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Thread: Consumer Walkie Talkies

  1. #21

    Default Re: Consumer Walkie Talkies

    If you are interested in hearing aeronautical broadcasts, can just get any shortwave receiver with SSB (single side band) and able to select Upper Side Band and Lower Side Band capability.... just a long wire antenna and hang it out. Freqs for nearby asian airports/planes can be heard on 8942, 15536kHz. Its pretty fun even in today's world of "DIGITAL" and also its legal, plus you can get world band radio. But for receiving I think getting a scanner would be great, just that its illegal....but not that illegal.

    http://www.youtube.com/watch?v=blI-csVoQX4

    Pls do not anyhow broadcast with an illegal transceiver, the IDA can get you by triangulation with their multi-million listening equipment system. Think they have listening stations at NTU, one up north, and one at Changi something like that. SG is a small country, interference is always a very probable reality so they have to "protect". Anywhere you just jam and of the stuff you will be found out eventually but usually they will just listen and get clues about your location as that would be faster (eg Chinese restaurant, chit chat at PSA cranes etc). Obviously do not jam GSM, several guys used those non-approved 900MHz cordless phone and interfered with shopping center cellular systems, think if you google you can find the case study in Ngee Ann City. WiFi, I think you jam also nobody cares much also.

    For UHF/VHF, line of sight.......you can get hundreds of kilometers as long as the noise floor is low enough and receiver sensitive enough. With good propagation, even 500mW can get you hundreds of km between mountain tops, there have been cases before. There is also radio hamming in the VHF and UHF ham bands between ground stations thousands of KM between them with just a few watts of power and directional antenna eg Yagi antenna - with the aid of a ham satellite with a repeater on it. LOS mah...

    http://www.amsat.org/amsat-new/satellites/status.php

    Wah....9V-Orion-Images a pilot ah.

    PS. Even if cannot legally own a scanner, can hear from the internet lah. But the feeling is definitely different.
    http://www.radioreference.com/apps/audio/?feedId=899
    The feed consists of the LAPD. The Largest Police Department in the USA. This is a Non Trunked APCO 25 digital system. It is a system with 10,000 officers, across 4 bureau's and 20 divisions. It is a huge system and very busy.

    Pls use Windows Media Player
    Last edited by 2100; 15th February 2011 at 09:54 PM.

  2. #22

    Default Re: Consumer Walkie Talkies

    Yeah....other than what 9V said, say you transmit on 100MHz, on 200MHz you can hear a much lower signal like -80dB down, 400MHz -100dB down...etc etc. I think tripling also got.... Those are the main ones. Forgot what's that phenomenon. And many other spurious spikes on other freqs....so prob if you are near the airport and since they are using quite high power, can hear. Last time if you go to Pearl's Hill Police St (when Police
    s Alpha division was still there, CID also there I think) with the huge antenna you can also hear the transmission. Its not illegal to hear, just that you may not discuss anything about it.

    With a lousy radio with lousy rejection, yeah sure can hear esp if you are near the antenna.

  3. #23
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    Default Re: Consumer Walkie Talkies

    But then you still need to apply licence to use.

  4. #24
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    Default Re: Consumer Walkie Talkies

    Quote Originally Posted by qwerty628 View Post
    Quote Originally Posted by 9V-Orion Images View Post


    From my understanding, this phenomenon is known as Radio Frequency (RF) breakthrough as caused by image frequency interference that just happened to picked up by poorly shielded electroacoustic transducers and radio equipments with inadequate filtering, the Very High Frequency (VHF) broadcast band of FM radio stations ranges from 87.50 to 108.00 MHz while those of the VHF aviation broadcast band ranges from 108.00 to 137.00 MHz and as you may notice they in fact lie side by side within the radio spectrum.

    While tuning into certain FM radio station you may inevitably pick up unencrypted transmission from Singapore Arrival, Singapore Tower and Singapore Ground operating on 118.60 MHz/118.25 MHz, 119.30 MHz and 124.30 MHz/121.725 MHz respectively for example, that has managed in breaking through.


    ----------------------------------------------------------------------------------------


    Just a quick calculation...,

    121.725 - (10.7 x 2) = 100.325...

    ... And so Singapore Ground 121.725 happened to be the image frequency of Radio 1003.


    wonderful, time to go Changi listen 100.3

    You may require a really crappy AM/FM radio receiver. Anyway itís just Changi ground controllers giving pushback clearance and providing taxiing instructions for aircraft ground movements on the aerodrome manoeuvring areas on that particular frequency, nothing really interesting about it especially not with the transmission happening in the background competing against contemporary mandarin hits.
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  5. #25
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    Default Re: Consumer Walkie Talkies

    Quote Originally Posted by qwerty628 View Post
    Quote Originally Posted by 9V-Orion Images View Post


    I'm not underestimating the capability of the Motorola GP Professional Series of transceivers though I can't recall the exact model that I had used but being able to receive and transmit 3.20 kilometres away from inside a car to another vehicle in an underground location meters below the surface amongst the highly built-up urbanised Singapore Central Business District (CBD) without assistance of a repeater is rather remarkable.


