Newbie antenna question?

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kingzogofalbania

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I dont know much about scanner, so please bear with me:
What's the shortcoming of the antenna my PS800 came with? Won't it cover most situations?
What could a 800MHZ antenna do that I cant already do?
What other antennas would be needed for specific monitoring situations ... e.g. aircraft; ENS; RR's, Police; ambulances etc?
 

Rt169Radio

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ka3jjz

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I dont know much about scanner, so please bear with me:
What's the shortcoming of the antenna my PS800 came with? Won't it cover most situations?
What could a 800MHZ antenna do that I cant already do?
What other antennas would be needed for specific monitoring situations ... e.g. aircraft; ENS; RR's, Police; ambulances etc?
Without getting into all the technicalities, most little antennas that come with handhelds are compromises at best, especially so as you get lower in frequency. I haven't heard of anyone doing measurements on the antenna that comes with the 800, but I suspect it's reasonably decent at 800 and 400 mhz, but as you go lower in frequency, the antenna loses a great deal of efficiency. By the time you get down to the VHF lo band, the antenna would likely be no better than a wet noodle.

In addition, indoor antennas work noticeably less well than their outdoor cousins, particularly if the outdoor antenna is clear of obstructions and mounted nice and high. This is due to the effects of terrain, trees and other obstacles. House wiring, aluminum siding and other conductive (and semi conductive) surfaces will play havoc with a signal as it enters your home.

You would think, then, that a good sized antenna (such as a large discone), mounted outdoors, is the answer to receiving a broad range of services such as the ones you mentioned. However, like my old physics teacher once told me, their ain't no such thing as a free lunch. Consumer handhelds simply aren't built to handle the larger signal levels such antennas can sometimes provide; trying to use them would introduce a whole host of other problems, many of which would be related to overloading. While this would be unlikely to damage the scanner, it would likely damage your nerves :wink:, as well as costing additional bucks to add filtering to eliminate or reduce your problem(s).

In addition GRE radios are generally notorious for overloading on VHF hi frequencies; It is a given that this varies from area to area; not all areas have this kind of issue (this has largely to do with the sheer RF density of the area - an urban area is much more likely to have issues simply because there are so many more transmitters in a given area)

So while you can put another antenna on your 800 (outdoors), you should be aware of the potential pitfalls. There are other whip ('duckie') antennas (such as the ones Rt169 mentioned) that are broadbanded that seem to work pretty well, but here too, they would be subject to the same indoor restrictions as using the original OEM antenna in an indoor environment. They are an improvement, but I wouldn't expect miracles.

best regards...Mike
 
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W2PMX

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You would think, then, that a good sized antenna (such as a large discone), mounted outdoors, is the answer to receiving a broad range of services such as the ones you mentioned.
A well-designed discone can have a frequency range as great as 4:1, so covering VHF=lo to 800 MHz (or even VHF-lo to 450 MHz) isn't something they can do well. And most of the discones a scanner hobbyist will buy aren't designed well - you're lucky if the range is 3:1. That would give you 30-90 MHz, or 150-450MHz. And they fall off pretty sharply outside their design range. For good signals (we used one in NYC designed to cover 150-470MHz) they're not bad, but you don't dig out the weak ones with an antenna that has -3db gain over a quarter wave vertical.
 

Arizona_Scanner

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A pretty tech-savvy guy on here actually did (scientific) tests, and determined that the stock 800 antenna stinks. The antenna that GRE/RS sell for the 500/106 did much better, in most every area. That said, many swear by the GRE/RS 800mhz antenna, but some like myself who monitor everything from 118 mhz up don't use it for general use.
 

Ed_Seedhouse

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A pretty tech-savvy guy on here actually did (scientific) tests, and determined that the stock 800 antenna stinks.
But the tests were not, to my mind, actually proving anything about the stock antenna with the 800. The two together form a system and the tests I saw only applied to the antenna on it's own. It may be that the 800 is designed to compensate for the deficiencies of the antenna so that the two together work well.

I doubt that they designed the radio without any concern about it's performance with the stock antenna. Good engineering would design the receiver and antenna as a system, surely.

I don't know that this is so, and in fact I find performance with a "better" antenna does seem to improve. I am merely saying that the tests I read do not, actually, prove anything about the antenna's performance with the 800 since they only tested the antenna on it's own.
 

