[Milsurplus] MF on Navy ships 1960-1980

[w8au at sssnet.com]

At 09:41 AM 3/9/2008, Rob Flory wrote:
>I am trying figure out what if any antenna was used at 500kc on the 
>NEW JERSEY in its later configuration.

>Do later transmitters like SRT-15 use a matched output to a 50-ohm 
>line, or do they tune a reactive load like the older TAJ/TBL 
>etc.?  If a 50-ohm coaxial, maybe I would be looking for a coaxial 
>feedline to a tuner abovedecks.


Rob:

SRT series used SRA-18 type remote tuners at the base of the standard 
Navy 35' whip.
Each 35' whip was dedicated to a specific transmitter, so they were 
used from MF thru]
HF.  The SRA-22 was capable of matching LOW-Z/High Xc to the 50 ohm 
RG-17 feed from the transmitter room.  Obviously there would be a lot 
of High Voltage flying around the output feedthru insulators of the 
tuners when tuned to MF, especially 500 kHz.  The SRT xmtrs
would run MF only at the lowest power rating of 100 watts, obviously 
a safety factor
considering the short whip.

I don't recall any time that my ship transmitted at 600M. (we did 
listen)  Running our typical 2-3 MHz traffic produced enough Xc high 
voltage arc-overs on the SRA-18's anyway...

Today, on Museum ship USS LST325, the TDE feeds a 275' Inverted L 
longwire (mast to bow)
thru a short "trunk" from the radio room out to the starboard 
side.  The Z at 500 kHz is
approx 5 ohms.  (Haven't calculated the Xc HV, but nothing arcs) :-)

>The project at hand is a preliminary investigation into the 
>feasibility of setting up a TAJ on board.

With a TAJ you may have to restore the original wire antenna and feed 
arrangement.  Hope there are some "trunks" still available.  Although 
the trunks approximate a HUGE coaxial cable (air filled), at least 
there is less loss than with regular coax.  I view them as a solid 
version of the old six-wire cage feedline...600 ohms or so.  (nothing 
new under the sun?) :-)

Perry   w8au