RFI Air Choke For A Wellbrook?

[ridgescan]

Hey guys.
I bought another 100' batch of LMR240 coax at HRO with the idea in mind, of making an inline Ugly Balun for noise reduction up close to the Wellbrook.
Would this 20-turn coax coil, wound on a 6" x 2' plastic form I obtained, actually improve signal-to-noise on an active loop? I did one back when I ran a random wire and saw some nice results.
I am running a Timewave ANC-4 and it improves some noises somewhat, but I need to get an external wire up outside for that to see more.
Meantime, I wanted to also deploy this choke figuring it can't hurt-right?
Thanks for your opinions

 

[ridgescan]

Thanks for the stimulating conversation all...
anyway FWIW I built my 1:1 air choke. Here it is-BTW it is 18-21' not turns..I correct myself. Mine is 20' in-coilform.


when I get it up there I will let you know how it performs.

 

[SCPD]

Ridge, a 1:1 choke like you built above, is primarily use for transmitting antennas. They are installed near the antenna. The theory being that when you send RF down the transmission line, the RF will go out exclusively via the antenna. Without a choke, there's a possibility of RF coming back down the coax. This can sometimes lead to HAM operators getting minor shocks at their station when transmitting. This is usually compounded by other factors as well -- poor grounding, etc.

AFAIK, a choke will not help your receiving performance.

 

[ridgescan]

Well crap-where were ya when I needed ya Nick? LOL.
I did see a good effect on the 100' wire when I did a choke on that, and I even mentioned it here a few times with no rebuttals.
I saw this guy's thing about power line noise remedies
big ugly balun - Power Line Noise, de NØRQ
which added to what I read Herzian post in here a while back about his using one on his receive system for stopping common-mode noise from riding back down the feed to the radio.
Ima put it up there anyway, figuring nothing to lose, plus I think I did a pretty nice job on it-it'd be a shame to undo such a non-technical masterpiece
anyway Nick thanks for the knowledge-73!

 

[SCPD]

Well crap-where were ya when I needed ya Nick? LOL.

I'm often on the IRC #WUNCLUB channel daily which even you have trickled in once or twice before!

I did see a good effect on the 100' wire when I did a choke on that, and I even mentioned it here a few times with no rebuttals.

Yes, that's because the 1:1 choke is also a balun. By adding the choke you "balanced" the system and it probably removed some noise that you were picking up on your coax. Your loop system is already balanced.

I saw this guy's thing about power line noise remedies
big ugly balun - Power Line Noise, de NØRQ

He's using a 40m vertical for transmitting.

...I read Herzian post in here a while back about his using one on his receive system for stopping common-mode noise from riding back down the feed to the radio.

Yep, again, he added a balun which helped to balance the RF currents. This is the same thing as when we used a simple wire plugged into a shortwave portable. Eventually we used coax. To use coax however, you have to balance the system from the high impedance of the wire to the low impedance of the coax. Done properly, this will make the system balanced and the SNR will likely improve. Most of those devices were not true baluns -- they were "un-uns" (unbalanced to unbalanced) devices. They usually were 9:1 ratios to cover a very broad range of frequencies.

Ima put it up there anyway, figuring nothing to lose.

Find a lightly strong BCB station -- say one that is close to S9. Install the choke. On that same station you should see a slight drop in the S-meter reading. If so, then your choke is working as intended but you could limit your weak-signal detection a bit.

 

[ridgescan]

All great learning information for me and others who may want to try this-thanks Nick for your replies here.
Good idea on the MW station signal test because I was thinking I wouldn't have a reliable comparison in HF because of propagation, although it is there where I would want the most effect to happen. My MW here is excellent noise wise. I am going to do it today so I will report back.
P.S. I dont go into the IRC anymore cause they want money and I am cheap (Brandon once gave me a 'free' link but I have lost track of it)

 

[SCPD]

P.S. I dont go into the IRC anymore cause they want money and I am cheap (Brandon once gave me a 'free' link but I have lost track of it)

It's 100% free Ridge... always has been.

