View Single Post
  #15   Report Post  
posted to rec.boats.electronics
Bruce in Alaska
 
Posts: n/a
Default what size wire to use for 30amp 12v circuit ?

In article ,
"Lynn Coffelt" wrote:

Oh, my gosh, it's just killing me to sit here without jumping in! Then
when I heard SGC mentioned, I knew that someone besides me had experienced
"Bruce's Law". I am compelled to defend his position and scientific
observations without reservation.

How much midnight oil I've spent working on the DC supply system on
"commercial" vessels, trying to reduce the voltage drop. Until the "code"
made batterys in the pilot house almost mandatory, can't you imagine running
an SGC711 from engine room batterys? Here's a typical example (it is a
genuine "commercial", by the way) of a vessel still using this one time
popular rig:

http://www.alaskaboat.com/sn033.htm

Those SGC711's were hard to coax to even 75 watts PEP with any wire
less than #4 if you were more than two feet away from the battery! (OK,
stretching a little here) And the built-in wire antenna tuner was a charmer,
hey? But as the URL and dozens more can show, that not everyone has yet to
install an Icom M802.

Some earlier SEA's and Icom's with first generation digital VCO tuning
were cool, too. A sneeze or laugh in the mic was as apt to change channels
as anything if the antenna was fed directly from the radio, and some joker
installed #10 wire for DC power!

Early automatic antenna tuners were (are) cool, too. A little pitching
and rolling in the North Pacific and they would lock up and refuse to even
try to tune anymore. Then the transmitter's fabulous SWR power foldback
circuit hit the fan and 5 to 10 watts could be used to heat up the tuner's
coils and capacitors. (condensers, actually)

Lots of this early stuff is still out there. By the thousands. Modern
marine SSB radios certainly have improved their ability to survive poor
installations, but is that any reason to go as cheap as possible with DC
wiring and antenna installations? (RF ground on "Tupperware" boats is
probably just as important, but I digress)

Old Chief Lynn

(besides, tubes help heat the pilothouse and ease aching joints)


Ah Oh, I feel a Story coming on....

StonerWatts .... A Real Tale about MF/HF Marine Radio......

Years ago, I was working for Northern Radio, as a Field Tech/Radioman
and getting the Alaska State Ferries ready for their Annual SOLAS
Inspections. The State wanted to replace the venerable Northern N550
MF/HF SSB Radios with something totally SolidState, and had put out
the refit for BID. Well Don Stoner, and his partner PeeAir Gorrale,
wanted to get their SGC711 into the US Market, so they bid the job
really LOW, and got the contract to refit all the State Ferries.
Their guys did the installations, and had left the vessels, for
me to get them thru FCC/SOLAS Inspections. I did everything else, first
and left the MF/HF Radio's for last, and when I finnally got around to
doing the preinspection testing, found that all but one wouldn't meet
Frequency Tolerance, and NONE of them would meet PowerOutput Requirments,
using the accepted Testing Procedures, expected by the FCC Field
Engineers, of the day. I got ahold of the Port Captain, and explained
the problem, and since these radios were NEW and under Warrentee (sp)
that it was SGC's problem to rectify, but since the Inspection was setup
for the next morning, SGC better get their collective Ass in gear, or the
ships would fail the Inspection and not be ready to sail on schedual.
SGC was summoned and one of their Field Techs reset all the Crystal
Frequencies and did his best to get the Power Output up to spec's.

They worked all night on the first boat due for inspection, and when I
showed up, one hour before Inspection time, the Power problem still
wasn't resolved. Finally, the Tech, called his office and Don Stoner,
drove out, and showed up just as Bob Zinns, the FCC Engineer, did and
they came aboard together. While Bob and I went thru all the other
Inspection Items, don worked on the 711. After 2 hours, Bob and I were
ready to do the MF/HF Radio Inpsection, and we were presented with Don
Stoner, and his very expensive Tek Storage OScope, connected across a 50
Ohm Dummy Load, and he said he would demonstrate the Power Output of the
711 with this Test Setup. Mr. Zinns looked very skeptical, and I didn't
say a word, but Don proceeded with his demontration. He picked the Mic
and mashed the PTT and sope the test phrase "Five, five, five", into the
mic. He had the Storage Oscope set to capture the Peak Voltage Pulse of
the transmission, and then showed the assembliadge the reading, and got
out his calculator, and computed the PEAK Envelope Power for that, very
narrow Pulse. "Yup" he said, "just exactly 152 PEP Watts". Mr Zinns
asked hm to demonstrate that on a Peak Reading Bird WattMeter, and Don
stated that he would not, that his demonstation was sufficent. Mr Zinns
took out an 801 PinkSlip and Failed the vessels SOLAS Inspection, citing
the lack of spec'd Transmit Output Power. I tested the radio, in the
accepted way using a Bird Wattmeter, and found that we could get maybe
80 Watts PEP out of it with a Maximum Scream in the Mic. Everyone went
home and the FCC and SGC had a WAR of Fax's and Phonecalls, between the
Seattle Field Offce, FCC Headquarters, State of Alaska Ferry Systems,
Port Captain, and SGC, ect. After three days of this, it was determined
by the FCC's Chief Engineer, that Don Stoner's method of testing did in
fact prove that the radio was in compliance, and that the FCC Field
Offices would accept that method of testing, for the SGC711 only, and
Issue SOLAS Certificates for the Alaska State Ferries which had SGC711
Radios fitted.
The long and short of the story is: All the SGC's were stripped off all
the Alaska State Ferries within 6 Months, for the simple reason that
they couldn't talk to any of their regular BaseStations, on a consistant
basis, as they were used to doing with the N550's previously fitted.
All were replace with Icom's first generation MF/HF Radios that actually
would "Whistle up" to 150PEP on a Wattmenter. Northern Radio continued
to do all the FCC/SOLAS Annual Inspections, untill I left the company.
The State of Alaska Communications Shop, took over the job
and was still doing it when I joined the FCC a few years later, as the
Southeastern Alaska Resident Field Agent and started doing the FCC/SOLAS
Inspection on the Alaska Ferries as the FCC Inspector.
The StonerWatts Story is still around in FCC Lore, and told in Marine
Radio Shops, all around the North Pacific.


Bruce in alaska just cause you can see the spike on a scope doesn't
mean you can actually talk to someone......
--
add a 2 before @