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The Uniden Tavern - For general chit-chat and non-technical discussion specific to Uniden and does not fall within the above forum topics. This is not the forum to get technical advice from.

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Old 06-10-2018, 1:58 PM
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Default Sds100 and g5 type stub antenna

Has anyone tried the sds100 with a g5 type stub antenna in your location with simulcast?
Im wondering if the sds100 will receive simulcast on a stub antenna like it does with the stock ant.
I am waiting for a stub ant to ship, hopefully it works good.
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Old 06-10-2018, 2:29 PM
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Originally Posted by vocoder View Post
Has anyone tried the sds100 with a g5 type stub antenna in your location with simulcast?
Im wondering if the sds100 will receive simulcast on a stub antenna like it does with the stock ant.
I am waiting for a stub ant to ship, hopefully it works good.
Tried to discuss this in another thread. You know that the Unication antenna has the opposite gender SMA connector, right? I've not yet found a 7/800MHz stubby that looks suitable for the SDS100.....
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Old 06-11-2018, 9:24 AM
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Md390 has the sma male antenna and it comes with a 3" duck. Thats the shortest ive found.
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Old 06-11-2018, 9:31 AM
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https://www.amazon.com/Comet-Origina.../dp/B00OI3PY1U

Performance is meh, but it's really short. If signal is strong in your area, it's OK.
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Old 06-11-2018, 11:09 AM
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Md390 has the sma male antenna and it comes with a 3" duck. Thats the shortest ive found.
That's not going to work that well in 700/800/900mhz...
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Old 06-11-2018, 11:41 PM
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That's not going to work that well in 700/800/900mhz...
If you are in the middle of a multi site lsm with all towers in a 15 mile radius it doesnt have to be tuned to 800. I dont know how any stub can be tuned to 800mhz. Except the g4 stub i guess is tuned?!
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Old 06-12-2018, 5:53 AM
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If you are in the middle of a multi site lsm with all towers in a 15 mile radius it doesnt have to be tuned to 800. I dont know how any stub can be tuned to 800mhz. Except the g4 stub i guess is tuned?!
Far easier to make an 800mhz stubby than a VHF stubby.
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Old 06-12-2018, 6:25 AM
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Stubby antennas are the worse thing to ever come out for use on radios. I say this from being involved with the actual use on the radios used in many public safety systems. The users of the radios don't like the normal long antenna poking them in their arm pits or getting caught on their jackets and shirts.

But in actual public safety use they are a very poor selection. Unless your really close to the towers, the performance is not poor, but bad. Range from the towers is limited due to poor signal. If you can't hear the tower very good, your not going to get into the tower any better.

So with this said, your performance on a scanner is not going to be any better. Sure the antenna is short and won't get hung up on much, but don't expect it to perform very well. You need to be able to have a signal for your receiver to be able to detect the audio. Poor detection will give crappy audio out of the speaker. This is just the facts of life in a radio system.

Do as you please, but don't come crying back here complaining your stubby antenna has trouble hearing the towers.
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Old 06-12-2018, 9:15 AM
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Lightbulb What If?

There are those that only care about near field comms, want to conceal their radio in a pocket without magical wands popping out, and don't want to look like dorks carrying around a "walkie talkie", especially on their waist.
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Old 06-12-2018, 9:34 AM
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Accio RFium!
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Old 06-12-2018, 9:40 AM
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Originally Posted by jim202 View Post
Stubby antennas are the worse thing to ever come out for use on radios.
Except on my Unication G4 where the performance is spectacular and the antenna is only 1/3 the size of my pinky finger. Did you ever wonder why that is?
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Old 06-12-2018, 9:46 AM
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Its antenna performance is still crap compared to an antenna whose physical and electrical lengths are similar. You can't beat the laws of physics.

Where the Unication shines is decoding bits from signals that standard receivers can't parse due to not being designed for simulcast. Now that it has some competition, you'll find that a larger antenna does have advantages, even with simulcast.
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Old 06-12-2018, 11:46 AM
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One difference with Unication is that the antenna is designed specifically for the 7/800MHz band (the G5 uses an internal antenna, not the stubby, for the VHF/UHF band), so it can be tuned for that specific frequency range, even if it is coiled or otherwise shortened a bit. A scanner antenna attempts to cover a much wider frequency range, and so will likely not perform as well on a specific band.

The same goes for the receiver, though. I just got my SDS100 last night, so I'm still getting acclimated, but so-far, it seems that it can't handle a distant 770MHz P25 system that the G5 receives quite solidly, using the same outdoor antenna. The SDS100 gets bits and pieces here and there, but is unusable. To be honest, I was surprised when I first discovered that the G5 could hear it, but it seems quite consistent.
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Old 06-12-2018, 8:12 PM
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No, no, no

Then unication stubby must be a magic wand

G5 stubby works great on phase 1 simulcast 30 miles away
G5 stubby works great on phase 2 tdma simulcast 25 miles away

This is why i want to try it out or a stub in general on my sds100

We put a 800mhz specific ant on g5 and did not change a thing!

