The basics of scanning.

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Re: The basics of scanning.

Postby m0lsx » Mon Apr 18, 2016 10:07 pm

Short Wave Listeners sometimes use a reception report called either SINPO or SINFO.

S= Signal Strength. I= Interference. N = Atmospheric Noise. P/F = Propergation, does if (F) Fade.. O= Overall.
There is a etiquette for the way these reports are written, some numbers should never be higher than others. And as it is difficult to write a good SINPO report, often they are not used now.

SINPO/SINFO is based upon a score of 5 for each catagory.

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Re: The basics of scanning.

Postby m0lsx » Tue Apr 19, 2016 8:57 am

Modes..


FM = Frequency Modulation. Some scanners have a wide & a narrow mode. On a scanner the wide mode is for Broadcast Radio & the Narrow is for everything else. (VHF/UHF trancivers may use Wide for amateur radio & Narrow for PMR)
Most analogue VHF/UHF voice transmissions are FM. It is clearer that AM in general.

AM= Amplitude Modulation. Airband is AM. AM is in terms of VHF/UHF the old fashioned mode, it is a carrier with a top & a bottom side band both containing the audio.

SSB= An AM signal minus it's carrier & with only one of the audio streams transmitted, that being the Upper or Lower Side Band. On Amateur radio the convention is to use the Lower Side Band (LSB) below 10 MHz & the Upper Side Band (USB) above 10 mhz. It is possible to hear FM on an AM radio & AM on a FM radio, even if the audio is not as clear as it should be. However SSB cannot be heard on a FM radio, but there are ways to "resolve" the audio using a pair of AM radios, although that does require some experience. In general the right kind of radio or an extra box is really needed to listen to more than an occasional SSB signal.
SSB is a much narrower signal that AM or FM & it sounds very different, so it takes most people some time to get use to it's sound, to hear it properly & it also takes time to properly tune it in, so it is not a Scanner mode.

The above are the main modes. Others include.
CW (Continuous Wave) also known as Morse Code as CW is turned on & off in short or long busts to produce dit's & dah's, thus producing a language.
SSTV, Slow Scan TV. This slowly builds up a image on a screen, line by line.
RTTY, Radio Teletype, this is now an old fashioned mode & not as widely used as it was in the 70's & 80's.
ATV, Amateur TV. Normally high quality TV signals.
PSK, a reasonably new digital mode, that is comparatively simple to send & receive. A sound card & freeware is all that is really needed.
IRLP, Internet Radio Linking Protocol. This is simply linking radios via repeaters & the internet. Can be used on 446, Amateur radio etc etc.
Various digital voice modes. Many of these are based on FM. Like other voice modes they require the right kind of receiver or an extra box, (PC in this case) to resolve the audio. And like other modes, digital can either be encoded or un encoded. So some Tetra (Terrestrial Trunked Radio) users as an example are encoded, while others are not.

Trunked Radio. In effect a method of using spectrum more efficiently. It allows a number of different users or members of the same talk group, to use the same small lump of spectrum differently.
Conventional AM/FM assigns a frequency. Trunked Radio is in effect a network of channels, that are used dynamically, so there is no exact setting for any single user or any single QSO.
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Re: The basics of scanning.

Postby m0lsx » Tue Apr 19, 2016 9:15 am

PMR =

PMR is in general radio aimed primarily, although not exclusively at business users. It is a cover all term used for radio transceivers, users & bands which are used for general communication.
Voice traffic on PMR can vary from CB type activity to exclusively business related traffic.

Repeaters

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Re: The basics of scanning.

Postby mike43 » Tue Sep 27, 2016 5:43 am

Thanks for the information Alan, very helpful and lots of good info' for a newbie to scanning.
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Re: The basics of scanning.

Postby m0lsx » Thu Dec 15, 2016 1:34 pm

Channel steps.
We may say the bus stop is outside of number 25. But the bus may be partly out side of number 24 & number 26 when it stops there.
The frequency given is the centre of a channel.
Digital in general is the narrowest band width.
CW, Morse Code is the narrowest of the old modes.
SSB is next.
AM fter that.
And FM is in general the widest.

Most VHF & UHF signals are FM, with AM used for the Airbands. More digital signals are becoming available to listen to. But only if your scanner is digi capable.

So for most analouge scanning listening incorrect step sizes do not make a huge difference, providing those steps are not too big.
Smaller steps means you will always be closer to a signals centre frequency. But it means you scan more channels per signal & that is a big trade off.
Many transmissions we listen to are only a few words long. So even if your scanner has a good scan speed. You could still miss things as a result of too small a step size.
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Re: The basics of scanning.

Postby M6IXE » Thu Dec 15, 2016 7:57 pm

Rey informative posts alan :thumbup:
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Re: The basics of scanning.

Postby m0lsx » Tue Jan 10, 2017 6:07 pm

http://www.csgnetwork.com/antennaedcalc.html

To optimize the antenna for a frequency RANGE, do the calculations twice, once for the low end of the range and once for the high end; then average the two.


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L end to end on a half wave Dipole is just under half a wavelength..I'll not confuse with why. But it is not a full half wavelength.
thus E is just under a quarter of a wavelength.
The name DI-Pole, means it gas two legs. Thus by it's nature a end fed dipole is not a dipole. But half a dipole.
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Re: The basics of scanning.

Postby m0lsx » Tue Jan 10, 2017 6:29 pm

Dipole fan.
Radio waves are clever things. It is rasily possible to feed more than one dipole with a single length of coax. And at VHF/UHF it is made even simpler due to the fact that the wave lengths are shorter.
Take the following design & make it a vertical instead of a horizontal design..An easy thing to do with short wavelengths. Stiff wire will do the job just fine.
Almost everything we listen to as scanner enthusiasts is vertical polarised. That is it's from a vertical antenna.
Using a horizontal antenna on vertical signals (And vice versa) will loose 3dB (50%) of the signal.

http://www.hamuniverse.com/multidipole.html

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