An Astatic D-104 microphone was my final, last-minute purchase from the Shelby Hamfest. We were walking to the gate heading out when I spotted a table I hadn’t visited off to the side and decided to wander over to have a look. The D-104 on the table naturally caught my eye, and decided to grab it.
Another Astatic D-104 microhone
Another Astatic D-104 microphone
This one was missing the bottom cover plate, and the microphone connector was removed. Looked like there might have been some re-wiring done at some point and two of the wires from the cord are unconnected, unlike my other D-104 microphone. The electrical tape on the wires connecting the microphone element suggests that maybe it was replaced at some point as well.
D-104 microphone element
At least there’s no rotting foam in this one. The microphone element housing is also a little different from my other one. This one is basically just a ring with some bits of foam supporting the microphone element while my other D-104 is more case-like.
I’ll have to see what I can do about finding or making a new cover plate for this microphone.
We made the road trip out to the Shelby Hamfest for the first time. It’s one I had been wanting to get to for quite a while now, but it happens the same weekend as Dragon*Con so I never made it until this year.
We drove up Friday afternoon, and Saturday was the only day we spent at Shelby. Got there bright and early as the gates were opening, so we were able to get a decent parking spot. Spent the early morning wandering around the boneyard/flea market checking out the early birds that opened up their tables until the indoor stuff opened up. Checked out the indoor people, then spent the rest of the morning exploring the boneyard.
Lots of people out in the flea market area selling the usual range of really nice gear to miscellaneous stuff. Saw at least 3 or 4 people selling some really nice looking Collins radios, ranging from complete sets to single cabinets. I can see why people like to collect Collins gear. They’re really nice looking units. I got a bit drooly looking at them.
Didn’t really have a big shopping list going to the hamfest, but did end up picking up a few things with the goal of putting mobile VHF radios into the cars in mind. In the boneyard, I found a couple of Fluke multimeters for a pretty good price. Seller didn’t know what condition they were in, but I figured for $10, they would either be decent workbench instruments or fun projects to work on. Also found a D104 mic missing the bottom plate and connector for pretty cheap so I grabbed that too. A few other miscellaneous tool type items rounded out the shopping day at the hamfest. Didn’t see too many Morse code keys, but there was one table that had a selection of older Vibroplex bugs that I was kind of tempted by.
The crowd seemed to be a lot lighter than I expected, even during the middle of the morning and early afternoon. There were a lot of cars in the parking are by the time we left but it didn’t seem that crowded while we were there. I suppose the size of the hamfest helps spread everybody out. Had some fun random encounters with a few other hams that we new, and a nice conversation with Bill Morine/N2COP, ARRL Roanoke Division Vice-Director.
I was too busy wandering around checking things out and trying to decide if I “needed” it or not to get any pictures of the hamfest, but Connie got this early morning-ish photo of the boneyard off in the background.
I can finally get around to some of the things that have been sitting in boxes in the garage for the last year or so.
Here we have a Tempo S1 handheld 2m FM transceiver that’s had some obvious modifications done to it. The battery pack was replaced with a car power adapter, the original telescoping antenna was replaced with a BNC connector and, based on photos of other Tempo S1 units I’ve seen online, the earphone and antenna jacks have been replaced.
Tempo S1 handheld FM transceiver
Tempo S1 handheld FM transceiver control panel
Tempo S1 handheld FM transceiver back
Tempo S1 handheld 2m FM transceiver
Frequency selection is done by setting the thumb wheel switches to the desired frequency. A slide switch for the 1 kHz place lets you select 0 or 5 kHz, giving the radio 5 kHz tuning steps. In the photo, the radio is currently tuned for 145.690 MHz. To get 145.695, you’d slide the switch over to the +5k position.
Getting inside the unit is a simple matter of undoing 4 somewhat rusty screws. The back lifts off to reveal the radio guts and the battery compartment where the car power adapter was wired in.
Tempo S1 handheld FM transceiver power connection
According to the manual, an 8 cell NiCad battery pack providing 9.6V fit into that space. Charging the battery was done by plugging an external charger into the 1/8″ jack next to the offset selector switch.
The radio guts consist of two circuit boards. One appears to handle the RF side of things, while the other one looks like it handles the controls. It’s quite the nest of wires inside.
