radio aerial

Discussion in 'Motorhome Chat' started by Jaws, Jul 21, 2013.

  1. Jaws

    Jaws Funster Life Member

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    I think I asked this before.. but do not remember getting a reply ?

    Does anyone know where I can buy a decent car radio aerial from ?

    I want something that has a mast at least 1.2 metres long, that costs a bit more than the crap you get in most places and can be side mounted ( as in the side of the wing.. )

    I have been trying to locate something half decent for 18 months now and so far can only report total failure and abject frustration
     
  2. chaser

    chaser Funster

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    Rubbish radio in Peugeot based mh, got it out and shoved a piece of wire in instead of the aerial and layed it on the van floor, perfect, so now working out where I can thread it through the dash. I did connect it to the van tv aerial but it was no better than the bit of wire on its own but think that's where I will put it for perminent once I can decide where to route it
     
  3. Jaws

    Jaws Funster Life Member

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    Sorry, but I want a decent aerial.. I have all manner of odds and sods of stuff.. What is really nuts is that I have to hand a range of antenna that will work at frequencies from 3.5 meg to 1.2 gig, with a range of suitable mounts for them too.. But of course these are trans-ceiver types and all based on 50 Ohm impedance systems, not the 300 to 600 ohn a car radio likes to 'see'
    I can build and design an antenna for any frequency including standard uk vhf broadcast ones, but the coax used to match the system is really weird ( think I have mentioned it before ( and the maths are shot to hell because of it.. ) I could build something and put an ATU in the line but that would make it useless for AM reception :Sad:

    A decent quality antenna should not be THAT hard to find.. But it seems it actually is !! :Doh:
     
  4. cbrookson

    cbrookson Funster

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    Something like this ? Not cheap .............. has an amplifier built in ....

    Cheers

    Just noticed it is too short for you!
     
    Last edited: Jul 21, 2013
  5. Jaws

    Jaws Funster Life Member

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    Well I would settle for a shorter mast from those people as the amp would compensate but sadly it is the sort of mount that needs a horizontal surface ( or at least vaguely horizontal ! ) to put it through.. I really need something that can mount on the side of a wing
     
  6. poppys

    poppys Read Only Funster

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    Im keeping eye on this topic as I also would like to find a decent aerial to replace the standard stubby Peugeot Boxer one that I have.Iknow the standard radio is not the best but I think the aerial is the weak link.
     
  7. cbrookson

    cbrookson Funster

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    The only alternative (large and expensive) is a marine one with stainless steel mount!

    Something like this! They do hefty stainless steel mounts for boats! You can buy them in the UK.

    Cheers
     
  8. G8WVW

    G8WVW Read Only Funster

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    www.ebay.co.uk/itm/400508236748

    www.ebay.co.uk/itm/290656098608

    Cut the whip to 75cm. Don't worry about the cable being 50 ohm and not 75; won't make a scrap of difference. Note there is no plug on the cable. Suggest fitting BNC then BNC to radio adaptor.

    Cheers.
     
  9. Jaws

    Jaws Funster Life Member

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    Dunno about buy them.. I can sell you some if you like !! Used to design and build them !! :Wink:

    I am trying to get the best from the radio.. I have taken a couple apart to check and they both had components in the pye tank that indicated an impedance of ABOUT 400ohms ( crappy coils and surface mount stuff makes it kinda hard to figure it out exactly )

    Having said that it would proly be fine using 50 or 75 ohm for broadcast FM reception, but long and medium wave would suffer terribly..

    Having said all that I might well end up doing something like that.. Got some philips plugs kicking around from the good old bad old days so maybe a bit of experimentation is the way forward :thumb:
     
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  10. G8WVW

    G8WVW Read Only Funster

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    Impedance of a 75cm whip at 900KHz will be a tiny fraction of an ohm ... 0.001-Ohm or something. Coax impedance becomes irrelevant. Difficult to get any decent signal mobile on MW/LW these days; just so much electrical interference about. Have you thought about DAB?
     
  11. BwB

    BwB Funster Life Member

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  12. Jaws

    Jaws Funster Life Member

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    And now you have hit my problem firmly on the head and perhaps I should have explained first off

    MW is stonking in the van.. I get really good reception with very impressive range.. ( radio unit does not have lw sadly ), but FM ! Absolute joke.

    To give you an idea..

    I am 19 miles ( as the crow flies ) from Tacolneston which is a biggy, pushing something like 250kW out on radio four

    Any other vehicle radio gets virtually a DC signal from it here.

    In the van ? Full of white noise and fading

    I have tried two different radios and several antenna .. always the same result

    I have tried all the usual stuff, double checking all joints and 100% making sure all the paint is off inside the wing and I have a solid earth connection

    The ONLY time I got a decent signal was when I borrowed an aerial off a friend .. I think it was an old Hirschman

    I am completely flumoxed now, which is why I am gonna take your advice and try a transceiver type base and stick to see what that does :Smile:



    That would certainly fit but is just too short again.. But thank you for looking and trying :thumb:
     
  13. Jaws

    Jaws Funster Life Member

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    Right... I have been playing.. a lot !

    I have tried all sorts of configurations, and yes, tried as G8 suggested using a completely separate installation with new cable, steel metre long whip and a new mount..

    No matter WHAT I do the reception barely improves over what I already have..

    I can therefore only conclude the radio is deaf.. I know the OEM fitted Pug did not have what you could call a lively front end, but the one fitted ( A halfrauds special with built in DVD player ) really is mutton geoff !!

    Next step will be to try another radio unit from a known good installation..

    And if that is no different ?

    I will have to conclude the bloody van is not a van but some sort of Faraday Cage !!!!!!!!!!!!
     
  14. Mr Ed

    Mr Ed Funster

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    Come on John.please tell me how you sorted this......Martin
     
  15. sdc77

    sdc77 Funster

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    Be interested to see where this goes. You see lots of French vans with aerials mounted on the front wing. We get a completely sh1te signal from our radio. We currently have a screen mounted aerial that's worthless. I can't imagine an aerial can be mounted through that plastic panel ........ or can it? Or can we route a cable to the tv aerial?
     
  16. Pilote87

    Pilote87 Funster

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    That may be because the French are heavily in to CB radio and, when on tour, travel in twos threes and mores.

    J
     
  17. Lenny HB

    Lenny HB Funster

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    Didn't know you had a Carthago :D They claim their vans are a Faraday Cage.:LOL:
     
  18. scotjimland

    scotjimland Funster Life Member

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    it was drastic... he sorted it by changing motorhomes.. :)
     
  19. tonyidle

    tonyidle Funster

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    Car radio expects 75ohm or DAB 50ohm. The 'traditional' car aerial has a capacitor in the co-ax near the radio plug to, and I use the term loosely, resonate the aerial on the MW/LW bands.
     
  20. tonyidle

    tonyidle Funster

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    Also found this on another Forum. I've no reason to assume that it is accurate or inaccurate but it aligns with what I've always understood:

    "Car radios are actually two radios in one (AM-FM). The whip antenna has a characteristic impedance of about 36 ohms at the 1/4 wave resonant frequency (FM section). The whip is usually extended to about 31" to 34" to raise its impedance to around 75 ohms. The input impedance of the radio's FM section is usually 75 ohms, so any length of 75 ohm cable may be used to connect the whip antenna.

    This whip, however, is far too short to resonate at the AM section's 1/4 wave frequency(hundreds of feet long) so the radio uses special circuitry to match impedance to the short whip. Older radios added a trimmer capacitor with a low capacitance RF cable (any impedance) to fine tune the short whip thus matching the unknown impedance to the AM section's input. Since the length of the RF cable affects the matching network, the trimmer cap had to be retuned to compensate for any changes to the RF cable or its length.

    In recent years newer radios now incorporate an automatic tuning network that matches impedance variations of the antenna system to the radio.

    Car radios have excellent sensitivity. If you plan to use the radio to listen to weak AM stations inside a building using a whip or random length of wire as an antenna, you will likely get disappointing results. Whip antenna's are highly vulnerable to localize interference. A coil loop or ferrite rod antenna will provide far better results inside. Unfortunately, it will not work as well for the FM section."

    Read more: http://darkliferadio.proboards.com/thread/401/car-radio-coax-impedance#ixzz3yOcEQuqM
     
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