 

[invergordon]

I once did exactly this on my Wellbrook loop but in all honesty, I didn't see a heck of a difference so I've removed it.

@Ridgescan - Do I read your signature correct and your Wellbrook loop is 50 feet above the ground? That's very high, I tried mine at 8 metres, 5 metres, 3 metres and 1 metre above the ground but at these heights I got a lot of QRM/QRN and poor signal reception and have eliminated just about all the noise and thus improved S/N ratio by placing the loop 100mm (yep 6 inches) above the ground on its aluminium stub hammered into the ground at the back of the garden.

Have you tried low level?

 

[ridgescan]

It's 100% free Ridge... always has been.

gimme the link you use then-when I try what I have it says my trial time has expired.

I once did exactly this on my Wellbrook loop but in all honesty, I didn't see a heck of a difference so I've removed it.

@Ridgescan - Do I read your signature correct and your Wellbrook loop is 50 feet above the ground? That's very high, I tried mine at 8 metres, 5 metres, 3 metres and 1 metre above the ground but at these heights I got a lot of QRM/QRN and poor signal reception and have eliminated just about all the noise and thus improved S/N ratio by placing the loop 100mm (yep 6 inches) above the ground on its aluminium stub hammered into the ground at the back of the garden.

Have you tried low level?

I can't. I have no place to put it except in the 'common' garden that belongs to 9 other neighbors and I don't trust them to not somehow sabotage the antenna when it's within reach. Plus that garden is surrounded by buildings. I do not doubt one bit that its 50' height is why I catch so much garbage on HF. I totally agree with you.
I had to cancel the air coil install today as it's wet out. Plus, I didn't allow enough lead aft of the coil to get from the stationary mast up 6' to the loop so I need to build a patch now for that run. Maybe I will wind up just putting up the new feedline and calling it good based upon what has been said here.
Thanks Gordon and Nick!

 

[prcguy]

The choke Ridgescan made will work the same on receive as it would on transmit and it can improve reception if there is noise traveling up to coax towards the antenna. They can be installed near the antenna or near the radio depending on the purpose.

However, an ugly balun is fairly narrow band and one size will not be benificial over the entire HF band, you would need several different and specific values.

But wait, you can make an RF choke that has very good common mode noise rejection over the HF band using a ferrite toroid. A common size and mix for HF is an FT-240-43 with 10 to 12 turns of coax like RG-58 wrapped around it. The core cost about $9 from Amidon Associates and others. For receive only you can use a smaller version like an FT-114A-43 and wrap with 10-12 turns of RG-174. If one has any positive effect at the antenna then another at the radio end can sometimes reduce noise even more.
prcguy

Ridge, a 1:1 choke like you built above, is primarily use for transmitting antennas. They are installed near the antenna. The theory being that when you send RF down the transmission line, the RF will go out exclusively via the antenna. Without a choke, there's a possibility of RF coming back down the coax. This can sometimes lead to HAM operators getting minor shocks at their station when transmitting. This is usually compounded by other factors as well -- poor grounding, etc.

AFAIK, a choke will not help your receiving performance.

 

[ridgescan]

The choke Ridgescan made will work the same on receive as it would on transmit and it can improve reception if there is noise traveling up to coax towards the antenna. They can be installed near the antenna or near the radio depending on the purpose.

However, an ugly balun is fairly narrow band and one size will not be benificial over the entire HF band, you would need several different and specific values.

