The Official Charlie Tango CB and Amateur Radio DX Group
 
HomeEventsGallerySearchRegisterLog in
Navigation
Homepage
Register
Forum Index
Memberlist
Edit Profile
Club Events
Search
Buy and Sell
Old CT Forum
Call Sign List
Donate
CT CB Radio Store
Forum FAQ
Log in
Username:
Password:
Log in automatically: 
:: I forgot my password
Search
 
 

Display results as :
 
Rechercher Advanced Search
Social bookmarking
Social bookmarking digg  Social bookmarking delicious  Social bookmarking reddit  Social bookmarking stumbleupon  Social bookmarking slashdot  Social bookmarking yahoo  Social bookmarking google  Social bookmarking blogmarks  Social bookmarking live      

Bookmark and share the address of The Official Charlie Tango DX Radio Group on your social bookmarking website
Latest topics
» FREQUENCY CHART GUIDE
Tuning and balun on home made T2LT Icon_minitimeToday at 4:55 am by GaryWilson

» How Can i tell ??
Tuning and balun on home made T2LT Icon_minitimeToday at 4:47 am by GaryWilson

» Silver rod install
Tuning and balun on home made T2LT Icon_minitimeToday at 2:12 am by kopitedor96

» We need an Aberdeen/NE Scotland net
Tuning and balun on home made T2LT Icon_minitimeYesterday at 10:53 pm by flashg0rd0n

» SS9900 Squeak
Tuning and balun on home made T2LT Icon_minitimeYesterday at 9:57 pm by Master Virus

» parcel force damaging a 747
Tuning and balun on home made T2LT Icon_minitimeYesterday at 9:11 pm by Master Virus

» Call sign Request (Issued)
Tuning and balun on home made T2LT Icon_minitimeYesterday at 9:09 pm by Sydthecat

» Space Weather News 28.11.2019 Chance of good radio propagation
Tuning and balun on home made T2LT Icon_minitimeYesterday at 8:35 pm by Adrian smith

» Hello Just arrived on the new site (Issued)
Tuning and balun on home made T2LT Icon_minitimeYesterday at 8:13 pm by Airburst

Most active topic starters
Sydthecat
Tuning and balun on home made T2LT Vote_lcapTuning and balun on home made T2LT Voting_barTuning and balun on home made T2LT Vote_rcap 
Badgeruk1980
Tuning and balun on home made T2LT Vote_lcapTuning and balun on home made T2LT Voting_barTuning and balun on home made T2LT Vote_rcap 
Firetrap
Tuning and balun on home made T2LT Vote_lcapTuning and balun on home made T2LT Voting_barTuning and balun on home made T2LT Vote_rcap 
mickyboy
Tuning and balun on home made T2LT Vote_lcapTuning and balun on home made T2LT Voting_barTuning and balun on home made T2LT Vote_rcap 
Master Virus
Tuning and balun on home made T2LT Vote_lcapTuning and balun on home made T2LT Voting_barTuning and balun on home made T2LT Vote_rcap 
rabbi
Tuning and balun on home made T2LT Vote_lcapTuning and balun on home made T2LT Voting_barTuning and balun on home made T2LT Vote_rcap 
Ultimitmale (John)
Tuning and balun on home made T2LT Vote_lcapTuning and balun on home made T2LT Voting_barTuning and balun on home made T2LT Vote_rcap 
Matt86
Tuning and balun on home made T2LT Vote_lcapTuning and balun on home made T2LT Voting_barTuning and balun on home made T2LT Vote_rcap 
Sgt Bilko
Tuning and balun on home made T2LT Vote_lcapTuning and balun on home made T2LT Voting_barTuning and balun on home made T2LT Vote_rcap 
Fred in the shed
Tuning and balun on home made T2LT Vote_lcapTuning and balun on home made T2LT Voting_barTuning and balun on home made T2LT Vote_rcap 
Keywords
call sign silver alan Gain division request list bash Sirio lincoln antenna Mckinley callsign Messages gainmaster Service frequency midland Zetagi manuals file ss9900 president Buxton yaesu
December 2019
MonTueWedThuFriSatSun
      1
2345678
9101112131415
16171819202122
23242526272829
3031     
CalendarCalendar
Classified Adverts

