12v supply to masthead


John Lemay
 

Morning all

I'm looking at my requirements for a stable 13.5v supply at around 20 amps
to the top of my mast. If the supply voltage sags under load (which it
will), I anticipate that amplifier(s) "up top" will have lower power output
and poor IMD.

So, I'm thinking of running a higher voltage (say 48v) to an additional
masthead box which will contain a DC/DC converter. Prices look sensible and
it would add just around 1kg. Efficiency is approaching 90%, and it appears
to me to be a better option than running extra heavy cable up the mast.

Has anyone gone this route before, and is it successful ?

John G4ZTR


Paul G8AQA
 

Good morning John,

An alternative would be to use a power supply with a sense input and then run the 2 sense wires from the masthead back to the power supply. You would need to make sure that the power supply could make up for the cable loss.

Paul G8AQA

On 12/02/2020 07:54, John Lemay wrote:
Morning all

I'm looking at my requirements for a stable 13.5v supply at around 20 amps
to the top of my mast. If the supply voltage sags under load (which it
will), I anticipate that amplifier(s) "up top" will have lower power output
and poor IMD.

So, I'm thinking of running a higher voltage (say 48v) to an additional
masthead box which will contain a DC/DC converter. Prices look sensible and
it would add just around 1kg. Efficiency is approaching 90%, and it appears
to me to be a better option than running extra heavy cable up the mast.

Has anyone gone this route before, and is it successful ?

John G4ZTR









Andy G4JNT
 

I've seen, reported here, people running mains to the top of the masthead for this purpose.   Seems sensible enough an idea to me.



On Wed, 12 Feb 2020 at 08:01, PAUL NICKALLS via Groups.Io <paulnick=btinternet.com@groups.io> wrote:
Good morning John,

An alternative would be to use a power supply with a sense input and then run the 2 sense wires from the masthead back to the power supply. You would need to make sure that the power supply could make up for the cable loss.

Paul G8AQA

On 12/02/2020 07:54, John Lemay wrote:
Morning all

I'm looking at my requirements for a stable 13.5v supply at around 20 amps
to the top of my mast. If the supply voltage sags under load (which it
will), I anticipate that amplifier(s) "up top" will have lower power output
and poor IMD.

So, I'm thinking of running a higher voltage (say 48v) to an additional
masthead box which will contain a DC/DC converter. Prices look sensible and
it would add just around 1kg. Efficiency is approaching 90%, and it appears
to me to be a better option than running extra heavy cable up the mast.

Has anyone gone this route before, and is it successful ?

John G4ZTR









Jon Eyre
 

Can't you just mast mount the 13.5v supply. I have both my 13 and 24v power supplies mast mounted and they have been there for a couple of years with no problem, I just leave them switched on to eliminate condensation.
Jon G7TZZ


Denis Stanton G0OLX
 

John
Why not use a power supply with remote sense, the two extra wires can be relatively light compared to the main feed and these will take into account any voltage drop on load that may happen.
I have used that in the past for power equipment located some way from the supply.
Hope that helps
Denis
G0OLX

On 12 Feb 2020, at 07:55, John Lemay <john@carltonhouse.eclipse.co.uk> wrote:

Morning all

I'm looking at my requirements for a stable 13.5v supply at around 20 amps
to the top of my mast. If the supply voltage sags under load (which it
will), I anticipate that amplifier(s) "up top" will have lower power output
and poor IMD.

So, I'm thinking of running a higher voltage (say 48v) to an additional
masthead box which will contain a DC/DC converter. Prices look sensible and
it would add just around 1kg. Efficiency is approaching 90%, and it appears
to me to be a better option than running extra heavy cable up the mast.

Has anyone gone this route before, and is it successful ?

John G4ZTR







Neil Smith G4DBN
 

I have a remote Meanwell SMPS which runs on a +-55VAC feed from a big yellow site transformer. Feels a bit safer than running 240 up the mast.  The unit is rated for 90-264 VAC in and seems to behave fine with the 105V or so it gets via the feed cable.

