Two radios on one antenna

[tinaeuc]

I’m adding a screen room onto my radio shed and want to have a radio in it.

I don’t want a switch I want to listen on both radios but TX on one at a time.

This is for 2 GMRS radios. Inside will be a BTECH 50x1 and In the screen room will be just the face plat of a Motorola MCS 2000.

Any help would be much appreciated.

Thanks in advance 

update……

I changed my mind and I will only be listening and transmitting on 1 radio at a time.

Thanks for all the help.

[KAF6045]

22 minutes ago, WROZ250 said:

#3. You mentioned a screen room in your shack.  I am assuming you mean an RF shielded room (a.k.a. Faraday Shield) for working on sensitive receiver alignment and such equipment where ambient RF would make such work next to impossible.  Any wiring into the room, including and especially AC power, had to go through a series of RF filters to keep the shielding intact.

He also mentioned just having the control panel (face plate) in said room. That should mean the cable just passes audio (speaker/mike) and control signals -- no RF.

"screen room" is a bit ambiguous.. It could mean a "screened"/"shielded" room -- or as I first interpreted it, a dedicated room for display/control-monitors, keyboards et al.

 

Using an antenna switch (in reverse) can be a risk as they don't have perfect isolation -- some of the power going from radio A can leak into radio B, and if the attenuation between ports A and B isn't sufficient, the leak could damage the non-selected radio. After all, receive circuits are expecting milliWatts or less; even 1 Watt leakage is massive.

[WROZ250]

21 hours ago, KAF6045 said:

He also mentioned just having the control panel (face plate) in said room. That should mean the cable just passes audio (speaker/mike) and control signals -- no RF.

"screen room" is a bit ambiguous.. It could mean a "screened"/"shielded" room -- or as I first interpreted it, a dedicated room for display/control-monitors, keyboards et al.

 

Using an antenna switch (in reverse) can be a risk as they don't have perfect isolation -- some of the power going from radio A can leak into radio B, and if the attenuation between ports A and B isn't sufficient, the leak could damage the non-selected radio. After all, receive circuits are expecting milliWatts or less; even 1 Watt leakage is massive.

I agree that 'screen room' without elaboration/details is perhaps a little ambiguous.  I only know the one room type labeled 'screen room'.  A room that is isolated for monitors and such, is not a 'screen room', even if it has some level of shielding.  So calling an isolated room a 'screen room' is like calling an automobile an airplane (IMHO).

Assuming the OP was talking about an actual 'screen room', the control panel thing would still be a no-go as any cabling, including audio/control signals, entering such a room must be filtered, as any cable can conduct RF.  Indeed, it isn't what type of information is being carried but rather any 'wire' can and will act as both an antenna and a radiator.

I also agree that an antenna switch used as described probably would not work because, as you mention, there simply is not enough isolation.  There are switched that have up to 50-60 dB isolation between ports, but they are quite expensive.  There really is no viable way to isolate a receiver from a transmitter on the same frequency while sharing an antenna.

As far as the screen room thing, perhaps my responses are a mute point because, as I think about it, anyone with an actual 'screen room' would or should already know the issues. LOL!

In hindsight, I can't help but wonder why the OP even mentioned 'screen room' if they don't actually have a 'screen room'.

[wayoverthere]

On 9/21/2022 at 10:15 AM, KAF6045 said:

"screen room" is a bit ambiguous.. It could mean a "screened"/"shielded" room -- or as I first interpreted it, a dedicated room for display/control-monitors, keyboards et al.

Alternate take: perhaps (given the backgrounds) we're overthinking the possibilities, and by screen room, what the OP meant was a literal "screened room" similar to a screened in porch, just meant to keep the bugs away?

[Sshannon]

28 minutes ago, wayoverthere said:

Alternate take: perhaps (given the backgrounds) we're overthinking the possibilities, and by screen room, what the OP meant was a literal "screened room" similar to a screened in porch, just meant to keep the bugs away?

That’s what I thought he meant also. 

[Bytor]

I have used these with great results

https://www.amazon.com/Alpha-Delta-Original-DELTA-2B-2-Position/dp/B00CUFHYY8

[MichaelLAX]

Yes: Alpha-Delta which also has a 4 output model. I have both: one for HF antenna to two radios and the other for my Comet VHF/UHF tri-band antenna to four radios. 

Avoid cheap knockoffs that perform poorly. 

[Sshannon]

5 minutes ago, MichaelLAX said:

Yes: Alpha-Delta which also has a 4 output model. I have both: one for HF antenna to two radios and the other for my Comet VHF/UHF tri-band antenna to four radios. 

Avoid cheap knockoffs that perform poorly. 

I’m impressed with the quality of the Alpha Delta items that I have. I don’t have an antenna switch yet but I have several other items including their excellent lightning arrester. Having a second arc-plug in their switch adds another incremental amount of protection for the most common issues.