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Right Angles If they’re not right...they’re wrong Home Contact Me April 3, 2024 15:30 by: Dan 0 comment(s) comments RSS trackback permalink Automating the Expert Linear ATU tuning process Most people will recognize CHIRP as a desktop application, which it is. However, one of the early design points for the architecture was a clear separation between the UI and the driver model. That provides a mostly clean abstraction between the task of communicating and interpreting the memory of the radio and the presentation or user interaction. While the chirp python module is not a stable library, it’s pretty internally-consistent and doesn’t change much over time. What that means is that it’s also possible to re-use the driver code in other tooling for specific purposes. I recently got an SPE Expert 1.3K-FA linear amplifier with the integrated antenna tuner. It’s a really nice piece of gear, and it’s very well thought-out. The ATU works differently than I was expecting though, in that you pre-tune it for basically everywhere you want to operate and it automatically tracks as the frequency changes via CAT. That means it’s constantly adjusting the ATU as you dial around, which is great, but it means that you need to have done that pre-tuning ahead of time. In order to do that, the manual gives you a large table of sub-band center frequencies” across all the supported bands. If you make changes to your antenna, or operate on a temporary antenna, you need to re-tune every single one of them. The OEM process consists of these steps: Look up the next frequency in the list Dial the radio to that frequency Set the radio to CW or RTTY (which my radio is never in) Press the tune button on the amp Key the radio until the tuner finishes Goto step 1 (until you’ve done them all) For me, step 2 takes the most time, either typing each frequency in on the direct-entry keypad or using the dial. Multiply that procedure by the 153 center frequencies (if you do all the bands) and you can see why it takes some time. My thought was that I can/should automate that using the infrastructure in CHIRP. So I did, and what I came up with works really nice with my setup to make a full re-tune much quicker. The tool’s fully-automated workflow looks like this: Command the radio to the next frequency in the list, RTTY mode Monitor the output to see that you key the radio, and when you un-key: Switches to CW mode and sends your callsign for ID (if supported), then loops back to #1 The only the thing user has to do is hit the tune button on the amp and transmit when prompted, over and over again. It’s much faster and less work. Here’s a sample interaction: It’s tempting to use the USB interface on the amplifier itself to fully automate this process, which is very doable. However, it’s probably most prudent to require some user interaction in order to listen for a clear frequency before tuning and, of course, monitor for problems (like a failure to achieve a suitable match, etc). I tested this on an IC-7610, IC-7300, and IC-7200. It’s certainly possible it will run with ease on other such models, but I don’t have them handy to test with. Since this uses a bunch of control frames that are not normally used (and tested) as part of CHIRP, it’s hard to say if they will all work with other models. If you want to check it out you can see it here . It requires the chirp python module to be installed (or be locally resident). An all-in-one binary could be made. Posted in Radio Tagged chirp , expert , icom November 14, 2022 15:03 by: Dan trackback permalink Adding a second mic to a Kenwood TK-8180 The Kenwood TK-8180 is my go-to preferred radio for GMRS stuff. It is a rugged radio with an excellent remote-head kit, and a nice display. It’s generally pretty easy to find them in good condition on eBay, and accessories are plentiful and compatible with a long line of Kenwood radios. The TK-8180 (and TK-7180 VHF radio) have an excellent expansion port in the back that uses a standard DB-25 female connector, which makes it super easy to interface with. In my Jeep, I mount the remote head high above the roll bars near the roof to keep it out of the way and the body of the radio under my seat. However, I don’t want to have the mic up there, with the cable drooping in my face. Luckily the expansion jack can take mic audio and PTT signals instead of the mic jack on the head. Even though this is rather trivial, I’m documenting the connection here for my future self, and others, as I have seen people ask about this before. I’m using a KMC-35 mic, but this should work with most any Kenwood commercial mic (keypad mics that use the serial connection will not have DTMF functionality). I used a simple surface-mount box meant for ethernet to provide a mic jack low on the center console. If you’re familiar with (and/or your surface-mount box is marked for) T568B ethernet wiring, I kept the wire colors consistent here to make it easier. I used the software to set AUXI/O7 (pin 12) to External PTT (Voice)” and Active Low”. If you choose a different pin for PTT, make sure to adjust accordingly in the table below. RJ-45 Pin DB-25 Pin Signal T568B Standard Color 1 W/Orange 2 Orange 3 6 Mic Audio W/Green 4 25 Mic Gnd Blue 5 12 PTT W/Blue 6 7 Gnd Green 7 14 SB (+12v) W/Brown 8 Brown The TK-8180 can also tolerate both mics being connected at the same time, and the radio will route audio from the proper one depending on which PTT is pressed. This is not important for my application, but may be for others. Posted in Radio Tagged audio , external , jeep , kenwood , mic , radio , tk-7180 , tk-8180 October 23, 2022 20:57 by: Dan trackback permalink Fixing a Kenwood TM-281 serial interface I have a Kenwood TM-281 that I got second-hand from an unknown source, and have always programmed it by hand since it’s so simple. Recent efforts in the chirp py3 branch require a lot of re-testing of radios, so I decided to pull out my TM-281 for a quick verify. Come to find out, it was totally dead in terms of serial communications. Neither chirp nor Kenwood’s own program would talk to the radio, and a serial terminal confirmed no communication at all. I whipped out the schematic and traced the two serial lines from the mic connector that are required to operate. The HOOK line is used as data RX for the radio, and has a zener diode (D902) between that line and ground, presumably to clamp RS-232 level voltage to the 5v it expects. I found this diode to be shorted, failing a diode direction test and registering about 4ohms to the chassis. Since I’m using a proper 5v TTL cable, I decided to lift one side of the diode to break the short to see if that would allow communication. Luckily, it did and the radio immediately started responding to serial commands normally. Here’s a picture of the diode lifted: Obviously the proper fix is to replace the zener with a suitable substitute, although it’s not clear to me what the right part is. The service manual shows it as UDZW6.2(B) ZENER DIODE” which does not resolve to much for me. However, I suspect it’s just a 5V zener. Posted in Radio Tagged chirp , kenwood , radio , serial , tm-281 July 29, 2022 13:31 by: Dan trackback permalink GenRight TJ Aluminum Front Fender Notes I recently installed GenRight regular aluminum front fenders on my TJ. It was my first time doing fenders and it turned out to be a lot more than I was planning for, so I thought I’d document some of my notes here for anyone else that might be wondering about the process. I’ll also include some thoughts on GenRight and the fenders in general. First off, I called GenRight before I ordered, asking for the install instructions ahead of time. I hate when companies don’t just publish these on their site, both for pre-order information, but also because I want to maintain a PDF copy long-term and refer to that during install. They were super nice on the phone and assured me that the install was very easy if you also go with their inner fender...