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
HomeEventsCalendarFAQLatest imagesSearchRegisterLog in
Join in with the fun of the Charlie Tango DX Group Summer 10m Challenge - from April 1st 2024
Useful Radio Sites
Log in
Log in automatically: 
:: I forgot my password
CT Bill Board

Views This Year
All Time Views
Classified Adverts

Latest topics
» EU conditions have started
1:9 UNUN, why? Icon_minitimeToday at 9:57 am by Razz229

» Mobile antenna advice please.
1:9 UNUN, why? Icon_minitimeToday at 9:49 am by Razz229

» Southern Area and South Coast SSB Net
1:9 UNUN, why? Icon_minitimeToday at 9:42 am by Razz229

» 10m DXCC Summer Challenge contacts 2024
1:9 UNUN, why? Icon_minitimeYesterday at 9:58 pm by SangueG

» New Old Member (Admin Sorted)
1:9 UNUN, why? Icon_minitimeYesterday at 9:44 pm by Skywalker One

» Measuring antenna length
1:9 UNUN, why? Icon_minitimeYesterday at 3:19 pm by John79

» Ct call sign (Issued)
1:9 UNUN, why? Icon_minitimeYesterday at 11:34 am by John123

» New member (Issued)
1:9 UNUN, why? Icon_minitimeYesterday at 6:14 am by Victor

» South Coast PMR net report
1:9 UNUN, why? Icon_minitimeFri Jul 12, 2024 9:36 pm by Razz229

2022 2024 sign Baofeng callsign Sirio lincoln president software ALINCO anytone power ss9900 meter 2023 Mckinley list chart Mobile yaesu 6900 display call frequency 9900 antenna
QRZ Database


 1:9 UNUN, why?

Go down 
3 posters
Senior contributor
Senior contributor

Call Sign : 19-CT-024 / PD0GOL
Posts : 166
Times Thanked : 6
Join date : 2020-05-21
QTH or Location : Steenwijk, JO32bs
Equipment Used : Dynascan AT5555,Yaesu FT-897, CB silver rod as mutiband HF antenna, OSJ-pole for 2m/70cm, MFJ-925
Age : 65

1:9 UNUN, why? Empty
PostSubject: 1:9 UNUN, why?   1:9 UNUN, why? Icon_minitimeSun Jun 23, 2024 4:03 pm

As those who followed my struggles with the silver rod/HFmultiband antenna might know i used a 9:1 UNUN to connect to it. Now i'm evaluating the whole (slow) progress i made and come up with some questions about why????

Reading the manual of the MFJ-925 tuner i found this:
• Automatically matches antennas from 6 to 1600 ohms impedance (SWR up to 32:1)

The CocoaNEC model i developed gives a max inductance/SWR of:
Feedpoint(1) - Z: (325.820 - i 597.660)    I: (0.0007 + i 0.0013)     VSWR(Zo=50 Ω): 28.6:1

Looking back i now have doubts about the use of the 9:1 UNUN. Without it the MFJ-925 should handle it all just fine in my opinion. Maybe even better, as i think the little adjustments the 925 makes will be mutiplied by 9. When on it's own i suppose it could work with less coarse tuning steps.

Or am i missing something (as usual 1:9 UNUN, why? 263a )

Back to top Go down
Alan Pilot
Major contributor
Major contributor
Alan Pilot

Call Sign : 163-CT-220...MW7TTA
Posts : 2550
Times Thanked : 69
Join date : 2019-11-19
QTH or Location : Anglesey North Wales
Equipment Used : Yaesu FT-991A,,Yaesu FTDX-10,,Icom ic-7300,,Anytone AT-D878UV PLUS",,LINCOLN II+.
Age : 15

1:9 UNUN, why? Empty
PostSubject: Re: 1:9 UNUN, why?   1:9 UNUN, why? Icon_minitimeSun Jun 23, 2024 5:27 pm

A dipole yes i would try it but not sure on the silverrod ???.
Watching this or rather waiting for input.
Back to top Go down
CT Directors
CT Directors

Call Sign : 26-CT-3228 / M7VIC
Posts : 5829
Times Thanked : 355
Join date : 2019-11-10
QTH or Location : Bedford
Equipment Used : Various

1:9 UNUN, why? Empty
PostSubject: Re: 1:9 UNUN, why?   1:9 UNUN, why? Icon_minitimeMon Jun 24, 2024 5:51 am

As you've already figured out Karel your 9:1 transformer works best when the antenna presents a 450 ohm load at the frequencies of interest, (so requiring a specific antenna length).

The problem with just simply using a 'tuner' is that you have to account for losses in your feedline and most get around this by utilising a remote tuner at the antenna end to avoid such issues. Others (like myself) utilise ladder-line feeders to circumvent such losses that would be presented with coaxial cable but even then it isn't a magic cure-all often requiring additional or less feedline lengths to avoid extremes.

The last thing you'd want to do is burn out your MFJ tuner when presented with such extremes a mismatched antenna can present nor introduce massive losses on your feeder making your actual antenna fairly useless. You'll also want to avoid common mode current issues and the easiest way to get around that is the introduction of a 1:1 common mode choke between your transceiver and ATU.

Try to think of your antenna experiments as a 'whole' antenna system with everything from the back of your rig to the tip of your antenna being inclusively important.

If this helps any I'll provide a link (although to a commercial site not endorsed by myself or CT) that provides some additional information when utilising antenna impedance matching systems :-

There's much more information out there besides and worth exploring more but you may find yourself having to trawl through misinformation, myths or hype plus it's always best not to make quick assumptions of your own.

I wish you all the best with your antenna experimentation and although it can be frustrating at times just ensure that you're enjoying yourself.

(I think I've had more fun with antenna experimentation since becoming a Ham than anything else! 1:9 UNUN, why? 1f44d )


Alan Pilot and karelgol like this post

Back to top Go down
Sponsored content

1:9 UNUN, why? Empty
PostSubject: Re: 1:9 UNUN, why?   1:9 UNUN, why? Icon_minitime

Back to top Go down
1:9 UNUN, why?
Back to top 
Page 1 of 1
 Similar topics
» What Balun/Unun should I use?

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: