Questions tagged [choke-balun]

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Does a grounding block on a Yagi antenna with a balun and coax feed have the potential to add signal interference?

I have a commercial UHF/VHF Yagi designed for TV reception, also used for 2 meter reception, that has been installed for years but seems lately there's increasing amounts of signal disruption. I have ...
acker9's user avatar
  • 113
3 votes
3 answers
266 views

Dipole antenna using current on outside of coax as intentional radiator?

Is there an antenna design somewhat like a coaxial dipole, where the coax ends in a quarter-wave radiator, but instead of an explicit coaxial radiator running back over the coax body, the outer ...
ralph vanhoek's user avatar
1 vote
1 answer
67 views

I would like to know more about designing broad bandwidth transformers and current baluns using binocular cores

Internet pickings seem mighty slim, would appreciate links to books, articles or websites. If there are good "how to" items that explain the design, that too. Thanks and 73s
Jimbo47's user avatar
  • 86
2 votes
2 answers
1k views

End fed long wire antenna causing issues

I use a hex beam to operate from 20 meters to 6 meters with amazing results. I wish to operate 40 meters and 80 meters also, and can only really install an end fed long wire due to my installation ...
Engineer999's user avatar
2 votes
2 answers
136 views

Can I convert an inline 1:1 CMC into a balun feed for a dipole?

I built my first 1:1 CMC transformer recently using 100 ohm CAT5e pairs in parallel. I used an FT-114-43 with 9 turns on each side and squeezed it into a small box with female coax connectors. I plan ...
wbg's user avatar
  • 301
6 votes
2 answers
286 views

How much attenuation (dB) from a balun is expected?

I'm building a dipole antenna for 433 MHz, first one ever. I will have to use a ferrite bead to balance the feed. How many decibels of attenuation should I expect from the ferrite bead?
AllYourBaseAreBelongToUs's user avatar
1 vote
1 answer
904 views

Common-mode choke (CMC) hurting my SWR. Live with it? Drop the choke?

I have been using a Par EndFedz Mk2 Trail Friendly 40/20/10 though using the matchbox from an EndFedz EF-QUAD (with Vibroplex’s blessing) so I could transmit at more than 25W. On all three bands I ...
QuantumMechanic's user avatar
1 vote
1 answer
332 views

There are good guides for building 1:1 current baluns. What about 4:1?

Some dedicated hams have spent a lot of effort gathering empirical data on various constructions for common-mode chokes. For example, G3TXQ's work is commonly referenced, and K9YC's is pretty well-...
Dominick Pastore's user avatar
3 votes
2 answers
1k views

How do you calculate the number of turns for a common mode choke?

I want to build a common mode choke for my end-fed wire antenna, using turns of coax through an FT140 or FT240 ferrite. I can find various finished products for sale, but I want to make my own. I ...
Joel Clark's user avatar
1 vote
0 answers
47 views

J Pole, what is the best way to deal with Common Mode Current? [duplicate]

I am planning on utilising a ferrite choke on a J Pole antenna for CMC. Placement directly on the feedpoint poses possible mechanical restraints. Is it okay to place it a quarter wave down the coaxial ...
Francis Archibald's user avatar
3 votes
5 answers
3k views

Do chokes at the antenna feedpoint stop the coax from receiving signals as well, or just transmitting?

It seems common knowledge that a choke at the antenna feedpoint stops the outside of the coax shield from radiating when transmitting into the antenna. But what about stopping the outside of the coax ...
user3191449's user avatar
9 votes
2 answers
5k views

When would we ever want to use a voltage balun in ham radio?

In a world where common mode current is the enemy, and we're constantly doing what we can to avoid RF in the shack, why would we ever choose a voltage type balun over a current balun? I understand ...
user3191449's user avatar
9 votes
2 answers
2k views

Importance of Ferrite Size in Coax Choke Balun

The question is quite simple: When making a coax choke balun, does the size of the ferrite matter, and if so, why? I have seen design notes that say to use a single FT240-43 toroid for powers up to ...
M1GEO's user avatar
  • 223
19 votes
3 answers
3k views

Why do amateur radio operators call an RF choke a balun?

