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Questions tagged [choke-balun]

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6
votes
2answers
485 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 ...
6
votes
1answer
854 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 ...
6
votes
4answers
2k 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 ...
5
votes
3answers
423 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 ...
5
votes
3answers
416 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 ...
5
votes
2answers
2k 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 ...
4
votes
2answers
89 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 ...
3
votes
2answers
233 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:...
2
votes
2answers
197 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 ...
2
votes
1answer
182 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?
2
votes
2answers
368 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 ...
2
votes
2answers
215 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 ...
2
votes
2answers
423 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?
1
vote
1answer
56 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 ...