Need 5v masthead amp power supply

[2pods]

I've asked this on a couple of forums, but I should have tried here first,
seeing as I read the ng everyday.

Our old Freeview tv was connected via the aforesaid masthead amp and a
power supply of unknown power behind the TV stand. Everything in Freeview
land was good.

Then came DSO (I'm in PA19, but I'm also in a bad reception dip) and my
channels had disappeared. I reset the TV, tuned, and got nothing. So I
assumed it was the power supply, took it out and dumped it without looking
at it....I know, I was an idiot. However I knew the tv had a 5v power
option. Stuck this on, and every channel turned up OK.

Roll on to yesterday, when the new tv arrives, and remembering I needed the
inbuilt 5v for Freeview to work, discovered there wasn't this option in the
new tv's setup menu.

I've had a look for this power supply on line (I doubt there will be
anything locally) but all I can find are 12v supplies. Would this fry the
masthead amp or the tv, or even both ?

Yours, confused of Inverclyde

[Ian]

"2pods" <mun...@munged.net> wrote in message
news:4ea7eafc$0$2972$fa0f...@news.zen.co.uk...

5V supplies are available. For example:

http://uk.farnell.com/ideal-power/25hk-cp13-a05/psu-desktop-plug-in-12-5w-5v/dp/1354813

http://uk.farnell.com/ideal-power/25hk-cp13-a05/psu-desktop-plug-in-12-5w-5v/dp/1354813

I assume that the 5V is to power only the masthead amp. Presumably there is
a box connected between the aerial and the television into which the 5V
supply connects.
I suspect that a 12V supply would not be appreciated by the masthead amp.
What make and model is your new television? I'm wondering if it has a
(hidden) 5V option.

Hope this is of some help.
Regards, Ian.



--- Posted via news://freenews.netfront.net/ - Complaints to ne...@netfront.net ---

[2pods]

"Ian" <nos...@nospam-please-I-am-veggie.net> wrote in message
news:j88qo9$1lpm$1...@adenine.netfront.net...

Thanks Ian.
The only box I know of is up at the mast head.
Would that would be the amplifier itself ?

The TV is a Samsung UE40D6100.

I had the tv plugged straight into the aerial cable with the 5v on.

Peter

[2pods]

"Ian" <nos...@nospam-please-I-am-veggie.net> wrote in message
news:j88qo9$1lpm$1...@adenine.netfront.net...

I see what you mean by another box now. I was looking for something along
the lines of the self contained 12v jobs with the coax connectors built in,
as I haven't got anything like that.

I could kick myself for not noting the specs of the old psu.

Peter

[Bill Wright]

Masthead amps made since about 1985 will either run from 12V only or
from 5 to 12V (some newer types), so you need a normal 12V PSU. I've
never heard of a masthead amp that would only run on 5V.

Just get any old 12V PSU from CPC or somewhere. It's most unlikely that
you have an amp that needs more current than any of the PSUs on the
market can provide.

Bill

[2pods]

"Bill Wright" <bi...@invalid.com> wrote in message
news:j88tpv$gjh$1...@speranza.aioe.org...

Thanks Bill.
Just to be clear, I need a box with 12v power with coax connectors that
plugs in ?

I just want to make sure that if it fries anything, if will be the amp and
not the tv. The other thing I wondered about was why was the 5v, rather
than a 12v, or any external voltage at all, built in to the old tv ?
It wasn't that old. It was a three year old LG37 lcd.

You can tell it's computers and not tellly with me, can't you ? ;-)
Thanks
Peter

[Peter Duncanson]

I think someone explain this sometime in the last few years. If my
memory is working properly (no guarantees, folks!) many TV users in many
parts of the world use set-top aerials ("rabbit ears" type, for
instance) which have a built-in amplifier and need power.

>You can tell it's computers and not tellly with me, can't you ? ;-)
>Thanks
>Peter

--
Peter Duncanson
(in uk.tech.digital-tv)

[2pods]

Peter Duncanson" <ma...@peterduncanson.net> wrote in message
news:484ga7tq1gnmnbbec...@4ax.com...

