Tag Archives: Kenwood TH-D74

March 2021 Satellite Operations Gear

At the time of posting, I’m actually in the midst of changing my satellite gear so it is no longer my current setup. That said, I wanted to document it before I forgot about it and pass along my thoughts in case anyone else finds the information useful in the future.

In general, the radios and antennas for my ham radio satellite operations I’ve used have not changed since my last gear update (February 2020 Satellite Operations Gear). Check out that post for more details, but basically I use a Kenwood TH-D74 for a receive radio, an Yaesu FT-817ND as a transmit radio, an Arrow Antenna (now a custom-drilled version by WY7AA), with a variety of cables and adapters in between. In the last six months, I added a 3 Ah Bioenno battery pack to power the FT-817ND as well as a David Clark PC headset to replace the cheap PC headset I previously used.

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Powering a Ham Radio with USB Power Delivery

A while back, I built a cable to power 12V devices (in my case a Kenwood TH-D74 HT) using the QuickCharge standard available in some USB power adapters. This allowed me to use a USB charger to charge my HT rather than bringing a dedicated wall wart which helped save some space when I traveled. While my homemade cable was electrically simple and worked as expected, it was a bit clunky. Also, QuickCharge is largely being replaced by USB Power Delivery (USB-PD), and since my laptop chargers using USB-PD, I found that I could consolidate my charging needs further by getting an adapter that works with USB-PD. 

Of course, I’m not the first person to try to adapt USB-PD for other purposes, so I was able to find a few products that partially solved this problem. I quickly came across a line of small adapter boards that negotiate the USB-PD protocol and provide an adjustable or preset voltage based on the standard. These are available on Amazon (affiliate links on this page) but can also be found even cheaper on eBay if you’re willing to wait for shipping from China.

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Replacing Top Panel and Belt Clip on Kenwood TH-D74

I’ve enjoyed using the Kenwood TH-D74 for the last four years or so, and despite its regular use and fragile design, it has survived that period without any major damage. However, a couple years ago, a small crack started to develop on the back of the case next to the belt clip. I don’t recall dropping the radio ever, so I assume this must be from bumping into other stuff when traveling with the radio in my backpack. I filled the crack with some glue to try to stop it from growing and that seemed to mostly work, although I was still concerned about water ingress. I’ve tried to be careful since and haven’t had any issues.

Fast forward to a few weeks ago, and I’m out hiking with the D74 to test APRS with a new antenna. As I go to clip the radio on my pocket, the belt clip snaps in half. I didn’t use the belt clip too often, but the plastic must have just weakened over time. I noticed that the spring is quite tight so that even when snapped in half, there is enough pressure on the clip to close it all the way to the radio body as you can see in the first photo above. Perhaps a poor design, but in any case, I needed to fix this one.

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February 2020 Satellite Operations Gear

To track things over time, I thought I’d do an overview of my satellite gear as of February 2020. I actually have two different setups for satellite operations: one for the FM/APRS sats and one for the linear transponder sats. Since I do FM sats much more often, I’ve tried to slim that setup down so I can quickly run out to catch a pass.

In both setups, my Kenwood TH-D74A serves as the receiving radio and APRS transceiver. This radio, while not full duplex like its brother the TH-D72A, it is a great option for satellite operations in a two-radio configuration. My favorite feature is the built-in audio recording function. This makes recording audio from satellite passes for later transcription a snap without a mess of additionally cabling and a dangling audio recorder. This radio also contains an APRS function which can be used with the ISS and other APRS satellites with just a couple configuration changes. Finally, this radio has a wideband all-mode receiver which lets it work for SSB on linear satellites. Of course, tuning is a bit tricky without a big knob, but it is doable. For FM sats, I simply hang it from a lanyard around my neck and use a 2.5mm mono to 3.5mm stereo audio adapter cable to connect it to earbuds. I also have all the FM sat frequencies programmed into memory so there is little preparation required for a particular pass.

For FM sats, my transmitting radio is typically the Ailunce HD1. This radio is dual band DMR/FM radio, which makes it versatile outside of sat operations and a way for me to keep my ham radio equipment list to a minimum (blasphemy, right?). There is nothing special about it other than it rated for 10W RF output which can be a nice extra boost when needed (like when using my Shorty Arrow).

Chest rig with Yaesu FT-817ND and Kenwood TH-D74

Chest rig with Yaesu FT-817ND and Kenwood TH-D74

For linear sats, my transmitting radio is the venerable Yaesu FT-817ND. It serves double duty as my QRP HF radio, so it is easy to bring my HF and sat setups together on trips. In order to make it a bit more user friendly for satellites, I’ve added a computer headset with a couple adapters and a handheld button for PTT. I also have made a chest rig made from dual-shoulder camera straps and two MOLLE pouches which hold the 817 and D74 at an angle for easy viewing. This works fine but I’d like something a bit more secure to hold the D74.

