Posts Tagged ‘Choke’

NanoVNA and checking a common mode choke

 


Last week a new toy arrived a Nanovna and I have been playing around with it and learning the ins and outs of the unit. This unit allows me to check antenna SWR, attenuation and coax switch isolation to name a few things. I am not going to get into the details of the Nanovna as there is lots of information for those interested available on the internet. My first project was to check the attenuation on one of the common mode chokes I made. It was made from RG316 coax, FT 240-31 mix toroid and had 10 turns on it. I never put this common mode choke through any testing as I did not have anything to test it. I was going by some charts, the type of toroid mix and the number of turns needed for 40m to 10m. 


Now that I had a Nanovna I could perform an attenuation test on the common mode choke I was using and see some actual numbers. I have been reading and -30dB or more across 40m-10m is great for a common mode choke. I calibrated the Nanovna and performed an attenuation test and to my surprise, the common mode choke I made failed! The common mode choke I made was above -30dB from 40m to 10m. It was not time to fix the problem and bring my readings below -30dB. 

The red line is the results

 

I tried reducing the windings around the core increasing them and doing a Nanovna sweep each time to see the results. My final result was 14 windings and that gave me the ideal results. The Nanovna indicated -35dB on a full band sweep (6.5MHz to 30MHz) on individual band sweeps the readings were 10m -44dB, 15m -34.5dB, 20m -35dB and 40m -35dB. I am much more pleased with these readings. 

Full band sweep


The software to display the readings is called Nanovna saver, it's free and works great. I am very pleased with the results from the Nanovna and I was able to check and fix my common mode choke. I will now move on to the next project and that is the isolation between antenna 1 and 2 on my LDG AT200pro2 but more on that in another post.

The 1:1 isolation choke do-over.

 

New 1:1 choke with RG316 coax

 I have the Hustler 4BTV vertical antenna and have a 1:1 choke at the base of the antenna made by Balun designs. Some time ago I made a second choke that was placed at the radio end and posted the build here on the blog. I had a few comments regarding the coax that I used (RG8X) and that there could be an issue with the bending radius of the coax around the core. I was informed that over time the centre conductor could migrate toward the braid.

I also did some internet searching and found that the bending radius could pose an issue and I know the "issue" if and when it happened would do so at the most inopportune time. I decided to make another 1:1 choke from a thinner coax. I did have some RG316 coax from a mobile antenna mount I was not using and it would be ideal for the tight turning radius.

 On one end of the coax, there was a mini-UHF to PL-259 adapter which meant I only had to add one PL-259 connector. I will be using again an FT240-31 core with 10 turns. I decided on 10 turns as this will afford me decent characteristics on the HF bands. Using the RG316 coax the bending radius is no longer an issue. 


 

Ham Radio & PLT devices

Over the past few years and again recently I have heard a lot of chatter regarding PLT interference. Especially with Ham radio and shortwave bands. These devices plug into a power wall socket in your house and allow you to create a wired network via your mains wiring in the property. It’s a perfect solution for properties that cannot send a wireless signal from one end to another (Just like mine).  It does however have a draw back. In creating a wired network these PLT devices create a lot of mains born interference and this can effectively block out any amateur radio bands.

In recent stories I have heard audio samples and read stories of how these devices can create S9+20db of noise. Thus reducing the amateur bands unusable.

I wanted to see for myself the effect of using PLT devices in my property. So I visited PC World and purchased 2 devices from NetGear. The Powerline 500 promise 500Mbit/s and this would solve a huge problem I have in my home right now, but feared for what it would do to my beloved radio.

The results were interesting and nothing what I expected. You can see my full test in the video below – but for a spoiler alert keep reading....


The results were - It did nothing. It had zero effect on any of the bands I use at home. After the video I monitored the shortwave bands and tried other frequencies. Again, nothing.  I tried it while the network was busy - I streamed 4K films and copied a 25Gb file. Guess what. Nothing.

The moral ? – Don’t believe the hype.

Ham Radio & PLT devices

Over the past few years and again recently I have heard a lot of chatter regarding PLT interference. Especially with Ham radio and shortwave bands. These devices plug into a power wall socket in your house and allow you to create a wired network via your mains wiring in the property. It’s a perfect solution for properties that cannot send a wireless signal from one end to another (Just like mine).  It does however have a draw back. In creating a wired network these PLT devices create a lot of mains born interference and this can effectively block out any amateur radio bands.

In recent stories I have heard audio samples and read stories of how these devices can create S9+20db of noise. Thus reducing the amateur bands unusable.

I wanted to see for myself the effect of using PLT devices in my property. So I visited PC World and purchased 2 devices from NetGear. The Powerline 500 promise 500Mbit/s and this would solve a huge problem I have in my home right now, but feared for what it would do to my beloved radio.

The results were interesting and nothing what I expected. You can see my full test in the video below – but for a spoiler alert keep reading....


The results were - It did nothing. It had zero effect on any of the bands I use at home. After the video I monitored the shortwave bands and tried other frequencies. Again, nothing.  I tried it while the network was busy - I streamed 4K films and copied a 25Gb file. Guess what. Nothing.

The moral ? – Don’t believe the hype.

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