This page is about my high APRS Digi, KD4BBM-6. [Updated 1/16/2006]
First, about the site. It's 1400' up the WTVJ, NBC Channel 6 Tower in South Dade. It shares a rather small cabinet with the SFFMA 147.00 MHz and the WT4X 442.350 MHz Repeaters. As you can see here, the radio is a GE Phoenix and the TNC is a KPC-3+ with version 8.2 firmware. This radio holds up well in a high RF area. The TNC is THE choice today for Wide Digi's. It's ability to cut down on needless duplication of packets has cut way down on useless traffic.
The entire tower is fed by a UPS and generator, so there are no provisions for back up power within the rack. The antenna is a very heavy duty quarterwave on the NW leg at about 1400'. This puts it at about 60' above the cabinet on 1/2" Heliax. Also in line is a 2m BandPass filter. I plan to upgrade this to a better one at some point. Nothing indicates that it's needed, but since there's a full power FM broadcast antenna on the opposite leg, I figure any out of band suppression will help. The output power was set to 35 watts.
The range so far has been impressive. I've seen connections to Jacksonville up for hours. I've been told it's been heard in Texas.
My thanks to George, WT4X and WTVJ.
Here are some pics from our recent trip up the Channel 6 tower in Homestead.
The digi. Here's the radio and TNC in the cabinet. Yes, there is corrosion. While the cabinet is waterproof, the ocean air at 1400' does have a big effect on anything electronic. It's the black radio (GE Phoenix) and black TNC (KPC-3+). The rest is the SFFMA 147.000 Mastr 2 Repeater. Here's how they're connected.
The APRS antenna is at about 1500'. It's the unity gain heavy duty ground plane antenna above the two UHF yagi's
This is George, WT4X, at the front of the rack where the Digi, the 442.350 and 147.00 are located.
George on the left at the front, me on the right changing antenna connections.
Here are the settings I use on my Wide area Digi on the channel 6 tower:
Updated as of 1/14/2006. Details of the tower trip available here at the SFFMA site.
Old settings (before 1/13/2006)
An important correction:
I notice on your pagehttp//www.rayvaughan.com/kd4bbm-6.htm
You showUIFLOOD WIDE,30,ID
Please note that on Bob's APRS pagehttp//web.usna.navy.mil/~bruninga/aprs/fix14439.html he reccomends that you set that to NOID
FIXING THE ID/NOID DIGIPEATERSOne thing that is quite broken in the APRS network are the large number of digipeaters that are incorrectly set with the UIFLOOD parameter of "ID" set. This setting forces an unwanted DIGI ID into every packet transmitted by that digi at the expense of obliterating any prior useful PATH data. Thus in areas with "ID" set, no path can arrive at any receiver with its FIRST-digi-used callsign intact. Thus we cannot trace packets to where they entered the network, and users have no flexibility in path choice for their specific applications. Please read why this is so important. To help APRS users find out which digipeaters are improperly set with the UIFLOOD, ID parameter, we searched the net and came up with a list of Apparent ID-Digis
Do you agree with that statement, and if so, will you update your page?
Brian L Short
On Feb. 24, 2007, the digi was removed from the tower. We found water damage from Hurricane Wilma finally did it in.
Damage inside the KPC-3+. Hard to see from this angle, but water entered via the unused coaxial power connector. Damage appears to be limited to the connector only.
This is the inside of the GE Phoenix Radio. Heavy water damage as the water was driven well into the radio through the connector slots. There may have been some arcing between the first and second pins of the left connector. When you look at it carefully, you can see a water line where the water stopped.
This is the radio connector at the back of the TNC. The DB-9 connector shows serious corrosion but the connections were still working. Power is delivered to the TNC using this connector.
When the replacement unit goes back up, I'm expecting to use a Kantronics KPC+ and a Kenwood TM-271a radio. The modification for the radio is here:
Last update: 01/14/08 13:11