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Discussion Starter · #1 ·
Firstly I cannot condone breaking the law in any way and as such I cannot recommend doing the following modification ;) . If you proceed to do this then it is entirely at your own risk and you need to check if it breaks any laws for your area first.


If you use an Autocom system and a Kenwood PMR radio for bike to bike communications then this one might interest you.

Anyway, this modification will allow you to fit a better performing external aerial to your Kenwood TK 3201 (full 500mw UK spec model only with fixed rubber aerial). The reason behind doing this is to try and increase the performance of the radio without the need to use a non standard ‘high power’ radio such as the TK 3207, and to be able to hide a radio away on the bike where some tealeaf can’t remove it without your permit ion. Problem with hiding the radio is that it inevitably cuts it’s performance by a very big margin, and hence reduces the radio’s effective range (and makes it more prone to interference from the bike electronics). So fitting an external aerial would allow you to hide the radio and keep the best performance.

Sounds like a lot of trouble to go to in order to fit an external aerial however, after doing the change you will have increased the performance of the radio considerably.


The change done is to fit a new ‘SMA’ socket to the radio in place of the original ‘rubber duck’ antenna and that is it. These sockets can be purchased from Kenwood radio dealers (or the internet) and are the same part as used in many other Kenwood radios such as the TK 3202, TK 3207 etc. Unfortunately you will not find an official dealer in the EU that will do the modification for you, as this strictly speaking breaks the PMR specification for a ‘fixed’ aerial and hence cannot be done. However, if you know a local TV-radio repair shop or you are handy with the soldering iron and you are able to get the part then you may want to go for it.

The change is very easy to do, simply strip the battery and belt clip from the radio, remove all the screws that fix the alloy radio chassis to the plastic front face (not the one next to the top battery terminal) and gently lift the chassis at the radio base. Once free from the front (about 0.5cm at the base) slide out the chassis including the coil aerial from the front facia in a downwards direction, be careful not to damage the speaker wires as you go. You will see that the coil aerial is inserted into a rubber tube that appears to be part of the front facia (it isn’t). Once the main radio chassis is free (complete with the little speaker) then push the rubber aerial sheath out from the front facia (it pushes from the outside in), and flick out the rubber grommet that sits at its base.

The next bit is tricky, de-solder the connection on the main radio circuit board where the coil aerial fixes, you will need a solder sucker as this is soldered on both sides of the PCB (printed circuit board). Once you have de soldered the old coil aerial gently pull it out along with the plastic base. This can now be discarded. Now fit the centre wire from your new SMA socket into the same hole in the PCB and fit two small screws into the chassis to secure the new socket (I think they are 2.5mm screws but you need to check, also watch the screw length is correct as long screws will damage the PCB). Next solder the SMA socket centre wire in place ensuring that enough solder is used to make the connection on the back of the PCB as well as the front, it needs to ‘soak’ through.

The only other thing to do is reassemble the radio (and if you have one) fit a new rubber aerial which will now screw into the sma socket (again, only use a Kenwood rubber aerial that is suitable for 446MHz UHF).

Now this modification itself will not give any performance gains as the small rubber type Kenwood aerials all have similar performance, poor. The trick here is to use an SMA to BNC adaptor and couple up the radio to a suitable mobile 1/2 wave aerial. This will give the desired boost in performance. One final point, it is always a good idea to get the SWR checked when you use a new external aerial with a suitable SWR meter.

THE ACID TEST:

After doing the modification and using two radios, one fixed location with a house aerial (base station style) and the other on my bike (with a motorcycle specific aerial, one with built in ground plane), I set off away from the base radio. (bearing in mind that most PMR 446 units fail in built up areas at about half a mile range sometimes less).

At one mile out communication was 100% clear with no problems at all, like being on the phone with a good line, 2-5 miles out some noise but still 100% (now way out of normal PMR range), at 5-9 miles communication starting to fade in built up area’s but when on high clear ground back to 100%. Had a conversation with base using just ¼ watt power (half the normal PMR signal strength) and parked up on very high ground (clear line of sight between both units) and it was like talking to someone next door, very clear. From 9-18 miles (which should be way out of any PMR radio range), communication was intermittent (although there was no clear line of sight on this test so difficult to say whether if we had it then ‘comms’ would be good). Last transmit ion clearly received was at 18.4 miles (my radio to base using ½ watt power), and from base to me was at 21.6 miles (using slightly more power).

This test just goes to show how poor aerials used on PMR radio’s restrict performance and a small change can pay dividends, although this mod cost over £70 (owch) including the new aerials.

Incidentally, the modification done now allows me to use the standard ‘rubber duck’ type aerial used on other Kenwood 446MHz radio’s (cost £4.99 on ebay), so I have also have the option to use it as a ‘walki talki’ as well as on the bike you could say best of both worlds


I will post some pictures later today
 

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Discussion Starter · #2 ·
Here are the pictures of the part required the SMA socket, the bike fitted with the new aerial, and some fantastic location somewhere in Norway (nice)
 

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Serial Scenic Router
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hmm not my bag realy but what and where from are the stove bottle bands!
 
