APX7000 VHF/7-800 with stubby non VHF antenna Question

[GhostEMS]

Hey guys. Our Newly issued APX7000 radios are VHF/7-800 + GPS dual band radios.

I wanted to know what would happen if we did have VHF frequencies on C-1,2,3 for example and we were using a stubby antenna which is only 7-800 +GPS with non VHF capabilities.

What would happen if someone keyed in on a VHF channel without the VHF antenna.

I have heard that my radio will have a melt down but im not going to take the chance to find out.

My only observation is that if i remove the antenna completely and key in on a vhf frequency then nothing happens. Why should it be any different with a 7-800 antenna without the VHF capability.

Appreciate all commentary.

 

[cmdrwill]

Transmitting with the wrong frequency range antenna or no antenna will damage the radio's transmitter.

 

[KG4INW]

Right, not a matter of if but when, if done too long!

 

[GhostEMS]

so you're saying if I PTT for an instant as a mistake nothing would happen if I held it down for a few seconds for an extended amount of time then I would damage the radio correct? I am just trying to get a feel if the stubby antenna is worth it for me or I will fry my radio right away is a mistake were to occur.

 

[mmckenna]

A mismatched antenna, in this case a stubby 800 trying to be used on VHF will result in the power output from the radio getting reflected back into the finals. Since this energy has nowhere to go, it gets turned into heat. That heat will eventually damage the final stage of the RF amplifier. It's not usually a catastrophic failure, but it's a failure none the less. As a public safety professional, I'm willing to bet that you rely on your radio pretty heavily, maybe even consider it a necessity for your safety. Knowingly doing something that will damage that radio isn't a good idea. Willingly doing it pretty much rates on the list of "stupid radio user tricks".

The radio, which sounds like it's not yours, but your agencies, could eventually be damaged by this. When it goes into the shop, they'll figure out what's wrong, and you'll likely need to explain to your agency why you did something to their radio that damaged it.

The other thing that will happen is that the one time you need to use VHF and only have the 800MHz antenna on it, it's not going to work very well, and it's not going to work very long. I might be slightly surprised if an agency spent $4500 or more on your radio with no intention of you ever using the VHF side, so I'd caution you against assuming you'll never use it.

Keep in mind that if someone else ever uses your radio, they may not know that it doesn't have the right antenna on it. They won't know not to use it on VHF.

I know that some people that use radios every day take a particular dislike to having their ribs and/or arm pits jabbed with an antenna for an entire shift. We've had some of our guys switch out to the stubby 800MHz antennas because of this. I'm find with it, but when they come in complaining about how my system "sucks", I remind them that they are not using the antenna that I gave them with the radio.

If you rely on your radio, replacing the antenna that it was given to you with isn't a good idea. The radio system itself is designed to work with things set up a certain way. Switching out to a underperforming antenna is going to reduce the performance of your radio. As an EMT/Paramedic, this doesn't sound like a wise choice. As a "customer" of EMT's/Paramedics, I'd like to think you guys have the right equipment to do your jobs, not a substandard radio antenna. But, that's just my opinion.

I'd be really careful about doing this with someone else's radio. It will work fine if you ONLY use 800MHz, but there are too many places where this can go wrong. APX radios are expensive and they cost a lot to repair. On the other hand, guys who carry radios can be expendable and easily replaced.

 

[Spankymedic7]

Very nice

A mismatched antenna, in this case a stubby 800 trying to be used on VHF will result in the power output from the radio getting reflected back into the finals. Since this energy has nowhere to go, it gets turned into heat. That heat will eventually damage the final stage of the RF amplifier. It's not usually a catastrophic failure, but it's a failure none the less. As a public safety professional, I'm willing to bet that you rely on your radio pretty heavily, maybe even consider it a necessity for your safety. Knowingly doing something that will damage that radio isn't a good idea. Willingly doing it pretty much rates on the list of "stupid radio user tricks".

The radio, which sounds like it's not yours, but your agencies, could eventually be damaged by this. When it goes into the shop, they'll figure out what's wrong, and you'll likely need to explain to your agency why you did something to their radio that damaged it.

The other thing that will happen is that the one time you need to use VHF and only have the 800MHz antenna on it, it's not going to work very well, and it's not going to work very long. I might be slightly surprised if an agency spent $4500 or more on your radio with no intention of you ever using the VHF side, so I'd caution you against assuming you'll never use it.

Keep in mind that if someone else ever uses your radio, they may not know that it doesn't have the right antenna on it. They won't know not to use it on VHF.

I know that some people that use radios every day take a particular dislike to having their ribs and/or arm pits jabbed with an antenna for an entire shift. We've had some of our guys switch out to the stubby 800MHz antennas because of this. I'm find with it, but when they come in complaining about how my system "sucks", I remind them that they are not using the antenna that I gave them with the radio.

If you rely on your radio, replacing the antenna that it was given to you with isn't a good idea. The radio system itself is designed to work with things set up a certain way. Switching out to a underperforming antenna is going to reduce the performance of your radio. As an EMT/Paramedic, this doesn't sound like a wise choice. As a "customer" of EMT's/Paramedics, I'd like to think you guys have the right equipment to do your jobs, not a substandard radio antenna. But, that's just my opinion.

I'd be really careful about doing this with someone else's radio. It will work fine if you ONLY use 800MHz, but there are too many places where this can go wrong. APX radios are expensive and they cost a lot to repair. On the other hand, guys who carry radios can be expendable and easily replaced.

Wow, very well said. I'm impressed.

 

[mmckenna]

Wow, very well said. I'm impressed.

It's almost like I do this for a living......

 

[dfbarnes]

I'm hoping you're following this thread... since you know what you're talking about. I'm in a similar situation. End user and I hate the antenna. What's more, I hate speaker mics with long coiled cords.

This is what I'd like to do in my little dream world:

1. Purchase a Public Safety Speaker Mic with the 18" straight cord, and put the stubby VHF antenna on it.

2. Put a 700/800 GPS antenna on the radio.

Question 1: Will the radio split up the RF and use the two different antennas, or will it try to feed everything through the PSM's VHF antenna?

Question 2: If the radio is capable of using the two different antennas, would it require programming to accomplish this? (My agency would not be open to having our vendor program the change for me... they've already purchased these top-of-the-line radios and disabled most of the top-of-the-line features through the programming... typical county operating. Let's buy these and then disable them to the point that we could have bought radios half the cost and done the same thing.)

Thank you sir!

 

[mmckenna]

The antenna connection is either/or, but not both. When you connect the speaker mic, it disconnects the antenna on the radio and routes RF to/from the PSM.

For question 2, it's likely not that your agency has disabled functions, it's that they ordered the radio with only the options they needed. To enable the options it doesn't have, it requires a new piece of software from Motorola. This is the way Motorola has done it for quite a while, you buy the radio, which has all the correct innards in it. Your agency pays extra to turn those parts on.
So, yes, the agency bought the fancy radio with most of the options likely turned off by Motorola. Without that expense flash update, the options are not available, even using the programming software.

As for buying a radio for half the cost that will do everything you need, that is entirely possible. Unfortunately, if they really needed dual band radios, they are pretty much stuck. Often it's a case of buying whatever the system operator requires, or what everyone else has. There is a lot of money wasted in the public safety radio purchasing.