Neil G4DBN

On 12/02/2020 09:02, Jon Eyre wrote:
Can't you just mast mount the 13.5v supply. I have both my 13 and 24v power supplies mast mounted and they have been there for a couple of years with no problem, I just leave them switched on to eliminate condensation.
Jon G7TZZ


Pete - GM4BYF
 

Run 2 lots of 10A Mains flex up the mast. Either with the lives and neutrals parallel or the conductors in each joined to each other so one cable is +ve and the other -ve.

73
Pete GM4BYF

On 12/02/20 07:54, John Lemay wrote:
Morning all

I'm looking at my requirements for a stable 13.5v supply at around 20 amps
to the top of my mast. If the supply voltage sags under load (which it
will), I anticipate that amplifier(s) "up top" will have lower power output
and poor IMD.

So, I'm thinking of running a higher voltage (say 48v) to an additional
masthead box which will contain a DC/DC converter. Prices look sensible and
it would add just around 1kg. Efficiency is approaching 90%, and it appears
to me to be a better option than running extra heavy cable up the mast.

Has anyone gone this route before, and is it successful ?

John G4ZTR





--
vry 73
Pete GM4BYF


John Quarmby
 

I feed 17V DC to the masthead and then use linear regulators - but that's only for <10A, 20A would require heavier cable (I use 4mm2), the DC-DC converter approach will reduce the size/weight of cable needed. If using a DC-DC Converter then make sure there's enough filtering on the output to suppress modulation of the TX by the power supply switching ripple, and that you don't create extra noise on receive.

73

John G3XDY

On 12/02/2020 07:54, John Lemay wrote:
Morning all

I'm looking at my requirements for a stable 13.5v supply at around 20 amps
to the top of my mast. If the supply voltage sags under load (which it
will), I anticipate that amplifier(s) "up top" will have lower power output
and poor IMD.

So, I'm thinking of running a higher voltage (say 48v) to an additional
masthead box which will contain a DC/DC converter. Prices look sensible and
it would add just around 1kg. Efficiency is approaching 90%, and it appears
to me to be a better option than running extra heavy cable up the mast.

Has anyone gone this route before, and is it successful ?

John G4ZTR






Richard GD8EXI
 

John
I run sensing wires back from my 23cms linear to its 28 volt 56 amp Mean Well power supply so as to maintain 28 volts at the linear even on speech peaks.

The Linear is not masthead but I cannot see why this would not work masthead.

Reducing the number of things that can go wrong masthead is always a good thing particularly when we get the sort of weather we have had for the last 4 days.

Richard
GD8EXI


On 12/02/2020, 08:01, "PAUL NICKALLS via Groups.Io" <paulnick@...> wrote:

  Good morning John,
 
 An alternative would be to use a power supply with a sense input and then run the 2 sense wires from the masthead back to the power supply. You would need to make sure that the power supply could make up for the cable loss.
 
 Paul G8AQA
 

On 12/02/2020 07:54, John Lemay wrote:
 
 

Morning all

I'm looking at my requirements for a stable 13.5v supply at around 20 amps
to the top of my mast. If the supply voltage sags under load (which it
will), I anticipate that amplifier(s) "up top" will have lower power output
and poor IMD.

So, I'm thinking of running a higher voltage (say 48v) to an additional
masthead box which will contain a DC/DC converter. Prices look sensible and
it would add just around 1kg. Efficiency is approaching 90%, and it appears
to me to be a better option than running extra heavy cable up the mast.

Has anyone gone this route before, and is it successful ?

John G4ZTR







 

 


Andy G4JNT
 

I have the gut-feeling that running sense wires back from the masthead could be a disaster.   Part of a feedback loop; if they pick anything up, RF, noise, groundloop effects, that will be fed into the PSU regulator with possible worse consequences than any SMPSU leakage you'd be likely to see.  ANd you can't add extra decpouipling to sense wires, that would degrade the PSU dynamic stability.

