Finally, the COVID-19 has calmed down. Recently, club members have been gathering in the radio room more and more.
Now, JQ1YLK does not have a dedicated club room. However, since it is also “the Emergency Communications Base” in this area, we cannot change rooms every time we have an activity, so we share the location with other facilities.
We use a corner of a printing room, so it fills up when club members gather. Some sit in front of the rig and some gather around it, and those who can’t get there form a different circle of conversation later. This is a natural scene here.
Now, when this happens, QRM (interference) occurs not on the radio waves at a certain MHz, but in the room where the receiving sound resonates. You might think, “That’s something that can be solved by just turning up the volume,” but that’s not the case.
Let’s think about it from a different perspective. Imagine you have a tiny business to take care of in a certain room at the community center. You are free to enter and leave that room at any time. However, when you go there and open the door, it seems that the “piano club” is there, playing Chopin’s etudes. So, what would you do? (1)Open the door and go about your business. (2) Wait until the piano gets stuck or finishes playing before entering. (3) Give up.
That’s what we do. In any case, it’s important not to create a “different world” like this. For radio clubs, headphones are effective in this situation. However, headphones usually only have one output per radio. “This station has been coming in a lot lately”, “Someone is responding me in JA6”, “Ah, we’re starting to hear Europe now”….. It’s sad when you can’t have such conversations even though there are a lot of people.
So….(Sorry, I always make long introductory remarks….), I tried making a headphone distributor.
The inside is quite simple, only resistors except jacks. The resistors are connected in a star shape, with a jack attached to each end, and one is a plug.
The resistance value in this case is R = 8 (N-1) / (N+1), where the impedance is 8Ω, and N is one input plug + number of distributions (3 in this case). For 2-way distribution, R = 2.7Ω, for 3-way distribution, R = 4.8Ω, for 8-way distribution, R = 6.2Ω…
I don’t use such low resistors very often, so I went to Akizuki Electronics to buy some, and they were selling 100 pieces for 50 yen. It was cheaper than buying 8 pieces separately, so I bought this.
When I got home and looked at the low frequency output of my rig, it was 2W. Hmm, what I bought was only 1/4W… so I thought it would be okay, but just to be sure, I connected two in parallel and two in series to get a 4.7Ω 1W resistor for 4 pieces. So 32 pieces of 4.7Ω are used! Well, it’s only 16 yen.
Three headphones can be too crowded, so I made it so one can be paired via Bluetooth. You can join the watch even if you’re a little far away from the radio.
I didn’t know this, but with some Bluetooth devices you can pair two headphones to one transmitter at the same time. This means that this splitter can share the signal with up to six people, or up to 12 if you push it a bit.
(2023.3.25)
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