W2PMX

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But the tests were not, to my mind, actually proving anything about the stock antenna with the 800.
No, they were antennas against a 50 ohm receiver input. If GRE chooses to design receivers with non-standard input impedance (I'm not saying that they did), that's their choice, but it has no effect on whether a particular 50 ohm antenna is better or worse on a particular frequency than another 50 ohm antenna - when feeding a 50 ohm receiver.

Measuring apples against apples usually works - measuring apples against ducks doesn't. (If you're talking about the ground plane effect of various scanners - when not being held by chunk of flesh about the size of an adult human they're all about equally useless.)
 

Ed_Seedhouse

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No, they were antennas against a 50 ohm receiver input.
But the GRE-800 may be designed to compensate. It would surely, for example, be easily possible to put an antenna tuner onto the scanner's board. Since the scanner always knows what frequency it is receiving the tuner could always adjust the reactance and or capacitance of the input circuit to transform the antenna's impedance at that frequency to 50 ohms. I don't know if they did, and expect they probably didn't, and I expect you are right about the supplied antenna not being optimal for the unit, and I do in fact use different antennas both at home and in the field.

All I am saying is that if you didn't measure the antenna's performance with the unit it came with your tests don't prove that.

Also, impedance matching is not nearly as important with receivers as it is with transmitters. A sensitive enough receiver could probably work with a wet noodle, but on transmit you need a good impedance match especially if you are pushing out real power.
 

n5ims

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I dont know much about scanner, so please bear with me:
Welcome to scanning. RR is a great place to learn and feel free to ask questions, regardless of how "dumb" they may sound. We all had to start somewhere. One thing though, search both the forums (search is in the upper right corner of the page) and the WIKI since many answers are there if you look.

Another thing (yea, I said above "one thing though", but this is important) provide details on your question, including links to the systems, agencies, counties, etc. if appropriate. It's much easier to provide a good answer to a question like "I'm having trouble trying to pick up my local Sheriff on my RS Pro-95. I think that they're on this system Jacksonville City Public Safety - First Coast Radio (Motorola) Trunking System, Jacksonville, Florida - Scanner Frequencies. I know I have it programmed right since I can hear the trash trucks and busses." (The answer would be that the Sheriff is digital that the Pro-95 can't get and they're encrypted so no scanner will get them.)

What's the shortcoming of the antenna my PS800 came with? Won't it cover most situations?
The stock antenna is a general purpose antenna that will work for most anything, but not necessarily well on any of them. It's good if you need to scan all bands, but can easily be beat if you only listen to one or two.

What could a 800MHZ antenna do that I cant already do?
It is optimized for the 800 MHz band and will work very well there. It won't work nearly as well on other bands (like VHF-Low - 40 MHz or so, VHF-Hi = 150 MHz or so, or UHF - 450 MHz or so). Since so many of the systems are in the 800 MHz band it's a good antenna to use. If your local systems aren't there though, other antennas will work better.

What other antennas would be needed for specific monitoring situations ... e.g. aircraft; ENS; RR's, Police; ambulances etc?
Be aware that an antenna is designed for a certain frequency band and not for a certain type of communication. An antenna won't care if the signal is analog or digital or if the users are PD, Fire, or your local taxi company. If the antenna is designed to work best for the range 140 - 160 MHz it'll work well for any signals in that range. It will also work on other frequencies, but not necessarily very well.

Be aware that some folks will say that an antenna covers "all scanner frequencies" and will transmit on only a few short ranges. You should read that as the antenna is designed to work on the few ranges it will transmit on and you may also get some signals on the other frequencies, but don't count on it working well on them.

Some antennas can be designed to work well on multiple frequency ranges. These are often the 140-160 MHz (VHF-Hi) band and the 430 - 470 MHz (UHF) band. This is due to the popularity of dual-band ham radios. These antennas are good performers for scanning in these ranges as well. You can often get good performance on receive both above and below the specified ranges, but as you move further away their performance may drop as well. There are also scanner antennas with more ranges that are popular as well.

First check to see what frequency range(s) you need the best performance on (the fewer the better) and second what connector you need for your scanner (most often it's BNC or SMA). For a portable antenna you'll need both to get one that mounts directly on your scanner. Then search the web for an antenna that'll do what you need and has the correct connector on it. Once you've selected one or two search to see what folks are saying on RR about them or ask if you can't find anything (rare, but it can happen).

