Introduction:
The VHF / UHF radio spectrum is an amazing treasure trove, full of many different people and groups who are all using two-way radios for various purposes. Some of these are groups such as CB and Amateur radio operators who either have fixed channels such as UHF CB operators with 80 fixed channels or amateurs with their many megahertz of bands they can use. Other bands such as the VHF air band and the 156MHz marine are very fixed in nature so you can be fairly sure that any frequencies you find in those bands are somehow related to those services, however this is not always a given as I will show below.
The focus of this document is Tasmanian however most of the information is relevant to anybody with an interest in being a “frequency detective”.
Below is a quick rundown of the major bands and what you can hear on each of them in Tasmania.
25 -50MHz: low power transmitters, 27MHz CB, cordless phones (not recommended), some older types of baby monitors, defence communications.
50 -54MHz: Amateur 6M band
70 -87MHz: Commercial users, government, emergency services.
88-108MHz: FM broadcasts band
108-137 MHz: Aircraft band
144-148 MHz: Amateur 2M band
148-150.00 MHz: Pagers
150-174 MHz: VHF Marine band, Commercial users, government.
225-400 MHz: Defence allocations, includes some satellite communications
403-420 MHz: Commercial users, government, emergency services
420-450 MHz: Amateur 70cm band.
450-520 MHz: Commercial users, government, UHF CB
820-960 MHz: trunking, links (The TASGRN can be found from 865-870MHz)
960MHz up: mainly links, very little voice communications to be heard.
When I first started out in the radio scanning hobby back in 1999, I did not know anybody else who was in to radio scanning as a hobby. With the lack of websites and other sources for assistance at that time, I was on my own as far as searching for frequencies and finding out whom each frequency belonged to and for what it was used. Because of this I was forced to spend many hours searching the bands looking for new frequencies and then listening to them while making notes to help work out whom it was using each frequency.
There are a few different situations that would require you to have to do a bit of detective work and we will look at each of these in turn.
Finding a new frequency active and trying to ID the user:
The easiest way would be to simply look it up on the ACMA database and see those to whom it is assigned. Now that would be the easiest way but in some cases, you will find that the frequency is not assigned to anybody in your area, this means you have to do some research and detective work to who is using the frequency.
I have found the easiest way is to get a piece of paper and write down as much as you can find out from listening to the traffic that frequency carries; you need to look for things like this:
When is the frequency active? Is it 9-5 business hours or is it in use during the night and weekend?
Are call signs or codes used? Do any of these sounds like what is used on any other channels you hear. Or do the codes suggest who it might be?
Range / coverage area? Can you only hear it when you are in some parts of the city, or does it seem to have wide area coverage and is the signal stronger in some places then others?
Content? What do they talk about? Is there anything said that could help you work out who they are? Things like places, times, names. Do they talk about any products or areas? Do the opening / closing times relate to any business / places you know of?
In late 2004 while searching the UHF band I came across the frequency of 474.225MHz active, which was not on the ACMA database is use at all in Tasmania. Nobody on our scanning group knew who it was, over a few months of listening to them and noting down key parts of what they said I was able to work out who and where it was being used.
Finding a frequency for a known user:
The easiest way would be to simply look it up the company name on the ACMA database and see if they have any frequencies assigned to them, but in some cases you will find that there are no frequencies assigned to them or there are some listed but none seem to be the one you want. There are a few things you can do, first look for any frequencies that they do have assigned to them, if they are mostly in a single band say around 474MHz then this would be the best area to search for them. Also keep an eye out for any handheld or cars with aerial, basically the longer the aerial the lower the frequency in use.
If you have one of the newer Uniden scanners with “Close Call” then give this a try and see if you can find them when close by somebody using a radio. Common sense and caution should be exercised when doing this.
Scanning / search at major events:
I like to keep an eye out on both the TV news and the local paper for any events coming up that are likely to see a major use of radios, some events include things like major sporting events (AFL, V8 car racing), Targa Tasmania and the Launceston Cup. Other events worth searching the bands for include the Launceston Show in October, Carols by Candlelight every December, Festivale in mid-February, visits by the prime minister / other heads of state, concerts and other events that will see a large group of people in one area.
There are many methods that you can use when scanning these types of events and to a large extent it will depend on how close you want / can get to the event and if scanning / searching within the event is possible. I would be incredibly careful these days with having any radio equipment in view of the public and trying to sneak in radio gear to events that ban it would be a big no no.
Using various stealth techniques can be useful, this is something I have done in the past and which I have used to produce superior results. Some of the basic tips for this are:
- Carry your scanners in such a way that they can be mistaken for something else; a digital camera bag is great for this.
- Do not display you radios so that the public / event staff can see them.
- In a lot of cases being close to but not inside the venue is the safest bet.
- Close Call is your best friend
- White earphones make you look like somebody using an Apple device, use this to your advantage.
- Smaller aerials work best, they are easier to carry and reduce the signal level so that only strong local stations can be heard.
- Focus on the UHF band as this is where most handheld radios operate.
The first thing I do is check out any ads or websites for the event and see if any companies who are sponsoring the event are known radio users, if they are you can be fairly sure that their radio channels might be in use.
Once the event is being set up / underway if you can get close enough and have a scanner that supports “close call” then give this a run and see if it picks up anything worthwhile / related to the event.
I have done some testing of the close call feature and depending on how “dirty” the RF spectrum is depending on how well this feature works.
In the past doing some testing on an average suburban street I have got these results using the close call feature on a Uniden 396T:
5W UHF CB – 500m
2W 146MHz Handheld – 300m
0.5W 433MHz handheld – 120m
0.05W 173MHz Wireless microphone – 30m
If you don’t have a close call capable scanner then you will need to do some searching of the bands, most handheld’s these days are in the UHF band, try search 460MHz to 512MHz in 12.5KHz steps, if this does turn up any users then try both the VHF high band and the VHF Mid band and see what you can find.
ID’ing an “unknown” user on a shared frequency:
Recently a number of transmissions have been logged on “shared” frequencies, this includes a number of UHF simplex channels and also the standard frequencies loaded in to “Baofeng” type radios. From my monitoring, this appears to be a mix of “kids” and some business users. I have found the recorder feature on the UBCD436PT is great for this purpose, I can create a system with these channels in it, let it record and then review these recordings later. When doing this, keep note of any names, locations or other details which might help you to work out who the user is.
Final Thoughts:
After all of the above, please also do keep in mind that just because a frequency is in a given band such as the air band or VHF marine band, it does not mean that all transmissions are related to those services. In 2006 a number of radio transmissions were heard in the greater Launceston area on VHF marine band frequencies which were related to the day to day operations of a business, they had sourced some VHF marine band hand held radios and were using these for their business. Once they were made aware of this, they moved to the UHF CB band.
Finally, a note of caution. Not every user of two-way radios are happy about the fact that their transmissions can be heard and these can be linked back to them. Twice I have been contacted by business two-way radio users who have asked that their frequencies remain “confidential” due to the nature of what they are doing. In both cases these companies had taken steps to not link their transmissions to their business name, my detective work allowed me to match these up. I also am overly cautious with sharing any details related to a number of government frequencies including those used by agencies involved in tactical law enforcement at a state or national level. While these frequencies use a variety of secure encryption methods, the mere existence of a transmission on one of their frequencies, even if the content is encrypted can be a guide as to that is happening. It is especially important when using “close call” and this information should not be shared.
I personally find hunting out and searching for new frequencies and users to be one of the most enjoyable parts of the radio scanner hobby and I am surprised that more people do not seem to do it.
Go on, hit that search button, and see what you can find.
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