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  #1 (permalink)  
Old 12-27-2013, 3:11 AM
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Default "Commercial grad" reception

Perhaps this is a question Upman can chime in on.

If the new 536HP scanner were configured to only receive say the public safety and HAM frequency ranges, would it be able to be able to be made more sensitive and able to receive things such as 700-800MHz better?

I know it would never be made, but for the non hobbyist such as news media and law/fire departments, that would be a cool option to have. I am just curious how much reception ability is compromised by shoving such a wide range of receiver capability into these scanners.

Paul
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Old 12-27-2013, 6:34 AM
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Paul,
Being able to decode or receive several different types of modulation will have no effect on a receiver's sensitivity. Having a wide front end can decrease effective sensitivity by allowing off frequency signals to degrade or desense the receiver. But just limiting the receiver to just a few bands would not be an advantage because the reduction in intermod and off frequency signals would be minimal.
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Old 12-27-2013, 10:56 AM
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Default Commercial Grade Reception

I know what you are talking about when you say reception could be better if the scanner was limited to just a single band or a couple bands. The scanner might be able to be tuned more accurately and hence you get better reception. I don't know specifics. I am not a radio tech. However I do remember reading on an antenna blog some time ago that when you have a scanner that covers 30MHz all the way past 1000MHz you can not have one antenna that will receive with the same accuracy (if you will) all those different bands. You would have to have separate Lo band, High band, UHF band and 700/800 band antennas to receive everything more accurately.

I have always thought (though not all the way through) that you could come up with a Lo band scanner, High band/UHF scanner and a 700/800 scanner all made separately. You could then get a band specific antenna to have substantially better reception for each scanner. But.................I am sure that will never make money for any electronics company. And probably would not fly with modern radio hobbyists. Kind of like the direction of MT, Pop Comm etc to digital only technology. I hate it. I want to hold the book in my hand. Period. But it looks like that ain't gonna happen.

Just my thoughts. Hope not to offend anyone.
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Old 12-27-2013, 11:14 AM
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Quote:
Originally Posted by scanman1958 View Post
I hate it. I want to hold the book in my hand. Period. But it looks like that ain't gonna happen.

Just my thoughts. Hope not to offend anyone.
You can if you have a tablet
I, too, prefer to read a book/magazine in my hands. It is because of the printing and distribution costs that they are doing this. I have three new books to read by a favorite author on my tablet, and haven't even cracked a page yet.
Larry
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Old 12-27-2013, 11:28 AM
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Now, to get back on topic.....The only way we are going to have radios with the individual bands, is to buy commercial radios. Some ham radios in the VHF/UHF will do a much better job of receiving than scanners because they are more selective. Even subscribers on digital trunked systems have a hard time transmitting and receiving.
I know of a county nearby that bought a VHF, P-25 system and FD/SO/PD can't be heard in various parts of the county. They were trying out another county's system and getting better results.
With the constant change in digital systems with encryption, which by the way is not the federal mandate. Has all of us who have monitored the public safety frequencies for more years than we want to admit, leaves stuck between a rock and a hard place.
Do we go and spend money on the latest scanners with promises that they will work on trunk systems that already have their own problems?
With counties and cities going to TRBO, NXDN, and now in my state UHF TETRA being mentioned, we need to make a statement to the manufacturers of scanners....Don't give us promises. Give us results.
JMTCW,
Larry
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Old 12-27-2013, 11:38 AM
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Default ham radio?

I have had both ham radios and scanners at the same time and see zero difference in reception,My uniden 996xt actually worked better on the ham bands than some not all of my ham radios.Scanners have wide open front ends and so do all new UHF/VHF equipment.Reception in uv or microvolts is close if not the same.So I disagree with that statement abot ham radios.
Commercial radios set for specific systems will do a better job decoding because thats all they do.
As for the new Unidens,I think they should have got the patents for the other decoding systems,having the ability to only decode only one more type of P25 system (ie Phase 2 ) is probably not enough to push people to get new scanners.So I think they dropped the ball on this one!
Tetra is getting big and so is Turbo and Nexden,so they are still not able to be monitored without a computer tag-along.

Last edited by k2rty; 12-27-2013 at 11:44 AM..
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Old 12-29-2013, 6:55 AM
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What helps Uniden keep things under control with such a wide front end is the use of triple-conversion to avoid image problems, along with stages of bandpass filtering. If they wanted to, they could put even more stages of bandpass filtering, but of course we would be paying more.

