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#254676 - 19/04/2005 15:03 DAB unit
thinfourth2
Pooh-Bah

Registered: 13/04/2001
Posts: 1742
Loc: The land of the pale blue peop...
So whats the opinions on this wee unit. revo

seriously considering one to compliment the empeg.
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#254677 - 19/04/2005 19:17 Re: DAB unit [Re: thinfourth2]
andym
carpal tunnel

Registered: 17/01/2002
Posts: 3996
Loc: Manchester UK
Expensive, limited performance in marginal areas, messy install, other than that, I'm sure it's fine.
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#254678 - 20/04/2005 04:19 Re: DAB unit [Re: andym]
boxer
pooh-bah

Registered: 16/04/2002
Posts: 2011
Loc: Yorkshire UK
I looked at it, but £200 for a compromise solution seems over the top. DAB home units are at the £50-60 mark, car HU's are only hovering just above the £200 mark and now that the major brands have latched on to DAB, prices are bound to fall.

I just had a closer look, you can get a DAB HU for £150, which includes FM/AM//MP3.
Home and portable adaptors are £50 each: But you can get a standalone Matsui home adaptor for £60 (It works well, I have one) and you can get a personal portable for £80 (Double the battery life and much less cumbersome).
So I would think that these people will need to drop prices to stay in the game, and they may well not have the margins.


Edited by boxer (20/04/2005 04:40)

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#254679 - 20/04/2005 06:15 Re: DAB unit [Re: boxer]
thinfourth2
Pooh-Bah

Registered: 13/04/2001
Posts: 1742
Loc: The land of the pale blue peop...
Problem is that i have a pretty good MP3 head unit that won't be coming out and i can't be assed with installing a second head unit.

This might not be the cheapest solution but i'v never been in the school of thought that cheaper is better.

So just wondering if anyone has used one.
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#254680 - 20/04/2005 06:26 Re: DAB unit [Re: thinfourth2]
boxer
pooh-bah

Registered: 16/04/2002
Posts: 2011
Loc: Yorkshire UK
From memory, Andy was looking at adapting one of the Curry's/Dixons
Matsui units for the car, I can't find the thread, so don't know whether he succeeded.
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#254681 - 20/04/2005 07:03 Re: DAB unit [Re: boxer]
andy
carpal tunnel

Registered: 10/06/1999
Posts: 5916
Loc: Wivenhoe, Essex, UK
I haven't had much time to play with it yet. I did go for one quick drive and found that reception wasn't good.

I need to find out whether I can replace the "damp piece" of string aerial with something more substantial.

The thread in question is this one http://empegbbs.com/ubbthreads/showflat.php?Cat=0&Board=offtopic&Number=242500


Edited by andy (20/04/2005 07:07)
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#254682 - 20/04/2005 10:04 Re: DAB unit [Re: andy]
boxer
pooh-bah

Registered: 16/04/2002
Posts: 2011
Loc: Yorkshire UK
Quote:
"damp piece" of string aerial

That is the major downside, it pulls in less stations than the wavefinder (Which I've now sold anyway), and is highly susceptible to people walking past, I've put it near the ceiling on a long line lead to get over the problem, for some reason, extending the aerial wire makes reception worse.
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#254683 - 20/04/2005 14:22 Re: DAB unit [Re: boxer]
andy
carpal tunnel

Registered: 10/06/1999
Posts: 5916
Loc: Wivenhoe, Essex, UK
I took it for another test drive today. When it works, it works well, when it doesn't it sucks.

I drove from Reigate to Hook (30 miles or so) and it only managed to lock onto the BBC national MUX for about 5% of the time.

So I need to look at improving the aerial to see if that helps. You say it got worse when you extended it ?

I was looking at either extending it, or fitting a proper DAB aerial.

I know nothing much about aerials. The aerial is just a single wire, I'm guessing that a proper DAB aerial has two connections, antenna and ground ??? If so I guess I have to find somewhere to connect the ground to ???
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#254684 - 20/04/2005 17:06 Re: DAB unit [Re: boxer]
andym
carpal tunnel

Registered: 17/01/2002
Posts: 3996
Loc: Manchester UK
Quote:
I've put it near the ceiling on a long line lead to get over the problem, for some reason, extending the aerial wire makes reception worse.


Code:
 

Half wave aerial length (in feet):

468
---------
wavelength (mhz)

Quarter wave aerial length (in feet):

236
---------
wavelength (mhz)




See, I did learn something at uni!

Basically there for a given frequency there is an optimum length of aerial. This length can be reduced but only by certain divisors like 1/2 or 1/4. I would imagine the damp string is probably about 80cms long if it's a half-wavelength or possibly 40cms at quarter-wavelength.
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#254685 - 20/04/2005 19:10 Re: DAB unit [Re: andym]
boxer
pooh-bah

Registered: 16/04/2002
Posts: 2011
Loc: Yorkshire UK
And indeed, I vaguely remember that from my Royal Signals training, but when you threw your aerial in to a tree, you were just glad it didn't come back and clonk you on the head, 1/2 wave and 1/4 wave didn't occur to you.
And I bet none of you lot know the correct knotting procedure for joining a field telephone cable!
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#254686 - 21/04/2005 05:07 Re: DAB unit [Re: andym]
andy
carpal tunnel

Registered: 10/06/1999
Posts: 5916
Loc: Wivenhoe, Essex, UK
According to this page:

http://www.crompton.com/wa3dsp/hamradio/antcalc.html

the half wavelength length is 63 centimeters

Are you saying that there is nothing to be gained in increasing the length of the damp peice of string beyond this ?

Assuming that extending the aerial is a non-starter then I guess a proper in-car DAB antenna is the solution. There are various different types available, here are two that don't require you to drill a whole in the car body:

http://www.caraudiodirect.co.uk/product_info.php?products_id=3688
http://www.caraudiodirect.co.uk/product_info.php?products_id=3687

They all share one thing, a length of coax that needs to be connected somewhere. I know one side of the coax goes to where the damp peice of string is wired, but where would I wire the earth to ? Do I need to find some where in the tuner to wire it, or eath it to the car body ?

Is this likely to work, or am I going to be foiled by impedance matching issues (a quick flash back to an antenna lecture during my failed EEE degree).
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#254687 - 21/04/2005 12:51 Re: DAB unit [Re: boxer]
mtempsch
pooh-bah

Registered: 02/06/2000
Posts: 1996
Loc: Gothenburg, Sweden
Quote:
And indeed, I vaguely remember that from my Royal Signals training, but when you threw your aerial in to a tree, you were just glad it didn't come back and clonk you on the head, 1/2 wave and 1/4 wave didn't occur to you.


Heh, wasted 7.5 months in basic and with a the staff company of a armo(u)r/haubits battallion... but the antennas used were all truck mounted and automatic.

Quote:
And I bet none of you lot know the correct knotting procedure for joining a field telephone cable!


Dunno if there's an international standard for it, but I do know what the Swedish army considers the proper way... with or without the crimp tool (and a bunch of other useless things like how often to tie off the wire when laying it on ground, running it in in the air, considerations/procedures for crossing a road etc) Rolled out and collected way to much of that stuff
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#254688 - 21/04/2005 14:03 Re: DAB unit [Re: mtempsch]
boxer
pooh-bah

Registered: 16/04/2002
Posts: 2011
Loc: Yorkshire UK
Ah, the Swedish Army had probably moved from SW to FM by the time that they let you loose! I bet you didn't have a 120v and a 1.5 HT & LT batteries to lug about.
When I was crossing fields with a back breaking roll of cable bending me double, a crimping tool would have been a luxury: We had a pair of pliers and a roll of insulating tape!
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#254689 - 21/04/2005 15:25 Re: DAB unit [Re: boxer]
mtempsch
pooh-bah

Registered: 02/06/2000
Posts: 1996
Loc: Gothenburg, Sweden
Quote:
Ah, the Swedish Army had probably moved from SW to FM by the time that they let you loose! I bet you didn't have a 120v and a 1.5 HT & LT batteries to lug about.


