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Scanner / Receiver Antennas For discussion of any type of receiving antenna used by a scanner or receiver base, mobile or handheld.

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  #1 (permalink)  
Old 04-16-2012, 2:10 PM
   
Join Date: Apr 2012
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Default scanner pro 405

I have a Radio Shack pro405 desktop scanner with a 25 - 1300MHz antenna also from Radio Shack. Is there anything I can do to get it to bring in more? I'm just listening to my county and I live about 7 miles out of town limits. I feel like it needs to be just a little stronger but I don't really know. It will pick up on a transmition and sometimes it will slowely just fade out and come back in strong again. I'm just listening to police and fire department and ems. So is there anything I can do to help it out? THANKS
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Old 04-16-2012, 7:04 PM
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There are several things you can do, but be aware that putting a good antenna on a handheld introduces other problems, which I'll get to in a moment;

a. It would be most helpful to know where you are (county/state is fine), and to what you are listening. Go to the blue toolbar under the site title on the left, float your mouse over Database, select Frequency Database and use the various pulldowns and maps to get to your area. C'mon back with the URL

b. In your statement you didn't mention anything about how high the antenna is off the ground or whether it's outdoors. In general, outdoors is best and higher is better, but that leads into the next topic, which is;

c. You didn't say anything about the coax you're using. While you can get away with cheap RG58 types if all you're listening to is VHF low band, as you start going higher in frequency, and the antenna gets higher, losses on such runs become correspondingly higher.

Now for the big BUT on this whole shebang - little handhelds like the 405 are not really designed to handle high signal levels very well. There is the possibility of overloading - which can manifest itself as hearing things like pagers and such where you didn't before, or actually losing sensitivity on one or more bands. Additional filtering can and often does improve the situation, but obviously at an increased cost.

A little more information needed here, I think...Mike
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Old 04-16-2012, 7:20 PM
   
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Ok that is helpfull and I apreciate it.

- My area is Oconee SC Oconee County, South Carolina (SC) Scanner Frequencies and Radio Frequency Reference

- The antenna length is 22inchs and 16 ft RSG58 cable with BNC and TNC connectors. The antenna is about 16ft off the ground and it is outdoors attacted to my window. If you could recommend a better coax and it would help, I wouldn't mind getting it or whatever else I need.

-You also said something about filtering. How would I go about doing that if I need to?

Don't mean to sound dumb in this area just never fooled with this kind of stuff and getting interested in it. And again thinks alot
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Old 04-17-2012, 10:05 AM
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allnightrambler

As a rule I’m against pre-amps with most general radio dealer type budget off the shelf scanners – most scanners/receivers in that price range don’t have the front-end sensitivity/selectivity or resistance to 2nd & 3rd order inter-modulation required to handle the variation in rf signal level & quality we are faced with in modern day rf environments.

From what you have said, and ignoring the coax & antenna side of things – which other members have quite correctly pointed out can be improved on. It wouldn’t suprize me if you realized a significant improvement in received & demodulated signal if you added a good quality VHF/UHF inline/coax type pre-amp – and by significant I mean a good 10dB + across the VHF/UHF range of freqs.

…… and as far as preamps go there isn’t much around that beats the real world performance improvements that the products from Angle Linear offer (Angle Linear Home Page) – new, or off eBay.


A quick note on antennas: your 25Mhz-1300Mhz omni is a big big compromise. My guess is that it isn’t offering you any decent Gain (+) across much more than say about 150Mhz – 200Mhz of its overall bandwidth - at best! In other words, for the rest of it’s coverage it’s going to be reducing the received signal level – and the further you are from town (or the signal source) the greater that compromise & reduction in signal level presented to the receiver fron-end is going to be.

By all means keep it, but take a look at the antenna I posted up on this thread (Co-phasing LPDA questions – reply #21): It’s a Yagi type antenna – with an average of around 6.5dB gain from around 250Mhz – 1200Mhz bandwidth. It also has another nice characteristic: it’s pretty good at blocking out any signals that don’t fall within its’ forward facing 20degree odd wide beam-width, meaning it will also block out a ton of noise that would otherwise interfere with whatever you are trying to listen to. 20degree coverage from 7miles out of town should cover all if not just about all the town signal source area you listen to(?).

You come across them on eBay often – but they are also well within the average DIY’ers scope to construct. Loads & loads of plans and theory about Yagi type antennas on the internet.

NB
As a rule preamps should be connected inline at the antenna end of the coax – not the scanner/receiver end of the coax.

Last edited by benbenrf; 04-17-2012 at 10:08 AM..
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Old 04-17-2012, 10:18 AM
   
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ok all that is very helpfull. thanks a lot
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