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Author Topic: A few questions about building a simple HT CW keyer.  (Read 2968 times)
KJ6FCK
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Posts: 6




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« on: June 30, 2011, 06:29:54 AM »

I want to build a FM morse keyer using N1HFX plans http://www.rason.org/Projects/fmkeyer/fmkeyer.htm but I am a total newbie (I didn't want to use that word but can't think of a better one) my question is how to wire it to the mic plug going in to the HT, I know my Puxing PX-777 has PTT running to the mic plug, do I run the connection to the mic plug to one and the connection to the PPT to the other wire or do they both go to one and I run ground to the other? Also I can just run the speaker circuit in parallel off of leg three of the 555 chip, right?

Here is an IMG of how it should be laid out, I just need to know where the mic plug wire and the PPT wire run to.
http://i6.photobucket.com/albums/y203/paraframe/HTCW.png

Like I said, I am a total newbie and I can use any help. thank you very much.

73 from KJ6FCK.
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KE3WD
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Posts: 5694




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« Reply #1 on: June 30, 2011, 06:54:38 AM »

This is Modulated CW.  The circuit is an oscillator that generates an audio tone which is introduced to the Mic input of the HT instead of the Mic. 

The PTT is a separate entity which must be closed first so that the HT is put into transmit mode, awaiting the modulated code oscillations from the keyer. 

A typical three-wire Mic circuit such as found in HTs shares the Ground or Common terminal between the Audio input and the PTT. 

Not familiar with the little chinese HT you mention, but it should be easy for you to ascertain which of the three connections are which.  First of all, the shared Gnd point is likely to be the one that is also the mic's shield connection, which is typically going to be the Sleeve connect on a miniature phone jack.  You can use your ohmmeter to figure that out as well, it will likely have continuity with the GND part of your antenna connector. 

Of the other two wires, one should be the PTT, when grounded it should put the HT into Transmit mode.  With nothing at all connected to the Mic Audio input, the *other* wire, it should throw a dead carrier (and will throw a dead carrier when the keyer circuit is also hooked to Mic jack but you haven't keyed it). 

In your pictorial you show two wires only coming from your plug.  Compare the shaft of your plug carefully with the one on the MIC.  I have a feeling you may be trying to use a two-wire MONO plug where a three-wire, or TRS (Tip, Ring, Sleeve) plug that carries through three connections is what you need here. 


73
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KJ6FCK
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Posts: 6




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« Reply #2 on: June 30, 2011, 07:05:08 AM »

Thanks, I haven't bought the plug yet, good to know I need a three wire plug, now it all (kind of  Cheesy) makes sense, so I do ground the CW keyer to the ground on the mic plug, right?
Thanks again.

So it should look something like this?
http://i6.photobucket.com/albums/y203/paraframe/HTCW-1.png

73 from KJ6FCK. 
« Last Edit: June 30, 2011, 07:18:55 AM by KJ6FCK » Logged
AA4PB
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« Reply #3 on: June 30, 2011, 07:57:06 AM »

According to the manual and other info on the Internet, the Puxing speaker-microphone connection is rather unusual. The common ground connection for the PTT and the Microphone circuits is the sleeve of the smaller 2.5mm jack. The PTT is the sleeve of the larger 3.5mm jack and the mike audio is the ring of the 3.5mm jack. You have to use both jacks to accomplish what you need.

Both jacks are "stereo" type with three connections; tip, ring, and sleeve. One jack is 2.5mm and the other is 3.5mm. Puxing uses a special connector containing both plugs, properly spaced, on their speaker-mike unit. You can probably use individual plugs provided there is room to insert both at the same time.

Here's a schematic of the speaker-microphone connections:

http://ha4bf.ham-radio-op.net/puxing/puxing_sp_mic.jpg

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KJ6FCK
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« Reply #4 on: June 30, 2011, 08:07:18 AM »

Thanks AA4PB, that schematic tells me everything I need to know to go forward with this project, now I just need to gather the supplies.
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KB9TMP
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« Reply #5 on: July 03, 2011, 06:39:17 PM »

And for a parts source or wiring diagrams for speaker/mics think Kenwood HTs. They are both wired the same.
73 KB9TMP
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KJ6FCK
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« Reply #6 on: July 04, 2011, 08:56:55 AM »

Thanks KB9TMP, I knew they shared the same plugs but it is good info for anyone who comes across this thread in the future when searching. My local electrical warehouse was/is closed for the 4th since Friday but I should be able to get my parts tomorrow and start building.
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