[Milsurplus] TCS Antenna advice

[Laura and Jim]

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?

Jim Falls
KG6FWT
Eureka, CA
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