Best way to get 13.8v to the dish ?


Nick Gregory G0HIK
 

I'm on with building a small 23cms amp and DDK pre-amp at the dish. The run is about 25mtrs and current around 12 amps.

The dish is on a trailer and I intend to use it at home and also out portable.

What means do folk use to get a 13.8v to their remote amplifiers.

I've come up with three ideas

1) SLAB at the dish on trickle charge.
2) Supply 24v with regulator or DC/DC converter at the dish.
3) PSU in the shack with sense terminals.

I've discount option 4) runs mains to the dish.

Option One is my favorite at the moment as it is simple and lends itself to easily being used while out portable.

Option Two, hash from a DC/DC converter and finding a good one in budget, a linear regulator maybe better, but I would still need to arrange it to be run from batteries while out portable.

Option Three, I dont know how quick sense circuits work, i.e. speech peaks and splatter, if a sense wire fails damage from over voltage so crow bar required.

Any comments and suggestions would be great.

Nick G0HIK


SAM JEWELL
 

A number of microwave EME ops run 110v AC from a ‘builders’ mains (yellow) transformer to the dish installation. 
Many SMPSUs will accept 100 to 240V input and allow fairly high current output at whatever voltage you want.
The advantage of this arrangement is that the (mean) ac voltage at the dish is 55V wrt ground. Whilst not pleasant you would probably survive accidental contact at these voltages.
Plugs, sockets, pre-terminated leads etc are readily available, relatively cheap, weather ‘tolerant’ and about as safe as you choose to make your installation wrt accidental contact with anything you shouldn’t touch.....
Be careful...

73 de Sam, G4DDK

On Thursday, May 7, 2020, 1:22 pm, Nick Gregory G0HIK via groups.io <nickg0hik@...> wrote:

I'm on with building a small 23cms amp and DDK pre-amp at the dish. The run is about 25mtrs and current around 12 amps.

The dish is on a trailer and I intend to use it at home and also out portable.

What means do folk use to get a 13.8v to their remote amplifiers.

I've come up with three ideas

1) SLAB at the dish on trickle charge.
2) Supply 24v with regulator or DC/DC converter at the dish.
3) PSU in the shack with sense terminals.

I've discount option 4) runs mains to the dish.

Option One is my favorite at the moment as it is simple and lends itself to easily being used while out portable.

Option Two, hash from a DC/DC converter and finding a good one in budget, a linear regulator maybe better, but I would still need to arrange it to be run from batteries while out portable.

Option Three, I dont know how quick sense circuits work, i.e. speech peaks and splatter, if a sense wire fails damage from over voltage so crow bar required.

Any comments and suggestions would be great.

Nick G0HIK


Nick Gregory G0HIK
 

Thanks Sam,

Yes a "Yellow" transformer sounds reasonable and it's fairly water tight too.

Ideally I want to make it all runable from batteries so I dont need a geny while out. I may end up running it from dual supplies though.

Nick G0HIK


Nick Gregory G0HIK
 

Ive just been asked what is my dish mounted on.

It is a small boat trailer that I have shortend.

The dish mount is the standard Channel Master mounting post that fit on nicely.

I've also added a Barenco post mount that accepts the telescopic mast for beam aerials. I've also included some eye bolts for guying the telescopic mast so it needs no external guys, I've had 10 over 10 for 2 mtrs on it so far.

I intend to change the steadies for adjustable ones to make it easier to get it level now I have the dish on it.

Nick G0HIK


Neil Smith G4DBN
 

I'd add options like:

4) use 50V PAs or 28V PAs to reduce current demand (assuming you have a way to generate those voltages while portable)

5) send 15/16V up to the masthead with a high-current LDO (as above).

6) send 110 V AC up to the masthead as Sam suggests

Might not be easy to do any of those if you are running off batteries without an inverter.

For the "send DC up the mast" options, if you can't provide a floating negative return to the high-current supply, you need to allow for weird things happening like the coax rising a volt or more above "ground" when you are on transmit because of voltage drop across the negative lead to the PA.  If you use serious coax up the mast, you can always use the screen as one leg of the supply to save a bit of weight, but then you still have to deal with the voltage offset from the resistive drop on TX for any remote switching or monitoring unless it is optoisolated or otherwise not DC connected.