Ah! I begin to see.
Thanks,
Peter

[R. Mark Clayton]

"2pods" <mun...@munged.net> wrote in message

news:4ea805eb$0$2485$db0f...@news.zen.co.uk...

Never had a TV with a built in PSU for a mast head amp.

The down down lead side should be isolated from the PSU by a capacitor, this
would be inside the specific product or you could insert one yourself.

If you put too many volts into a 5V amp it may fry or overdrive. Too few
into a 12V amp it may give low gain or not work at all.

12V is a very common voltage for DC supplies as it is the same as cars and
many early devices.

5V is also very common as it was the TTL and main PC rail votlage and the
now sort of standardised USB power supplies.

You can buy variable voltage power supplies from Maplin, CPC, etc.

[Bill Wright]

2pods wrote:

> Thanks Bill.
> Just to be clear, I need a box with 12v power with coax connectors that
> plugs in ?

The PSU will have two sockets (either belling or 'f' types). One is
labelled 'TV set' (or whatever) and the other is labelled 'aerial' (or
whatever). The power will only go to the one labelled 'aerial'.

>
> I just want to make sure that if it fries anything, if will be the amp
> and not the tv.

Over the years I've seen the results of 12VDC being shoved up a telly's
unwilling spout several times, but I've never known it do damage. Odd
really...

The other thing I wondered about was why was the 5v,
> rather than a 12v, or any external voltage at all, built in to the old tv ?
> It wasn't that old. It was a three year old LG37 lcd.

I can only assume that somewhere in the world there are powered set-top
aerials in use that work from either batteries or a 5V line power
voltage. Don't know though. The masthead amp industry responded by
making their products work from 5V to 12V (or maybe they always had and
it was just acknowledged.) Andy Wade will be along in a minute to
provide chapter and verse.

>
> You can tell it's computers and not tellly with me, can't you ? ;-)

Yes, now could you tell how to format my floppies?

Bill

[Peter Duncanson]

I've just explored. My TV sets can't power aerial amps. But both my
Humax Freeview boxes, a PVR 9200T and a HDR-Fox T2, have a setting in
the menu for putting 5v on the incoming aerial cable.

[2pods]

> I can only assume that somewhere in the world there are powered set-top
> aerials in use that work from either batteries or a 5V line power
> voltage. Don't know though. The masthead amp industry responded by
> making their products work from 5V to 12V (or maybe they always had and
> it was just acknowledged.) Andy Wade will be along in a minute to
> provide chapter and verse.
>
>>
>> You can tell it's computers and not tellly with me, can't you ? ;-)
> Yes, now could you tell how to format my floppies?
>
> Bill

Carefully Bill. Carefully ;-)

Peter

[Ian Field]

"R. Mark Clayton" <nospam...@btinternet.com> wrote in message
news:NsydnV8R_voEoTXT...@bt.com...

Possibly one of the easier to obtain possibilities, many computer shops will
stock them or one can be rescued from a retired USB hub.

Bear in mind they're invariably SMPSU type, so it may be neccessary to loop
the output lead through one or two ferrite collars.

[Bill Wright]

Did I mention that my hard drive hasn't worked since 1988?

Bill

[Bill Wright]

Ian Field wrote:

> Possibly one of the easier to obtain possibilities, many computer shops will
> stock them or one can be rescued from a retired USB hub.
>
> Bear in mind they're invariably SMPSU type, so it may be neccessary to loop
> the output lead through one or two ferrite collars.
>
>

But a proper masthead amp PSU includes the components for getting the DC
into the coax without disturbing the RF path.

Bill

[Brian Gaff]

Erm, well don't try to get a new hard drive as the factories are all under
water in you know where.
Brian

--
Brian Gaff....Note, this account does not accept Bcc: email.
graphics are great, but the blind can't hear them
Email: bri...@blueyonder.co.uk
______________________________________________________________________________________________________________

"Bill Wright" <bi...@invalid.com> wrote in message

news:j8a43c$r58$1...@speranza.aioe.org...

