Featured in QST, AUGUST 2000

Written by WX2NJ

A portable communications center featuring a VHF/UHF, 50/35 watt transceiver (Kenwood TM-V7A)

Can also accommodate a Kenwood TM- G707 or TM-261 (same size chassis and Mounting Bracket)

A built-in 12.5 amp switching power supply runs off 120 VAC. Box can also be powered from external DC.

Enclosed 36 amp/hour, (2) 6 volt gel-cells, can power the unit at low (5 watts), intermediate (10 watts) or high power.

The gel-cells are charged when connected to line voltage and external DC. Four voltage LED's provide battery status.

A cooling fan with two speeds circulates air around hot components and exhausts at the rear.

A 4 inch, front mounted speaker, can be switched off. Two top mounted jacks are provided for headphones or audio out for packet operation.

Basic needs are stored in the top, such as pens, flashlight, spare fuses, adapters and the microphone.

Another recent update is the addition of a self-contained battery desulfator built into the unit which greatly extends the Gel-Cell battery life, especially when being float charged for extended periods of time.

This project was built by WX2NJ in approximately 20 hours. Schematic diagrams are available below.

"Boom Box" upgraded with a Dual Band Kenwood TM-V7A Transceiver

"Boom Box" upgraded with a Dual Band Kenwood TM-G707 Transceiver

Original Box with a Kenwood TM-261 Transceiver

Internals with Kenwood TM-261 Transceiver

Subchassis and Radio Bracket

Kenwood TM-V7A/G707 Transceiver

This is the PCV J-Pole antenna I use with the Boom Box. It is a larger version of the Bicycle Jurassic Duck featured at the bottom of my ARES home page. The PVC antenna sets up in about 10 minutes and is stored, broken down, in the back of my truck for emergency use. Unlike the bicycle antenna, which uses small CPVC plastic pipe, this version is built into an 8 foot length of 1/2 inch PVC pipe. Several sections of 1 1/4 inch PVC, reinforced with a wood center, act as a mast for the J-Pole and are screwed together. The feed line exits via a PVC tee at the base of the J-Pole and is sealed against the elements with RTV sealant. Just connect up a coax feedline to the pigtail at the tee fitting and you're in business. Overall height is about 22 feet. The tripod stand is bolted to a foldable 1/2 inch plywood base. For windy conditions, the mast can be guyed with synthetic lines and a couple of concrete blocks can be placed on the plywood base.

PVC J-Pole antenna broken down. Note wood supports that overlap threaded connections.

Boom Box Schematic in Word format

Voltage Monitor Schematic in Word format

Desulfator Schematic/Parts List in Word Format

MAJOR PARTS LIST

Yellow Tool Box from Home Depot, Work Force #22001

or

ZAG (Stanley Subsidiary), #22001, 22" Classic Line, www.zag.co.il

Switching Power Supply, Mean Well S-150-12, Jameco # 123422 (800-831-4242), output adjusted to 13.8 VDC

2 - Radio Shack 275-710 DPDT 20A Switch

2 - Radio Shack 275-711 SPDT 20A Switch

2 - Radio Shack 275-603 SPST 5A Switch

1 - Radio Shack 275-609 SPST Momentary PB Switch

Voltage Monitor Board from FAR Circuits, Sept. 1998 QST, Pg 33, Board # 2, $4.50 for just this board

Exhaust Fan, 3.63 x 3.63 x 1.00 inch, 12 vdc, 80 ma

3 - 3.63 inch Metal Grill Guards, Jameco # 123511

Communications Speaker, Radio Shack 21-549, back removed

Chassis Mount Binding Post, Radio Shack 274-718

120 VAC Input Socket, CEE-22, From an old computer power supply
(You can also use the exhaust fan and grill from an old PS)

2 - Gel Cell Batteries, 6 Volt, 36 Amp/Hour, 6 1/2" tall x 3 1/4" wide x 6 1/4" long
(Available from Sure-Way Electric Inc., Phone 973-890-0615, Model PM6360)

NOTE: the 1N3880 Diode is a 6 amp component. Any power diode of 6 amps or greater is acceptable.

2004 update

Also, with the release of Westmountain Products, PowerGate, you can eliminate most of the above switching by installing PowerGate with  PowerPole terminals between the Power Supply and battery. The PowerGate provides charging current to the battery and automatic swap over to battery power with a loss of AC. See www.cheapham.com for the best prices.

Questions? Comments? Contact WX2NJ