PMR446 Base Station

[Werthers]

I've just been thinking of some ideas for a PMR446 base station radio.

First of all I have an old CB base station which works with very crackly potentiometers and isn't very valuable its just a standard 40 channel FM CB radio perfect for converting to UHF.... well almost.

So your thinking how the hell am I going to convert a CB radio to UHF? basically by replacing some of the guts.

Before I get started on this I'd like to be able to use the CB's original channel selector if possible with the digit display which will be 16 channels instead of 40. I'll be using as many original parts of the CB as possible like the speaker, signal meter, mic socket, SO239 socket, on/off button. The squelch will be left on but not used. The volume pot will have to be changed but will still have the CB's original knob put back on it.

The built in mains transformer I will try to use it although I will have to build a circuit to add onto it to give me 4 volts to power the UHF board which will be from a Baofeng BF-888S.

I will program up the Boafengs 16 channels and turn the voice off. Looking at the board it looks nice and easy to de solder and solder wires too and from. I'll be removing the speaker and mic as those wont be needed. The volume control and channel selector will also be removed and will have wires soldered to the pins going to the front panel of the CB. The SMA socket will also go.

I'll probably need to add some band filtering and some other stuff as well.

I may also build a RF amp just to increase the power a "little more" these BF888s only do 2 to 3 watts and I'd probably be losing some power so a small low powered RF amp should take care of that.

First things first before I do anything I need to test out the BF-888 on an external antenna to see how it performs then depending on what results I get I can then determine whether the BF-888 is suitable for the project.

Next I will need to find out a bit more about how the CB's channel selector works.

[DX-Digger]

Good luck with that one. Buffing 888's are as wide as a barn door, and get desensed even by car keyfobs on 433.920.
Highly recommend you choose a decent radio for such a project.

[Werthers]

Good luck with that one. Buffing 888's are as wide as a barn door, and get desensed even by car keyfobs on 433.920.
Highly recommend you choose a decent radio for such a project.

Yeah your definitely correct there, they are pretty bad. The ones I bought back in 2014 are miles better and don't have the issues as the ones you get today. Back then they were about 15 to 18 pounds for one but now you can get two for the same price so they have made them worse to sell cheaper it would seem. I wish I had bought more back then, they were much better then than they are now.

I wont be using them for my project. I've been having a sort out and I've got some old Motorola Saber radios missing there batteries, I think they work and I have the programming cable but not the programming software, depending on whether I can track down a working CPS to program these radios then I could use one of these plus I found a 25 watt PMR UHF RF amp also made by Motorola. I'm not going to use the whole 25 watts I'll probably just have it about 10 watts to keep the transmitter happy and also don't wanna be running to much on 446 anyway.

[DX-Digger]

I wont be using them for my project. I've been having a sort out and I've got some old Motorola Saber radios missing there batteries, I think they work and I have the programming cable but not the programming software, depending on whether I can track down a working CPS to program these radios then I could use one of these plus I found a 25 watt PMR UHF RF amp also made by Motorola. I'm not going to use the whole 25 watts I'll probably just have it about 10 watts to keep the transmitter happy and also don't wanna be running to much on 446 anyway.

Yeah because other users radios are as wide as a barndoor so you will probably de-sense them and if they are used for business and they find out they are being blocked they may contact Ofcom, and with it being a business they will investigate.
So my advice is tread carefully and definitely use bandpass filters on the output. as your 2nd harmonic will come out on about 892MHz (mobile phones)
and 3rd harmonic comes out on 1300MHz Aircraft and airport Radar and the like.
Be careful is all I am saying

[Werthers]

I wont be using them for my project. I've been having a sort out and I've got some old Motorola Saber radios missing there batteries, I think they work and I have the programming cable but not the programming software, depending on whether I can track down a working CPS to program these radios then I could use one of these plus I found a 25 watt PMR UHF RF amp also made by Motorola. I'm not going to use the whole 25 watts I'll probably just have it about 10 watts to keep the transmitter happy and also don't wanna be running to much on 446 anyway.

Yeah because other users radios are as wide as a barndoor so you will probably de-sense them and if they are used for business and they find out they are being blocked they may contact Ofcom, and with it being a business they will investigate.
So my advice is tread carefully and definitely use bandpass filters on the output. as your 2nd harmonic will come out on about 892MHz (mobile phones)
and 3rd harmonic comes out on 1300MHz Aircraft and airport Radar and the like.
Be careful is all I am saying

Its more for fun of building a PMR446 base station and get it all working right, it probably wont get used as running a PMR446 station from my home QTH isn't a good idea but it will still be good for taking to other places but more fun just for the sake of building it.

[LondonCbRadio]

You sound like phil from forest gate ?

[Werthers]

You sound like phil from forest gate ?

Interesting... Well it would appear Ofcom don't give a ?%^& so why not. Yep more fun building it... I did it, and using it on 5 watts but may just step it up to 25w seeing that there is no threat from ofcom now. CQ on channel 8 listen out in Thurrock area.

[Werthers]

I just wanted to add that its interesting the kinda people you can get on PMR446 who have no clue about radio but are interested in getting into radio. I spoke with some woman earlier on PMR446 who was amazed that a two way radio didn't need a network for people to communicate freely. PMR466 has a lot of potential I can tell ya that in regards to getting new comers into the hobby.

[LondonCbRadio]

Is pmr446 active in London ?

[26mb04]

Yes, I was up there at the weekend and there were loads of people on. Mainly kids and crane operators/banksmen etc which could be an interesting combination. I wonder what the HSE would say about that? "Sorry the crane collapsed, I told the driver to stop but all I heard was someone telling a child not to push the hoover down the stairs" etc.

[paulears]

That’s the trouble with technology. If it works, people use it. The idea of not hoovers on stairs, but somebody deliberately messing this one up is quite scary, and I can’t believe their risk assessment has not identified the significant risk.

[Mikel]

I was an advisor for the (Health and Safety Executive) HSE for 10 years and as paulears has mentioned a companies risk assessment should identify a suitable and safe method of communications for safety critical tasks.

Regulation 3 of the 'Management of health and safety at work regulations 1999' makes this risk assessment a legal requirement.

Ultimately a court of law would determine whether a company had done 'all that is reasonably practicable' to ensure the safety of employees and others not in their employment in any given circumstance as is required under 'The Health and Safety at Work etc Act 1974', sections 2 and 3 respectively.

if a 'crane company' had asked my advice (as many did) I would have advised them to contact a reputable communications specialist to set them up with a 'suitable' means of safely transferring information and instructions between employees which would most likely not be PMR446!

But as I previously stated it would ultimately be down to a court of law to determine where liability lay if an 'incident' occurred.

[Werthers]

Is pmr446 active in London ?

I imagine it would be quite active in London.

[Mikel]

I love London I must admit, my sister lives in in Syon Park not far from Kew Gardens and I hope to visit her again before Christmas hopefully.

I will be taking some radio equipment for VHF and UHF with me so will find out for my self.

Hoping to find some 70cm nets around Heathrow airport if I am lucky. Last visit I only took a scanner with me and that was a laugh.

[Werthers]

I find that London is a bit of a dump. It used to be good and a unique place for people to visit now there is nothing. Everywhere has become gentrified and boring with very few places left to go to. The London life that was once there has gone. Unless your a champagne socialist who likes over priced crap, poor quality food and likes to look at ugly modern glass buildings and dirt and grime everywhere then its ok but each to there own. I only ever go to London now to mudlark on the Thames.

70cms simplex was alive today with some activity yesterday as well.