[Rick]

"Bill Wright" <bi...@invalid.com> wrote in message

news:j8a43c$r58$1...@speranza.aioe.org...

Yes, whatever did happen to Libido, did they eventually get swallowed up by
Western Digital?

[AnthonyL]

On Thu, 27 Oct 2011 00:11:34 +0100, Bill Wright <bi...@invalid.com>
wrote:

>2pods wrote:
>>>>
>>>> You can tell it's computers and not tellly with me, can't you ? ;-)
>>> Yes, now could you tell how to format my floppies?
>>>
>>> Bill
>>
>> Carefully Bill. Carefully ;-)
>>
>> Peter
>Did I mention that my hard drive hasn't worked since 1988?
>

Would you like me to put you on some mailing lists that could help you
out there?


--
AnthonyL

[2pods]

"Bill Wright" <bi...@invalid.com> wrote in message

news:j89ehb$373$1...@speranza.aioe.org...

Well, I ordered a 12v Antiference job, which has done the trick. As long as
it doesn't fry the amp, I'll be laughing.

Peter

[R. Mark Clayton]

"Bill Wright" <bi...@invalid.com> wrote in message

news:j8a4qd$t4l$2...@speranza.aioe.org...

You mean a capacitor?

>
> Bill

[Bill Wright]

2pods wrote:


> Well, I ordered a 12v Antiference job, which has done the trick. As long
> as it doesn't fry the amp, I'll be laughing.

It won't fry yer chuffin' amp. But just in case it does let us know.
Then we'll be laughing...

Actually, I bet you deal with the GBP just like I do. Now promise me
that if the amp dies in 2022 you won't come back and say, "I knew you
were wrong!"

Bill

[Bill Wright]

I thought you were clued up about these things.

It needs a capacitor between the RF input and output so the DC doesn't
go to the RF output, and a choke so the RF doesn't leak into the actual
PSU, and a second capacitor to help the choke minimise any RF hash from
the PSU.

Here's one I made earlier
http://dl.dropbox.com/u/11023364/line%20power%20injector%201.jpg

Bill

[2pods]

"Bill Wright" <bi...@invalid.com> wrote in message

news:j8ec4t$t9q$4...@speranza.aioe.org...

:-)

Incidentally, I think I know what's wrong with your hard drive Bill. Someone
has had the platters out of it :-)

http://dl.dropbox.com/u/11023364/line%20power%20injector%201.jpg

Peter

[Graham.]

Have you noticed all the hard drives pictured on ebay have their tops
missing and the platters and heads are exposed to the elements?


--

Graham.

%Profound_observation%

[Ian Field]

"Bill Wright" <bi...@invalid.com> wrote in message

news:j8ecru$1kq$1...@speranza.aioe.org...

> R. Mark Clayton wrote:
>> "Bill Wright" <bi...@invalid.com> wrote in message
>> news:j8a4qd$t4l$2...@speranza.aioe.org...
>>> Ian Field wrote:
>>>
>>>> Possibly one of the easier to obtain possibilities, many computer shops
>>>> will stock them or one can be rescued from a retired USB hub.
>>>>
>>>> Bear in mind they're invariably SMPSU type, so it may be neccessary to
>>>> loop the output lead through one or two ferrite collars.
>>> But a proper masthead amp PSU includes the components for getting the DC
>>> into the coax without disturbing the RF path.
>>
>> You mean a capacitor?
>
> I thought you were clued up about these things.
>
> It needs a capacitor between the RF input and output so the DC doesn't go
> to the RF output, and a choke so the RF doesn't leak into the actual PSU,
> and a second capacitor to help the choke minimise any RF hash from the
> PSU.

Err............won't the first capacitor block the power on coax that is the
whole point of the combiner box?

[Graham.]

