EME181 SERIES BIAS TEE KITS

EME181 SERIES BIAS TEE KITS
Saturday 21st January 2012

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The EME181 Series Bias Tee Kits are designed to power many receive only preamplifier kits including the EME173 & 179 Series Kits via a coaxial cable. The Kits are easy to construct & are available for the 6m ( 50MHz ), to the 23cm ( 1.2GHz ) Bands. The Bias Tee can supply up to 25 volts DC at 160mA. It is not recommended that they be used for RX/TX applications as they can only handle low RF power levels.

EME181 KIT CONSTRUCTORS ALERT

1/ For a better return loss on 2M, the choke for 2M has been changed from a T37-6 to a T37-2 Toroid. The turns remain the same at 21 turns 270 degrees spacing. If you only have a T37-6 Toroid, then change the turns to 25 for the required inductance.

CONSTRUCTION OF THE EME181 KIT

The Image left shows the basic RX Bias Tee Kit for 70cm fitted in an optional Hammond 1590H box with SMA connectors.

MOUNTING INTO A DICAST ENCLOSURE

PARTS LIST

1 x ENCL01 Die cast 1590H Hammond

2 x SMA39 PC Board Female socket

1 x DC JACK01 2.1mm Bulkhead Mount

1 x 10nF Ceramic Capacitor

Mounting procedure.

Construct the PC board as per the EME181 Kit notes but DO NOT fit the SMA sockets to the board.
Carefully mark & drill the two 6.5mm & single 8mm holes in the die cast enclosure as shown in the picture above.
Loosely fit the two SMA39 sockets to the enclosure in a position that will allow the PC board to be slid between the guides on the rear of the sockets. The board may need some filing on the ends to make it easily fit between the SMA sockets.
turn the PC board & sockets in the enclosure until the board sits in its normal horizontal position. Tighten the SMA sockets firmly & then align the SMA socket pins carefully with the PC board strip lines.
Solder the top of the PC board to the two SMA sockets & then undo the nuts on the SMA sockets & rotate the board in the enclosure, & then solder the connectors to the bottom ground plane side of the board.
Connect a wire from the DC input of the board that can then be soldered to the DC socket for power.
Realign the PC board in the enclosure in its final position, & then firmly tighten both nuts on the SMA connectors.
Fit the 2.1mm DC socket to the enclosure along with a 10nF capacitor. Solder the wire that was connected to the PC board to the DC connection lug on the rear of the DC socket. The wire should be routed under the board so that it does not affect the RF operation of the circuit.
This concludes the construction of the complete boxed Kit which can now be tested.
Please note that when tightening up the nuts on the sma sockets & adaptor, be careful not to twist the PC board which could crack the smd components. When connecting cables to the sockets, only do up hand tight to avoid twisting the connectors that could place strain and twist the PC board.

EME181 PERFORMANCE TEST

2 & 6m Bias Tee through loss from 10 to 500MHz

2 & 6m Bias Tee Return Loss from 10 to 200MHz

70cm Bias Tee through loss from 0.1 to 1GHz

70cm Bias Tee Return Loss from 0.1 to 1GHz

23cm Bias Tee through loss from 0.8 to 2GHz

23cm Bias Tee Return Loss from 0.8 to 2GHz

KIT FAULTS & MODIFICATIONS EME181 KIT

1/ There are no current issues.