Does a (resonnant) EFHW reduce urban noise?

I am currently using an end-fed wire of about 23 m. The KX3 ATU achieves a “reasonable” tune on it with the help of a 1:4 balun and a random counterpoise. It radiates something useful as can be seen with RBN.

But the noise level on receive is very high. Around S9 on all bands. It makes SOTA chasing virtually impossible as I am so to speak deaf.

I wonder if going through the trouble of building a 1:49 unum and tuning the wire to a 40m EFHW would reduce the receive noise.

Opinions? ideas?

73 de ON4KJM

Probably not. What might help is a simple choke balun. Put it at the radio end of your feedline.

73 Fred kt5x

1 Like

Jean I have an EFHW with a 49:1 unun and I still get the same noise level as yourself even with a line isolator in place it makes no difference and I have noticed that it starts at the same time each morning so it may be down to british telecom as we call it here.

Best 73 Allen

1 Like

No it doesn’t.

This Clean Up Your Shack – 2019 | GM3SEK's Technical Blog might be of some help as it is likely that some of the noise is entering in other ways.

S9 on all bands is pretty high level of QRM. Maybe some local strong RFI gets into receiver. This can be tested with radio internal attenuator or with external stepped attenuator like Elecraft AT1.

Some commercial solutions

Balun like Elecract BL2 or choke balun from DX wire at antenna feed point helps to reduce RFI fed back from receiver system to the antenna as pointed out by others already.

73, Jaakko ac1bb/oh7bf

Assuming you have eliminated all possible noise sources in your own house, by switching everything off, the next thing is to ensure that the feed-in system is not capable of picking up noise itself and bringing it to the radio. Run the radio on battery power temporarily to eliminate the power supply.

If your antenna is partly vertical and low to the ground, to connect to your balun and the random counterpoise, it seems likely that the lower sections of the antenna are exposed to noise generated within your own house, as well as the neighbours’ houses.

Is the counterpoise really a counterpoise, lying on the ground to couple to real ground capacitively? If it’s in the air, it just part of the antenna, which is in that case, an Off Centre Fed antenna.

Hope this is food for thought and experimentation.

73 Andrew VK1DA/VK2UH

1 Like

I feel your pain. I live in an urban environment, surrounded by solar panel installations, switch mode power supplies running electronics and houses with grow lights. My baseline noise level is S7 and that’s after cleaning up all the noise sources in my home (lots of ferrite, using linear power supplies, eliminating LED lights, etc). If I really want to spend a day chasing, I end up working portable…

That said, the first thing I would do if I were you is go someplace RF quiet and check the baseline noise level of your system. You should be sure that your base system noise level is acceptable. The second thing I would do is clear out all the RF noise you are generating in your home. Track down the work done by K9YC for a good primer on this or the ARRL book on RFI. The third thing I would do is understand the limits of chokes, especially when applied to unbalanced antennas like endfeds or any antenna that is intended to be multi-band so you have a realistic idea about what kind of improvement is possible.

Good luck! 73 Bill K7WXW

As Richard said changing the method of feed for an end fed antenna doesn’t change its noise pick up. The antenna can’t change the environment. The advice Andrew gives in locating noise sources you own is good. Locating and doing something about other noise sources is a whole new subject.

My experience supports the idea that a balanced doublet with balanced feed picks up less noise than end fed or vertical types.

Many VKs retire to the countryside just to escape the noise. Being a regular SOTA activator also helps. If you are a member of a Club perhaps you can organise a remote station in a quiet place. Several VKs have put a lot of effort into setting up a remote station on a hill with beams from 20 m to 2 m. They work extraordinary DX.

Check out VK3MO and VK3OE/R.

My noise level used to be from S6 down to S2 for 80 m to 10 m. Now it is S9 all the way through. Broadband internet?

Life isn’t always easy.


No, it won’t, I’ve tried it myself. The only success that I got was to set up a vertical as far away from the house as possible. Verticals are notoriously noisy but this one was about four S-points quieter than the main antenna which is a doublet fed with window line, and that was a couple of S-points quieter than an antenna in the roof space. Modern houses are full of noise makers, if you cure all yours you still get noise from the neighbours. MFJ sell a unit that will null out a noise source but will not cope with more than one source.

We’re all doomed! :rage:

…nearly doomed… We have a “proper” fibre - the glass variety not what most providers describe as fibre when what they mean is a pair of copper wires… That still leaves about 400 billion switched mode power supplies (and that is just the ones used by my children), a neghbours solar panels and the one remaining neigbour who has stayed on ADSL, and something - yet to be identified which pops up occasionally accross all of HF- might be the ADSL… so there is hope but it involves a digger and lots of optical fibre.

PS In a twist of irony the noisiest power supply now covered in ferrites is the one for the fibre modem supplied by … BT… 73 Paul

As nobody’s mentioned it . Have you looked at installing a Delta or Quad loop antenna ? The closed loop antenna picks up considerably less noise in an urban environment than a vertical or other horizontal wire antenna in my experience.


Hi Jean-Marc, @ON4KJM
I have some QRM here too after 17z and using this QRM Eliminator :

Working for me :+1:
73 Éric

Thank you all for pointing me in the right direction. The noise is coming from the shack. First source is the power supply : when I disconnect it (and listen on the internal batteries), the noise drops 1 s point. A clip-on ferrit didn’t help. As I have a lot of computer related stuff (for work) that can be part of the problem. I think it is an up-hill battle.

I will see what I can do but I think that I will continue to focus on being radio-active in the outdoors.

73 de ON4KJM

1 Like