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John, Thanks for the schematic!? That all makes sense to me, and it matches the math in your previous post, so I appreciate putting a picture to the words. I know in the past I have connected my

Hello Rob, Replying to your first question: a mic output is generally in the 10s of mV. On top of my head I have 50mv as a typical mic input voltage for radios, so 100mv was king of a safe value for a

Hi, There are several reverse polarity schemes that can protect the radio from damage in a reverse polarity episode. That is an episode of connecting DC power source with the positive and negative

I would say the diodes you saw were to prevent any signals greater than the forward bias voltage, rather than signal routing. -- 73 Dave ADOB ( https://www.qrz.com/db/AD0B ) Raduino bracket and

I have refined my requirements a little. - The default input (enabled, even if neither PTT line is activated) is the computer line-in.? Why?? So that I can do PTT via CAT control if desired. -

John, you mentioned 100mv for the audio signals, is that ballpark for both computer audio and mic audio?? I guess I'd assumed it was around 1 V p-p or line level or somesuch.? But I haven't measured

Attached. Stop blowing stuff up… -- This email has been checked for viruses by AVG. https://www.avg.com

The fuse is there to protect the power supply in case your radio develops a short! 8-) _._

Ahem -- You can take Bill Cromwell's guidance to the bank. I used a 3amp fuse, and discarded the diode.? The way I figure it, every single power source in my house (and my zip code) has center pin

I will second Bill's assertion.? A fuse does not prevent the magic smoke from leaving your radio, though it's blowing "might" mitigate further damage if you're lucky. A fuse keeps your house or car

Rechecked and it will not work reliably.? Will need to look at it some more.? As stated, I just did a quick? sketch. Sorry, 73 Evan AC9TU

Rob, I was following the examples in the attached. https://hackaday.com/2016/12/ 09/diodes-the-switch-you- never-knew-you-had/ (

Hey Evan, thanks for the quick response.? I follow the logic of the NAND gate, and also the forward biasing.? What I'm confused about is the reversing biasing, i.e. turning off a given input.? My

ROB, The gates are NAN gates.? A NAN Gate logic is A? ?B? ? out ======== 0? ? 0? ? ?1 1? ? 0? ? ?1 0? ? 1? ? ?1 1? ? 1? ? ?0 For the input, we take the PTT of the Mic direct

Evan (looking at yours specifically in this reply), Can you help me understand what is happening in the "both PTT open" state? Specifically, I'm trying understand the status of the "Mic In" and

Hi Rob, Check the switching and circuits in your mic. I don't know what is inside ALL mics, especially not the el cheapos. My mics have always had a separate pole on the switch for the mic audio. If

Hey, all. I have two 6-pin (RJ14) ports on the front of my portable setup, one for a microphone and one for JS8, etc. It's really simple and requires no extra parts. The data transmit audio (and the

Hello Rob, I have the same situation and was looking at a simple solution too. Here are my thoughts based on your idea. Have a look at this page for

Interesting idea.? After some quick sketching, I think it could be done with 3 capacitors, 3 resistors, 4 diodes, and a Nan gate (Not And).? I have not worked out the details, but here is a rough

I have successfully used a dpdt arrangement. The center goes to the radio and the switched inds going to the mic/soundcard speaker and the other to the speaker/sound cardmic. One uBITX used a regular