Tempo S1 handheld FM transceiver circuit board
Tempo S1 handheld FM transceiver circuit board
Tempo S1 circuit boards
There’s a single IC on the board with a sticker labeled NIS-103, which I’m guessing might handle generating DTMF tones from the keypad on the front. A few wires have been soldered directly to the legs of the IC so whatever it is, removing it won’t be easy to do.
Tempo S1 handheld FM transceiver integrated circuit
An inspection of the components on the boards didn’t reveal anything that was obviously problematic. Lots of tantalum capacitors and a few electrolytic caps, but they looked fine.
Didn’t have 9V handy to connect to the power leads but I did have a 12V battery pack, so I connected that to the radio and turned it on. The radio came alive with static, which seemed like a good sign. Didn’t try anything else with the radio. I’ll work on making up a suitable connector so I can attach a 9V battery or find a suitable replacement battery pack for future experimenting.
Given the radio doesn’t have any CTCSS capability, it might be of limited use with repeaters these days unless they don’t use CTCSS tones. Still should be useful for simplex communications though.
This year was another back yard Field Day (1D SC) and invited neighbours over again to hang out, chat, listen to me play on the radio (none of them wanted to give the radio a try), and of course eat. Got the dipole up in the air and had it working pretty well on 40m, 20m, and 10m.
HF dipole up on the mast
This year I also set up the 2m radio outside to listen in on the repeaters using a ground plane antenna kit we picked up at HRO back in the spring. Made a makeshift mast out of some 2×4, a length of 1″ PVC pipe left over from another project, and a spare mounting base for an outdoor weather station. Had it propped up against the fence, but I didn’t have any coax long enough to reach the radio, so I moved the antenna closer and leaned it up against my ladder. Worked well pretty well and had 1.5 SWR across the 2m band, which is way better than the hacked together mag mount currently sitting in the shack.
2m quarter wave ground plane antenna on a makeshift mast
The ground plane antenna will probably find itself up in the attic at some point once I figure out how to run some coax down into the shack.
Got the radios and laptop set up on the back porch. Fortunately the rain went elsewhere, and the associated clouds kept things relatively cool for operating.
Radio and laptop set up for Field Day 2021.
Band conditions weren’t that great, but they weren’t terrible. I didn’t hear the usual cacophony of stations this year. Lots of faint stations, a few loud ones, and mostly static in between. Tried 40m, but there was a lot of really odd sounding noise and stations fading in and out. Lots of stations up and down the east coast early on and then later in the evening on 20m, the band went long toward the west and I started hearing stations out in CA and WA. Managed to break through the pileup to get W1AW in the log. Also heard the Walt Disney World DEARS club station, WD4WDW, but wasn’t able to get through their pileup. The operator was fun to listen to though.
Called it a night around 10PM after unsuccessfully trying to break a few more pileups for stations out on the west coast. My ultra-casual operation managed to get 19 contacts in the log, mainly on 20m and 10m, including a few Canadian stations, USVI, PR, and a DX station Costa Rica.
I’ve always liked the aesthetic of the D-104 microphones, so when I came across someone selling a couple of them at the local flea market a few months ago, I bought one of them.
Astatic D-104 microphone
Astatic D-104 microphone
Astatic D-104 microphone
None of my radios uses a 4-pin microphone connector, so I haven’t tried the D-104 out yet. I’ll need to make an adapter for it first.
In the meantime, time to take a look inside. I’ve read online that there are a number of modifications that can be made to the D-104, so I wanted to see what the state of this one was.
Undoing three screws allows the bottom base plate to be removed, revealing a terminal strip, the amplifier board, a volume potentiometer, and a battery. The battery was pretty dead (~4V on the DMM) but fortunately it hadn’t leaked.
Astatic D-104 microphone circuitry
Astatic D-104 microphone circuitry
Astatic D-104 microphone circuitry
Astatic D-104 microphone circuitry
Astatic D-104 circuitry in the base
I don’t know what the innards of a D-104 are supposed to look like, but this seemed pretty stock to me.
The back plate of the microphone head was removed by undoing 4 screws. The microphone element takes up most of the space inside the head. Foam attached to the back plate helps keep the microphone element in place. The foam here was pretty badly deteriorated.
Astatic D-104 microphone element
Astatic D-104 microphone element
Inside the head of the D-104 microphone.
The connections on the microphone element look pretty messy because of the rotted foam, so I might need to replace it.
A connection diagram is conveniently attached to the base plate.
Astatic D-104 schematic
I think this will be a fun microphone to use with the radio once I get a proper connection made up (and maybe a new microphone element).