LidStick

My Arrow Antenna turned LidStick

The antenna I use is either my standard Arrow Antenna (modified into a LidStick) or my Shorty Arrow (also LidStickified). In 2019, the Mini Circuits BLP-200+  popped into my Twitter feed as Mike, W8LID (also the creator of the LidStick), found that it worked well to prevent desense that is sometimes experienced on certain satellites and radio combinations. This filter is put on the 2m driven element BNC connector, and in my experience, it has completely removed the desense issues I had. You may notice it has a 1/2W rating; Mike got in touch with Mini Circuits and learned that this is really only an issue for out of band signals. Many of us have consistently put 5-10W or more of 2m signals through the filter without any issues.

To travel with my Arrow Antenna, I use a telescopic plastic tube which is commonly used to transport real arrows or posters. It is fairly lightweight, but strong enough that I’ve put it in my checked bag many times and it has kept my antenna protected. It is large enough to fit the full size Arrow Antenna, my Shorty Arrow mast, and even my rubber duck antenna for my HT. For the price, this is an excellent option for transport and storage.

For coax cables, I currently use RG-58/U and LMR-240 UF jumpers with BNC connectors. I recommend staying away from cheap RG-58/U (I’m using it temporarily), but the LMR-240 UF is high quality stuff.

The last part of my setup is my iPhone 11. Nothing special about it, but it runs GoSatWatch as my main satellite tracking app. The app costs $9.99 on the App Store, but it is well worth it for any sat op. I really like that it uses the IMU in your phone so that you can hold your phone up to the sky and physically orient yourself to where the pass will be in augmented reality. It has a simple but nice user interface and can support more than just ham radio satellites.

Theodolite iOS App Camera View

Theodolite Camera View

The other app I use occasionally is Theodolite. Photos from this app are often posted to Twitter, leading many to ask “what app is that?” It is useful to see your exact position and error of the GPS and record that for those gridline and corners that require evidence. It is $5.99 but again, well worth it as it has many other features that you may find useful.

 

USB Quick Charge 2.0 Adapter for 12V Non-Quick Charge-Enabled Devices

As I got interested in roving more for satellite operations, I was looking for ways to slim down the equipment I needed to carry, particularly on trips that require a flight. While packing one night, I noticed I had a Tronsmart WC2F USB power adapter that supports the Qualcomm Quick Charge 2.0 protocol. This is one of several protocols that let devices use higher voltages and currents over a standard USB A connector. There are a few versions, but in short, this protocol allows for the USB power adapter to supply 12V at 1.5A, among other less interesting voltages (to me anyway). This seemed like a perfect way to charge my 12V devices – my Kenwood TH-D74, Ailunce HD-1, and Yaesu FT-817ND – without having to bring along an additional wall wart.

After digging a bit, I found an article on Hackaday where someone made a custom power adapter using Digispark, a modified regulator, and some simple handshaking code. Going down into the comments, Sam Mallicoat mentions the handshake can simply be done with a couple resistors and a momentary switch. Even better, Horst Leykam replied that a regular old latching SPST could work instead of a momentary switch. Aha! Since I was trying to keep this compact, this seemed like a great option compared to adding a microcontroller to the system. My plan was to made a cable adapter with an in-line switch that contained the resistors. A USB A male connector on one end and 2.1mm barrel connector on the other would give me good compatibility with my devices.

12V Enable Circuit for USB QuickCharge 2.0

For the switch, I ended up buying a simple Leviton in-line lamp cord switch which is large enough to hold the resistors inside and can be found online or a hardware store. I unfortunately didn’t take photos at the time, and I admit it wasn’t pretty inside; I had to use some hot glue to keep wires where I wanted them and rip out the regular lamp cord contacts. But still, it was not too difficult of a project.  As this uses a SPST switch, the operation is as follows:

 

    1. Plug USB cable of adapter into Tronsmart
    2. Cycle the adapter switch to off (if it’s not off already)
    3. Switch adapter on
    4. Voila! After a moment, 12V will be coming out on the barrel connector

Note that this switch does not control power entirely; when the switch is in the off position and before cycling it, it will still be outputting 5V. This is likely not an issue for a 12V device, but of course, proceed at your own risk!

While I know my adapter could be prettier, I’ve been happy with it so far. I have 2.1mm y-splitter cable which allows me to charge two devices at a time, usually my D74 (with a small connector adapter) and HD-1 or D74 and 817ND. While it could actually run one of those devices at a time based on its current capability, the inexpensive switching regulator in the Tronsmart is expectedly noisy, so this really should only be used as a charger. Since the Tronsmart is a dual USB port charger, I can bring this adapter to charge my radios and iPhone or iPad all from the same outlet at the same time.