove Enterprises after I had read great things about it. Testing it head to head, my Diamond discone still outperformed it. Interesting thing about the scanner beam is that it had better reception aiming backwards at a target station.

 

[Ubbe]

Interesting thing about the scanner beam is that it had better reception aiming backwards at a target station.

Typical for overloading a receiver scenario. You absolutly need a variable attenuator when using external antennas or you will have no clue of what's going on.

/Ubbe

 

[DeepBlue]

Receiver Multicouplers, Passive and Active, HF to VHF/UHF

S.