Tuesday, May 21, 2002

Construction of the new 147.39 Rptr #3

A new 147.39 repeater is under construction for TEARA, and is on the air in 'test mode' at the time of this writing. Temporarily located near Rolesville, in the shop of WB4IUY, the new repeater is already getting signal reports and some activity from area amateurs. The following pages will contain a growing list of images for you to view. At the right is a picture of Steve KD4WIW, installing some of the terminal strips to be used to interconnect the controller to external devices.

Above is a picture of Tim Richards, as he completes the assembly of the Digital Voice Recorders. These are used to store various messages for the repeater in real human voice.

Tim (R) is installing a set of connections for the backup battery power input. The repeater will be fitted with a system that will change the courtesy tone and reduce output power when operating from emergency power. Steve KD4WIW (L) is working on the mounting brackets for the repeater controller 


The new repeater, sitting atop the HUGE Wacom duplexer. The duplexer is designed to handle high power, and should handle about anything we can afford to throw at it. Excuse the engineering department at WB4IUY...as usual, it is in a state of flux from several projects underway at once.

Here's another shot of the new repeater, with a myriad of wires and connections hanging all about. This phase is necessary, as _nothing_ ever works as one would expect. Also, it's always necessary to pull pieces of the repeater out for adjustments and debugging.

Here's a quick shot of other repeater projects underway. The gray cabinet is part of the new 442.300+ repeater, which will serve as the backbone for the 29.62 (10 meter) and 53.07 (6 meter) repeaters. The repeater in the bottom right of the photo is the 224.80 repeater. The next farthest assembly on the workbench is the 29.620 repeater transmitter and linking equipment (now on the air from my shop). On the distant workbench, just beyond and to the left of the gray cabinet, is the 10 meter repeater's receiver and linking equipment (also running from the shop for testing)  

The photo above is of the repeater as it continues to progress towards it's completed state. It was operational at the time of this photo. Here, you can see the two digital voice announcers (in white) installed in the rack, new blowers up high atop the PA's heat sinks, and a RCA test unit (sitting on the duplexer, along side of the repeater) connected for measurements.

Here, the repeater was online, retransmitting a local user, and operating at about 55 watts from the duplexer and into the antenna. With about 3db of duplexer loss, the transmitter would have to produce about 110 watts to get this much usable power from the cavities.

Here's a better picture of the digital voice announcers, and the S-Com 6K controller (far down in black).

Considerable testing was performed on the repeater's receiver sensitivity, when in "repeat" mode. The receiver was very sensitive, but would often become desensitized when the transmitter was online. Lots of testing was performed on the duplexers, transmitter, exciter, etc, in an effort to isolate the problem. Finally, it became apparent that the transmitter was intermittently generating wide band noise and exhibiting some instability in tuning. Here's the repeater, awaiting PA surgery...

Late in the night of 4/4, I decided to replace the transmitter's PA (power amplifier) assembly. On 4/5, Steve KD4WIW and I met to formulate a plan and decide what we'd use for the PA. We were all set to pull the entire RCA transmitter (exciter) and PA, and replace it with a 100 watt Motorola Micor (requiring the modification of the Micor, a lot of hardware and electrical modifications, etc) when we were able to locate an exact replacement RCA Series 1000 power amplifier. Here's Tim salvaging the replacement PA from another radio, to be transplanted into the repeater...

Steve, Tim, and I began work on 4/5 around 7pm, and by about 11:30pm, a new power amplifier was installed and tuned. The wide band noise problem is now non-existent, and the repeater rx/tx performance in "repeat mode" is what we were hoping for. Here's Tim (L) and Steve (R) transplanting the new PA board into the repeater. That's NO SMALL FEAT on a RCA Series 1000 PA!

Here, the last jumpers and connections were being made by Steve KD4WIW on the new PA board. After alignment, the PA was making better than 100 watts

Here's a shot of part of the control system, including the refurbished S-Com 6k controller (black rack mount case in the bottom of the photo). Just above the 6k is part of the original RCA interconnect panel, and two Interalia Digital Voice recorders (in white at the top of the photo). The Interalia DVR's were originally used by the phone company to store messages. They were repaired from salvage and modified for use in our repeater application 

This is a picture of the new DC blowers added to the repeater. By using DC blowers powered from the main 12vdc buss, the repeater will receive adequate cooling even in the event of operation from backup battery power. Two blowers are attached to the PA (large heat sink), and one blower is attached to the power control regulator bank (small heat sink).

This is a picture of the new cooling fans from the back side of the repeater. The fan on the extreme left actually passes some air down the backside of the rack, providing additional cooling to the power control board (seen here as a light beige pc board)

Here, Steve KD4WIW is completing the installation of new back up batteries for the DVR's, and cleaning up the debugged control wiring for the controller/DVR interface

A Radio Shack talking clock is being gutted and modified to provide remote time of day announcements over the repeater. The repeater will automatically 'speak' the time of day at the top of the hour. In addition, users will have an access code allowing the time of day announcement to be requested at will.

Another talking function being interfaced to the repeater is the initial ID'r. The initial ID is usually the first message to be played when the repeater is 'awakened' from sleep. This is being built from the electronics originally used in a talking greeting card by Hallmark. You can see the insides of the greeting card here, with the tiny light green PC board being the voice storage module to be removed and interfaced tot he repeater. This module has an estimated memory life of over 100 years!