    How much does GP series cost?



    You might want to check with these authorised Motorola two-way radio distributors.
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  6. #26
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    Default Re: Consumer Walkie Talkies

    Quote Originally Posted by 2100 View Post

    ...

    There used to be group chats between crane operators in PSA Tg Pagar/Pasir Panjang, lots of users. Suddenly silent liao. Got busted I guess. As in, no cars no police does not mean you whack on the e-way at 250kph.

    ...
    Shouldn't they be on the Marine VHF frequencies of between 156.00 to 174.00 MHz instead since even those container crane operators have to be in constant communication with the vessel's deck crew utilising Marine VHF transceivers on board the vessel throughout the loading and unloading process?

    Try saying something gibberish on Channel 16 (156.8 MHz) and not just the police but the air force and navy will come after you as well in an instance.
    Quote Originally Posted by 2100 View Post

    ...

    Freqs for nearby Asian airports/planes can be heard on 8942, 15536kHz. It’s pretty fun even in today's world of "DIGITAL" and also its legal, plus you can get world band radio. But for receiving I think getting a scanner would be great, just that it’s illegal....but not that illegal.

    ...
    Those High Frequencies (HF) are primarily used for Over The Horizon (OTH) communications with Singapore Radio, Manila Radio and Ho Chi Minh Radio on 8942 kHz providing HF radio coverage over the South China Sea (AKA Major World Air Route Area: South East Asia Area 2 (MWARA SEA-2)) and Aircraft Communications Addressing and Reporting System (ACARS)/High Frequency Data Link (HFDL) transmissions.
    Last edited by 9V-Orion Images; 20th February 2011 at 11:31 PM.
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  7. #27
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    Default Re: Consumer Walkie Talkies

    Quote Originally Posted by 2100 View Post
    For UHF/VHF, line of sight.......you can get hundreds of kilometers as long as the noise floor is low enough and receiver sensitive enough. With good propagation, even 500mW can get you hundreds of km between mountain tops, there have been cases before. There is also radio hamming in the VHF and UHF ham bands between ground stations thousands of KM between them with just a few watts of power and directional antenna eg Yagi antenna - with the aid of a ham satellite with a repeater on it. LOS mah...
    That’s considered cheating, with the appropriate antenna and processing software to significantly increase the Signal-to-Noise (SNR) you can even receive signal that is 20 billion times fainter than the power of a digital watch battery from a spacecraft more than 17 billion kilometres (15.91 light hours) away from Earth.


    Quote Originally Posted by 2100 View Post
    Wah....9V-Orion-Images a pilot ah.
    Just the guy doing all the sai kang while the pilot gets laid.
    Quote Originally Posted by 2100 View Post
    Last time if you go to Pearl's Hill Police St (when Polices Alpha division was still there, CID also there I think) with the huge antenna you can also hear the transmission. Its not illegal to hear, just that you may not discuss anything about it.

    With a lousy radio with lousy rejection, yeah sure can hear esp if you are near the antenna.
    Should be encrypted on secure frequencies loh.
    Last edited by 9V-Orion Images; 20th February 2011 at 11:38 PM.
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  8. #28

    Default Re: Consumer Walkie Talkies

    Quote Originally Posted by 9V-Orion Images View Post
    Should be encrypted on secure frequencies loh.
    The crane operators got official PSA trunked analog channels on 800+MHz range with commercial handsets. Same as what SATS would use at Changi. Now they all changed to digital liao, same freqs. They were using the "sourced from US" GMRS privately for group chats, ie soccer betting, GL pros, Toto/4D, where to eat, politics etc.... mainly in dialect. Probably during shifts there could be some stretches where there are no loading/unloading, i guess it kinda gets boring. They don't use the international marine freqs. Only the various PSA VTIS use the marine freqs for shore to ship comms....and Harbour Front Centre to the Indo ferries.
    Not sure how the crane operators talk to the vessels, my guess is that they don't as its all tracked and controlled/sequenced by computers way beforehand....I mean talk in Hokkien or Singlish to a Chinese captain = disaster.

    I think for your USA ATC -> Chinese pilot (supposed to be properly and highly trained) already got issue.
    http://www.youtube.com/watch?v=HQETCmzCOFE

    The police last time were using analog. Just A few years ago then changed to digital...
    Last edited by 2100; 21st February 2011 at 12:06 AM.

