[BC] Re: Vanguard & Vanguard II

[DHultsman5@aol.com]

In a message dated 5/17/05 12:04:22 A.M. Central Daylight Time,  
broadcast-request at radiolists.net writes:

Never  could remember whether it was the Vanguard I or II, but one of them   
looked just like the ice makers you see in motels (apart from being   
painted green).  The 1520 in Toledo had one at one time.   Probably long  
gone.  The other Vanguard was in a conventional  cabinet.




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The Vanguard was the original 1 kW single tube transmitter.  It was  
essentially a linear amplifier,  which had final amplifier efficiency of  
approximately 36-40%.  The low level RF stage included a modulator all  solid state.  The 
transmitter sounded pretty good. If it was tuned for  maximum power the sound 
and modulation degraded.
 
Phil can probably give more details on both transmitters.  As I recall  the 
final was a 4CX3000 tube.
 
The broadcast industry just could not accept the clothes dryer style or ice  
machine style cabinet at the time.  I recall many engineers stating  that..  
"it didn't look like a transmitter.."
Also during that period Gates continued to make their Class B modulated  
Class C RF Amplifier transmitter for the old salts that couldn't stand the  linear 
amplifier.
 
Gates later took essentially the same hardware and placed it in a standard  
rack cabinet and called it the Vanguard II.  Phil can probably tell us the  
difference in the two products.
 
Comments about power consumption may be more hearsay because using only one  
tube in linear with only one filament as compared to four filaments may be  
closer than we all think.  As I recall the two transmitters available at  the 
time of the Vanguard II, was the BC-1H. I will look I think I have manuals  on 
both products.
 
I only worked on two of these units.  One always sounded bad and I  suspected 
the load. I suggested that they have the load checked , they  didn't and 
continued to complain about the transmitter. The other sound bad  when I arrived 
but basically was loaded too tightly and clipping on positive  peaks.  I 
retuned and it sounded much better.
 
The first Vanguard I saw was at KNUZ, 1230 in Houston.  The station  was 
clean and loud for a 1 kW in Houston. They later upgraded to the Vanguard  II.
 
Dave Hultsman