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Old 06-12-2018, 9:02 PM
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Quote:
Originally Posted by jonwienke View Post
Its antenna performance is still crap compared to an antenna whose physical and electrical lengths are similar. You can't beat the laws of physics.

Where the Unication shines is decoding bits from signals that standard receivers can't parse due to not being designed for simulcast. Now that it has some competition, you'll find that a larger antenna does have advantages, even with simulcast.
Jon, I am having a little trouble understanding this post. Your second paragraph seems to contradict your first paragraph. Why would a longer antenna in of itself provide an advantage? It would still be violating the parameters you specified in the first paragraph.

Or, are you talking about a 1/2 wave antenna (the larger antenna) being an advantage over a 1/4 wave antenna (more like the length of the G4/G5 antenna?)

BTW, many G4/G5 users would not agree with you characterization of the G4/G5 antenna performance as "crap"
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Old 06-12-2018, 9:31 PM
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Jon, I am having a little trouble understanding this post. Your second paragraph seems to contradict your first paragraph. Why would a longer antenna in of itself provide an advantage? It would still be violating the parameters you specified in the first paragraph.
It's basic physics. Antenna performance decreases in direct proportion to how much shorter it is physically vs electrically. The shorter the antenna is physically, the less signal it picks up. There are no exceptions. If a UHF antenna is resonant on a frequency where 1/4-wavelength is 6 inches, but it is only 1 inch long, it will pick up 1/6 of the signal that a 6-inch antenna tuned to the same frequency will get. Even if it's made by Unication.
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Old 06-12-2018, 10:33 PM
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Quote:
Originally Posted by jonwienke View Post
It's basic physics. Antenna performance decreases in direct proportion to how much shorter it is physically vs electrically. The shorter the antenna is physically, the less signal it picks up. There are no exceptions. If a UHF antenna is resonant on a frequency where 1/4-wavelength is 6 inches, but it is only 1 inch long, it will pick up 1/6 of the signal that a 6-inch antenna tuned to the same frequency will get. Even if it's made by Unication.
So yes, resonance is the key, not just the length of the antenna (nor the manufacturer ). That was what I was questioning. There are a lot of emergency vehicles running around now with stubby 3" antennas on the roof, not 108" CB whips.

The G4/G5 antenna is made for 763-870 MHz according to the label on it. At its midpoint of 816 MHz, a 1/4 wavelength antenna would be 3.4" and 1/2 wavelength would be 6.9". So. it is neither at its 1" length. Nevertheless, physics aside, it is a good performer. For receive only applications, antenna length is not as critical unless one is in such a marginal location that every uv counts. I used to DX on the shortwave bands with an antenna I made from coat hangers and pulled in the world. It certainly wasn't resonant and looked horrible
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Old 06-12-2018, 10:40 PM
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So yes, resonance is the key, not just the length of the antenna (nor the manufacturer ).
But given equally resonant antennas, the longer one will pick up proportionately more signal. If the antenna's electrical length is 3.4" and its physical length is 1", it's picking up about 30% of the signal a full-length antenna would.
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Old 06-12-2018, 11:12 PM
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Originally Posted by jonwienke View Post
But given equally resonant antennas, the longer one will pick up proportionately more signal. If the antenna's electrical length is 3.4" and its physical length is 1", it's picking up about 30% of the signal a full-length antenna would.
I get what you are saying but this is said by some to be about more than just maximum signal to the receiver. I've talked to people with first-hand knowledge of how the Unication G4/5 is engineered (in general terms), and that antenna is exactly what it is for a reason. I believe Troymail has spoken to the intentional design of the stubby and what that does in his field testing vs. larger antennas, within a simulcast environment, but I don't want to put words in his mouth. I haven't done the testing to confirm any of this myself, so I'm just sharing what I've heard from people on that antenna.

I have tested a full size 700 MHz Motorola whip (as good as it gets for a handheld in that band for practical use) on the G4, and have even posted a video of it going from no signal to a link when trying to monitor a distant simulcast, simply by switching from the stubby to the Moto antenna, so there is no question that more signal was reaching the receiver with the Moto whip, even if just a bit more.

I'm interested in hearing more from those who say that overall, the stubby functions best in a simulcast environment.
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Old 06-12-2018, 11:31 PM
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On the g5's that we have changed out the oem with a specific 800mhz ant, we found that the 800 ant sometimes grabbed some noise from nearby electronics. Otherwise not much of a difference. We decided the oem is the best performer for the simulcast systems here. It is like the antenna high on simulcast.

A coworker who has trouble with other simulcast issues in the metro area, hooks his up to a simple collapsable / adjustable metal antenna mounted outside and gets very good results.
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