02/11/2007 - 26 Years Of Legal UK CB Radio

 

Click Here To Read About The Easter 2007 DX Event!

 

 

---

Intek M490 Plus CB Radio Review

 

 

I do agree with John Rodger with reference to 446 flatside operation, and as he correctly states it did work well on 934. I ran a double twelve minibeam (homebrew) flatside and it removed all cellphone interference on 934. I still have somewhere the build instructions for the beam perhaps it can be modified for 446 if I can find the specs I will send them on to you. I cannot see why it should not work on 446 and think of all that forward gain!                                            

Regards                                                  

Eric Thew -  2G1MT Greenwich South London.

---

Information about Merseyside Control

(Supplied by David Noon)

---

CB Radio On 70cm Band

E-Mail from Sam on 23/07/2002

Hi Delboy!

Since I last sent you an email I've done many experiments with PMR446 and ham 70cms.

My observations with the ham 70cms band is that it's a mess, and underused. There are segments allocated for "Fast Scan TV", but there are only a few if any stations running fast scan TV there because it interferes with repeaters, isn't wide enough for colour transmission, so the result is a blurry mono image. This has been realised, and the frequencies are already being reallocated to repeaters and things.

I would say that if you operated between 438 and 438.425 or 438.575 and 439.750, you will not be caught because nobody ever listens to them. I think that if you operated in that band, you could start something like CB in the early days in the UK and make an "illegal" system up, which the government could be forced to legalise.

The 438.575 to 439.750 band, at 25khz channel spacing (nice spacing!) could give 47 channels. Call it 40 channels, and you've got a nice number of channels. The amateurs wouldn't care about that band being taken, and I know people around me would actively encourage it, since a lot of activity on the top end of the band would make it difficult for the RA to "steal" it from us.

I would also like to suggest that it's actually 46 channels, with 8 of the top channels being for repeaters (4 top being outputs, 4 bottom being inputs, for example), making it a 30 simplex and 8 repeater system. This is something which I would strongly encourage.

This sure is one very wide band and could have a lot of good done with it. Make 10 bottom channels "local" 500mW channels, the next 10 "mid-range" 5W channels, and the top 10 "long range" 20W channels for DXing. The repeaters would have 4 "high power" 10W repeater channels and 4 "fill in" 2W repeater channels. Beams are allowable in all channels, but the power specified being ERP for all channels except the DXing channels, so you always put out 10W ERP for the repeater input, for example.

Repeaters use CTCSS mandatory, and all channels are CTCSS mandatory, except for one DXing calling channel.

I hope this system is of some interest for you, and is certainly one that would be supported by many. Make the use of Amateur equipment on the bands allowable by AMATEUR LICENSEES ONLY, and the proper UHF CB equipment usable by anyone with a CB license. Tri-banded CBs also should be allowed on the market.


I hope this is of some interest.

Sam

Follow up E-Mail on 25/07/2002:

I've slightly revised my ideas:-

25khz spacing:- 12.5khz spacing is too close for comfort. Get a strong signal on an adjacent channel, and it swamps out the needed signal. The deviation is also too low to give a good quality. Wider deviation and spacing result in superb range and quality. However, for the low range channels, 12.5khz will give more low range channels.

500mW for the local channels:- 500mW is proving with PMR446 to be ideal for on-site and similar paging. Perhaps I set this too high, and 50mW may be better. The idea of these channels is for on-site type communication. Reviewing it, I think that 50mW would be better.

Having the channel sequence something like:-

4x [High Power Repeater inputs] - 10W (10dBW) ERP [Channels 41-44]
4x [Low Power Repeater inputs] - 1W (0dBW) ERP [Channels 45-48]
20x [Low power channels] - 50mW (-13dBW) ERP [Channels 1-20]
10x [DXing channels] - 20W fed to the antenna [Channels 31-40]
10x [Mid power channels] - 5W fed to the antenna [Channels 21-30]
4x [High Power Repeater outputs] - 10W (10dBW) ERP [Channels 41-44]
4x [Low Power Repeater outputs] - 1W (0dBW) ERP [Channels 45-48]

This is my idea. The repeater inputs would then be away from any high power input into the repeater, such as the DXing channels. 10dBW should be more than sufficient to get into well sited repeaters in towns, as experience with 70cms repeaters shows. 10dBW out would allow people to know that if they can get it, they can get in.

The low power channels are designed to replace PMR446 and to do the job of on-site paging far more effectively. These would have about 1/2 mile range or so, and CTCSS would be mandatory on all channels. There would be 20 of these low range channels, and could be used for local chat, businesses,
whatever people want really. Children may like these for a better quality "walkie talkie" system. CTCSS means that OCI (on channel interference) is severely decreased. 20 of these. Voice encryption techniques can be used on these channels, namely spectrum band inversion. Each spectrum band inversion setting tallies with a different CTCSS code.

The mid power channels are designed to replace current 27mhz CB. 5W should be more than enough to get a good range. CTCSS used on all channels.

The high power DXing channels are used for DXing. 10 of these, but the top channel is used for the calling channel. It is inevitable that if a mid power channel was allocated for calling, then some would prefer the range of the DXing channels. This is a substitute for CB channel 19. It is also where people will be to try out the distance. CTCSS is not used on these DX channels.

On the repeaters, 12 CTCSS codes are available, and CTCSS is fully mandatory. A repeater will fire up without a toneburst, just 1 second of the correct CTCSS code is sufficient to key it up. Once it's been fired up, it will send it's ident in fast CW (35WPM), it's two letter identifying code (Like "AB") in reasonable voice, turn on the CTCSS encoder, send out a confirm tone (one single 750hz tone lasting 1/4 second) then send out silence for 10 seconds before dekeying. When it's sending out silence, that is when it's ready to run. The silence, fast CW and voice ident are without CTCSS. When someone speaks, their voice passes through as normal. After dekeying it waits 1 second, sends the 750hz tone, then send out 10 seconds of silence and if nothing heard, dekeys. The CTCSS decoder on the receiver is compulsory, unless a button is being held down to override it.

This repeater system sounds fairly complex, but will make repeaters very "quiet" in operation, with the speaker in the radio only being turned on if there is something worthwhile there to turn it on for.

The high power repeaters are used for main areas, like towns or cities. The lower power repeaters are for filling in areas of no reception or areas which want their own small repeaters for conversations.

I think that this plan would need a lot of comments before it is finally clarified, but it certainly starts the ball rolling for efficient use of an empty part of the spectrum. Set up in this way, it also is "foolproof" so to speak. Beams, etc, may be connected up, but the low power restriction in the low power channels must be observed. Manufacturers should implement a menu system in devices with an antenna jack which allows you to select the gain
of the antenna system you are using, in dBi.

I hope this slightly revised plan makes a bit more sense, and I hope I've put it in the right way for your website.

Sam

Many thanks for your very interesting comments Sam. I totally agree that the 70cm band is wasted in it's current form (I.E. 10MHz that hardly ever gets used in my area), and I genuinely fear that the Radio Authority already has plans for this part of the spectrum (Amateurs beware !). It will be interesting to see if anyone else would like to comment on your ideas !

 

GoStats web counter