Charlie Tango 11m DX Radio Group Forum
Would you like to react to this message? Create an account in a few clicks or log in to continue.


Welcome to the Charlie Tango DX Group. The home of ALL things Radio - CB, 11m DX, Amateur, PMR446, PLD, Network and Data. We welcome all radio enthusiasts of all knowledge levels. Join today and claim your own unique World Famous CT Call-sign
 
HomeEventsCalendarFAQSearchRegisterLog in
XMAS COMPETITION: Win a Brand New Yaesu ft891 with Wideband Modification and to help the winner use it we are including a 30 Amp Power Supply on top. This is our biggest prize yet. All this could be yours for Christmas for just £20. - See Latest News Forum for details.
Latest Buxton 2020 News: Unfortunately, due to the Covid-19 pandemic we have had to cancel this year's Buxton date. Sorry for any inconvenience.
Navigation
Useful Radio Sites
Log in
Username:
Password:
Log in automatically: 
:: I forgot my password
CT Bill Board





Views This Year
All Time Views
Classified Adverts

Latest topics
» Charlie Tango 2020 XMAS COMPETITION - Win a Yaesu FT891
What Balun/Unun should I use?  Icon_minitimeToday at 12:23 am by 43CT016

» 11m conditions
What Balun/Unun should I use?  Icon_minitimeYesterday at 10:57 pm by John123

» New Member - Hi to all
What Balun/Unun should I use?  Icon_minitimeYesterday at 10:43 pm by John123

» New member (Issued)
What Balun/Unun should I use?  Icon_minitimeYesterday at 5:31 pm by Ian menabney

» 2020 Xmas Raffle Numbers
What Balun/Unun should I use?  Icon_minitimeYesterday at 5:09 pm by Firetrap

» Cabling my shed office
What Balun/Unun should I use?  Icon_minitimeYesterday at 3:52 pm by cube

» Colt excalibur
What Balun/Unun should I use?  Icon_minitimeMon Sep 28, 2020 12:12 pm by Colt

» Big burners.? Why?
What Balun/Unun should I use?  Icon_minitimeMon Sep 28, 2020 11:23 am by stephen Gunrunner

» Getting disillusioned
What Balun/Unun should I use?  Icon_minitimeMon Sep 28, 2020 10:57 am by glenn dog

Keywords
power callsign ss6900n 9900 list radio alan Sirio ss9900 bazooka chart ALINCO president call tickets Mobile Mckinley frequency yaesu sign antenna lincoln Calling division Baofeng midland
QRZ Database
 

 What Balun/Unun should I use?

Go down 
AuthorMessage
Templar
Contributor
Contributor
Templar

Call Sign : 26-CT-3550 Ham:- M7DEW
Posts : 90
Times Thanked : 3
Join date : 2019-08-14
QTH or Location : Huddersfield West Yorkshire. UK
Equipment Used : Yaesu FT-450D. CRT SS 6900n. CRT Micron
Age : 61

What Balun/Unun should I use?  Empty
PostSubject: What Balun/Unun should I use?    What Balun/Unun should I use?  Icon_minitimeMon Jun 15, 2020 9:53 pm

Hi all.
A mate of mine has given me a homemade wire antenna (with a counterpoise) to put in my loft and try. It resembles a long wire endfed with as I said a counterpoise. His works fine, he doesn't use a Balun or a Unun, but I'm having difficulty with mine.
I'm trying to get it resonant on T5.
My Analyser is telling me the lowest my SWR will go is 5.5 this is after much trimming ect from an original reading of 13:1
However, my impedance and resistance (r & z?) (sorry don't know which way round it should be) ls reading 9 and 16 respectively. Now I do know these figures need to be at or around 50 ohms.
So my question is as in the title, what do I need to fit at the feed point to bring R&Z to 50?

Hope I've explained it well enough for you to understand what I'm trying to achieve,
because it baffles me. The wire as is receives quite well compared to my Dipole. I'm not however going to try transmitting until I get better numbers.
Cheers and thanks in advance for any advice.
Dale
Back to top Go down
View user profile
Northern Crusader
Major contributor
Major contributor


Call Sign : M0GVZ / 26CT1760
Posts : 285
Times Thanked : 20
Join date : 2019-11-13
QTH or Location : IO94SA
Equipment Used : Icom 7300, TS480, President McKinley, Albrecht AE6110, CRT Mike
Age : 50

What Balun/Unun should I use?  Empty
PostSubject: Re: What Balun/Unun should I use?    What Balun/Unun should I use?  Icon_minitimeWed Jun 17, 2020 4:57 am

Impedance is "resistance" for AC which is what RF is.

You need to look at two figures. You need to find where X is which is the reactance which will be at or very near 0 when you get to the resonant frequency of the antenna. You then need to look at the value of R and see what that is. It won't be 50 Ohms however it should get to 50 Ohms a little bit higher in frequency than where X=0 is.

The problem with putting one in the loft is that it'll "couple" to any wiring or any ducting or copper plumbing piping also in the loft area which will make it appear electrically longer. You have an antenna analyser so I would widen the frequency range you're sweeping to well below the 11m band. In fact I'd probably start as low as 24 MHz and do a sweep up to 28MHz and see if there's a dip.

As for the BALUN/UNUN yes you need one. For 11m band I'd go buy a FT240-61 mix toroid and you want 12 turns of RG58 around it. You need to use a toroid rather than just making an air wound one because you'll need a lot of choking with that antenna and air wound ones are both very narrow in bandwidth and reactive so it's easy to get it wrong. 12 turns of RG58 on a FT240-61 mix toroid will give you >8k Ohms choking over about 5MHz well and truly covering both 10 and 11m bands and it'll be entirely resistive.



Paddy and Templar like this post

Back to top Go down
View user profile
43CT016
New Member
New Member
43CT016

Call Sign : 43-CT-016 / VK6JK
Posts : 41
Times Thanked : 2
Join date : 2019-11-17
QTH or Location : Perth
Equipment Used : iCom IC-7610/IC-9700

What Balun/Unun should I use?  Empty
PostSubject: Re: What Balun/Unun should I use?    What Balun/Unun should I use?  Icon_minitimeWed Jun 17, 2020 7:26 am

I’m not sure what analyser you have, but  impedance (z) is made up of resistive (R) and reactive (x) components, all helpfully measured in ohms, so Z could be your complex impedance and R the resistive component.  What analyser is it?  My old analyser will show resistive and reactive components, but not the breakdown of the reactive component.

Ideally you want as close to 50ohm resistive impedance as possible with no reactive components, or the reactive components cancelled out. My analyser would show this as R=50 and X=0, or thereabouts.

For your SWR to be that high though, something is obviously wrong, and if you do just have a piece of wire with no matching that’s a good place to start....but if it is wire and counterpoise, how is it wired exactly?  How long is the wire? Is it running near pipes or other wiring?

If you sweep it, does the SWR get noticeably better at other frequencies, and coincidently the impedance get closer to 50 ohms? If so, it’s a tuning issue. If not, it’s likely something else, like a major mismatch.

Typically an end-fed long wire of any type has an impedance far higher than 50 ohms, so not sure how your mate is getting a match with no transformer or unun, unless it’s not really a long wire at all.  Convention usually sees a 9:1 used to match a random wire (and in fact, it’s not random, but certain specific lengths known to work and not be multiples or fractions of the wavelength you’re working on) and a 49:1 or 64:1 transformer to match the far higher impedance of an end-fed half wave (EFHW) which is what I use as a multi-band antenna.

The fact you have figures way lower than this makes me wonder if something else is going on?

Bit more info on the antenna would hopefully help troubleshoot further.

