What's An Ugly Choke?

[@paulbillingham4594]

Hi Don. I'm Running an FT857D here in the UK, feeding a random wire antenna for Top Band and HF. Although this seems fine on my Licensed 50 watts, I was interested to see what RF came back, especially on Top Band. Going around the shack with a field strength meter showed resonance on many things such as computer cables, but no real interference problems. I bought a little RF current kit from G4HUP to see what is returning as surface current on my RG58 coax cable. With the RF current kit was able to make an Ugly choke spot on an now have to really search fro stray RF. Thanks for posting the video I have copied your choke dimensions and it works well. I believe a home brew RF meter follows your video on You Tube. 73 Paul 2E0MIY

[@vk6cs456]

Hi Paul. Many thanks for the comment, it sounds like you've cracked it. I like the G4HUP RF current meter, much better than mine, no need to put it in series with the wire of interest, just like the MFJ device. I think I may modify mine to be a clamp type too.

[@buzzsah]

LOL, They know how to make you love them.

[@alanhughes1262]

Works great i have one just down from my antenna and one near my radio 10 turns each 213 coax / 100mm pvc .

[@justovelarde3456]

A question, for the 2 meter band at 145 Mhz and using RG8 cable, is it NECESSARY to put this RF Shock on it? And if so, what would the construction data look like? Thank you very much.

[@buzzastro6280]

Don;t feel bad, I have 8volts AC on all my antenna grounds. I drove a copper ground rod into ground and have 8 volts AC on a grounding rod with nothing attached. I blew two radios and now have all disconnected. It has also blown all my USB's in my computer.

[@vk6cs456]

Geez...

[@Mark300win]

Buzz Astro where are you living at? Alaska? Is there nearby cell tower or grid tower?

[@chanelkuini5883]

Good vidio

[@ea6wu]

thanks for the video!

[@kissingbanditt]

I'm confused, please help. Ok, is it the longer the ground wire the more noise you will pick up...ok...What if your tower is at the back of your house and the shack is at the front....you have a ground rod at the tower 30 feet away from your room...then another 20 feet another ground rod...i got 3 rods in the ground at 10 feet long... My electrical panel is at the front of the house, which is about 30 feet away from the tower...My shack is above the electrical panel at the 2nd floor another 10 feet up...so i have a ground cable from the tower going 30 feet to the electrical box, then from my room 10 feet down...that is like 40 feet of ground cable... When i listen to the CB band or shortwave i hear a buzzing sound in the back round...Not sure where it's coming from. Could be ground or something else, maybe conditions.. But please advise... My specs are the following. 20 foot tower with 10 foot mast on top... antenna is an Imax2000 for cb band. which is 24 feet long.. the coax shield coming out of the antenna a few inches below is is grounded to the top part of the tower. Each leg of the 3 legs of my tower are grounded together and the same ground wire at a ground rod right beside the tower, then 20 feet away. Radio is an Icom7000 but powered from 12V car battery only.. ground rod is 10 feet long. Am i doing anything wrong? Thank you..

[@vk6cs456]

I would forget the ground wires going to the electrical panel from the tower and your room. Just have the coax from the radio going to the tower and connect the coax braid onto the tower at the bottom as well as the connection you have at the top. Leave the tower grounding rod connections in place. The radio PSU will be grounded through the mains socket to the electrical panel. You probably just have earth loops causing the noise. Of course you might just be in a very noisy spot, or have flouro or LED lighting around the house and be stuck with the noise. Let me know how you get on.

[@izzzzzz6]

Keep it simple. What mode are you using? AM? AM often requires you to use the NB filter as it really is sensitive to power line noise etc. Check your power supply. Swap it out for a car battery, if that helps you might need a better power supply or new capacitors. If your antenna is old some connections could be corroded, this will not likely cause noise but check your SWR. The antenna mount should usually ground out to the pole it's mounted on and in turn to your tower. That should be plenty good. Use silicone dielectric grease to help protect all connections and grounds from corrosion. Check no water can seep into your coax. If you like you can ground the base of your tower to earth with a rod but it will probably make no difference. Regarding noise again, you might want to try searching your house or your neighbours for devices causing noise. Turn off the mains power and use a car battery. See if any noises disappear. I had a USB charger creating bad noise in my campervan / shack. But when i moved it to the house the noise was gone. try to use the correct antenna for the band you are using. If you can get a good SWR your off to a good start. The world of chokes and baluns is a bit of a black magic art-form. Most people have no clue what they are doing and you need to study it in detail and have the correct instruments to really know what your doing. For example, some antenna have certain impedance's way different to other antennas. You can get many different impedance feeder lines. 50 ohm coax 75 ohm coax. 300 ohm ladder etc. First you need to know which impedance your antenna likes and try to match the feeder. Then you can add a balun to match the impedance if you can't match it yourself. But you need to know the variables to choose the correct ratio balun. I'm still trying to understand balanced and unbalanced feeders / antennas. Did you try a choke did it work for you? Did you find the noise? I wish people would update their questions with the answers so as to help others in the future. Hope it worked out.

[@izzzzzz6]

Also if you are overloading your power supply it might start to create noise. Don't load it up with linears etc unless it can easily handle it.

[@izzzzzz6]

I thought the choke was supposed to be as close as possible to the antenna feed point. Also why not just construct antennas for the bands you use and try to avoid so much use of tuners and chokes?

[@christianpaul3303]

Agreed - unless your counting on the coax itself as a counterpoise. I do a lot of lightweight end fed half wave antennas (operate outside and need to pack on my motorcycle bags) and I put the choke near my FT-891 as I use that run of coax from antenna as the counterpoise. I'm not an engineer and can't explain it - I just know what works and what doesn't. ;) 73

[@arconeagain]

Yes a choke at the feedpoint may be desirable, however placement elsewhere can be just as valid. Some run a choke at the antenna and another at the shack. Or strategically placed in between. Then it depends on the antenna. You may have a quarter wave and want to choke CMC. This may perform better a quarter wave down from the the feedpoint or multiples thereof.

[@Etherionix]

Check this out. It will help you measure the current on the outer part of the coax. MFJ-854

[@vk6cs456]

Thanks Don. Interesting device, I may pick one up. They do a lot of interesting devices, you can tell it's run by hams. They do switchable inductance and switchable capacitance units too which would be handy for portable work.

[@marcelopu2mal247]

Can I use the rgc213 cable to build this balun?

[@vk6cs456]

Yes, that's what I'm using here.

[@jfrphoto01]

You should try to stay away from from coax with a polyurethane foam dielectric for your choke/line isolator as the center conductor will eventually migrate through the dielectric and cause a short (typical poly-foam coax includes the popular LMR low loss type coax, RG-8X, low loss RG-58 etc.). This is especially true if you wind it in a coil that has a tighter radius than the manufactures recommended bend radius (applies to all coax). Try to use coax with a polyethylene dielectric (solid) insulator (RG-58/U, RG-8/U, RG-213/U, etc.) for the longevity of your choke/line isolator!

[@adelarsen9776]

Why do you think real coax like LDF 4, 7 and 12 is copper coated on the alloy ? It's because one phase runs on the outside skin and the other pushing away from it underneath.

[@arconeagain]

Umm... it is also for cost savings and weight.

[@adelarsen9776]

@@arconeagain Exactly right. It's for weight and cost savings. Copper plating the inner conductor is all that is needed. That's where the RF flows.

[@arconeagain]

@@adelarsen9776 Precisely.

[@timg5tm941]

Would this help reduce noise on receive too?

[@vk6cs456]

Hi Tim. Unfortunately not.