Nah, the biggest batteries we used were the C-cells for the flashlights
For the tape/radio in the tent (unofficial of course, but ignored) )we used comms wire to our truck and a voltage regulator stuck in the battery compartment of the radio make the required 9V

Quote:
When I was crossing fields with a back breaking roll of cable bending me double, a crimping tool would have been a luxury: We had a pair of pliers and a roll of insulating tape!


Probably worked better...:) the crimp inserts were supposed to be insulated, but about 75% of the time you had to reinforce with tape anyway (and always check), so we didn't use them most of the time.
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#254690 - 21/04/2005 16:16 Re: DAB unit [Re: andy]
andym
carpal tunnel

Registered: 17/01/2002
Posts: 3996
Loc: Manchester UK
Quote:
According to this page:

http://www.crompton.com/wa3dsp/hamradio/antcalc.html

the half wavelength length is 63 centimeters



Depending upon which end of the frequency range you look at. I used the same page to check my calculations.

Quote:

Are you saying that there is nothing to be gained in increasing the length of the damp peice of string beyond this ?


Basically, yes. Extending the string wouldn't improve things. Might be worth investigating a different aerial though. I'd imagine earthing the ground of the aerial to the ground of the dab module would suffice. Suppose you need to investigate the impedance values of your module and aerial.
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Andy M

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#254691 - 21/04/2005 18:25 Re: DAB unit [Re: andym]
boxer
pooh-bah

Registered: 16/04/2002
Posts: 2011
Loc: Yorkshire UK
Quote:
Suppose you need to investigate the impedance values of your module and aerial

Sad though you well know me to be, I am a member of the Caravan club and, each month, the magazine passes briefly through my house and, I'm absolutely sure that somewhere it had an article on how to connect a home music centre (FM not DAB) to a car radio aerial, making exactly that point: The impedances didn't match, for the life of me I can't remember whether you need a resistor or capacitor or martian to correct this problem.
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#254692 - 21/04/2005 18:42 Re: DAB unit [Re: andym]
boxer
pooh-bah

Registered: 16/04/2002
Posts: 2011
Loc: Yorkshire UK
here's that boy, ready to do a bit of splicing now!
Sorry the spats and highly polished boots are missing!
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#254693 - 21/04/2005 18:55 Re: DAB unit [Re: boxer]
andym
carpal tunnel

Registered: 17/01/2002
Posts: 3996
Loc: Manchester UK
Is that really you? It's hard to tell at that size.
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Andy M

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#254694 - 21/04/2005 19:03 Re: DAB unit [Re: boxer]
andym
carpal tunnel

Registered: 17/01/2002
Posts: 3996
Loc: Manchester UK
Isn't it a resistor? It's supposed to match the impedance of the radio I think.
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Andy M

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#254695 - 21/04/2005 19:08 Re: DAB unit [Re: andym]
boxer
pooh-bah

Registered: 16/04/2002
Posts: 2011
Loc: Yorkshire UK
Quote:

Is that really you? It's hard to tell at that size.

Yep, why do you think I kept it that small!!!!
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#254696 - 21/04/2005 19:58 Re: DAB unit [Re: andym]
andy
carpal tunnel

Registered: 10/06/1999
Posts: 5916
Loc: Wivenhoe, Essex, UK
Quote:
Suppose you need to investigate the impedance values of your module and aerial.


The DAB car aerials seem to typically be 75 ohms impedance. How would I go about measuring the impedance of the aerial on the tuner ?
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#254697 - 22/04/2005 08:11 Re: DAB unit [Re: andy]
andym
carpal tunnel

Registered: 17/01/2002
Posts: 3996
Loc: Manchester UK
I would imagine it would be something you'd need to try and look up on the module.
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Andy M

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#254698 - 05/09/2006 10:34 Re: DAB unit [Re: thinfourth2]
jarob10
enthusiast

Registered: 07/01/2002
Posts: 274
Loc: Stockport, UK
Well, I took the plunge and bought a revo off ebay recently.

After installing, DAB reception was poor/non existent.

Upgrading the aerial had little effect, eventually I sent the unit back to revo for repair. They were great, and repaired the unit FOC (even though it was an ebay purchase).

The unit now works perfectly, and I would highly recommend.

Its a good work-around for the broken FM seek feature in 2.0 final also


Edited by jarob10 (05/09/2006 10:35)
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