Neil G4DBN

On 07/05/2020 13:34, SAM JEWELL via groups.io wrote:
A number of microwave EME ops run 110v AC from a ‘builders’ mains (yellow) transformer to the dish installation. 
Many SMPSUs will accept 100 to 240V input and allow fairly high current output at whatever voltage you want.
The advantage of this arrangement is that the (mean) ac voltage at the dish is 55V wrt ground. Whilst not pleasant you would probably survive accidental contact at these voltages.
Plugs, sockets, pre-terminated leads etc are readily available, relatively cheap, weather ‘tolerant’ and about as safe as you choose to make your installation wrt accidental contact with anything you shouldn’t touch.....
Be careful...

73 de Sam, G4DDK




Sent from Yahoo Mail for iPad

On Thursday, May 7, 2020, 1:22 pm, Nick Gregory G0HIK via groups.io <nickg0hik@...> wrote:

I'm on with building a small 23cms amp and DDK pre-amp at the dish. The run is about 25mtrs and current around 12 amps.

The dish is on a trailer and I intend to use it at home and also out portable.

What means do folk use to get a 13.8v to their remote amplifiers.

I've come up with three ideas

1) SLAB at the dish on trickle charge.
2) Supply 24v with regulator or DC/DC converter at the dish.
3) PSU in the shack with sense terminals.

I've discount option 4) runs mains to the dish.

Option One is my favorite at the moment as it is simple and lends itself to easily being used while out portable.

Option Two, hash from a DC/DC converter and finding a good one in budget, a linear regulator maybe better, but I would still need to arrange it to be run from batteries while out portable.

Option Three, I dont know how quick sense circuits work, i.e. speech peaks and splatter, if a sense wire fails damage from over voltage so crow bar required.

Any comments and suggestions would be great.

Nick G0HIK
-- 
Neil
http://g4dbn.uk


SAM JEWELL
 

For terrestrial use I do run 16v to masthead, using thick but flexible ‘car audio’ cable. I use LDO regulators to regulate down to 11V at upto 8A for my 10W, 10GHz PA. no sense wires, just plain over engineered for voltage drop!
It’s been in place for approaching 15 years without problems.
The power is left on all the time. Quiescent power dissipation is a few watts by the transverter and some other circuits inc. a masthead OCXO.

73 de Sam, G4DDK

On Thursday, May 7, 2020, 1:52 pm, Neil Smith G4DBN <neil@...> wrote:

I'd add options like:

4) use 50V PAs or 28V PAs to reduce current demand (assuming you have a way to generate those voltages while portable)

5) send 15/16V up to the masthead with a high-current LDO (as above).

6) send 110 V AC up to the masthead as Sam suggests

Might not be easy to do any of those if you are running off batteries without an inverter.

For the "send DC up the mast" options, if you can't provide a floating negative return to the high-current supply, you need to allow for weird things happening like the coax rising a volt or more above "ground" when you are on transmit because of voltage drop across the negative lead to the PA.  If you use serious coax up the mast, you can always use the screen as one leg of the supply to save a bit of weight, but then you still have to deal with the voltage offset from the resistive drop on TX for any remote switching or monitoring unless it is optoisolated or otherwise not DC connected.

Neil G4DBN

On 07/05/2020 13:34, SAM JEWELL via groups.io wrote:
A number of microwave EME ops run 110v AC from a ‘builders’ mains (yellow) transformer to the dish installation. 
Many SMPSUs will accept 100 to 240V input and allow fairly high current output at whatever voltage you want.
The advantage of this arrangement is that the (mean) ac voltage at the dish is 55V wrt ground. Whilst not pleasant you would probably survive accidental contact at these voltages.
Plugs, sockets, pre-terminated leads etc are readily available, relatively cheap, weather ‘tolerant’ and about as safe as you choose to make your installation wrt accidental contact with anything you shouldn’t touch.....
Be careful...

73 de Sam, G4DDK




Sent from Yahoo Mail for iPad

On Thursday, May 7, 2020, 1:22 pm, Nick Gregory G0HIK via groups.io <nickg0hik@...> wrote:

I'm on with building a small 23cms amp and DDK pre-amp at the dish. The run is about 25mtrs and current around 12 amps.

The dish is on a trailer and I intend to use it at home and also out portable.

What means do folk use to get a 13.8v to their remote amplifiers.

I've come up with three ideas

1) SLAB at the dish on trickle charge.
2) Supply 24v with regulator or DC/DC converter at the dish.
3) PSU in the shack with sense terminals.

I've discount option 4) runs mains to the dish.

Option One is my favorite at the moment as it is simple and lends itself to easily being used while out portable.

Option Two, hash from a DC/DC converter and finding a good one in budget, a linear regulator maybe better, but I would still need to arrange it to be run from batteries while out portable.

