Antenna Switch

[jazzboypro]

Hello all,

I would like to use the same antenna on 2 different radios. I will disconnect the feedline from the triplexer and plug it into the antenna switch and use two interconnect cables to connect the switch to the triplexer and the second radio



Everything in black is already in place and working. What's in red i will need to buy. I have 2 questions.

1- If any of you have the Delta-2 coax switch is it a good product ?
2- Is there anything else missing or that i should think of ?

Many thanks
73
De VA2FCS

 

[MDScanFan]

Looks fine to me. And the Alpha Delta switch is very high quality.

 

[K4EET]

Hi @jazzboypro,

You may want to consider adding some safety components as discussed in this old post that I made some time back:

Antenna Coax Grounding by Whitham D. Reeve based on the National Electrical Code (NEC) Article 810

In many threads about running coax to antennas, some of us will usually mention "be sure to properly ground things" without going into a whole lot of details. We may even mention that the National Electrical Code (NEC) requires it for all homes and businesses within the United States. I found...

forums.radioreference.com

73, Dave K4EET

 

[k6cpo]

I don't see the need for the triplexer in the first place, unless the first radio has separate outputs for VHF and UHF. What is the radio in black?

 

[MUTNAV]

Hello all,

I would like to use the same antenna on 2 different radios. I will disconnect the feedline from the triplexer and plug it into the antenna switch and use two interconnect cables to connect the switch to the triplexer and the second radio
View attachment 123991


Everything in black is already in place and working. What's in red i will need to buy. I have 2 questions.

1- If any of you have the Delta-2 coax switch is it a good product ?
2- Is there anything else missing or that i should think of ?

Many thanks
73
De VA2FCS

Don't forget to terminate anything "not used" with a 50 ohm termination.

Thanks
Joel

 

[jazzboypro]

I don't see the need for the triplexer in the first place, unless the first radio has separate outputs for VHF and UHF. What is the radio in black?

The radio is a 9700 it has 3 antenna connectors, one for each band

 

[jazzboypro]

Hi @jazzboypro,

You may want to consider adding some safety components as discussed in this old post that I made some time back:

Antenna Coax Grounding by Whitham D. Reeve based on the National Electrical Code (NEC) Article 810

In many threads about running coax to antennas, some of us will usually mention "be sure to properly ground things" without going into a whole lot of details. We may even mention that the National Electrical Code (NEC) requires it for all homes and businesses within the United States. I found...

forums.radioreference.com

73, Dave K4EET

The ground is there and the polyphaser is outside at the entry point. Good reminder thought, i need to revisit the ground system.

 

[k6cpo]

The radio is a 9700 it has 3 antenna connectors, one for each band

Gotcha...

 

[jazzboypro]

Hello again,

After some thoughts, i'm not so sure i want to go ahead with the antenna switch. Mainly i don't like the fact that i will have to use only one radio at a time. I am now thinking of installing another antenna instead.

My current setup is depicted by the upper portion of the image:

The GP-3 is connected to my 9700
The Discone is connected to 4 receivers
All feedlines are less than 75 feet of LMR400
Both antennas are roughly at the same height
Grounding and arresters already in place

My envisioned setup is the lower portion of the image. My question is in regard with the horizontal separation between the antennas. Should i be concerned of damaging any of the radios while transmitting on any of the 2 GP-3 ? The 9700 is rated at 100 W but i never have to use more than 3 watts for repeater work. With my portable DMR radio i currently use 7 watts to access repeaters successfully with the stock antenna, i have not tried with less power. I assume that a mobile DMR radio using the other GP-3 antenna would work as well with 7 watts or less but the radio is rated a 75 watts if need be.

Many thanks
73
De VA2FCS

 

[MUTNAV]

Hello again,

After some thoughts, i'm not so sure i want to go ahead with the antenna switch. Mainly i don't like the fact that i will have to use only one radio at a time. I am now thinking of installing another antenna instead.

My current setup is depicted by the upper portion of the image:

The GP-3 is connected to my 9700
The Discone is connected to 4 receivers
All feedlines are less than 75 feet of LMR400
Both antennas are roughly at the same height
Grounding and arresters already in place

My envisioned setup is the lower portion of the image. My question is in regard with the horizontal separation between the antennas. Should i be concerned of damaging any of the radios while transmitting on any of the 2 GP-3 ? The 9700 is rated at 100 W but i never have to use more than 3 watts for repeater work. With my portable DMR radio i currently use 7 watts to access repeaters successfully with the stock antenna, i have not tried with less power. I assume that a mobile DMR radio using the other GP-3 antenna would work as well with 7 watts or less but the radio is rated a 75 watts if need be.