For a mobile or base antenna there's a bit more to it since there's not only the antenna, but the antenna mount, the coax feedline, and possibly tower with grounding. I'll not touch on this now since you're probably a bit overloaded already. It's not really hard, but does take some learning.
 

W2PMX

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But the GRE-800 may be designed to compensate. It would surely, for example, be easily possible to put an antenna tuner onto the scanner's board.
So rather than spend the time - once - to design an antenna that's resonant on all bands the scanner covers (not a very difficult thing), they'll spend time to design a computer controlled tuner, then include the extra hardware in each scanner - just to give you the ability to use their random-length wire (which is what the antenna would be)?

I really don't care for some of the decisions GRE has made in recent years, but I've never accused them of being idiots.

All I am saying is that if you didn't measure the antenna's performance with the unit it came with your tests don't prove that
You prove how well the antenna performs as an antenna. Come on, Ed - if you don't test the gas in that model of car, you can't tell whether it's good gas?

Also, impedance matching is not nearly as important with receivers as it is with transmitters.
True. A badly mismatched antenna will burn out the finals in a transmitter. All it does in a receiver is turn it into a deaf box temporarily.
A sensitive enough receiver could probably work with a wet noodle
No matter how sensitive it is, it'll work better with a good antenna than with a poor one. "Antenna impedance doesn't matter with a receiver" is something those who sell crappy antennas want you to believe. It's not true. (Just ask the guy who received the signals directly from the PLSS transmitter on the surface of the moon. He wasn't using a wet noodle, or a mismatched antenna.)
 

Ed_Seedhouse

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So rather than spend the time - once - to design an antenna that's resonant on all bands the scanner covers (not a very difficult thing), they'll spend time to design a computer controlled tuner, then include the extra hardware in each scanner - just to give you the ability to use their random-length wire (which is what the antenna would be)?
Probably not, but on the other hand, what evidence do you have that they haven't?

You prove how well the antenna performs as an antenna. Come on, Ed - if you don't test the gas in that model of car, you can't tell whether it's good gas?
Antennas and Scanners aren't cars, so that's just a bad analogy. But you will notice that every car manufacturer specifies the octane level that works best with their car. And the size and type of tires that work best, and the general types of oil and probably a few other things as well. My last car's manual warned specifically against using what most people consider to be "better" high octane gasolines.

No matter how sensitive it is, it'll work better with a good antenna than with a poor one.
Well, no it won't necessarily. Too much signal will overload the front end of any receiver and make it perform worse, not better. If you live near a high power broadcast tower a better antenna might give you poorer performance because of the front end overload. I found out that when I stuck a 24db gain rf amp on my big VHF/UHF commercial vertical I hide away in my second floor bedroom. Made the 800 pretty well unusable. Works fine though with on Icom PCR 1500 with a "stealth" longwire. Because it is a TV signal amp it rolls off below 50 megs but lets enough signal for the lower bands to get through and helps at VHF where the longwire sucks. When I tried a wide range amp from MJF with the same longwire it messed up the whole frequency range and made the PCR-1500 unusable as long as it was in the loop.

I imagine GRE designed the 800 to work generally well with the antenna they selected to ship as stock. Interestingly, I decided to check out the stock antenna last night and this morning. As opposed to my 8" Wilson W 801 stick the little 4" stock stick actually seemed to work better on downtown trips on the bus last night and again this morning. This of course is only a subjective opinion and I make no claim that it proves anything one way or the other.

However even with that the front end overloaded when the bus went by the "CRD" building downtown where they have a huge antenna farm for the local fire/police/ambulance/etc trunking system, CREST. Kept forcing the squelch to break on frequencies with nothing but noise on them, which never happens when I'm not near that tower.

"Antenna impedance doesn't matter with a receiver" is something those who sell crappy antennas want you to believe. It's not true.
Who said that? Who are you quoting? Not me! I never said that nor implied it. You are bringing in the old straw man.

Once again, I am not saying you are wrong in your opinion of the stock 800 stick. I'm only pointing out that your particular tests don't actually prove it, just as my little subjective test described above doesn't prove anything either.
 
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