But wait, you can make an RF choke that has very good common mode noise rejection over the HF band using a ferrite toroid. A common size and mix for HF is an FT-240-43 with 10 to 12 turns of coax like RG-58 wrapped around it. The core cost about $9 from Amidon Associates and others. For receive only you can use a smaller version like an FT-114A-43 and wrap with 10-12 turns of RG-174. If one has any positive effect at the antenna then another at the radio end can sometimes reduce noise even more.
prcguy

Hey prcguy thanks for the reply and tip.
When I get the chance I am going to build a patch for the coil to loop and run it up there. Kind of disappointed because my intention was to do the coil continuous inline-but I guess an extra connector won't hurt it. I still want to try this coil out just to see. Still wet out. Seems we are getting some badly needed moisture here albeit weak.

 

[SCPD]

...if there is noise traveling up to coax...

That's a pretty big IF statement. Also as I said before it could help if had a random wire antenna but with the amplified Wellbrook loop he's not likely to get any significant gain by using one...

 

[E-Man]

gimme the link you use then-when I try what I have it says my trial time has expired

Hi Ridge, I think this may work?

XChat-WDK - Free download and software reviews - CNET Download.com

 

[ridgescan]

thanks eman for the link! I am back in there see ya there!

 

[ridgescan]

Update.
I deployed the air coil yesterday. I used the old feed to remake the coil onto the form, then added the necessary amount of new lmr240, via two pl259s and a double female barrel, for the run to the shack. I am glad I did it.
I want to be cautious about its attributes, as there seems to be some beautiful propagation conditions riding in here lately on HF as I am doing this. I do see about the same s-units of noise floor on the meter, but signals are a little cleaner in most cases at nightfall.
One interesting thing I am noticing, is that the loop seems to be more pointed in directionality on HF. No kidding. Signals seem a little better in the 7-10meg range but same elsewhere. I need to spin HF a while to pick up on differences if any-one day aint enough evidence. Also, MW is a little cleaner than it already was *(it was pretty clean already) even daytime. But no difference in s-units on the signals.
That's about all I can say.

 

[SCPD]

Hey Ridge. I was reading your thread. Awesome stuff your doing. Always good to be hands on and experimenting. Here is something you asked a few threads up

http://chat.mibbit.com/?channel=#wunclub&server=irc.starchat.net

BTW: How do you like the loop? Last i remember you had a long wire going to a discone

Bookmark it and set your nick when you use it

 

[ridgescan]

Thanks Mike! I like the loop a lot. It aint perfect, but it does everything that big ugly wire did plus more with a small footprint. If I didn't live in RFIville USA and it was closer to the ground I am sure it'd do even better. So I try stuff.

 

[majoco]

Hi Ridgy, long time no speak! IMHO a balun of any form is exactly that - it 'converts' a balanced input like a dipole into an unbalanced output like a bit of coax cable. I had a play with 'invergordon's Wellbrook Loop and it already had an unbalanced 50ohm output - so adding another choke in the way is not going to achieve much. Anyway, how do you determine the true input impedance of your radio? It may be a nominal 50ohms, but is likely to vary with the input frequency especially if you have a wideband input, ie, no individual band filters.
But, hey, we're having fun, aren't we?

 

[ridgescan]

Hey Marty-it's a relentless pursuit of noise demons in this crazy game of "radio solitaire" I am hooked on.
I paid darn good money for a loop I thought would eliminate most of the noise here but isn't.
I have an expensive magnetic loop antenna, double-shielded feedline, an air choke, and an ANC-4 noise canceller-and still get the usual buzzes and pops I don't want.
The "fun" factor is under assault.

 

[SCPD]

Ridge sorry if my questions are going to make you repeat yourself i just want to get up to speed and try to help. I'm by no means an RFI expert...

Does the buzz happen day and night?
Is the buzz across the spectrum for you DC-30?
What frequency range it is the worst?
Are all your radios having this issues with noise hooked up to the loop?
Are you using a splitter if so what kind?
What else is on the line from the antenna to the radio besides the air chokes?
Did your long wire in the past also buzz out your radios?

Would a high pass filter possibly help to knock out any local MW transmitter?
I know at the start of the thread you said you change out the coaxial cable and added chokes

Want me to send you one of my SDR's so we can all see the problem?

Mike