On 28/10/2011 21:55, Ian Field wrote:
> "Bill Wright"<bi...@invalid.com> wrote in message
> news:j8ecru$1kq$1...@speranza.aioe.org...
>> R. Mark Clayton wrote:
>>> "Bill Wright"<bi...@invalid.com> wrote in message
>>> news:j8a4qd$t4l$2...@speranza.aioe.org...
>>>> Ian Field wrote:
>>>>
>>>>> Possibly one of the easier to obtain possibilities, many computer shops
>>>>> will stock them or one can be rescued from a retired USB hub.
>>>>>
>>>>> Bear in mind they're invariably SMPSU type, so it may be neccessary to
>>>>> loop the output lead through one or two ferrite collars.
>>>> But a proper masthead amp PSU includes the components for getting the DC
>>>> into the coax without disturbing the RF path.
>>>
>>> You mean a capacitor?
>>
>> I thought you were clued up about these things.
>>
>> It needs a capacitor between the RF input and output so the DC doesn't go
>> to the RF output, and a choke so the RF doesn't leak into the actual PSU,
>> and a second capacitor to help the choke minimise any RF hash from the
>> PSU.
>
>
> Err............won't the first capacitor block the power on coax that is the
> whole point of the combiner box?

No. Look the picture.
The first capacitor is on the right, coupling the inners of the two RF
connectors together.
The masthead connects to the top connector.
Now do you understand?

--

Graham.

%Profound_observation%

[Graham.]

And it's not a combiner box unless you mean it combines DC with RF.
That is its only purpose.

--

Graham.

%Profound_observation%

[Bill Wright]

Graham. wrote:
> And it's not a combiner box unless you mean it combines DC with RF.
> That is its only purpose.
>

The background to this is that we took over a very large system on an
estate of flats and terraced houses. The system was based on 24V DC line
power. We had no drawings or plans, and there was no quick way of
finding out what was connected to what. The layout of the buildings was
higgledy-piggledy and as we were to discover the system design was even
more so. Yet there was urgency because some areas had little or no TV
reception. Ideally we would have changed the 24V DC for 55V AC, because
DC line power is very prone to damage by direct or indirect lightning
strike. That just wasn't possible though because the operation of
locating and replacing every line-powered amp would have taken far too
long. As an interim measure, while we gradually built up a full drawing
of the system, we decided to continue with 24VDC line power, but convert
it to 12V DC at each new repeater. The reason for this was that 24V DC
equipment is stupidly expensive due to being unusual. It's one thing to
buy one amp to replace a broken one, but you wouldn't want to buy 50.
And most of the amps needed to be replaced. See
http://dl.dropbox.com/u/11023364/1.jpg
http://dl.dropbox.com/u/11023364/2.jpg
That made you cough didn't it? I have 30 more pictures like that.
Anyway, good, solid, reliable, cheap 12V DC amps were readily available
by dint of stripping out the mains PSUs from certain commonly available
types. The 24/12 converters had overvoltage protection.
All this needed a lot of line power injectors, and the ones we tried
were shite. Unreliable as hell. In desperation I made a run of 20, like
the one in the pic, and they worked with no problems.
Then we discovered a line power injector made by Spaun that was
reliable. I ran ten of them at twice the rated current for a week just
to prove it. At the end of the week those electrons were still going
into and out of bits of coax without problems and the two 24V headlamp
bulbs were still alight! So I happily discontinued the DIY.
Here's a 24/12 board. This one passes the 24V DC down the line to the
next repeater.
http://dl.dropbox.com/u/11023364/Spaun%3B%20DC%20out.JPG

Although we still have work to do on that system the crisis is long
past, and it now seems unlikely that the Director of Housing's head will
be displayed on a stake at the entrance to the estate.

The system seems to be working well, and has survived several lightning
storms.

Bill

[Graham.]

Fascinating stuff Bill, and I trust you have rebuked Les Wallen for his
pretentious use of the "A" word.




--

Graham.

