Let me chime in, as I am in Ireland, and have at least some knowledge of the regulations. However I can see at other answers have already addressed this, so I am not going to repeat this.
Let me give you a solution for your family-day-fox-hunt
- 100 mW EIRP TX
- unlimited FREE RX devices for your family memembers
If it is just for the family fun day (and lets forget about the fun building electronic circuits) you can do the following:
- get a cheap/old Wifi router
- most of them run on 9V or 12V, so you can run it on a battery of some sort
- some you can turn down the power output if you want to make it challenging
- get mobile phones and install a "Wifi tracking or finder app"
- configure the Wifi router with a recognizable SSID
- hide the Wifi router where you have your family day.
- try to find it with phones....
Lots of fun, everyone has a phone, so you have not only solved the TX problem, you have given everyone a method of RX, for all ages !
Building transmitters if fun, and this is probably something where you could say: "we have all done it". The frequency which is most versatile to experiment with is 87-108 MHz, which is the FM broadcast band. You will need to experiment with filtering and the like. And with a max ERP of 50 nW there is not much of a range.
You do have to start somewhere when you want to do this, but it will be a while before you can build a transmitter with larger power output, which can be used for your intended family day. (as other answers have already covered this)
[EDIT after reading some more documents about the legality]
I was surprised about the frequency ranges mentioned, hence my edit here.
It seems to me that most of the frequencies you are listing have a very specific license exemption, e.g. cordless phones, baby monitors, radar-to-wall, and other applications.
I would strongly advice to stay away from those "seems to be good to use" frequencies. These frequencies are NOT for "Private Mobile Radio" (PMR for short). The license exempt allocations for PMR are:
- 434.04 – 434.79 MHz (10 mW)
- 446.00 - 446.10 MHz (500 mW) channelized
- 446.10 - 446.20 MHz (500 mW) channelized digital only
However for those license exempt frequencies there are actually type-approval requirements in the appropriate legistlation.
The relevant documents can be found on Electronic Irish Statute Book:
- S.I. 93 of 1998
- S.I. 405 of 2005
- S.I. 160 of 2006
Clearly stipulating that the equipment used for those need to be "type approved", and will bring a extensive list of requirements for such approval.
Furthermore, Document 06/47R stipulates the following:
All radio and telecommunications terminal equipment must comply with
the essential requirements and other relevant provisions of the R&TTE
Directive before being placed on the market or put into service in
Which was already mentioned in another answer, this will bring requirements in regards to spurious emissions and harmonics.
Under Irish legislation (The Wireless Telegraphy Acts 1926 - 1988),
all apparatus for Wireless Telegraphy requires a licence unless that
apparatus has been specifically exempted from licensing under Irish
legislation by means of an Exemption Order.
Which comes down to "you may not own a tranmitter, unless licensed, or unless license exempt" And we already know that the license exempt equipment need to be type approved.
So your options are getting narrower once you start reading the detail of the legislation.
The PMR devices (properly type approved and license exempt) are widely available in many stores around Ireland. They are called PMR446 devices, and sold as "walkie-talkie". These will have a 500 mW output and can be loads of fun. Some of them have microphone inputs where you can feed it with a signal of some sort.
For a "family day of fun in the park" and therefore in a public place, I would higly recommend you stick to type-approved equipment, or the Wifi I mentioned before.
Don't let this stop you from experimenting, there are some good answers here which can get you going in building simple transmitting circuits. Just don't expect to build anything with large power output and be sure you are able to measure and adjust/filter spurious emissions and harmonics... this will be a learning journey.
I believe that many experimenters do so in the 87-108 MHz FM broadcast band, and keep the power output under 50 nW. This I mention above as well. Technically speaking this license exemption for Short Range Devices, also need type approval, and also a CE mark certification. But I could not find any other frequency allocation for such experimentation.
I am not even sure if there is an allocation you could "officially" use for experimentation.
Did I built transmitters in that frequency range?
Yes I did, learned a lot, had some fun. But never with large power, and never used them for "public" functions/family-days-in-the-park.