[Milsurplus] TCS Antenna advice

[WA5CAB at cs.com]

Jim,

You've run into the quandry faced by all of the WW-II vintage sets that used 
open wire from the radio to the antenna.  However, I've never heard of a 
"standard" 20' whip antenna.  I've seen reference to a 16' whip used on small 
craft.  But I don't know of anyone who ever acquired one.  And there may have been 
a 25' whip, although I can't recall where I saw the reference.  The standard 
Navy shipboard whip antenna is (or at least was when I left the Blue Water Navy 
and transferred to the Mine Force in 1975) 35' tall and about 2" or 3" in 
diameter at the base insulator.  Generically referred to by all hands concerned 
with them as 35' whips.  An Essex Class Carrier would have had maybe two dozen 
of them in fixed mounts on the island structure and on fold-over mounts along 
the flight deck edge.  FRAM-2 DD's had maybe eight.  I never served on 
anything in between.

TCS's modified for submarine service have Type N connectors on the front 
panel and a different antenna loading coil unit also equipped with N connectors.

In Army vehicles early to mid-War, the length of the antenna (number of 3' 
mast sections used if the radio was VHF) was adjusted for the feed-line length 
inside the vehicle.  After which, conversions to coaxial cable became more 
common.

The two TCS on USS Valley Forge were both located in the island structure and 
fed wire antennas of about 30' length.  And can't recall the details of one 
of them but the one I often played with had about a 10' feedline supported on 
stand-off insulators to a feed-through insulator on the starboard bulkhead.  
The antenna was connected to the outer end of the insulator.  Coincidentally, 
that's about the same antenna that I have here.  Except that the antenna portion 
is nearly horizontal instead of nearly vertical up to the yard-arm.

In a message dated 6/15/2008 11:38:59 PM Central Daylight Time, 
mcenfalz at humboldt1.com writes: 
> I am trying to approximate the vertical antenna system a TCS drove while in 
> typical service so as to maximize its output. From what I have collected 
> online from PT Boat and Landing Craft sites, looks like the radio sat on the 
> side closest to the antenna trunk (~8 " square vertical metal conduit w/feed 
> line centered inside it). These trunks were located next to the conn/bridge and 
> look similar to what I have seen in photos of the LCI(L)-1091. Both had a fat 
> isolator/antenna mount at the top of the trunk to support the whip.
>   
>  However.......as I understand these beasts from prior discussions on this 
> forum, the TX expects the antenna to begin at the antenna lug on the exterior 
> of the case. So, my quandary: if this thing was designed to drive a "20 foot 
> whip" what about that extra cable running from the TX to the trunking and up 
> to the antenna? Is there an optimum feed line length? I have not found 
> anything in my TCS-13 manual as to onboard/vehicular mounting regarding whips and 
> feed line configurations.
>   
>  On the LCI(L)-1091, I understand that the feed line was a fat, 3/4"-1" wide 
> strap of copper braid that went from the TX in the radio room up the 
> interior wall to several insulators on the ceiling, forward most of 10-15 feet into 
> another cabin, then up thru the deck another ~15' inside the cable trunk that 
> ended near the top of the bridge/conn, and then into the famous 20' whip. By 
> definition, you had RF in the shack and a 50 foot inverted-L "antenna" 
> partially enclosed in a steel box.
>   
>  I ran mine at a local air show last week using a 16 foot whip and 15 feet 
> of feed line (RF safety) in conjunction w/ a single 1/4 wave tuned 
> counterpoise expecting great results, but the thing only indicated 0.7 RF A at best. It 
> supposedly should run closer to 1.5 A. When hooked into my old OCFD 
> (pseudo-Windom) via T network tuner, I would push 1 A. Figured the sky was the limit 
> w/the whip.
>   
>  I tried to "do the right thing" and go vertical w/dismal results. What 
> gives?
>  
> 

Robert & Susan Downs - Houston
<http://www.wa5cab.com> (Web Store)
MVPA 9480
<wa5cab at cs.com> (Primary email)
<wa5cab at comcast.net> (Backup email)
   
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