Dallas PD using 7/800 antenna on 460MHz....

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Motoballa

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I rode out with my Dallas PD friend this past weekend and on a couple of our calls this one Officer tagged along and I noticed he had a 7/800 stubby on his APX, which granted the radio is dual band on UHF and 7/800, so it would make since if he's on their 800 analog system...But he wasn't.

He was on the analog 460MHz system. I face palmed when I read "7/800 GPS" on the side of the stubby antenna and when he keyed up and tried to let dispatch know to let EMS in but couldn't get out.........Even with the crazy voter system they have. This is a huge safety issue and I don't know if they just buy their own antennas online thinking it'll work and be better than the standard armpit antenna that Motorola provides or what. Only if they knew what danger they were putting themselves in by using those..
 

bchappuie

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I swept a 800MHX antenna for handheld, and it actually came out alright up thru 150MHZ, so having it on 450 is no big deal. Maybe a couple of DB at most.
 

hiegtx

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They may have switched to the 700/800 antenna in preparation for the switchover to the new P25 Phase II system, tentatively scheduled for the 4th quarter of this year.
 

hiegtx

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NCTCOG system? or is it a new system alltogether?
It will be a "new" system. See this thread:

Supposedly, the target date to go live is the fourth quarter of this year. While there is a "Dallas Simulcast" site on the Dallas P25/NCTCOG system, that only has four sites and six frequencies, not near enough to handle the traffic for all city and Dallas County departments, plus any other agency that might join. I would expect that there will be additional sites and frequencies used. Perhaps, some of the existing frequencies for the current Type II Dallas City Local Government system would be moved to the new system. See the link to meeting notes in the earlier thread noted above.
 

IAmSixNine

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More then likely it was purchased on his own dime and he switched it out. Its not city issued.
A few years ago i knew a DPD officer who had the GPS only antenna on his radio. Think size of the stubby 800 but the thickness was the same from top to bottom. Basically if you use a public safety speaker mic this antenna gave the radio a true GPS antenna that the public safety mic didnt offer. So i invited him to my office and showed him the APX accessory catalog for Motorola and pointed out his antenna was not to be used for TX or RX as he was using it for. Well no wonder why he was having issues getting out to dispatch.
Lent him one of my UHF antennas while i ordered him a new one. Then explained the different radio systems he has access to and what antenna to use he will be using them.
 

Russell

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My understanding is that the Dallas P25 portion of the Dallas P25/NCTCOG is the "new" system. They have added or are in the process of adding additional towers. I have also seen freqs bounced back and forth from the 800 Mhz analog system to the new system, to prove it can be done dynamically. As users are unloaded from the 800 MHz analog system and loaded onto the P25 system the frequenices will follow.

Also, note the NCTCOG portion will continue to ride along on the Dallas P25 using the "20s" sites. Those system controllers are extremely expensive and have excess capacity than can easily be shared with the COG system.

I have little confidence in the projected time line.
 
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"just a few db"... 3dB loss is HALF, 3dB gain is TWICE as much.. Every dB counts. Officers, firemen, etc are often putting a shorter antenna on their radio so it doesn't hit them in the armpit, or just to look "cool" i guess. Some break them off and think if a replacement screws into the hole it must be made to work for it.
 

N9JIG

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I rode out with my Dallas PD friend this past weekend and on a couple of our calls this one Officer tagged along and I noticed he had a 7/800 stubby on his APX, which granted the radio is dual band on UHF and 7/800, so it would make since if he's on their 800 analog system...But he wasn't.

He was on the analog 460MHz system. I face palmed when I read "7/800 GPS" on the side of the stubby antenna and when he keyed up and tried to let dispatch know to let EMS in but couldn't get out.........Even with the crazy voter system they have. This is a huge safety issue and I don't know if they just buy their own antennas online thinking it'll work and be better than the standard armpit antenna that Motorola provides or what. Only if they knew what danger they were putting themselves in by using those..
On dual band APX's the PSM antenna is 7/800 only. The antenna on the radio itself is for the alternate band (in this case UHF) and GPS (if so equipped) when a PSM is attached.

If the antenna you saw was on the PSM then that would have been correct, assuming he had a UHF, dual or dual/GPS antenna on the radio itself.
 

Motoballa

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On dual band APX's the PSM antenna is 7/800 only. The antenna on the radio itself is for the alternate band (in this case UHF) and GPS (if so equipped) when a PSM is attached.

If the antenna you saw was on the PSM then that would have been correct, assuming he had a UHF, dual or dual/GPS antenna on the radio itself.
It was on the radio itself, he didn't have an antenna on the RSM or the capability of having one. The RSM he was using just had the emergency button. Which is also useless in their current programming :p - good info tho.
 
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