In the sticks, you can get away with a wideband antenna. But if you have a specific interest, then what you can do is use a *narrowband* antenna designed for the frequency of interest if you suspect overload and desense. This is far better than attenuation. For example, if all you are interested in is 800mhz, then don't use a wideband antenna, but one for 800mhz only.

Another example is that I use my Unidens for vhf airband 118-135 mhz quite a bit. While they are ok with so-called wideband antennas, they actually perform better than some commercial aviation radios when mated to a narrowband commercial airband duck like the Icom FA-B02AR, which beats the canonical RH-77CA in this application. Being narrowband, and *verified* to be so and not just marketed as such, it is ideal for lesser quality scanners that have much wider or non-existent bandpass filtering in this range, or those that rely on dual-conversion rather than triple.

What I'm getting at here is that you can almost achieve commercial monoband performance by mating a Uniden to a narrowband antenna of interest - almost - unless you want to pay 10 times as much.

Last edited by hertzian; 12-29-2013 at 6:59 AM..
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Old 12-29-2013, 10:18 AM
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Typically, the biggest single thing I've found lacking in scanners is synthesizer noise. The results in even strong signals that never fully quiet, giving the impression of poor sensitivity and selectivity.
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Old 12-29-2013, 4:31 PM
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Default "Commercial grad" reception

I have thought about the same thing. If a scanner was made that only covered 800MHz could they do a better job with reception on 800MHz and simulcast.

Mike
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Old 12-29-2013, 11:52 PM
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Quote:
Originally Posted by kb8rvp View Post
I have thought about the same thing. If a scanner was made that only covered 800MHz could they do a better job with reception on 800MHz and simulcast.
Not necessarily so.

The usual thinking would have all scanner reception faults related to the wide range of frequencies that are required, and that's really not true. Very sensitive wideband front ends are quite feasible. Getting that wideband front end to have any overload resistance is more difficult, as we all know, but even that's fixable. There are high IP3 and low NF PHEMPT MMIC's that would be ideal for a scanner front end for $3 or so. I'd like to see new scanner designs incorporate some of these new devices to make them less prone to overload.

It's my opinion that most scanner reception troubles are all in the synthesizers. Like I said in my previous post, phase noise of the synthesizer cause a noticeable hiss, no matter how strong the signal is. That will lead you to believe that the signal isn't very strong. Scanner synthesizers also tend to have a lot of spurs, making the receiver prone to birdies and reception of strong signals well removed from the desired frequency.

The requirement for extremely high lock speed, and low cost make a tradeoff necessary. Low cast and high speed frequency changing at the expense of spectral purity.

In high end commercial radios, the components used in the VCO and synthesizer alone probably exceed the cost of a whole scanner.

If you had a scanner that had an exceptionally clean sysnthesizer, and nothing else was changed, you would be floored by how well it performed and how clean signals sounded.

Other things like a more powerful audio channel, and perhaps better audio tailoring after the detector would improve things as well.

All of the above could be done in a multiband scanner.
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Old 12-30-2013, 2:36 PM
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You make great points. And as many people have said (roughly) "the reception issues with our scanners is the difference between a $500 scanner and a $5000 professional radio. But I still stand by my statement (in general) that one single band antenna will not receive all the available bands on a scanner equally. If it is tuned to the VHF Hi band the reception is going to be noticeably worse on Lo band and 700MHz.

I guess nothing will ever be perfect for us in the scanner world but companies like Uniden should be making every effort to improve reception and leave out a couple bells and whistles. IMHO

Try using specific antennas tuned to a specific frequency range and hook their respective cables to a splitter specific to the frequency ranges you want to monitor and see what happen. Maybe good, maybe not.

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Old 12-30-2013, 9:39 PM
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If sensitivity, or the desire to pull in distant signals is critical to me, I'd probably go with an outside antenna, mounting it as high as possible and use the best coax I can afford.

My gut feeling is that Uniden wants to have a product that appeals to a broad base of customers, which keeps the prices reasonable. If they were to limit the "spectrum" (for lack of a better term), to just certain frequency ranges, that is likely to drive the price of scanners way up, possibly close to what "real radios" cost.
 

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