%Profound_observation%

[Bill Wright]

Graham. wrote:

> Fascinating stuff Bill, and I trust you have rebuked Les Wallen for his
> pretentious use of the "A" word.

I decided to let him off because the converters are so very good.
Highly recommended. The output is remarkably clean.

Bill

[R. Mark Clayton]

"Bill Wright" <bi...@invalid.com> wrote in message

news:j8ecru$1kq$1...@speranza.aioe.org...

> R. Mark Clayton wrote:
>> "Bill Wright" <bi...@invalid.com> wrote in message
>> news:j8a4qd$t4l$2...@speranza.aioe.org...
>>> Ian Field wrote:
>>>
>>>> Possibly one of the easier to obtain possibilities, many computer shops
>>>> will stock them or one can be rescued from a retired USB hub.
>>>>
>>>> Bear in mind they're invariably SMPSU type, so it may be neccessary to
>>>> loop the output lead through one or two ferrite collars.
>>> But a proper masthead amp PSU includes the components for getting the DC
>>> into the coax without disturbing the RF path.
>>
>> You mean a capacitor?
>
> I thought you were clued up about these things.
>
> It needs a capacitor between the RF input and output so the DC doesn't go
> to the RF output,

Yes.

> and a choke so the RF doesn't leak into the actual PSU

Who cares? RF in the mains is unlikely to make it through the PSU.

> , and a second capacitor to help the choke minimise any RF hash from the
> PSU.

Well I was sort of assuming a regulated PSU, but if all you have is a
transformer and a bridge rectifier then OK you might just need one.

I am not Earl Muntz, but I can see you have a surplus component or two in
your circuit: -

http://www.national.com/rap/Story/0,1562,17,00.html

with thanks to Bob Pease RIP

>
> Here's one I made earlier
> http://dl.dropbox.com/u/11023364/line%20power%20injector%201.jpg

Fairly neat.

>
> Bill
>

[Bill Wright]

R. Mark Clayton wrote:

>>> You mean a capacitor?
>> I thought you were clued up about these things.
>>
>> It needs a capacitor between the RF input and output so the DC doesn't go
>> to the RF output,
>
> Yes.
>
>> and a choke so the RF doesn't leak into the actual PSU
>
> Who cares? RF in the mains is unlikely to make it through the PSU.

It would cause through-loss on the RF path, and there would also be an
impedance mismatch within the unit so the VSWR would be poor and there
would be standing waves on the RF path.

>
>> , and a second capacitor to help the choke minimise any RF hash from the
>> PSU.
>
> Well I was sort of assuming a regulated PSU, but if all you have is a
> transformer and a bridge rectifier then OK you might just need one.

The PSU in our case was regulated and I could detect no RF to speak of
on the output, but even so, if you look at virtually any TV amplifier
the psu will feed to the RF part via a feed-thro' cap, and the psu will
be in a screened compartment seperate to the RF part.

>
> I am not Earl Muntz, but I can see you have a surplus component or two in
> your circuit: -
>
> http://www.national.com/rap/Story/0,1562,17,00.html

What a cowboy! Making tellys that would disappoint people.

>> Here's one I made earlier
>> http://dl.dropbox.com/u/11023364/line%20power%20injector%201.jpg
>
> Fairly neat.

Well, I'm not a professional. Soldering is not a familiar occupation.

Bill

[Ian Jackson]

In message <j8i373$hvv$1...@speranza.aioe.org>, Bill Wright
<bi...@invalid.com> writes

There's a lot more to the design and construction of a line power
inserter/taker-offer than meets the inexperienced eye - especially if
has to work over the full VHF and UHF range (and even beyond).
--
Ian

[Bill Wright]

Ian Jackson wrote:

> There's a lot more to the design and construction of a line power
> inserter/taker-offer than meets the inexperienced eye - especially if
> has to work over the full VHF and UHF range (and even beyond).

Our home made ones had negligible through-loss and mismatch across the
UHF TV band. Didn't check them otherwise. I think it makes a big
difference using a metal (as opposed to plastic) box.

