[time-nuts] Where does 28V come from?

dave powis g4hup at btinternet.com
Tue Jul 21 16:21:31 UTC 2009


Phone companies work off a standard 48v (often referred to as 50v) for exchanges and 'in building' installations.  This includes mobile phone operators.  But a significant amount of equipment in the mobile network is not in the exchange sites - it is in the BTS (Base Transmitter System) cabinets, where 28v is used.  Henace a lot of ex-mobile phone co equipment, such the HP/Symmetricom Z380xx, Lucent RFTG's that were around, and power amplifiers used on 23 and 13cm amateur bands, is normally capable of being powered from either 28V or 48V supplies, since it could be deployed in either situation.

73,
Dave, G4HUP




________________________________
From: Roy Phillips <phill.r1 at btinternet.com>
To: Discussion of precise time and frequency measurement <time-nuts at febo.com>
Sent: Tuesday, 21 July, 2009 4:42:01 PM
Subject: Re: [time-nuts] Where does 28V come from?

abcde
----- Original Message ----- From: "Roy Phillips" <phill.r1 at btinternet.com>
To: "Discussion of precise time and frequency measurement" <time-nuts at febo.com>
Sent: Tuesday, July 21, 2009 12:04 PM
Subject: Re: [time-nuts] Where does 28V come from?


> Hal
> I think you will find that 28 volts DC is standard in many aviation and military mobile equipment power requirements. It is the nominal battery voltage that comes from two 12 volt cells in series that are fully charged. The voltage to run such equipment is not critical (can be less than 28 volts), as you normally charge two series 12 volt cells at 27.6 volts - this is indicative of the nominal voltage of such supplies. Trust that this is the information you are looking for ?
> Roy Phillips.
> 
> ----- Original Message ----- From: "Hal Murray" <hmurray at megapathdsl.net>
> To: "Discussion of precise time and frequency measurement" <time-nuts at febo.com>
> Sent: Tuesday, July 21, 2009 7:59 AM
> Subject: [time-nuts] Where does 28V come from?
> 
> 
>> 
>>> That said, the modules also appear to be powered by 28VDC, add some
>>> regulation, you could use the chassis to power the Thunderbolt, and
>>> mount it in one of the blank panels.
>> 
>> Lead acid batteries are close to 2V per cell.  For cars/trucks, they come
>> conviently packaged in 6V and 12V units.  The phone company works off 48V.
>> 
>> But where does 28V come from?
>> 
>> The Isotemp OSCO 127-10 data sheet says 27 V, but that's +3, -6 or 21-30V
>> which straddles both 24V and 28V.
>> 
>> 
>> -- These are my opinions, not necessarily my employer's.  I hate spam.
>> 
>> 
>> 
>> 
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> 
> 
> 
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