When using a balanced antenna such as a half wave dipole, with an unbalanced feed line such as coax, an RF choke can be used to block RF current emitted by the transmitter from splitting up at the ...
Andrew's user avatar
  • 3,665
1 vote
1 answer
106 views

Rotatable Dipole & RF Choke

I have a Diamond HFV-5 (rotatable dipole) in the attic fed by ~30ft of coax. The antenna system comes with a Balun at the feedpoint. Would it be worthwhile to add an inline RF Choke (Unun) in addition ...
Inisheer's user avatar
  • 135
4 votes
2 answers
439 views

Dipole increased CM current using choke balun

My 20 meter inverted vee dipole is fed with 56 feet of 50-ohm coax. The SWR measures 1.2 at the center of the band. According to http://arrl.org/grounding a balanced antenna doesn't need a ground, so ...
Peter Buxton's user avatar
2 votes
4 answers
7k views

Voltage vs. Current Balun for Dipole

I'm a new radio amateur setting up a half-wave 10-meter inverted vee antenna fed by 50 ohm coax. I understand that the inverted vee lowers the normal 72 ohm dipole closer to 50 ohms, so I only need to ...
Peter Buxton's user avatar
4 votes
2 answers
2k views

Can I use a 1:1 current balun to feed a 1/4λ vertical?

I have an LDG RBA-1:1 current balun, and I was wondering if it behaves as a common-mode choke that I can use for a ground-mounted quarter wave vertical w/ 16 radials. The other choice I have is a 4:...
Rimio's user avatar
  • 137
6 votes
3 answers
3k views

Coax or bifilar windings for a choke?

Making a common mode choke out of bifilar windings has proven rather difficult. For me the difficulty lies in getting the impedance to remain a constant 50 ohms from on the HF bands. I've tried 14 ...
user3191449's user avatar
3 votes
2 answers
1k views

Magnetic Loop Antenna with RFI Choke

Because of space limitations, am purchasing a magnetic loop antenna. Because of needing to move the antenna around, do i need a RFI choke in the feed line?
user13930's user avatar
7 votes
1 answer
4k views

How to determine number of turns for a 1:1 balun?

I would like to make a 1:1 balun with М1000НМ ferrite core (magnetic permeability - 1000) and 1 mm thick copper wire using triple bifilar winding. Unfortunately I didn't manage to find a clear ...
Aleksander Alekseev - R2AUK's user avatar
5 votes
3 answers
2k views

Is this the Correct Ferrite Core to Reduce RFI as a Common Mode Choke?

I have a Flex 3000 connected via RG-11 coax to a inverted V fan dipole tuned for 40m and 20m on my roof. I have an "ugly" balun up on the mast by the antenna. I further have the feed-line going into a ...
Etep - VE6ETP's user avatar
2 votes
2 answers
600 views

Choke at feed point of delta loop with Q match

I am working on putting together a 40 meter delta loop using a 1/4 wavelength of RG-6 as the matching section. However I'm unsure of where to create my feedpoint choke. Do I coil up the RG6 right at ...
user3191449's user avatar
2 votes
2 answers
808 views

G5RV Jr. fed with ladder line and coax

I am a new ham and I was just given a G5RV Jr. I have about 20 feet of coax plus about 60 feet of 450 ohm ladder line I can feed it with. Can I extend the G5RV Jr. feed line with the ladder line I ...
K8KV's user avatar
  • 377
6 votes
3 answers
5k views

Why do we distinguish between balanced and unbalanced?

I hear all the time, "you need a balun between your balanced dipole and unbalanced coax to stop the common-mode current" when it seems the proper advice is "you need something to stop common-mode ...
Dominick Pastore's user avatar
7 votes
2 answers
2k views

What is the maximum number of turns in a ferrite core used as a common mode choke?

Is there a way to estimate the maximum number of turns which can be used with a ferrite core used as a common mode choke? It is known that the impedance of such a choke is proportional to the square ...
Chris K8NVH's user avatar
  • 1,042
2 votes
2 answers
2k views

What core material do I need to construct a 1:1 unun for 6M?

I want to build a 1:1 unun for a 6M dipole. Power level 100W. What core material should I use?
Bruce A Friend's user avatar
7 votes
2 answers
5k views

Do end-fed dipole antennas need choke baluns?

I have a couple of end-fed wire antennas I bought that came with matching baluns. One has a 9:1 unun, and I'm not sure about the other one. In addition to those, should I also put a choke balun on the ...
Pablo Fernandez's user avatar