Who is online?
In total there are 54 users online :: 2 Registered, 0 Hidden and 52 Guests :: 2 Bots

StevieG, Victor

Most users ever online was 230 on Thu Aug 08, 2019 3:46 pm

Share
 

 Tuning and balun on home made T2LT

Go down 
AuthorMessage
Dogfish

Dogfish

Posts : 16
Reputation : 3
Join date : 2019-06-27
QTH or Location : Surrey Hills
Call Sign : CT2379
Equipment Used : Grant 2 + Tankwhip mobile with Sirio Gainmaster 5/8ths homebased

Tuning and balun on home made T2LT Empty
PostSubject: Tuning and balun on home made T2LT   Tuning and balun on home made T2LT Icon_minitimeMon Dec 02, 2019 11:31 pm

I can't seem to get the SWR to an acceptable level, 2.5:1. I am not happy to run a linear with the SWR that high.

The dimensions are:
Element length = 2.950m.
Balan to element length = 1.640m
Coax balun on 11cm diameter stiff cardboard with 5 turns of Super 8 xx coax.

Would increasing the balun to 18cm help?
Would just raising or lowering the choke reduce the SWR?

I am waiting some HF antenna books so I could learn more but in the meantime thought I'd ask here.

TIA, Simon.

Back to top Go down
Pappy Nick



Posts : 27
Reputation : 0
Join date : 2019-09-26
QTH or Location : Bristol, UK
Call Sign : 26SW1919
Equipment Used : CRT SS6900 N, CRT One N, Baofeng UV-5R, Alinco DJ-X3

Tuning and balun on home made T2LT Empty
PostSubject: Re: Tuning and balun on home made T2LT   Tuning and balun on home made T2LT Icon_minitimeTue Dec 03, 2019 7:52 am

Hi Simon ....

I'm no expert, and stand to be corrected, but most T2LT "designs" I've come across use RG58 coax which may have a different velocity factor to Super 8, which affects the dimensions of the element etc; so that may be one thing to look at.

Another thing is the height above ground. I've seen that affecting the SWR of some people's T2LT antennas too. I have a vague recollection of it needing to be at least a 1/4 wave-length high.

And, finally, check your connections. I couldn't get the SWR down on my dipole until I sorted out my rather crappy first attempt at soldering a P-259 plug on to the feeder.

73s

Nick
Back to top Go down
Bean



Posts : 23
Reputation : 0
Join date : 2019-06-29

Tuning and balun on home made T2LT Empty
PostSubject: Re: Tuning and balun on home made T2LT   Tuning and balun on home made T2LT Icon_minitimeTue Dec 03, 2019 8:20 am

Back to top Go down
26TC62

26TC62

Posts : 58
Reputation : 8
Join date : 2019-06-27
QTH or Location : Portsmouth
Call Sign : 26TC62, 26CT2817
Equipment Used : Yaesu 891, 10m pole, wire 5/8, T2LT

Tuning and balun on home made T2LT Empty
PostSubject: Re: Tuning and balun on home made T2LT   Tuning and balun on home made T2LT Icon_minitimeTue Dec 03, 2019 1:21 pm

The dimensions look a bit odd. 5 turns on 11cm for the choke/balun looks as per the usual design, but the quarter wave sections - i.e. the coax above the choke, and the length of wire or coax inner above it would both usually be about 2.6m/102". The principle of operation is that the T2LT is a dipole, so the two halves of it should be about the same length - though it is usual to trim the top section to get a decent match.