Many thanks
73
De VA2FCS

View attachment 124195

Just as an idea, if it's possible to separate the antennas vertically rather than horizontally, it may work out better. If you have access to an ARRL antenna handbook, they have charts that show how the vertical separation works. It would be under the repeater antenna section of the book.

 

[mmckenna]

Or a combination of vertical -and- horizontal.

But, I think you'll be fine with your plan. 14 feet is quite a bit of air gap considering what some run on mobiles.

 

[jazzboypro]

Or a combination of vertical -and- horizontal.

But, I think you'll be fine with your plan. 14 feet is quite a bit of air gap considering what some run on mobiles.

How many feet are we talking about on the vertical plane ?

 

[mmckenna]

How many feet are we talking about on the vertical plane ?

The more the better.

But I expect you are not running enough power for that to be an issue. The right answer is to take a watt meter with a 50Ω load and test the unused antennas while transmitting. Anything under 250mw should be safe, but I'd doubt you'd see even that much.

 

[jazzboypro]

The more the better.

But I expect you are not running enough power for that to be an issue. The right answer is to take a watt meter with a 50Ω load and test the unused antennas while transmitting. Anything under 250mw should be safe, but I'd doubt you'd see even that much.

I will see if i can borrow a watt meter since i don't have one.

 

[mmckenna]

I will see if i can borrow a watt meter since i don't have one.

Think about getting yourself a basic SWR meter and a dummy load. It's an inexpensive test setup that will tell you a lot about your system.

 

[Ubbe]

Anything under 250mw should be safe, but I'd doubt you'd see even that much.

If transmitting 10W at 145MHz it will be 10mW from the other antenna, if both antennas are tuned to the frequency. If transmitting at 450MHz it will be 10dB higher, 100mW.

/Ubbe

 

[jazzboypro]

Think about getting yourself a basic SWR meter and a dummy load. It's an inexpensive test setup that will tell you a lot about your system.

Can you suggest a brand and model ?

If transmitting 10W at 145MHz it will be 10mW from the other antenna, if both antennas are tuned to the frequency. If transmitting at 450MHz it will be 10dB higher, 100mW.

/Ubbe

Actually the DMR radio would be on UHF most of the time because we only have 2 VHF DMR repeaters and they are out of reach for me. My 9700 is used mostly on VHF when in analog mode and VHF/UHF when in D-star mode.

 

[mmckenna]

Can you suggest a brand and model ?

Bird 43.
But those are expensive.
Get yourself a basic MFJ SWR meter that covers the 2 meter/70 centimeter band. Diamond makes some nice ones, there's cheap Chinese models, also.

Actually the DMR radio would be on UHF most of the time because we only have 2 VHF DMR repeaters and they are out of reach for me. My 9700 is used mostly on VHF when in analog mode and VHF/UHF when in D-star mode.

The RF front end of the radio is still exposed to the antenna, so it doesn't go away just because you are using a different band.

 

[jazzboypro]

Bird 43.
But those are expensive.
Get yourself a basic MFJ SWR meter that covers the 2 meter/70 centimeter band. Diamond makes some nice ones, there's cheap Chinese models, also.



The RF front end of the radio is still exposed to the antenna, so it doesn't go away just because you are using a different band.

Yes i get that. Just wandering if the problem would be less important if the radios are on different bands. Thanks for the watt meter suggestions

 

[mmckenna]

If it's strictly a VHF radio only, and a UHF radio only, and they don't have "wide as a barn door filtering" like many of the ham radios with wide RX coverage do, then yes, it helps.

If it's dual band radios, then no, not necessarily, but can depend on the design.

An inexpensive watt meter that will read down to the 1/4 watt or less level and a 50Ω dummy load designed to handle the full output of your radio will be a good addition to your test equipment.
Obviously it'll let you check SWR.
You can attach the dummy load in place of the antenna and check transmitter output power.
You can attach the antenna/dummy load and see the interaction between the two antennas when transmitting.