Paddy and Templar like this post

Back to top Go down
View user profile
Northern Crusader
Major contributor
Major contributor


Call Sign : M0GVZ / 26CT1760
Posts : 285
Times Thanked : 20
Join date : 2019-11-13
QTH or Location : IO94SA
Equipment Used : Icom 7300, TS480, President McKinley, Albrecht AE6110, CRT Mike
Age : 50

What Balun/Unun should I use?  Empty
PostSubject: Re: What Balun/Unun should I use?    What Balun/Unun should I use?  Icon_minitimeWed Jun 17, 2020 6:19 pm

As above, knowing the length of the radiating element would help. If it was over 1/4 wave/9ft long it'll be going over 50 Ohms no matter what you do, if it got to 1/2 wavelength long without a matching circuit you'd be looking at a feedpoint impedance in the thousands of ohms.

Templar likes this post

Back to top Go down
View user profile
Templar
Contributor
Contributor
Templar

Call Sign : 26-CT-3550 Ham:- M7DEW
Posts : 90
Times Thanked : 3
Join date : 2019-08-14
QTH or Location : Huddersfield West Yorkshire. UK
Equipment Used : Yaesu FT-450D. CRT SS 6900n. CRT Micron
Age : 61

What Balun/Unun should I use?  Empty
PostSubject: Re: What Balun/Unun should I use?    What Balun/Unun should I use?  Icon_minitimeTue Jul 14, 2020 5:32 pm

Hi guy's thanks for the replies, sorry for not responding sooner, I forgot I'd posted this query as I ditched the antenna in question and decided to start with something simpler like a Dipole. And yes, there is metal up there - a large RSJ running the length of the loft. Hence why I had to invest in a Analyser. 
Since I got back into this hobby I really don't like/want to live here anymore. It's handy for shops ect but not being allowed to put up an external antenna is the bummer for me. I've spent over £80 on Antenna books yet I still feel none the wiser. 
I've put the double bazooka back up because to a degree it works. But as you've probably read in another post fellow forum member Northern Crusader said I'd be better off with a straight forward Dipole, which I'm going to have a go at building (my 1:1 balun came today) and with luck I'll see some improvement. 
I just wish I could understand why 1 is better than the other? when to me they appear the same. A mate at work said (now that I've got a balun) try a half square - just keep it away from the RSJ - any thoughts? 
Anyway sorry for the rant, I'm aching all over from going up and down in the loft, and not seeing any improvement for my efforts is a bit depressing. I hope my morale comes back soon. 
Any thoughts /advice greatfully received.

Cheers 
73's 
Dale
Back to top Go down
View user profile
43CT016
New Member
New Member
43CT016

Call Sign : 43-CT-016 / VK6JK
Posts : 41
Times Thanked : 2
Join date : 2019-11-17
QTH or Location : Perth
Equipment Used : iCom IC-7610/IC-9700

What Balun/Unun should I use?  Empty
PostSubject: Re: What Balun/Unun should I use?    What Balun/Unun should I use?  Icon_minitimeWed Jul 15, 2020 7:31 am

"Better" is subjective, and very dependent on use case and environment.  My EFHW is a compromise, but it's better than the other options I tried first!  What I'd like is a tower and a beam, which would be better!

Experimenting is part of the fun, but it can be very frustrating too.  I'd just about given up with a multi-band vertical that I couldn't tune, until I eventually tracked it down to a bad lightning arrestor, of all things.  My own stupid fault for not going back to basics at the start thinking it couldn't be anything that simple and chasing a poor ground issue (Which I did also have).

Hard to say what the issue with the other antenna was without the details, but some designs simply work better for certain situations/environments, or at least, are less impacted by them.

With your RSJ, you'll see less impact with wires crossing it with as much separation as possible, than running parallel with it.  Could that be the difference?

Templar likes this post

Back to top Go down
View user profile
 
What Balun/Unun should I use?
Back to top 
Page 1 of 1

Permissions in this forum:You cannot reply to topics in this forum
Charlie Tango 11m DX Radio Group Forum :: Help and Discussion Forums :: Antenna Discussion-
Jump to: