DIY DAB Car Aerial
Graham
they are rather expensive for what they are (quarter wave external rod
mounted on body or a half wave dipole that sticks on the inside of the
glass). The VHF/MW/LW socket is separate on this radio (understandably) so I
am going to connect that the existing aerial in the usual way and as
this is going to be fitted to my campervan where a second aerial is easy to
fit and will not look out of place, I am thinking of using an old Pye
Finglass PMR aerial I used to use for 145MHz. The metal rod is around 19
inches long at the moment, so a bit long for 200MHz, but its easy to cut it
to resonance if needed (somewhere around 16 inches I seems to remember). I
have used this aerial base for transmitting a watt or two at 200MHz in the
past and it resonated up nicely. Anyway the base and coax are designed for
use up to UHF, so should be fine.
I notice some of the DAB car aerials have a powered box along the coax and
presume this is a splitter as two flying leads are coming out of it. This
must be a compromise of trying to get 200MHZ and Band II (not to mention
MW/LW) working off the same element in the air. Not ideal. Handy that Band
III is double the frequency of Band II as that must help the compromise
aerial design, but I am still in favour of a separate DAB aerial, so will
give that a try and report back in a few weeks.
Now just got to find a connector to fit the DAB aerial socket on this
radio. Looks like SMA, but without the thread, so a standard SMA microwave
connector may fit. I think I have some somewhere.
Graham
Graham
"Paul Martin" <p...@zetnet.net> wrote in message
news:slrngbal...@thinkpad.nowster.org.uk...
> In article <FdudnYAgLqpUzCjV...@posted.metronet>,
> Graham wrote:
>> Finglass PMR aerial I used to use for 145MHz. The metal rod is around 19
>> inches long at the moment, so a bit long for 200MHz, but its easy to cut
>> it
>> to resonance if needed (somewhere around 16 inches I seems to remember).
>> I
>> have used this aerial base for transmitting a watt or two at 200MHz in
>> the
>> past and it resonated up nicely. Anyway the base and coax are designed
>> for
>> use up to UHF, so should be fine.
>
> the differing speed of light in copper, which ought to make it shorter.
>
Yeah, that is correct for 210MHz. The last time I used this aerial was for
transmitting on 200.250MHz and although the theory says it should be
15inches (or 13˝ taking into account velocity factor), I found 16ź inches
gave the best match from a 50 ohm output. Of course the DAB rx is designed
for 75 ohm, but all this is semantics as it will make hardly any difference
in practice for the receiver, providing the aerial length is close. If it
works well with my old 16ź inch rod, I'll not bother cutting it. I'd only do
that for a tx. Once I get the feel of how well DAB performs in the car
around here (middle of nowhere), it will be interesting to see how much I
can degrade the aerial before things get worse. As the aerial rods swap with
just an allen key, I'm tempted to swap with my old band II aerial rod and
see if that works. After all, it is a half wave.
Just done a google search for DAB ensemble frequencies and it says that UK
broadcast using ensembles between 220 and 227MHz.
http://www.radio-electronics.com/info/broadcast/dab/dab_frequencies.php
Graham
Ashley Booth
> In article <FdudnYAgLqpUzCjV...@posted.metronet>,
> Graham wrote:
> > Finglass PMR aerial I used to use for 145MHz. The metal rod is
> > around 19 inches long at the moment, so a bit long for 200MHz, but
> > its easy to cut it to resonance if needed (somewhere around 16
> > inches I seems to remember). I have used this aerial base for
> > transmitting a watt or two at 200MHz in the past and it resonated
> > up nicely. Anyway the base and coax are designed for use up to UHF,
> > so should be fine.
>
> It's around 14 inches for a quarter wave at 210MHz, not correcting for
> the differing speed of light in copper, which ought to make it
> shorter.
I wonder how fast light travels in copper?
:)
--
Ashley
Graham
"Ashley Booth" <a...@snglinks.com> wrote in message
news:MMydnbjYfeaS5SjV...@bt.com...
Bit slower than in a vacuum. About 95% I think.
Graham
"Graham" <nos...@nospam.com> wrote in message
news:38mdnaAebpPgHSjV...@posted.metronet...
Dave Liquorice
> Just done a google search for DAB ensemble frequencies and it says that
> UK broadcast using ensembles between 220 and 227MHz.
That might be dropping down to 200 or 210MHz in the not too distant
future. The VHF Shared PMSE spot frequencies on 209.0, 216.1. 216.6 and
216.8 were withdrawn at the end of 2007 "to make way for DAB".
--
Cheers
Dave.
Mark Carver
>> Bit slower than in a vacuum. About 95% I think.
>>
>>
> Ok, how fast RF travels in copper. Brain locked into RF mode.
Velocity factor ? Normally about 60-70% for 50-75ish Ohm cable at VHF/UHF ?
--
Mark
Please replace invalid and invalid with gmx and net to reply.
tony sayer
<nos...@nospam.com> scribeth thus
It travels at different speeds in different metals..
Not a lot of difference 'tho, in our aerial designer software we have a
fair old few options for different grades of Ally and stainless steel...
--
Tony Sayer
tony sayer
<p...@zetnet.net> scribeth thus
>In article <FdudnYAgLqpUzCjV...@posted.metronet>,
> Graham wrote:
>> inches long at the moment, so a bit long for 200MHz, but its easy to cut it
>> to resonance if needed (somewhere around 16 inches I seems to remember). I
>> have used this aerial base for transmitting a watt or two at 200MHz in the
>> past and it resonated up nicely. Anyway the base and coax are designed for
>> use up to UHF, so should be fine.
>
>the differing speed of light in copper, which ought to make it shorter.
>
Frequency into 300 which will give the wavelength in metres divide by
four and times it by .95 , thats good enough...
--
Tony Sayer
Graham
"Mark Carver" <mark....@invalid.invalid> wrote in message
news:6hlj9kF...@mid.individual.net...
> Graham wrote:
>
>>> Bit slower than in a vacuum. About 95% I think.
>>>
>>>
>> Ok, how fast RF travels in copper. Brain locked into RF mode.
>
> Velocity factor ? Normally about 60-70% for 50-75ish Ohm cable at VHF/UHF
> ?
We were talking about a aerial rod in free space. Aerials in the clear need
to have a velocity factor of 0.95 applied after the wavelength calculation.
Mark Carver
Yep, Ofcom's next batch of local muxes will use Ch 10B, 10C, 10 D all 213-216
ish MHz, plus a Suffolk mux on 5A (175 MHz)
Mark Carver
Sorry, yes you're quite right. When I saw copper mentioned, I had feeders
stuck in my brain !
Graham
"Mark Carver" <mark....@invalid.invalid> wrote in message
> Graham wrote:
>> "Mark Carver" <mark....@invalid.invalid> wrote in message
>> news:6hlj9kF...@mid.individual.net...
>>> Graham wrote:
>>>
>>>>> Bit slower than in a vacuum. About 95% I think.
>>>>>
>>>>>
>>>> Ok, how fast RF travels in copper. Brain locked into RF mode.
>
>>> Velocity factor ? Normally about 60-70% for 50-75ish Ohm cable at
>>> VHF/UHF ?
>>
>> We were talking about a aerial rod in free space. Aerials in the clear
>> need to have a velocity factor of 0.95 applied after the wavelength
>> calculation.
>
> Sorry, yes you're quite right. When I saw copper mentioned, I had feeders
> stuck in my brain !
Must say I read it that way first time too. Been a long while since I used
the velocity factor for coax. Only used it when designing phasing harnesses
and matching etc.Takes me back.
Graham
Graham
"Mark Carver" <mark....@invalid.invalid> wrote in message
> Dave Liquorice wrote:
>> On Wed, 27 Aug 2008 16:49:50 +0100, Graham wrote:
>>
>>> Just done a google search for DAB ensemble frequencies and it says that
>>> UK broadcast using ensembles between 220 and 227MHz.
>>
>> That might be dropping down to 200 or 210MHz in the not too distant
>> future. The VHF Shared PMSE spot frequencies on 209.0, 216.1. 216.6 and
>> 216.8 were withdrawn at the end of 2007 "to make way for DAB".
>
> Yep, Ofcom's next batch of local muxes will use Ch 10B, 10C, 10 D all
> 213-216 ish MHz, plus a Suffolk mux on 5A (175 MHz)
Oh, Suffolk. That will be me then. Hope my new DAB car radio will work that
far down? Are there still any radio mics on there :-))
I wonder if the old taxi/pmr "High band" is still in operation. That used to
extend to 175MHz as its upper band edge. I'm sure I used to work on sets up
as far as 174.775, perhaps higher.
Can't see anything in my DAB car radio destructions about what frequencies
it covers. Just mentions Band III and L band. I am not sure where L band is.
1.5GHz perhaps? Probably for the US or Eastern market and may not even be
built into my model, but says it in the loose spec they give.
Graham
Mark Carver
> Can't see anything in my DAB car radio destructions about what frequencies
> it covers. Just mentions Band III and L band. I am not sure where L band is.
> 1.5GHz perhaps? Probably for the US or Eastern market and may not even be
> built into my model, but says it in the loose spec they give.
L-Band is not used (yet) in the UK. It is used in France though. You're right,
it's about 1.4-1.5 GHz
Try this site for all you need to know and more on DAB
http://www.wohnort.org/DAB/freqs.html
Dave Plowman (News)
Graham <nos...@nospam.com> wrote:
> Just got my new DAB car radio and thinking about making my own DAB
> aerial as they are rather expensive for what they are (quarter wave
> external rod mounted on body or a half wave dipole that sticks on the
> inside of the glass). The VHF/MW/LW socket is separate on this radio
> (understandably) so I am going to connect that the existing aerial in
> the usual way and as this is going to be fitted to my campervan where a
> second aerial is easy to fit and will not look out of place,
Might as you say be ok on a camper van, but on my car after a deal of
experimenting, I ended up with one of those awfully expensive roof
mounting jobbies that does everything. Separate feeds from it for DAB and
everything else - and two RF amps too. Works a treat. The inside of the
glass thingies are useless. As is splitting a normal telescopic to feed
both.
--
*I'm planning to be spontaneous tomorrow *
Dave Plowman da...@davenoise.co.uk London SW
To e-mail, change noise into sound.
Paul Ratcliffe
> Coppers travel as fast as they like, as long as the light is blue.
Especially in North Wales, even if it isn't shining.
tony sayer
<mark....@invalid.invalid> scribeth thus
>Dave Liquorice wrote:
>> On Wed, 27 Aug 2008 16:49:50 +0100, Graham wrote:
>>
>>> Just done a google search for DAB ensemble frequencies and it says that
>>> UK broadcast using ensembles between 220 and 227MHz.
>>
>> That might be dropping down to 200 or 210MHz in the not too distant
>> future. The VHF Shared PMSE spot frequencies on 209.0, 216.1. 216.6 and
>> 216.8 were withdrawn at the end of 2007 "to make way for DAB".
>
>Yep, Ofcom's next batch of local muxes will use Ch 10B, 10C, 10 D all 213-216
>ish MHz, plus a Suffolk mux on 5A (175 MHz)
>
>
Thats if they ever get started.. From all I hear in the commercial radio
industry they wish DAB would die and go away as no one is making any
real money on it ;!...
--
Tony Sayer
tony sayer
<nos...@nospam.com> scribeth thus
>
>"Mark Carver" <mark....@invalid.invalid> wrote in message
>news:6hlpg9F...@mid.individual.net...
>> Dave Liquorice wrote:
>>> On Wed, 27 Aug 2008 16:49:50 +0100, Graham wrote:
>>>
>>>> Just done a google search for DAB ensemble frequencies and it says that
>>>> UK broadcast using ensembles between 220 and 227MHz.
>>>
>>> That might be dropping down to 200 or 210MHz in the not too distant
>>> future. The VHF Shared PMSE spot frequencies on 209.0, 216.1. 216.6 and
>>> 216.8 were withdrawn at the end of 2007 "to make way for DAB".
>>
>> Yep, Ofcom's next batch of local muxes will use Ch 10B, 10C, 10 D all
>> 213-216 ish MHz, plus a Suffolk mux on 5A (175 MHz)
>
>Oh, Suffolk. That will be me then. Hope my new DAB car radio will work that
>far down? Are there still any radio mics on there :-))
>I wonder if the old taxi/pmr "High band" is still in operation.
Yes it is, 'tho not as crowded as it once was but still in use and still
there...
>That used to
>extend to 175MHz as its upper band edge. I'm sure I used to work on sets up
>as far as 174.775, perhaps higher.
Nope just over 173 MHz..
Licence exempt radio mics are next up..
>
>Can't see anything in my DAB car radio destructions about what frequencies
>it covers. Just mentions Band III and L band. I am not sure where L band is.
>1.5GHz perhaps?
Near as dammit..
>Probably for the US or Eastern market and may not even be
>built into my model, but says it in the loose spec they give.
>
>Graham
>
>
--
Tony Sayer
Marky P
wrote:
The local DAB for Beds, Buck & Herts should've been on air by now, but
it's all 'on hold' at the moment. Bit like the builders.
Marky P.
Mark Carver
>> That might be dropping down to 200 or 210MHz in the not too distant
>> future. The VHF Shared PMSE spot frequencies on 209.0, 216.1. 216.6 and
>> 216.8 were withdrawn at the end of 2007 "to make way for DAB".
>
> What a pity most DAB receivers on sale now will need reconfiguring to
> allow that... (Most only scan the upper channels by default.)
Both of my DAB receivers (both about 5 years old) take quite a long time to
start finding muxes, that round here start at 11B and end at 12D. Therefore I
assume they are starting their scan at 174MHz/5A ?
tony sayer
<bromham_ho...@yahoo.co.uk> scribeth thus
Indeed...
--
Tony Sayer
Andy Burns
> Both of my DAB receivers (both about 5 years old) take quite a long time
> to start finding muxes, that round here start at 11B and end at 12D.
> Therefore I assume they are starting their scan at 174MHz/5A ?
Manual tuning on my Evoke3 allows from 5A=174.92MHz to 13F=239.20MHz
(and LA=1452.96MHz to LW=1490.62MHz but that's not much use in the UK)
Graham
on the 12B multiplex with only a foot of wire stuffed in the aerial socket.
No burbling and sounded perfect. It tries to get the Digital One 11D
multiplex from Cambridge, but drops out straight away. I'm in the middle of
nowhere in NW Suffolk, so surprised I got anything at all, let alone on a
bit of wire stuffed in the back.
Bill Wright
> Just got my new DAB car radio and thinking about making my own DAB aerial
> as
> they are rather expensive for what they are
I did this and it was very successful. I posted an account of the thing
somewhere or other. Basically I used a cheap Hirshman car radio aerial (the
one in the CPC book) and replaced the glass fibre whip with a length of
stiff wire, which I trimmed whilst watching the signal level. The peak was
about where you'd expect it, so I cut the glass fibre whip to that length
and stuck in in the mount. The thing works really well, and driving on
routes where the £50 Bosch DAB aerial on another van performs about the
same.
I made another one for our Paul because he was dissatisfied with the
windscreen aerial he had, and he said the home-made one was a massive
improvement.
Bill
tony sayer
<nos...@nospam.com> scribeth thus
Shouldn't be too far from Genesis Green then by the sound of it?..
--
Tony Sayer
tony sayer
<insertmybu...@f2s.com> scribeth thus
Anything...absolutly anything is better than a thro the glass
abortion;!...
--
Tony Sayer
Andy Champ
> "Graham" <nos...@nospam.com> wrote in message
> news:FdudnYAgLqpUzCjV...@posted.metronet...
>> Just got my new DAB car radio and thinking about making my own DAB aerial
>> as
>> they are rather expensive for what they are
>
> I did this and it was very successful. I posted an account of the thing
> somewhere or other. Basically I used a cheap Hirshman car radio aerial (the
> one in the CPC book) and replaced the glass fibre whip with a length of
> stiff wire, which I trimmed whilst watching the signal level. The peak was
> about where you'd expect it, so I cut the glass fibre whip to that length
> and stuck in in the mount. The thing works really well, and driving on
> routes where the £50 Bosch DAB aerial on another van performs about the
> same.
I don't suppose you'd like to tell us how long you cut it to?
Andy
Bill Wright
"Andy Champ" <no....@nospam.com> wrote in message
news:G_qdnXkQHuE_5ifV...@eclipse.net.uk...
>
> I don't suppose you'd like to tell us how long you cut it to?
Hang on a minute. I'll just go and get some steps and a tape measure.
(intermission)
It's 350mm. I found the length with the rod upright, but in fact gain seems
to drop only slightly with it angled back slightly. Gain worsened
significantly with the rod lower than about 45deg, although I didn't test
this properly from the directivity point of view.
The aerial is in the middle of a large flat steel roof -- a perfect ground
plane.
Interestingly the length of the Bosch aerial I mentioned is only 300mm.
Since this is presumably cut for the middle of the band and I cut my aerial
for best signal at 230MHz it ought to be the other way round . . .
But not to worry, they both seem to work fine.
My other conclusion having experimented with this and other DAB and FM
aerials on vehicles over a long period is that background noise can be very
significant. I've had terrible problems with noise from flat screen
displays, electronic panel meters, inverters, and mains voltage chargers for
phones etc. This has been radiated and also carried on supply lines, and
often transmitted by a totally confusing mixture of modes which at first
defies a cure. It can be instructive to park in a very screened location,
where there's only very faint reception, and turn equipment on and off. The
effects of some of these interference sources can be indistinguishable from
a weak signal or inefficient aerial, with a straightforward increase in
noise causing a worsened s/n ratio.
Bill
Dave Plowman (News)
Bill Wright <insertmybu...@f2s.com> wrote:
> My other conclusion having experimented with this and other DAB and FM
> aerials on vehicles over a long period is that background noise can be
> very significant. I've had terrible problems with noise from flat
> screen displays, electronic panel meters, inverters, and mains voltage
> chargers for phones etc. This has been radiated and also carried on
> supply lines, and often transmitted by a totally confusing mixture of
> modes which at first defies a cure. It can be instructive to park in a
> very screened location, where there's only very faint reception, and
> turn equipment on and off. The effects of some of these interference
> sources can be indistinguishable from a weak signal or inefficient
> aerial, with a straightforward increase in noise causing a worsened s/n
> ratio.
Probably granma and eggs, but running a separate feed direct from the
battery to the radio can make a big difference. As can a nice chunky
ground.
--
*TEAMWORK...means never having to take all the blame yourself *
Jerry
"Dave Plowman (News)" <da...@davenoise.co.uk> wrote in message
news:4fd785a...@davenoise.co.uk...
<snip>
>
> Probably granma and eggs, but running a separate feed direct from
> the
> battery to the radio can make a big difference. As can a nice chunky
> ground.
>
Assuming that there is a nice 'chunky' cable running from ground to
the battery, not always the case these days [1], the number of
'boy-racer' cars I've seen were the owner has installed a nice
'chunky' feed direct from the positive side of the battery and a nice
'chunky' grounding cable from audio system to the vehicles bodywork
only for there to be a ~6 mm grounding cable between body and
battery...
[1] many engines, and thus starters are earthed direct between battery
and engine block now.
--
Wikipedia: the Internet equivalent of
Hyde Park and 'speakers corner'...
Bill Wright
> battery to the radio can make a big difference. As can a nice chunky
> ground.
Yes, I'd definitely agree with that. I had a real bad problem once which
turned out to be caused by the neg supply to the radio being very thin
stuff. I realised pretty quick because when I disconnected the aerial with a
CD playing the dial light dimmed slightly!
I've taken to connecting the radio chassis to the vehicle chassis by several
different thick cables.
Re the idea of giving the radio a dedicated supply I wonder if the battery
acts as a big smoothing cap. . .
I have found chokes and caps useful on the supply line, but I can't
undertand why this isn't done adequately inside the radio.
12V fluo lights can wipe AM out completely!
Bill
Andy Champ
>
> It's 350mm. I found the length with the rod upright, but in fact gain seems
> to drop only slightly with it angled back slightly. Gain worsened
> significantly with the rod lower than about 45deg, although I didn't test
> this properly from the directivity point of view.
Thanks.
>
> The aerial is in the middle of a large flat steel roof -- a perfect ground
> plane.
Ah. I have only one large flat metal plane on my car, and I'm not going
to put an aerial in the middle of the bonnet.
Another idea bites the dust!
Andy
Bill Wright
In any case it would be too low down and the roof would screen it a bit, so
I wouldn't bother. Could you not erect some sort of mast? If the base were
to be fixed to the transmission tunnel and a good secure fixing was obtained
where the mast passed through the roof I would think a height of at least 10
metres would be feasible. Presumably you don't drive under bridges very
often?
Bill
Marky P
<da...@davenoise.co.uk> wrote:
>In article <UJGdnbjplL8AFCfV...@pipex.net>,
> Bill Wright <insertmybu...@f2s.com> wrote:
>> My other conclusion having experimented with this and other DAB and FM
>> aerials on vehicles over a long period is that background noise can be
>> very significant. I've had terrible problems with noise from flat
>> screen displays, electronic panel meters, inverters, and mains voltage
>> chargers for phones etc. This has been radiated and also carried on
>> supply lines, and often transmitted by a totally confusing mixture of
>> modes which at first defies a cure. It can be instructive to park in a
>> very screened location, where there's only very faint reception, and
>> turn equipment on and off. The effects of some of these interference
>> sources can be indistinguishable from a weak signal or inefficient
>> aerial, with a straightforward increase in noise causing a worsened s/n
>> ratio.
>
>Probably granma and eggs, but running a separate feed direct from the
>battery to the radio can make a big difference. As can a nice chunky
>ground.
That would stop my radio from turning off after 30 mins without the
engine running :-)
Marky P.
Richard Lamont
> In article <UJGdnbjplL8AFCfV...@pipex.net>,
> Bill Wright <insertmybu...@f2s.com> wrote:
>> My other conclusion having experimented with this and other DAB and FM
>> aerials on vehicles over a long period is that background noise can be
>> very significant. I've had terrible problems with noise from flat
>> screen displays, electronic panel meters, inverters, and mains voltage
>> chargers for phones etc. This has been radiated and also carried on
>> supply lines, and often transmitted by a totally confusing mixture of
>> modes which at first defies a cure. It can be instructive to park in a
>> very screened location, where there's only very faint reception, and
>> turn equipment on and off. The effects of some of these interference
>> sources can be indistinguishable from a weak signal or inefficient
>> aerial, with a straightforward increase in noise causing a worsened s/n
>> ratio.
>
> Probably granma and eggs, but running a separate feed direct from the
> battery to the radio can make a big difference. As can a nice chunky
> ground.
If you do that, make sure you double-pole fuse the radio next to the
battery. On one occasion I saw, the battery's main earth strap came
adrift, meaning that the only connection between the chassis and the
battery negative was via the aerial coax outer, PMR transceiver and the
radio's negative supply wire connected direct to the battery.
The radio's PCB didn't enjoy supplying full current to the starter motor
much, and it was fortunate that the vehicle didn't catch fire.
--
Richard Lamont http://www.lamont.me.uk/
<ric...@lamont.me.uk>
OpenPGP Key ID: 0xBD89BE41
Fingerprint: CE78 C285 1F97 0BDA 886D BA78 26D8 6C34 BD89 BE41
Andy Champ
> In any case it would be too low down and the roof would screen it a bit, so
> I wouldn't bother. Could you not erect some sort of mast? If the base were
> to be fixed to the transmission tunnel and a good secure fixing was obtained
> where the mast passed through the roof I would think a height of at least 10
> metres would be feasible. Presumably you don't drive under bridges very
> often?
I have a roof, there just isn't much metal in it. No transmission
tunnel either! I guess a short mast is the best answer, but I won't get
your ground plane.
Andy
Bill Wright
"Richard Lamont" <ric...@lamont.me.uk> wrote in message
news:48bda6c0$0$524$5a6a...@news.aaisp.net.uk...
> If you do that, make sure you double-pole fuse the radio next to the
> battery. On one occasion I saw, the battery's main earth strap came
> adrift, meaning that the only connection between the chassis and the
> battery negative was via the aerial coax outer, PMR transceiver and the
> radio's negative supply wire connected direct to the battery.
>
> The radio's PCB didn't enjoy supplying full current to the starter motor
> much, and it was fortunate that the vehicle didn't catch fire.
This is certainly food for thought. No it isn't, it's a must.
Bill
bucket
"Richard Lamont" <ric...@lamont.me.uk> wrote in message
news:48bda6c0$0$524$5a6a...@news.aaisp.net.uk...
>
> battery. On one occasion I saw, the battery's main earth strap came
> adrift, meaning that the only connection between the chassis and the
> battery negative was via the aerial coax outer, PMR transceiver and the
> radio's negative supply wire connected direct to the battery.
>
> The radio's PCB didn't enjoy supplying full current to the starter motor
> much, and it was fortunate that the vehicle didn't catch fire.
I'm always banging on about this too, but mostly falls on deaf ears. I can't
seem to get across the fuse needs to be as close to the battery as possible
as its not there to protect the equipment, but the wiring.
In the old days when I used to fit PMR taxi rigs to cars, we used to fit two
inline fuse holders next to the battery terminals, but had them back to back
so it was impossible to connect them the wrong way around. As I recall it
was the short side of the inline fuse holder that went to positive, but that
was just our convention.
Graham
Jerry
"bucket" <nos...@nospam.co.uk> wrote in message
news:8dGdnWS5Btw...@posted.metronet...
>
<snip>
>
> In the old days when I used to fit PMR taxi rigs to cars, we used to
> fit two inline fuse holders next to the battery terminals, but had
> them back to back so it was impossible to connect them the wrong way
> around. As I recall it was the short side of the inline fuse holder
> that went to positive, but that was just our convention.
>
If you mean the old glass inline fuses then surely the long end should
be connected to the battery (ve+ [1]) due to the fact that there is
less chance for the un-fused terminal becoming exposed and shorting to
the vehicles body?
[1] assuming ve- vehicle grounding
Graham
"Jerry" <INV...@INVALID.INVALID> wrote in message
news:g9lvr1$tki$1...@registered.motzarella.org...
>
> "bucket" <nos...@nospam.co.uk> wrote in message
> news:8dGdnWS5Btw...@posted.metronet...
>>
> <snip>
>>
>> In the old days when I used to fit PMR taxi rigs to cars, we used to fit
>> two inline fuse holders next to the battery terminals, but had them back
>> to back so it was impossible to connect them the wrong way around. As I
>> recall it was the short side of the inline fuse holder that went to
>> positive, but that was just our convention.
>>
>
> If you mean the old glass inline fuses
I'm not sure we are talking about the same type of fuseholer here as these
fuse holders are still currently in common use and not old, but we had a
cable tie on the batt positve end of the fuse holder so it could not poke
its conductor outside of the plastic. With the type of inline holder I am
thinking of (only type there has ever been in common use to my knowledge)
either side can reveal the contacts when undone by the plastic casing siding
down the cable unless measures are taken to prevent it happening.
Graham
Bill
<nos...@nospam.com> writes
>> If you mean the old glass inline fuses
>
>I'm not sure we are talking about the same type of fuseholer here as these
>fuse holders are still currently in common use and not old, but we had a
>cable tie on the batt positve end of the fuse holder so it could not poke
>its conductor outside of the plastic.
A cable tie!! You must have had money to burn, we used to tie a knot in
the cable and pull it tight against the back of the holder. :-)
--
Bill
Graham
"Bill" <Bi...@birchnet.demon.co.uk> wrote in message
news:MFkPlsa4...@birchnet.demon.co.uk...
This was 1977 and the cable was rather thick and good for providing enough
power for an old valve tx/rx with an inveter that needed a fair old current
to start up. The OD of the cable was a snug fit into the inline fuse holder.
Certainly good for 10 amps continuous and 20 for short periods. Tying a knot
would not be possible. In those days it was transmitters like the Pye
Vangaurd which had many valves and was so large it was mounted in the boot.
Also the Pye Cambridge that was mostly transistor, but still had valves for
the RF output and drivers. That did have a dash mound version but still very
large and drew plenty of current. Good old bomb proof gear and very well
made.
Graham
Bill
<nos...@nospam.com> writes
>This was 1977 and the cable was rather thick and good for providing enough
>power for an old valve tx/rx with an inveter that needed a fair old current
>to start up. The OD of the cable was a snug fit into the inline fuse holder.
>Certainly good for 10 amps continuous and 20 for short periods. Tying a knot
>would not be possible. In those days it was transmitters like the Pye
>Vangaurd which had many valves and was so large it was mounted in the boot.
>Also the Pye Cambridge that was mostly transistor, but still had valves for
>the RF output and drivers. That did have a dash mound version but still very
>large and drew plenty of current. Good old bomb proof gear and very well
>made.
>
>Graham
>
>
--
Bill