Balun a DiPole or not....

Subject: Balun a DiPole or not.... Thu Oct 21, 2021 12:52 pm

I get a lot of noise.

I have a DiPole and use an UglyBulan choke.
It is mounted a few meters over the roof tops.

I am surrounded with electrical interference as Im in the middle of a city, and cannot do anything bar move .
The interference is all over 10 and 11 meters, and is active only when my twig is outside the house [as a pose to indoors to test] [unless its raining or after 11PM ]

As a Dipole is a balanced aerial, a Bulan is not really nessacery, but would it help to filter out opposing interferences?

I Have spent much time scouring the internet for an answer, but it's a mixed bag of results, and usually people have a habit of not actually answering with a factual statement.

I expect it will be try one and see.........

Thanks in advance for your replies, and I value your opinions.
73's

Subject: Re: Balun a DiPole or not.... Thu Oct 21, 2021 2:13 pm

Hi Andy. I am running technically a fan dipole. Adding a ferrite core wound balun did reduce noise for me. It is worth trying, as even if you buy one already constructed the cost is minimal, unless you want one to handle mega power.

Subject: Re: Balun a DiPole or not.... Thu Oct 21, 2021 3:04 pm

Same here as Neal, (SangueG), with a multiband fan dipole in my loft space.

Had a coax choke at first but knew it could be improved so added a typical ferrite balun which improved matters. Recently changed over to a 1:1 Common Mode Choke and the difference is absolutely dramatic with my noise floor dropping 2 - 3 S points! Loads more signals now coming through that would have been buried in the noise before. (The bathroom extractor used to wipe out my HF reception but now you'd never know if was on or not. Balun a DiPole or not.... 1f44d

)

It's not all just about preventing RF coming back on the coax, common mode noise is a big issue too.

They're easy to make, have a Google for "HFKits" and you'll come across their Dutch site with details of CMC's and even how to wind your own. You don't need an expensive FT240 toroid if you're using lower powers, ( <150W ), and can get away with a cheaper FT140 toroid.

A Ham friend has seen the difference it made to my setup and is now incorporating one on his End-Fed antenna.

Best of luck with it all,
Victor

Subject: Re: Balun a DiPole or not.... Thu Oct 21, 2021 5:09 pm

Thank you Victor for your wholesome reply.

I was looking at a FT240-31 Fair-Rite Toroid ring, until what you said about your 1:1 balun, so Ive seen a "Super Yagi 1:1 current balun high common mode choke wideband 400w" <as ebay titled> which might be the better to go for...[besides its all made up in a box]..going for it

Subject: Re: Balun a DiPole or not.... Fri Oct 22, 2021 7:42 am

NoMad wrote:: As a Dipole is a balanced aerial, a Bulan is not really nessacery, but would it help to filter out opposing interferences?

Well, a Dipole is balanced, but your coax isn't...hence, a BALUN (Being BALanced to UNbalanced) is exactly what is used, though not always required. Very Happy

However, don't confuse a balun used for this purpose from what is really a choke, to choke off common mode currents and noise...the terms seem to get used interchangeably.

Either may help with noise, but equally may not...it really depends on the source of the noise. However, they certainly won't hurt.

31 material is better suited to low end HF, whereas 43 and 52 mix are generally better for higher HF bands. Best reference I have found is that from G3TXQ, now sadly a silent key.

http://www.karinya.net/g3txq/chokes/

Subject: Re: Balun a DiPole or not.... Fri Oct 22, 2021 11:53 am

43CT016 ;

That's an interesting read, albeit a little confusing.

So as my cable length is set to 19M-70cm, [preset swr length for my 1/4 wave excalibur previously used] it sugguests that I do NOT need a choke.

All I know is signal is good until the screen side of my pl259 connects to the SO259 at radio end, when the meter jumps from S2 to S7 !

There are no shorts, and the dipole radials are both set at 259cm, aparently the best swr.

My 6900 inbuilt swr meter goes through the roof though !?

The noise is from outside, and got dramatically worse at two changes----1, my neighbour got internet and the installer wrapped his twisted pairs all over the metal railings outside the block of flats, and I suspect he's using a wifi over mains adapter [grrr],
2 - City Fibre installed a DP right outside my block.

Maybe then I should remove my air choke at my antenna ? [Ive not actually tried it without as my install went up with it made already]

Your help & Advice is very much welcomed, as Im dispairing to dump this all in a bin.

73's.

Subject: Re: Balun a DiPole or not.... Fri Oct 29, 2021 1:43 pm

I have now installed my 1:1 balun in place of the uglybalun/airchoke.

There is minimal difference in signal, the noise level is exactly the same, but maybe some qrm pulsing/clicking sound has been reduced. Thats all.

FM averages S4 and SSB averages S7 ! So I will struggle to hear anyone.
It's a shame.

Any thoughts ?