Of all the suggestions seen here so far, the one of feeding 110V AC from an isolating transformer to a standard SMPSU seems by-far the most pragmatic route.  Think I'd just use mains instead, not caring about all that safety stuff as much as others seem to, but it's going to be the same PSU at the mast head, most modern ones are rated 90 - 260V (ish) 

Of course, if you already have 50V DC at high current for other purposes in the shack, then a small modular telecomms type PSU will be a neat solution at the top, but if you have to acquire the 50V supply from scratch, not worth the effort.
 


On Wed, 12 Feb 2020 at 09:37, Richard GD8EXI <perwick@...> wrote:
John
I run sensing wires back from my 23cms linear to its 28 volt 56 amp Mean Well power supply so as to maintain 28 volts at the linear even on speech peaks.

The Linear is not masthead but I cannot see why this would not work masthead.

Reducing the number of things that can go wrong masthead is always a good thing particularly when we get the sort of weather we have had for the last 4 days.

Richard
GD8EXI


On 12/02/2020, 08:01, "PAUL NICKALLS via Groups.Io" <paulnick@...> wrote:

  Good morning John,
 
 An alternative would be to use a power supply with a sense input and then run the 2 sense wires from the masthead back to the power supply. You would need to make sure that the power supply could make up for the cable loss.
 
 Paul G8AQA
 

On 12/02/2020 07:54, John Lemay wrote:
 
 

Morning all

I'm looking at my requirements for a stable 13.5v supply at around 20 amps
to the top of my mast. If the supply voltage sags under load (which it
will), I anticipate that amplifier(s) "up top" will have lower power output
and poor IMD.

So, I'm thinking of running a higher voltage (say 48v) to an additional
masthead box which will contain a DC/DC converter. Prices look sensible and
it would add just around 1kg. Efficiency is approaching 90%, and it appears
to me to be a better option than running extra heavy cable up the mast.

Has anyone gone this route before, and is it successful ?

John G4ZTR







 

 


ian hope (2E0IJH)
 

Funny this, Ian SEK had similar thoughts, we were talking about the other day
 
Ian
2E0IJH

 
 
Sent: Wednesday, February 12, 2020 at 9:16 AM
From: "Neil Smith G4DBN" <neil@...>
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] 12v supply to masthead
I have a remote Meanwell SMPS which runs on a +-55VAC feed from a big
yellow site transformer. Feels a bit safer than running 240 up the
mast.  The unit is rated for 90-264 VAC in and seems to behave fine with
the 105V or so it gets via the feed cable.

Neil G4DBN

On 12/02/2020 09:02, Jon Eyre wrote:
> Can't you just mast mount the 13.5v supply. I have both my 13 and 24v
> power supplies mast mounted and they have been there for a couple of
> years with no problem, I just leave them switched on to eliminate
> condensation.
> Jon G7TZZ



 


Dominique Dehays
 

Hi all

I'm a bit reckless as I run 240v ac up to the tower.My current drain is too high for BT.
A pair of isolating transformers helps.
But I believe that running the psu reference wires up the tower is even more reckless:what is going to happen if a wire breaks (believe me,it will)73
Dom


Envoyé depuis mon smartphone Samsung Galaxy.


-------- Message d'origine --------
De : "ian hope (2E0IJH)" <ian@...>
Date : 12/02/2020 10:46 (GMT+01:00)
À : UKMicrowaves@groups.io
Objet : Re: [UKMicrowaves] 12v supply to masthead

Funny this, Ian SEK had similar thoughts, we were talking about the other day
 
Ian
2E0IJH
 
 
Sent: Wednesday, February 12, 2020 at 9:16 AM
From: "Neil Smith G4DBN" <neil@...>
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] 12v supply to masthead
I have a remote Meanwell SMPS which runs on a +-55VAC feed from a big
yellow site transformer. Feels a bit safer than running 240 up the
mast.  The unit is rated for 90-264 VAC in and seems to behave fine with
the 105V or so it gets via the feed cable.

