[ARC5] SCR274 field test

[WA5CAB--- via ARC5]

What dynamotors are you using?  There was a 14 volt dynamotor made for the 
receivers (DY-1/ARR-2 and a Navy equivalent for the RAT or R-148)) but never 
one for the transmitters.  For a 14 volt system you should be using at 
least #10 AWG wire  and a solid ground to the vehicle on whatever dynamotor 
supply you are using.  And don't try to run the transmitters without the engine 
running.  

Before I went to Vietnam in 1967, I had a 4-transmitter 8-receiver 
installation in my International Scout 80 and could reliably work into central and 
western Oklahoma on 4010 KC from up the hill near my parents home in north 
central Louisiana.  The Scout had a 14/28 VDC system installed, though, with a 
second 14 V generator piggy-backed on the first.  The radios were all box 
stock.  Antenna was a commercial center-loaded whip but I can't recall the 
brand name.

FYI, starting current for a typical shunt or compound wound dynamotor is 
about 3X the FLA.  So for the 9 A you reported earlier, around 27-28 A.  Far 
from huge.

Robert Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480

In a message dated 07/18/2015 22:34:18 PM Central Daylight Time, 
arc5 at mailman.qth.net writes: 
> Yes the startup current is huge, I was aware of that, but the drop is 
> after it's already running in standby under transmit load. (the dyno runs 
> continuously in CW mode). The startup inrush current will pop a 20A fuse, but 
> not a 30.
> 
> I made the voltage measurements right at the battery terminals with key 
> down. The power cable is about 6 feet of #12 AWG. The drop is nominal and 
> there is no noticeable warmth, yet the transmitter can pull down the battery 
> voltage quite dramatically. 
> 
> 
>      On Saturday, July 18, 2015 10:04 PM, Roy Morgan <k1lky68 at gmail.com> 
> wrote:
>    
> 
> 
> On Jul 18, 2015, at 8:28 PM, J Mcvey via ARC5 <arc5 at mailman.qth.net> 
> wrote:
> 
> >...how can 16.5 amps draw a 130AH battery down to 11v from it's fully 
> charged resting voltage of 12.6v ? ( it recovers on key up)
> 
> Note well where you are measuring the voltage.  There may well be IR drop 
> in the leads from your battery to the radio - if you are measuring the 
> voltage at the radio, I’d bet on it.  And especially so if you are getting the 
> radio supply voltage from somewhere other than the battery terminal itself.
> 
> If the wire to the radio does not come off the battery itself (and the 
> connectors are bright and shiny inside) you’ll have voltage drop in the 
> vehicle harness.
> 
> Roy]
> 
> Roy Morgan
> k1lky68 at gmail.com
> K1LKY Since 1958