Option Three, I dont know how quick sense circuits work, i.e. speech peaks and splatter, if a sense wire fails damage from over voltage so crow bar required.

Any comments and suggestions would be great.

Nick G0HIK
-- 
Neil
http://g4dbn.uk


ian hope (2E0IJH)
 

I do something similar with my 23cm setup and we also use this contesting for safety
 
Ian
2E0IJH

 
 
Sent: Thursday, May 07, 2020 at 1:34 PM
From: "SAM JEWELL via groups.io" <jewell@...>
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Best way to get 13.8v to the dish ?
A number of microwave EME ops run 110v AC from a ‘builders’ mains (yellow) transformer to the dish installation. 
Many SMPSUs will accept 100 to 240V input and allow fairly high current output at whatever voltage you want.
The advantage of this arrangement is that the (mean) ac voltage at the dish is 55V wrt ground. Whilst not pleasant you would probably survive accidental contact at these voltages.
Plugs, sockets, pre-terminated leads etc are readily available, relatively cheap, weather ‘tolerant’ and about as safe as you choose to make your installation wrt accidental contact with anything you shouldn’t touch.....
Be careful...
 
73 de Sam, G4DDK
 



Sent from Yahoo Mail for iPad
 

On Thursday, May 7, 2020, 1:22 pm, Nick Gregory G0HIK via groups.io <nickg0hik@...> wrote:

I'm on with building a small 23cms amp and DDK pre-amp at the dish. The run is about 25mtrs and current around 12 amps.

The dish is on a trailer and I intend to use it at home and also out portable.

What means do folk use to get a 13.8v to their remote amplifiers.

I've come up with three ideas

1) SLAB at the dish on trickle charge.
2) Supply 24v with regulator or DC/DC converter at the dish.
3) PSU in the shack with sense terminals.

I've discount option 4) runs mains to the dish.

Option One is my favorite at the moment as it is simple and lends itself to easily being used while out portable.

Option Two, hash from a DC/DC converter and finding a good one in budget, a linear regulator maybe better, but I would still need to arrange it to be run from batteries while out portable.

Option Three, I dont know how quick sense circuits work, i.e. speech peaks and splatter, if a sense wire fails damage from over voltage so crow bar required.

Any comments and suggestions would be great.

Nick G0HIK
 


Nick Gregory G0HIK
 

Thanks Neil,

Well, initially I'm going to use the 12v amplifier I have already.

Yes, if possible as much 12v kit as possible, I will need a small inverter for the Az/El but a small 100 watt unit should suffice.

I've found the the IC-9700 is very tolerant to supply voltage and runs from batteries nicely. Looking at the circuit I see it has three DC/DC converters in there, but not on the PA supply, so I would imagine the quality of signal would start to deteriorate at 10.5v :), even though it's still giving full power out.

I had considered using a Bias Tee as I was going to used LDF4-50, now it's going to be Superflex, both have thick inners. I had not thought about using the screen on it's own though and I had not considered a P.D. imposed on the braid. Thanks for that info.

Nick G0HIK


Adrian G4UVZ
 

Initially you talk about 13.8volts at the dish ...if you use opion 1 you will find that your battery terminal voltage on a an SLAB will very quickly become close to 12 volts. For my masthead 10GHz set up which runs on nominally 12 volts I use a 13.8 volt feed into British Standard Cooker Cable!  

Adrian


Nick Gregory G0HIK
 

Hi Adrian,

I had thought that on SSB/CW the battery will not have time to discharge to very much below 13.8v, Data modes will be another matter, I'll also have to uprate the PA cooling (Waterproof fan ?).

I've got some 6mm T&E around somewhere I think. A quick online calc gives me a 0.4v voltdrop, if I also use the Coax screen I can maybe knock another 0.1 to 0.15v off that figure, very acceptable.

Nick G0HIK


G3PHO - Peter
 

I've been using one of these boosters for the past three years to feed my 5 watt  10GHz masthead system. I also occasionally run a mast head 20 watt 1296MHz transverter with it. It's  fed by 70 feet of 30 amp black & red DC cable with 14.8VDC from my shack PSU . This module is fitted in a plastic box just under the rotator and the pots adjusted to give 13 volts output, which is then fed by a short length of  red&black to the transverter behind the dish.


I've had no noise problems or voltage  drop on transmit.

Peter, G3PHO








Nick Gregory G0HIK
 

Hi Peter,

Thanks for the link, I have an 8 amp one of those I use for SOTA activations. It works well except for the switching noise up to at least 6mtrs and still detectable on "Two".
I will buy one of those and it a try.

Nick G0HIK