Neil G4DBN

On 12/02/2020 09:02, Jon Eyre wrote:
> Can't you just mast mount the 13.5v supply. I have both my 13 and 24v
> power supplies mast mounted and they have been there for a couple of
> years with no problem, I just leave them switched on to eliminate
> condensation.
> Jon G7TZZ



 


John Worsnop
 

I run my EME system off 28V fed by 4×7m lengths of 8mm stranded car audio cable taking around 27 Amps from a Psu indoors. No sense wires. For the bands with 12V PAs I have a further 28-12V 40A meanwell switcher at the dish with a metre or so to the focus box. Works well.

73 John

On Wed, 12 Feb 2020, 09:46 ian hope (2E0IJH), <ian@...> wrote:
Funny this, Ian SEK had similar thoughts, we were talking about the other day
 
Ian
2E0IJH
 
 
Sent: Wednesday, February 12, 2020 at 9:16 AM
From: "Neil Smith G4DBN" <neil@...>
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] 12v supply to masthead
I have a remote Meanwell SMPS which runs on a +-55VAC feed from a big
yellow site transformer. Feels a bit safer than running 240 up the
mast.  The unit is rated for 90-264 VAC in and seems to behave fine with
the 105V or so it gets via the feed cable.

Neil G4DBN

On 12/02/2020 09:02, Jon Eyre wrote:
> Can't you just mast mount the 13.5v supply. I have both my 13 and 24v
> power supplies mast mounted and they have been there for a couple of
> years with no problem, I just leave them switched on to eliminate
> condensation.
> Jon G7TZZ



 


G4LDR
 

I have used a DC to DC converter at the top of my mast for the last 13 years. It is 13.8V 20A o/p for about 22 to 30V i/p. I supply 27V from the shack. The unit I have is designed to power 13.8V equipment from a 27V vehicle supply.

73 Neil G4LDR


alwyn.seeds1
 

Dear All,

Have used both mains to mast-head and 110V also. 

I agree that using sense wires is very risky in a high RF environment.

For mains to the mast-head, make sure all the metal is bonded and earthed and that there are the usual residual current protections required for outdoor circuits.

Since chunky bonding and earthing is needed for lightning protection, this is no great burden. Make sure everything is properly labelled, so that anyone working on the tower is aware of the hazard.

One point about cable- ordinary mains cable is likely to embrittle with UV exposure, creating a safety issue.

There are special outdoor high UV exposure cables available- Olflex is the brand we use- that will last well.

Regards,

Alwyn
  


_____________________________________________________

Alwyn Seeds, Director
SynOptika Ltd.,
114 Beaufort Street,
London,
SW3 6BU,
England.


SynOptika Ltd., Registered in England and Wales: No. 04606737
Registered Office: 114 Beaufort Street, London, SW3 6BU, United Kingdom.
_____________________________________________________


Mark
 

Hi John
 
 
Just to say that 48v to 12v is common in the cellular world and so professional grade units are available, i have some here that came from a 12v stealth PA unit and they are very well built.
 
 
73 <DE Mark>


Richard GD8EXI
 

You can easily limit, in the shack, the max voltage the PSU can go to in the case of a sensing failure. However I can see that having the sensing wires near the antenna could be an issue without some care.
 
Remote voltage sensing is standard practice on boats where you have long, low voltage, high current cables. For example from an alternator or generator to a battery bank with 10 metres of cable carrying 100 amps. These systems fail safe with the output voltage dropping in the case of a sensing failure.

Richard
GD8EXI



On 12/02/2020, 09:59, "Dominique Dehays" <f6dro@...> wrote:

Hi all

I'm a bit reckless as I run 240v ac up to the tower.My current drain is too high for BT.
A pair of isolating transformers helps.
But I believe that running the psu reference wires up the tower is even more reckless:what is going to happen if a wire breaks (believe me,it will)73
Dom


Envoyé depuis mon smartphone Samsung Galaxy.