  9. #29

    Default Re: Consumer Walkie Talkies

    Quote Originally Posted by 9V-Orion Images View Post

    Just a quick calculation...,

    121.725 - (10.7 x 2) = 100.325...

    ... and so Singapore Ground 121.725 happened to be the image frequency of Radio 1003.
    Hi Orion,

    Curious, why 10.7 in particular 10.7 x 2?
    また再建しましょう~ ^_^

  10. #30
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    Default Re: Consumer Walkie Talkies

    It's only been a short while since I was away and the entire forum had a compete makeover.


    --------------------------------------------------------------------------------


    Quote Originally Posted by PaulKami View Post
    Hi Orion,

    Curious, why 10.7 in particular 10.7 x 2?
    Anyway, PaulKami. For superheterodyne radio receivers, the Image Frequency (fimage) is equal to plus (if the Reception Frequency (frx) is less than the Local Oscillator Frequency (flo)) or minus (if the Reception Frequency (frx) is greater than the Local Oscillator Frequency (flo)) twice the Intermediate Frequency (fIF) from the main station frequency (f).

    fimage = f + 2fIF (if frx < flo)
    fimage = f - 2fIF (If frx > flo)

    The Intermediate Frequency (fIF) can be calculated from utilising the following formula...

    fIF = f + flo (for signal up conversion)
    fIF = f - flo (for signal down conversion)

    ... Though by referring to my cheat sheet without knowing the specific Local Oscillator Frequency (flo), the Intermediate Frequency (fIF) for FM radio stations in Singapore happened to be 10.7 MHz.
    Last edited by 9V-Orion Images; 1st March 2011 at 01:31 PM.
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  11. #31

    Default Re: Consumer Walkie Talkies

    Quote Originally Posted by 9V-Orion Images View Post
    It's only been a short while since I was away and the entire forum had a compete makeover.


    --------------------------------------------------------------------------------



    Anyway, PaulKami. For superheterodyne radio receivers, the Image Frequency (fimage) is equal to plus (if the Reception Frequency (frx) is less than the Local Oscillator Frequency (flo)) or minus (if the Reception Frequency (frx) is greater than the Local Oscillator Frequency (flo)) twice the Intermediate Frequency (fIF) from the main station frequency (f).

    fimage = f + 2fIF (if frx < flo)
    fimage = f - 2fIF (If frx > flo)

    The Intermediate Frequency (fIF) can be calculated from utilising the following formula...

    fIF = f + flo (for signal up conversion)
    fIF = f - flo (for signal down conversion)

    ... Though by referring to my cheat sheet without knowing the specific Local Oscillator Frequency (flo), the Intermediate Frequency (fIF) for FM radio stations in Singapore happened to be 10.7 MHz.
    Ah, thanks for the info 9V-Orion, it's interesting to know about the superheterodyne receiver and IF theory behind.
    また再建しましょう~ ^_^

  12. #32
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    Default Re: Consumer Walkie Talkies

    Quote Originally Posted by 2100 View Post
    The crane operators got official PSA trunked analog channels on 800+MHz range with commercial handsets. Same as what SATS would use at Changi. Now they all changed to digital liao, same freqs. They were using the "sourced from US" GMRS privately for group chats, ie soccer betting, GL pros, Toto/4D, where to eat, politics etc.... mainly in dialect. Probably during shifts there could be some stretches where there are no loading/unloading, i guess it kinda gets boring. They don't use the international marine freqs. Only the various PSA VTIS use the marine freqs for shore to ship comms....and Harbour Front Centre to the Indo ferries.
    Not sure how the crane operators talk to the vessels, my guess is that they don't as its all tracked and controlled/sequenced by computers way beforehand....I mean talk in Hokkien or Singlish to a Chinese captain = disaster.

    I think for your USA ATC -> Chinese pilot (supposed to be properly and highly trained) already got issue.
    http://www.youtube.com/watch?v=HQETCmzCOFE

    The police last time were using analog. Just A few years ago then changed to digital...
    How come a pro photog know so much about all these? Do you happen to be a local ham registered with SARTS?
    Last edited by 9V-Orion Images; 2nd March 2011 at 08:35 PM. Reason: Grammer.
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  13. #33

    Default Re: Consumer Walkie Talkies

    Quote Originally Posted by 9V-Orion Images View Post
    Just to answer your question. Similarly with any mobile phone, you are fine to use the walkie-talkie without registering and obtaining a license as long as there is a IDA compliance label on it.
    It may have the IDA compliance label, but if you choose to use frequencies or program frequencies besides the PMR ones (assuming usual UHF spec) you are still flouting the law.

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