[TenTec] Omni V Maximum voltage

[Bob McGraw - K4TAX]

But....... we are speaking of a very old Motorola repeater power supply that 
operated at nearly a constant current with little concern for ripple due to 
the FM mode.

73
Bob, K4TAX


----- Original Message ----- 
From: "Dr. Gerald N. Johnson" <geraldj at storm.weather.net>
To: <tentec at contesting.com>
Sent: Monday, February 04, 2008 11:47 PM
Subject: Re: [TenTec] Omni V Maximum voltage


> On Mon, 2008-02-04 at 21:02 -0600, Bob McGraw - K4TAX wrote:
>> As I recall and I have one on the UHF repeater here, there is no voltage
>> adjust pot.  It is just a big old linear unregulated power supply.
>> Personally, I wouldn't connect my radio to that supply.
>>
>> I've used the Astron switching supplies with my Omni series and Paragon
>> series of radios with great success.
>>
>> As they say, it's your radio, it's your supply.  Don't let the smoke out 
>> of
>> the box because it likely won't work any more.
>>
>> And for those that will suggest adding a regulator to the output of the
>> supply, there's not enough head room voltage wise to hold 13.8 volts 
>> under
>> full load out of the supply.
>
> That may not be true. It is true for paralleled bipolar pass
> transistors, but I've been using a power MOSFET regulator in my hamshack
> supply for several year now that needs only .02 volts at the minimum of
> the ripple to hold regulation. My transformer is 12 volts RMS
> (buck/boost) each side of center with schottky rectifiers. At 30 amps
> load the liner supply efficiency is about 85%. The key to my regulator
> is that the unregulated supply doesn't droop with 20 or 25 amps load to
> less than the desired output plus 0.02 volts. It might actually need
> another 0.1 farad of filter capacitor on the unregulated to hold up the
> voltage under load. My unloaded voltage is about 16 volts. I could
> improve the load capacity by going from schottky rectifiers to
> synchronous FETs as rectifiers.
>
> 73, Jerry, K0CQ
>>
>>
>> 73
>> Bob, K4TAX
>>
>
>
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