-------- Message d'origine --------
De : "ian hope (2E0IJH)" <ian@...>
Date : 12/02/2020  10:46  (GMT+01:00)
À : UKMicrowaves@groups.io
Objet : Re: [UKMicrowaves] 12v supply to masthead

Funny this, Ian SEK had similar thoughts, we were talking about the other day
 
Ian
2E0IJH
 
 
Sent: Wednesday, February 12, 2020 at 9:16 AM
From: "Neil Smith G4DBN" <neil@...>
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] 12v supply to masthead
I have a remote Meanwell SMPS which runs on a +-55VAC feed from a big
yellow site transformer. Feels a bit safer than running 240 up the
mast.  The unit is rated for 90-264 VAC in and seems to behave fine with
the 105V or so it gets via the feed cable.

Neil G4DBN

On 12/02/2020 09:02, Jon Eyre wrote:
> Can't you just mast mount the 13.5v supply. I have both my 13 and 24v
> power supplies mast mounted and they have been there for a couple of
> years with no problem, I just leave them switched on to eliminate
> condensation.
> Jon G7TZZ



 


ian hope (2E0IJH)
 

Watch what version Olflex you use, The Tray grade versions are not UV stable.
 
Ian
2e0ijh

 
 
Sent: Wednesday, February 12, 2020 at 10:25 AM
From: "alwyn.seeds1" <a.seeds@...>
To: "UK Microwaves groups.io" <UKMicrowaves@groups.io>
Subject: Re: [UKMicrowaves] 12v supply to masthead
Dear All,
 
Have used both mains to mast-head and 110V also. 
 
I agree that using sense wires is very risky in a high RF environment.
 
For mains to the mast-head, make sure all the metal is bonded and earthed and that there are the usual residual current protections required for outdoor circuits.
 
Since chunky bonding and earthing is needed for lightning protection, this is no great burden. Make sure everything is properly labelled, so that anyone working on the tower is aware of the hazard.
 
One point about cable- ordinary mains cable is likely to embrittle with UV exposure, creating a safety issue.
 
There are special outdoor high UV exposure cables available- Olflex is the brand we use- that will last well.
 
Regards,
 
Alwyn
  
 
 
_____________________________________________________
 
Alwyn Seeds, Director
SynOptika Ltd.,
114 Beaufort Street,
London,
SW3 6BU,
England.


SynOptika Ltd., Registered in England and Wales: No. 04606737
Registered Office: 114 Beaufort Street, London, SW3 6BU, United Kingdom.
_____________________________________________________


John Lemay
 

All

 

Many thanks for your thoughtful suggestions.

 

I’m really rather cautious about sending 240v mains up the mast ! Perhaps the suggestion of 110v is as far as I would go – in fact I quite like that idea. No matter how careful I am, there have been odd occasions where a rogue cable has parted from the loom and wrapped itself round a bit of the Versatower, with awkward consequences.

 

I do already have a bench power supply that will allow me to run up to 80v DC up the mast, and that’s why the idea of a converter at the top was in my mind.

 

Regarding a 12v supply with remote sensing, that is what I currently (!) use. I too was very wary about RF pickup on the sense leads, and tackled that possibility by using screened cable and ferrite clamp-ons at both ends. I’m pleased to say this has worked well – so far. But there must be a limit to how much voltage drop can be compensated, and the power supply info is completely lacking in that department.

 

Meanwhile, my mast was luffed over for the weekend storm, and will remain that way for the action replay in a few days time.

 

Thanks again

 

John G4ZTR

 

 

From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of ian hope (2E0IJH)
Sent: 12 February 2020 10:52
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] 12v supply to masthead

 

Watch what version Olflex you use, The Tray grade versions are not UV stable.

 

Ian

2e0ijh

 

 

Sent: Wednesday, February 12, 2020 at 10:25 AM
From: "alwyn.seeds1" <a.seeds@...>
To: "UK Microwaves groups.io" <UKMicrowaves@groups.io>
Subject: Re: [UKMicrowaves] 12v supply to masthead

Dear All,

 

Have used both mains to mast-head and 110V also. 

 

I agree that using sense wires is very risky in a high RF environment.

