[AMRadio] Wiring issues for BC-1T


cemilton at aol.com cemilton at aol.com
Wed May 9 20:04:15 EDT 2007


I've been reading the Gates BC-1T manual and found two instances where
they state that #4 wire should be used. One says:

"3) ...provide #4 or larger primary wiring from entrance box to 
transmitter".

The other is about carrier shift at 100% modulation:

"9) Carrier shift: 3% or less between 0 and 100% modulation provided
wire size in point 3 (above) is followed..".

They have got to be kidding! Of course I know this is assuming
possibly 24/7 commercial operation at the full KW, but still, #4 wire
for a 1000 watt tx, PEP of 4000 watts w/100% modulation?

What the heck am I missing here?

GE Brian,

I don't think you're missing anything.........but would suggest you 
step back into the time frame when transmitters like the BC-1T were 
popular.

1.  Wiring insulation was a factor...............It's better today than 
back then.

2.  1Kw and .25kw  Bc transmitters were spread out over the USA and it 
was the small towns/rural communities that had "local" radio stations.  
Often, the transmitter was out in the country and often at the end or 
near end of a transmission line.  Voltage "sag" was a real issue.  
Dimming the lights at 100% modulation wasn't a joke.  Some engineering 
was done by a local electrician whose total experience level was 
connecting the chicken house to the main barn with two wires.  No 
disrespect here, but just the truth.

3.  I worked at a 5kw, 5-tower directional on 590kc (Collins driver and 
linear) and the transmitter was located in a rural county setting 
literally at the end of the line as far as AC was concerned.   We had 
the power company locate pole pigs on a stand directly behind the 
transmitter building.  The idea was to have as much voltage and current 
as possible as close to the transmitter as we could.

Like your suggestion, we tied the mains directly to the transmitter and 
amplifier through a breaker panel with one humongous (sp) switch.  
Leads were as large as possible (I don't recall the gauge) but were 
short by most standards due to the pole pigs being located within a few 
feet of the transmitter.  IR drop, etc..........

By ham radio standards, you probably don't need all the "punch" that 
Gates and other manufacturers recommended.  That said, I would wire the 
whole shebang with the largest wire I could afford.  Just keeping in 
mind the rest of the AC transmission system from the power company to 
the breaker box in the house (and beyond).

Hope this helps.  Best of luck with a great old transmitter.  We all 
want pictures when it's done. Preferably with the tubes lit and the 
background lighting subdued.

YMMV

73 de W4MIL
Chuck
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