Antenna Switcher Advice

[TailGator911]

Best way to do this besides having to go to the multi-couplers and plugging and unplugging, etc

I have 8 scanners that are fed by a rooftop discone to a Stridsberg 8-port multi-coupler.

I have 4 scanners fed by a rooftop directional yagi to a Stridsberg 4-port multi-coupler

Of the 4 scanners on the 4-port multi-coupler, I want to switch 2 of them (SDS100&200) between the yagi and the discone at the same time via the same switch, mounted right in front of me on the desk, back and forth, easy peasy, like a big A/B switch, I am thinking like some sort of selector. How would you do it, and what would you need/use?

All advice and suggestions welcomed and appreciated!

JD
kf4anc

 

[prcguy]

I would use a coaxial relay for each radio you want to switch between two antennas. You would wire the scanners to the common port of the switch, then another port to one Stridesberg and the other port to the other Stridesberg. Then you can have a small box or panel near the scanners with a toggle switch for each scanner that will select the antenna. You would also need a small power supply or wall wart supply to power the relays.

Here are some examples of coaxial switches and I've bought SMA type 18GHz rated versions for less than $15 each.
2 each, Coaxial relay, SPDT, BNC conn. 28 vdc, used, cleaned, tested. | eBay

 

[Ubbe]

Get a $7 dollar A/B coax switch, there are many to choose from, and connect to each Stridsberg. There's only one output from the switch so put a CATV 2-way splitter there and feed each scanner. It's an $11 solution not counting connectors or pigtails. Stridsberg have some gain thru their multicouplers so you will not loose any signal by using a 3dB splitter loss and additional 2x0.2dB loss in the impedance missmatch, if the scanners actually have a constant 50 ohm over it's frequency range.
https://www.amazon.com/dp/B00CQEH20E/
https://www.amazon.com/DealMux-Revtangle-Coaxial-Antenna-Splitter/dp/B01EZQ5WBG

/Ubbe

 

[TailGator911]

Great advice, thanks! This is a project I plan on after summer when I am winterizing the shack. I keep my SDS's on the directional yagi for the most part but I do switch back and forth when something busy happens. For a switch I would want a rocker switch on a box. I think I saw something like that at GigaParts. I'll have to look around. Thanks again, guys!

JD
kf4anc

 

[scan_madison]

Little bit off topic, but I would like to know how such splitters decrease signal by half. I can understand slight loss but 50% just seems too high. Please enlighten me. TIA.

 

[Ubbe]

You are absolutly correct, 3dB is 50% and the signal are reduced to half when you split it. There's always some additional loss in splitters as it isn't a 100% effeciancy in them so it's probably 3.5dB

/Ubbe

 

[kruser]

Little bit off topic, but I would like to know how such splitters decrease signal by half. I can understand slight loss but 50% just seems too high. Please enlighten me. TIA.

It's the nature of the beast. All passive splitters like CATV splitters will have at least 3.5 dB loss per port as Ubbe mentioned. That is per port for a three way splitter. If you need more than two devices, expect a loss of 7dB or so for ports three and four and even higher as you cascade more internal splits for five and more port splitters.
The way to get around this is using so called multicouplers or line amps. They amplify the signal just enough to overcome any loss in their internal splitters so in effect, you have no loss at the output. Ideally, the output should be flat or at the same level as the input. They can add some noise into the signal however. If monitoring a weak digital system, even a little bit of amplifier noise may be enough to wipe out the digital signal to the point the radio cannot decode it. Pay attention to specs if going this route.
The loss from a splitter can also be regained by using an antenna with gain higher than the splitter loss.