[ARC5] (no subject)

[George Babits]

Well, my take is that,  NO, you do not need a regulated power supply to run 
a dynamotor.  Many commercial regulated supplies will see a dynamotor as a 
short and shut down.  When I power a dynamotor from my Astron 35,  I put a 
1/2 ohm resistor in the line to start the dynamotor turning,  and then 
jumper across the resistor once it spins up.  All you need is something that 
will give you 28-30 volts no load, and "around" 24 volts under load.

Life was a whole lot simpler in the days of dynamotors and there is no need 
to make it more complicated just because a ricebox wants a regulated power 
supply.  And that really isn't true either because if you are mobile and the 
engine isn't running, the radio will see pretty close to 12 volts.  Start up 
the engine and it will see between 13 and 16 volts depending on the state of 
charge on the battery.

73,
George
W7HDL


----- Original Message ----- 
From: "J Mcvey via ARC5" <arc5 at mailman.qth.net>
To: "Mark K3MSB" <mark.k3msb at gmail.com>; "ARC5" <arc5 at mailman.qth.net>
Sent: Friday, July 28, 2017 9:17 AM
Subject: Re: [ARC5] (no subject)


How bad can the regulation be? My line voltage doesn't change but a volt or 
two.However, you will have to use some sort of regulation to bring down the 
voltage.29X1.4 = 40.6V !!! Silicon rectifiers will only drop it maybe a 
volt. A beefy variac would be the simple solution. Pot it down to 24- 25V.It 
works fine there.
I'm using a 25V/65A industrial SMPS for the task. The only thing I don't 
like about it is the noisey fan.Picked it up at a surplus/junk place for 
$20. No birdies that I have found yet...It's industrial, so I guess the 
shielding is pretty good.There are also the inexpensive LED 24V supplies on 
Ebay that will power it , too.These have issues with birdies on high HF and 
VHF but can be improved.


    On Friday, July 28, 2017 10:10 AM, Mark K3MSB <mark.k3msb at gmail.com> 
wrote:


 Good morning gang...My 28V power supply for my SCR-274N system isn’t quite 
stout enough so I’ve been using a standalone HV supply in place of the 
BC-456 dynamotor. I’m planning on getting the 274 on AM and would like to 
use the dynamotor (which I’ve rebuilt and runs fine).
I have a 29-0-29 50A transformer in the pile that I’m planning on using for 
a new supply (variac controlled) to power the dynamotor. Does a dynamotor 
need a regulated input? I recall reading that if the supply for a dynamotor 
is stout enough a regulated input isn’t needed, but I can no longer find the 
reference.Thanks!73 Mark 
K3MSB______________________________________________________________
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