Antennas

Antenna Systems
A mast can be a busy place, especially if the ship is equipped with complex IFF, ECM, navigation, communications, surface radar, and air-search radar antennas. Many ships carry back-ups or duplicate systems in case their primary system fails. Adding to the confusion, dummy antennas are sometimes added to confuse the enemy (and us!). Below are most of the antennas found on Destroyer escorts during WW II and into the early 1960s. The collection includes antenna systems for all versions and conversions of the Destroyer Escorts, to include the picket ship conversions. In addition, the USS Francis M. Robinson was used as an experimental platform for a variety of systems. When photographs or information was available, I included those systems as well. Enjoy!
Communications	Talk Between Ships (TBS) antenna. Notice the single vertical element and four horizontal elements. Prior to the invention of the TBS, convoys were hesitant to use their VHF radios to communicate for fear of being detected, and subsequently attacked, by U-Boats or enemy aircraft. Consequently, all communication had to be accomplished with signal flags or lights. The fears were greatly reduced with the introduction of the short-range TBS system. VHF communications antennas.
Surface Search Radar	Radar, also a British invention, was another great weapon developed during WW 2. By the time DEs were fielded, technology had improved enough to produce ship-mountable versions of both surface and air search radars. Surface Search - The DEs were first equipped with the Mk 26 SL, an S-Band microwave radar specially designed for the Destroyer Escorts. It was located in a 42" diameter radome atop the mast. The SL was subject to sea-clutter in rough seas and had a range of only 12 miles.
Surface Search Radar	Beginning in 1944, many DEs replaced the SL S-Band radar with the SU, a high resolution X-Band set. The SU was less susceptible to sea-clutter and had an effective range of 20 miles. The dome measured 24" in diameter.
Surface Search Radar	The SG-series surface search radar was the most widely distributed radar set during WW II. Issued first as the SG (top picture), it was field upgraded to the SGa, followed by the SG-1 model Surface Search Radar (bottom picture). For larger ships (and the DER conversion), this was the standard surface search radar used throughout WW II. SPS-8 Radar. These were mounted on some DE in the 1950s. I have pictures of the installation & will put them up soon.
Air Search Radar	The DEs Mark 26 S-Band Air Search Radar was the SA, easily identified by a rectangular-shaped grid mounted at the top of the mast, commonly called the "bedspring" antenna. The SA had a maximum range of 60 miles and was extraordinarily useful in maintaining convoy formations as well as detecting aircraft. War Status: Used on DEs with Mark 52 FCS. Purpose: Range-only Band: S Power: 50 KW Wavelength: 15 cm Transmitter Dimensions: 36 in (truncated paraboloid) Tracking Range: Bomber at 10,000 feet is 15,000 yards. Fighter at 1,000 feet is 700-12,000 yards. Range on a ship is 400-25,000 yards. Maximum Tracking range is 27,500 yards. Range Accuracy: 100 yards
Air Search Radar	The experimental XAF was one of the first radar sets mounted on ships sometime between January and March 1939. The Naval research Lab developed the XAF and following testing, made improvements that lead to an order for 20 units (now renamed CXAM) from RCA.
Air Search Radar	The CXAM was the first operational radar. RCA produced 19 of these units and had installed them on ships by December 1941. Before long, the power of the CXAM and detection range was increased and the new radar was named CXAM-1.
Air Search Radar	Further improvements to the CXAM-1 followed, power increased, frequency tuning added and the new system renamed SC, the first mass-produced radar. General Electric Corporation produced 500 sets for the USN.
Air Search Radar	SC-4 Air Search Radar with the BL-5 IFF Interrogator on top.
Direction Finding (HF/DF)	The ability to detect transmitters by direction finding (DF) was developed during WW I. During WW II, the U-Boat Wolf Packs were tightly controlled by High Frequency (HF) radio communication. HF radio waves do not follow the curvature of the earth, instead traveling tangent to it, hence a "line-of-sight" communication system. The waves then bounce off the ionosphere back to earth, where then can be received a second time. U-boats were required to make frequent reports on their HF radio on weather, fuel, position, targets, etc. They also had to report upon sighting a convoy so other U-boats could join the Wolf Pack. Prior to beginning the attack they communicated with each other to divide targets and coordinate their efforts. Clearly, this HF traffic, if detected, was close by and an obvious indication of an imminent attack. Once the allies figured this out, "Huff Duff" was installed on most escort ships. The High Frequency Direction Finding (HF/DF) antenna replaced the SA on most of the lend least DEs, as well as most DEs operating in the Atlantic. The HF/DF could also detect U-boat transmissions beyond the horizon, an advantage over the SL surface search radar. As submarines developed countermeasures, HF/DF became less effective and many DEs replaced the HF/DF antennas with the SA air search radar.	HF/DF
Radar Direction Finding and Electronic Counter Measures (ECM)	Later in the DE lifeline, a common conversion program was the Radar Picket ship (DER) modification. There were seven Buckley's that had this modification. They were DEs-51,57,153,213,223,577, and 578. One component of the DER conversion was the addition of two DBM Radar Direction Finding antennas which, unlike this photo, were usually mounted on separate masts. Two DBM antennas were required to cover all the necessary frequencies. The DBM antennas operate with the TDY radar jammer. The TDY jammer was designed to disrupt the land-based Japanese radars used to locate targets and direct Kamikaze attacks. The ECM system always consisted of two antenna systems. The passive systems used the DMS and AS-series antennas and detected the direction of the enemy radar. Once detected, the TDY jammer aimed in the direction indicated by the passive antennas and transmitted continuous noise which appeared as random spikes on the enemy radar screen, rendering them useless.	DBM DBM antennas with a HF/DF mounted overhead on the USS Greenwood (DE679). National Archives #80-G-636017
ECM	An early TDY radar jammer antenna mounted on the flying bridge of the USS England (DE-635) on July 21, 1945.	TDY TDY
Identify Friend or Foe (IFF) Transponder	The BK "ski-pole" antenna is the transponder portion of the IFF system. When interrogated by another aircraft or ship, it responded with (hopefully) the correct countersignal. The ship's interrogator antenna was a BL-series antenna. In the photograph of the SC-4 air search antenna on this page, the small rectangular antenna on top of the "bedspring" is a BL-5 interrogator antenna. The two antennas were combined to save masthead real estate.	BK "Ski pole"
Identify Friend or Foe (IFF) Interrogator	The BL "Stovepipe" antenna is the interrogator portion of an IFF system. The "stovepipe" is an early version that was probably replaced by more advanced models around 1944.	BL