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Latest Topics

Topic Created Posts Views Last Activity
DMR Handheld Mic Motorboating Jun 20th 2018, 19:53 1 1,401 on 20/6/18
Homebrew Balun Wire Feb 14th 2018, 09:05 4 1,162 on 15/2/18
Noise Antenna and MFJ-1026 Mar 14th 2017, 23:58 2 2,326 on 15/3/17
RFI with Laptop Power Supply Dec 16th 2016, 03:00 2 1,746 on 4/1/17

Latest Posts

Topic Author Posted On
DMR Handheld Mic Motorboating W9KJO on 20/6/18
I have a DMR handheld (5 Watt) and wish to use a two wire mic and ear piece with my handheld but with the two pin kenwood plug plugged into the handheld and the rubber duck antenna attached I get a lot of motor boating into my transmission.

This is clearly caused by the Time Slot carrier in near proximity to my mic cable. I know this because when I connect an external antenna to my radio, like my dual band antenna on the trunk of my car, the motor boating goes away.

I wish to use a mic/earpiece combo with my DMR handheld. Can someone tell me how to overcome this RFI problem? or perhaps someone knows a handheld mic and ear piece that will not present this RFI.

Thanks for your help.

73, W9KJO, Walter
Homebrew Balun Wire W9KJO on 14/2/18
Thanks for the response. However I need more information on wire size as this wire is very costly and experimentation would be cost prohibitive.

What size wire do you use for,

1. 300 watt balun
2. 1500 watt balun

HF Bands. 80M, 40M, 20M, and 160M

73, W9KJO
Homebrew Balun Wire W9KJO on 14/2/18
A few months ago there was an article about building baluns for antennas in QST. I have been doing some research and wish to build a few baluns. However, what type and size of wire is still not clear to me.

I have been told to use Teflon Coated wire, Is this a good example of teflon coated wire?

Also, what Gauge wire would be needed for,

1. 300 watt application
2. 1.5kw application

Thanks for any clear answers that might be offered.

73, W9KJO
Noise Antenna and MFJ-1026 W9KJO on 14/3/17
This may seem like a weird question and idea but here it goes.

I bought the MFJ-1026 and built a noise antenna and it does clean up the noise it can receive without the Modulation. However on 80m even a short antenna seems to receive the modulation before it receives the noise like lightning crashes.

So, my thought is, if I can filter out the modulation off of the noise antenna before I feed it into the MFJ-1026 then I could, perhaps, filter out the lightning crashes.

Is there a way to filter the modulation for a certain passband without filtering out the noise?

This seems counter intuitive as we hams usually want those signals but for the sake of phasing out noise this would be most helpful.

Any advice available would be very helpful.


73, W9KJO
RFI with Laptop Power Supply W9KJO on 16/12/16
I have a strange problem with my Laptop power supply.

I am using a 12vdc supply with my solar system and batteries. I bought a special supply that is supposed to be RFI quite on ham bands. It was for a while.

Now when it is plugged into the laptop, when the laptop is off, I get massive RFI bands on 80m and less RFI on 40m and 20m.

When the laptop is turned on the RFI switches to birdies floating through the bands, about equal on 80, 40, and 20.

If I remove the power supply from the Solar batteries and attach a separate battery the noise disappears all together and the laptop works fine.

I bought two of these supplies, one for the car, so I hooked up the second one, which to this point I have not used, and it has the same problem and identical RFI.

I could run the laptop on a separate battery but if I connect the separate battery to my solar batteries to keep it charged I'm sure I'll get the RFI back.

It's unusual and I'm not sure how to resolve this. suggestions are highly coveted.


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