Bill

[fred]

In article <j8i373$hvv$1...@speranza.aioe.org>, Bill Wright
<bi...@invalid.com> writes

>R. Mark Clayton wrote:
>
>>>> You mean a capacitor?
>>> I thought you were clued up about these things.
>>>
>>> It needs a capacitor between the RF input and output so the DC doesn't go
>>> to the RF output,
>>
>> Yes.
>>
>>> and a choke so the RF doesn't leak into the actual PSU
>>
>> Who cares? RF in the mains is unlikely to make it through the PSU.

>It would cause through-loss on the RF path, and there would also be an
>impedance mismatch within the unit so the VSWR would be poor and there
>would be standing waves on the RF path.
>

You're in a generous mood today ;-)

If the supply was a perfect voltage source it would be an AC short
circuit and kill the signal completely, but at UHF of course nothing is
a perfect anything. I wouldn't expect much signal to be left though once
it had been loaded up by the supply's o/p cap.
--
fred
time for a new sig I think . . .

[Ian Jackson]

In message <j8jl5m$f54$3...@speranza.aioe.org>, Bill Wright
<bi...@invalid.com> writes

Like young Dilbert, you've obviously got "The Knack"!

Actually, power inserter/extractor circuits for TV preamps isn't too
exacting. Those for cable TV - which may have to cover 5 to 1000MHz, and
carry up to 15A - can be a bit more taxing.
--
Ian

[Bill Wright]

Ian Jackson wrote:

>
> Actually, power inserter/extractor circuits for TV preamps isn't too
> exacting. Those for cable TV - which may have to cover 5 to 1000MHz, and
> carry up to 15A - can be a bit more taxing.

I would have thought the coax would be a bit hefty as well, to carry 15A
without wasting energy generating heat. CT233?

Those things I made used 7A chokes and we used them at about 3A max.
There wouldn't be more than about 1.5A on any one trunk cable though.

Actually that was another thing: splitters. The only one I could find
that was any good was the Labgear CM9025. Long obsolete but as it
happened I bought a lot about 20 yrs ago for bugger all* and still had
quite a few. When they ran out I was stuck and contemplated DIY but then
found that Spaun had a good product.

*Pound each for various taps, 9025s, 9026s, and 9027 LPIs. The latter I
only had a few of, alas.

Bill

[Terry Casey]

In article <j8k067$doq$1...@speranza.aioe.org>, bi...@invalid.com says...

>
> Ian Jackson wrote:
>
> >
> > Actually, power inserter/extractor circuits for TV preamps isn't too
> > exacting. Those for cable TV - which may have to cover 5 to 1000MHz, and
> > carry up to 15A - can be a bit more taxing.
>
> I would have thought the coax would be a bit hefty as well, to carry 15A
> without wasting energy generating heat. CT233?
>

The entire 15A wouldn't usually flow in one direction.

However, the cables I was most familiar with (CommScope QR540 and QR860)
are fairly hefty! (The numbers indicate the diameter of the outer
conductor as the decimal fraction of an inch, thus QR540 has an outer
conductor diameter of 0.540" 13.72mm. For the QR860 the figures are
0.860" 21.84mm.)

Loss @ 865MHz for QR540 is nominal (max) 6.23 (6.56) dB/100m
Loss @ 865MHz for QR860 is nominal (max) 4.10 (4.36) dB/100m

Loop resistance for QR540 is 0.528 ohms/100m
For QR860 it is 0.237 ohms/100m

This gives a voltage drop @ 15A QR540 of 7.92V/100m (QR540)
3.555V/100m (QR860)

On the build I am familiar with, QR540 was used for the majority of
trunk cables. However, a power inserter might often be found on one leg
of a three-way splitter, thus splitting the available 15A (assuming all
of it was required) in four different directions, so ~2V/100m might be a
more realistic figure.

Brief data I've found fot CT233 suggests a loss ~50% greater than QR540
and a loop resistance of ~1.1 ohms/100m.

--

Terry