[K3CAL] DB-224 and DB-416 Antenna Checks

[N3AE]

All, 

Dave, W3PQS, and I spent some time this morning checking out the two Decibel antennas CARA acquired for the new 440 repeater location and for APRS or Winlink on 2 meters. We used Chip's Rig Expert AA-600, hereafter called Chips Wonderful Meter (CWM) to test the antennas. 

The antennas were mounted on a wooden post for the tests. CWM was attached directly to the antenna phasing cable ends. 

Previously, the DB-416 antenna had a SWR over 3 to 1 at 444.950 MHz when we measured it at KC3AEN/KC3DAS house a few months ago. After Dave cleaned and resealed all the connections on this 16 bay dipole array, the SWR is now down to 1.9. We were able to get it down to 1.7 today using a stub match, but that matching network was designed to the feedpoint impedance we measured before the connections were cleaned. An SWR of 1.9 is "good enough," but if time permits I'll redo the stub match for the feed impedance we measured today ( 38.6 + j24.9 ). The stub was designed for a feedpoint impedance of 43.5 + j39.8. 

The DB-224 is built for the 152 - 154 MHz business band. In the 2 meter band, we measured the following: 

146.985 MHz (K3CAL Repeater) SWR 1.9 Impedance 33.8 + j20.5 

144.390 MHz (APRS Frequency) SWR 2.2 Impedance 22.9 + j3.8 

145.750 MHz (WL2K Gateway) SWR 2.1 Impedance 26.8 + j14.1 


A nice surprise was that the DB-224 works very well on it's third harmonic. At 444.950, the DB-224 had an SWR of just 1.2. No idea what the antenna pattern might be on 440, however. 

Shawn 
N3AE 



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