 

For mains to the mast-head, make sure all the metal is bonded and earthed and that there are the usual residual current protections required for outdoor circuits.

 

Since chunky bonding and earthing is needed for lightning protection, this is no great burden. Make sure everything is properly labelled, so that anyone working on the tower is aware of the hazard.

 

One point about cable- ordinary mains cable is likely to embrittle with UV exposure, creating a safety issue.

 

There are special outdoor high UV exposure cables available- Olflex is the brand we use- that will last well.

 

Regards,

 

Alwyn

  

 

 

_____________________________________________________

 

Alwyn Seeds, Director
SynOptika Ltd.,
114 Beaufort Street,
London,
SW3 6BU,
England.


SynOptika Ltd., Registered in England and Wales: No. 04606737
Registered Office: 114 Beaufort Street, London, SW3 6BU, United Kingdom.

_____________________________________________________


SAM JEWELL
 

I also have a 110V builder’s transformer in the shack and a yellow 14m ‘mains’ lead, in my duct, to the back of the dish.
I was attracted by the ability to use 90-240v ac input SMPSUs to power the gear out there.
GM4PMK put me onto this some years ago. He uses it at his Mull QTH, with his 23cm EME system.
55 -0- 55v transformers, with preterminated plugs and socket leads, as well as suitable separate cable and hardware, are readily available from ToolStation etc at reasonable prices. 
Seems the sensible way to go as long as you are sensible and take precautions to filter the SMPSU outputs.
73 de Sam, G4DDK

On Wednesday, February 12, 2020, 5:32 pm, John Lemay <john@...> wrote:

All

 

Many thanks for your thoughtful suggestions.

 

I’m really rather cautious about sending 240v mains up the mast ! Perhaps the suggestion of 110v is as far as I would go – in fact I quite like that idea. No matter how careful I am, there have been odd occasions where a rogue cable has parted from the loom and wrapped itself round a bit of the Versatower, with awkward consequences.

 

I do already have a bench power supply that will allow me to run up to 80v DC up the mast, and that’s why the idea of a converter at the top was in my mind.

 

Regarding a 12v supply with remote sensing, that is what I currently (!) use. I too was very wary about RF pickup on the sense leads, and tackled that possibility by using screened cable and ferrite clamp-ons at both ends. I’m pleased to say this has worked well – so far. But there must be a limit to how much voltage drop can be compensated, and the power supply info is completely lacking in that department.

 

Meanwhile, my mast was luffed over for the weekend storm, and will remain that way for the action replay in a few days time.

 

Thanks again

 

John G4ZTR

 

 

From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of ian hope (2E0IJH)
Sent: 12 February 2020 10:52
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] 12v supply to masthead

 

Watch what version Olflex you use, The Tray grade versions are not UV stable.

 

Ian

2e0ijh

 

 

Sent: Wednesday, February 12, 2020 at 10:25 AM
From: "alwyn.seeds1" <a.seeds@...>
To: "UK Microwaves groups.io" <UKMicrowaves@groups.io>
Subject: Re: [UKMicrowaves] 12v supply to masthead

Dear All,

 

Have used both mains to mast-head and 110V also. 

 

I agree that using sense wires is very risky in a high RF environment.

 

For mains to the mast-head, make sure all the metal is bonded and earthed and that there are the usual residual current protections required for outdoor circuits.

 

Since chunky bonding and earthing is needed for lightning protection, this is no great burden. Make sure everything is properly labelled, so that anyone working on the tower is aware of the hazard.

 

One point about cable- ordinary mains cable is likely to embrittle with UV exposure, creating a safety issue.

 

There are special outdoor high UV exposure cables available- Olflex is the brand we use- that will last well.

 

Regards,

 

Alwyn

  

 

 

_____________________________________________________

 

Alwyn Seeds, Director
SynOptika Ltd.,
114 Beaufort Street,
London,
SW3 6BU,
England.


SynOptika Ltd., Registered in England and Wales: No. 04606737
Registered Office: 114 Beaufort Street, London, SW3 6BU, United Kingdom.

_____________________________________________________