RadioShack versus Uniden Desensing

Seanm214

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Apr 15, 2019
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76
Location
Kings Park, NY
Hello,
I currently have a RadioShack pro-18 and am looking to upgrade my antenna in my vehicle for better reception and am looking to get the Pulse Larsen NMO 150/450/758 all band whip antenna to improve reception of 800 MHz trunked radio in my car. I tried this with the Laird whipless antenna to try and improve reception and it only made it worse because I think the scanner is receiving overload and desensing if that makes sense. I’m worried that the same thing will happen with the pulse Larsen antenna. I know it’s definitely a better antenna than the Laird but I’m not sure if the scanner was the problem or the antenna was the problem?!? I don’t want to get this new and better antenna if it’s just going to keep desensing again in my car. Do all scanners experience desensing or is it just my pro-18. I’m wondering if some of the more expensive scanners like the Uniden sds100 or the Uniden BCD436HP would also experience the same desensing that my pro-18 is experiencing in my area. Since the sds100 and the BCD436HP are so much more expensive I would not expect them to experience desensing to the level that my scanner is but I’m not sure.
Thanks
 

iMONITOR

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MACOMB, MI.
When using various P25 scanners (other than the SDS100 & 200) I always found the better the antenna the worse simulcast problem became. In fact when using them in a vehicle, what worked best was mounting the scanner under the instrument panel and using a rubber ducky mounted on the back of the scanner in a horizontal position! This success of this absolute worst solution is probably due to the fact that it minimized signal levels from numerous redundant signals from numerous simulcasts sites. Your results will definitely vary.
 

Seanm214

Member
Joined
Apr 15, 2019
Messages
76
Location
Kings Park, NY
When using various P25 scanners (other than the SDS100 & 200) I always found the better the antenna the worse simulcast problem became. In fact when using them in a vehicle, what worked best was mounting the scanner under the instrument panel and using a rubber ducky mounted on the back of the scanner in a horizontal position! This success of this absolute worst solution is probably due to the fact that it minimized signal levels from numerous redundant signals from numerous simulcasts sites. Your results will definitely vary.
So should I even try the Pulse Larsen or would I be wasting my time. I’m trying to figure out the best way to fix this problem of overload without having to get a new radio or something like that.
 

hiegtx

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7,668
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Dallas, TX
Hello,
I currently have a RadioShack pro-18 and am looking to upgrade my antenna in my vehicle for better reception and am looking to get the Pulse Larsen NMO 150/450/758 all band whip antenna to improve reception of 800 MHz trunked radio in my car. I tried this with the Laird whipless antenna to try and improve reception and it only made it worse because I think the scanner is receiving overload and desensing if that makes sense. I’m worried that the same thing will happen with the pulse Larsen antenna. I know it’s definitely a better antenna than the Laird but I’m not sure if the scanner was the problem or the antenna was the problem?!? I don’t want to get this new and better antenna if it’s just going to keep desensing again in my car. Do all scanners experience desensing or is it just my pro-18. I’m wondering if some of the more expensive scanners like the Uniden sds100 or the Uniden BCD436HP would also experience the same desensing that my pro-18 is experiencing in my area. Since the sds100 and the BCD436HP are so much more expensive I would not expect them to experience desensing to the level that my scanner is but I’m not sure.
Thanks
Which system are you having issues with?
This one?

If so, then you are likely dealing with simulcast. Here's the tower map for the 700MHz Simulcast Site:
1601754661620.png

As iMONITOR has already suggested, 'less antenna' might help. The Pro-18, as well as most of the older Radio Shack scanners, as well as their GRE designed siblings labeled under either GRE's name, or that of Whistler, are prone to overload, whether mostly from simulcast, or because other transmit sites, such as thosw for cellphones, can overload them.

Most of the Uniden models are more resistant to desense due to overload, but they also have issues with simulcast. The 436HP is better than the GRE designs, and also a bit better than the current Uniden P2 series. But if your real issue is simulcast, not simply signal overload, then the SDS series scanners are the most capable of dealing with that. The Unication pagers, as well as the Blue Tail P25 RX (see this thread for a lengthy discussion on this relatively new product) handle simulcast well, although they cannot scan the same wide variety of systems, at the same time, that you can do with the SDS scanners.

Try driving close to one of the simulcast sites, like a quarter mile or less distance. If your reception significantly improves, then simulcast is your problem. (Being very close to one of the sites, it's very strong signal overrides the out of synch transmissions from the other, more distant, sites.
 

hiegtx

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So should I even try the Pulse Larsen or would I be wasting my time. I’m trying to figure out the best way to fix this problem of overload without having to get a new radio or something like that.
I agree with iMONITOR. A "better" antenna is not likely to solve your issue. A 'worse' one, like the original stock antenna, or even a paper clip, might reduce the signal strength enough for your Pro-18 to perform more reliably.

Another option, relatively low cost, would be to use one of the SDR dongles, along with your PC and software you can download at zero, or low cost. But since a PC is required, that's not a "portable" solution. See this forum for a number of discussions on using the SDR radios. (I am not currently using this method, so I can't really comment on how to set it up.)
 

iMONITOR

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Location
MACOMB, MI.
So should I even try the Pulse Larsen or would I be wasting my time. I’m trying to figure out the best way to fix this problem of overload without having to get a new radio or something like that.
It's impossible for any of us to know. In your situation it's more of a trial and error process. For me that goes with the fun of the hobby, experimentation, success and yes even some failure along the way. But when you win the results are rewarding!
 

tvengr

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Feb 10, 2019
Messages
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Location
Baltimore County, MD
I currently have a RadioShack pro-18
One thing to consider trying is sending your Pro-18 to Whistler for the Legacy Upgrade. The Pro-18 is capable of P25 Phase 1 only. The Suffolk County P25 system is Phase 2 capable, with talkgroups currently operating as Phase 1. If talkgroups are changed to TDMA (Phase 2). you will no longer be able to receive them. The Legacy Upgrade will convert your scanner to a Whistler WS1080 and add P25 Phase 2 as well as DMR. With the conversion, you will be able to update to later firmware versions. There are many reports of the upgrade improving scanner performance.
 
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