Another Astatic D-104 microphone

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 microphone
Another Astatic D-104 microhone
Another Astatic D-104 microphone
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
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.

Tempo S1 FM transceiver

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.

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
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.

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
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.

Field Day 2021

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.

Dipole set up on the fiberglass mast
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 mounted on a makeshift mast.
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.
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.

Evening radio station illumination provided by the radio, SWR meter, and W4BXC edge lit acrylic sign.
Evening radio station illumination

Astatic D-104 microphone

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.

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.

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.

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
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).

Atlas 210X HF radio

One of the items in the KB4NNM (SK) collection that was donated to the club earlier this year was an Atlas 210X 5-band HF radio mounted in a 220-CS AC console. The console allows the radio to be operated off mains power, provides a speaker and VOX capabilities.

Atlas 210X mounted in a 220-CS AC console
Atlas 210X mounted in a 220-CS AC console

It’s a pretty nice looking setup. Until I did a bit of research on the radio, I didn’t realize that the radio and console were separate items. Turns out, the radio just slides into the console, and connects using some 1/4″ plugs and a banana jack-like connector for the antenna.

Atlas 210X removed from the console
Atlas 210X removed from the console

Sounds like the radio works, although the speaker produces a buzzing noise (60Hz hum I think) even when the radio’s AF gain is turned all the way down. Turning some of the dials and switches produces some static-y noises, so it sounds like those will need some cleaning. Haven’t had a look inside the radio yet. That will be later.

This seems like it might be a nice radio to use in the club room.

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