G

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PMR is really the same as CB, the goverment can;t charge for it (or in CB's case it used to be very little) so they restrict it to hell.

I used to walk around platt fields park in Manchester on a 1w handheld and talk throught the North Wales repeater on UHF (433Mhz)

Only problem with using UHF (446) for mobil usage is that it's very line of site at times, just a small hill or even a large building can attenuate the signal.

Kymmy :cool:
 

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Brrrummm!
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3D "Kymmy" (my eyes are back to normal) - I might give the new Yaesu FTM-10E a check out and install one to operate from the TA else it will be the VX-7R.
 

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hmm not my bag realy but what and where from are the stove bottle bands!
If you mean the straps that are holding the bottles to the pannier - they look very much like the Touratech ones, using their bottle holder.

Not bad prices for TT - £18.49 for the double and £14.29 for the single - straps included


I have the double holder on the front of one of my panniers - excellent for water and Trangia fuel....:p



And completely unobstrive when not loadedwith bottles (you can just make it out on the front of the pannier in this pic)

 

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Discussion Starter · #9 ·
they do look good with the black bike, good job for me I have a silver one

:D :p :) :p :D :)
 

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Hi Richardg,

Thanks for the post! I kinda always assumed it was possible, but wasn't sure what options / route to go for. My radio has been lying flat in my tank bag so I never could get much more than half a mile across a valley in line of sight :-( . Your post has now cleared that up for me and seems the neatest option too.

Can you kindly post the name of the supplier (website / phone no) and the part number of the SMA connector in your picture. I have bought two different types from RS online but neither seem as good a match as your picture. I suppose I could make them work, but we're not in Africa! While on the subject of the hardware needed for this, I have got a BM433 from Panorama Antennas but may change the base once the new bike arrives. Do you have any other suggestions for a supplier and model number for the external antenna for the bike? If posting such details of this kind of mod in a public forum is a bit twitchy then I am happy to chat off-forum.

TIA,
Kevin
 

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No problem with that! Reduce, reuse, recycle... and welcome! Can't help with the info you requested though.
 

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Thanks for the welcome messages!

Yeah, I noticed it was pretty old but it's still the best article on the subject I have found! If you don't ask you'll never get an answer...
 

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Never one to sit still, it seems the SMA connector from something like a TK-3202 is just what is needed. Hunting down the service manual online produced a part code E04-0451-05. Next thing was to find a supplier that also services Kenwoods and armed with the part number made the ordering process a breeze.

Coming at this from another angle: Is it possible to get a licenced radio that works in the 440-470 band (like the TK-3302) and use the Windows software to program one or two of the channels to "co-incide" with the PMR frequencies and chat with someone who has a PMR unit like the TK-3201. My thinking is to get the £75 for 5 years licence, two radios so my normal riding buddy and I can chat on my allocated frequency, but also have the unit participate on one or two of the frequencies from the PMR table given in the TK-3201 user manual (for group rides with people who only have PMR units). Hopefully, that way I will have the best of both worlds - a higher power unit with an external antenna and the ability to chat with other riders who have PMR units. Any ideas?
 
G

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Make up your mind.. do you want to be legal (with a licence) or illegal (using non-type approve, high power with an external antenna on PMR446) ??

;)

Most modern UHF radios will be programable from about 420-470 it does though depend on the software and firmware as to whether the tuning steps is small enough to put the unit accurately onto PMR frequencies which are in weird tuning steps that require an accuracy of 1.25Khz.. Most radios only have a minumum of 5Khz tuning steps
 

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Discussion Starter · #16 · (Edited)
I have found that only a few radios will acuratly tune in correctly to PMR 446. one being the TK 3160. But this radio is very pricey at £270 a pop :eek:

A lot of other units say they will communicate with PMR 446 but won't.

my view for what it's worth is that if you want to use PMR446 then use the radio's designed for it (TK 3201, 3301 and 3101) etc
 

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Discussion Starter · #17 ·
I know this is a very old thread and for those of you that wanted this information I am sorry for the very long time in getting back, however, If you want to modify the Kenwood tk 3201 by putting an antenna on to it (not legal to do in Europe), then the SMA socket you need is the same part as fitted to the UK standatd Kenwood TK 3202, or TK 2202. You can order this part from any UK Kenwood dealer, just state that it is for a TK 3202. If you tell them you want it to modify a tk 3201 they may refuse to sell you the part.

Both these radios are standard UHF (the 3202) and VHF (the 2202) full power UK radios. The chassis is identical to the TK 3201 and so the SMA socket will fit directly into the PCB without any mods.

Please note you will also need the two fixing screws and a standard rubber duck UHF antenna (to continue using your radio as a walki talki).

R
 
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