The velocity factor of the cable shouldn't matter as while the "bottom element" is made up of the coax, the radiation is taking place from the outside of the outer sheath, which will not be affected by the velocity factor. The choke isn't actually performing any balanced/unbalanced transformation, it is there simply to trap the RF at a quarter-wave length down the coax to create what behaves like half a half-wave dipole.
Back to top Go down
Northern Crusader



Posts : 18
Reputation : 0
Join date : 2019-11-13
QTH or Location : IO94SA
Equipment Used : Icom 7300, TS480, Albrecht AE6110

Tuning and balun on home made T2LT Empty
PostSubject: Re: Tuning and balun on home made T2LT   Tuning and balun on home made T2LT Icon_minitimeWed Dec 04, 2019 2:28 pm

26TC62 wrote:

The velocity factor of the cable shouldn't matter as while the "bottom element" is made up of the coax, the radiation is taking place from the outside of the outer sheath, which will not be affected by the velocity factor. The choke isn't actually performing any balanced/unbalanced transformation, it is there simply to trap the RF at a quarter-wave length down the coax to create what behaves like half a half-wave dipole.

The velocity factor is affected by no small part by the insulation of the cable so even though the radiation is happening from the outer sheath that is covered by insulation.

EVERYTHING that is in contact with the outer surface of a conductor, because RF flows on the surface of a conductor, affects the velocity factor. It is one of the reasons that wire antennas de-tune when it rains, even the water on the wire/insulation alters the VF of the wire.
Back to top Go down
26TC62

26TC62

Posts : 58
Reputation : 8
Join date : 2019-06-27
QTH or Location : Portsmouth
Call Sign : 26TC62, 26CT2817
Equipment Used : Yaesu 891, 10m pole, wire 5/8, T2LT

Tuning and balun on home made T2LT Empty
PostSubject: Re: Tuning and balun on home made T2LT   Tuning and balun on home made T2LT Icon_minitimeThu Dec 05, 2019 8:31 am

Northern Crusader wrote:

The velocity factor is affected by no small part by the insulation of the cable so even though the radiation is happening from the outer sheath that is covered by insulation.

EVERYTHING that is in contact with the outer surface of a conductor, because RF flows on the surface of a conductor, affects the velocity factor. It is one of the reasons that wire antennas de-tune when it rains, even the water on the wire/insulation alters the VF of the wire.

That's true, but the VF of the outer sheath of any kind of coax is not going to vary as much between different types of coax as the spread of VFs of different kinds of coax operating as a coax cable - there is about a 30% difference in wavelength in coax between one with 0.66 VF and 0.95. For the lower half of a T2LT, the VF of the coax *as coax* is irrelevant. There is not going to be enough variance in VF of the outer sheath between different kinds of coax to make much of a difference. That has been my own experience having made them out of RG58, Mini 8, RG213 and even RG59.
Back to top Go down
Dogfish

Dogfish

Posts : 16
Reputation : 3
Join date : 2019-06-27
QTH or Location : Surrey Hills
Call Sign : CT2379
Equipment Used : Grant 2 + Tankwhip mobile with Sirio Gainmaster 5/8ths homebased

Tuning and balun on home made T2LT Empty
PostSubject: Re: Tuning and balun on home made T2LT   Tuning and balun on home made T2LT Icon_minitimeSun Dec 08, 2019 7:05 pm

Pappy Nick. Thank you, I have rechecked the soldering and it seems fine, I did use the vf for super 8, and Im sending it up a 10m fiberglass only pole so the height should be ok'ish, good call though.

Bean. Thank you also, I have watched the video and used the internet calculators and have got to the position I am now in. Your contribution however is useful as I have now bookmarked the page!

26CT62.
but the quarter wave sections - i.e. the coax above the choke, and the length of wire or coax inner above it would both usually be about 2.6m/102". The principle of operation is that the T2LT is a dipole, so the two halves of it should be about the same length - though it is usual to trim the top section to get a decent match. wrote:

Yes, that is what I thought and found it a bit weird that the dipole calculator gave differing lengths.
I also understand about the VF factor which has a part to play, thank you to Northern Crusader for expanding my knowledge a little further on this particular aspect.
Northern Crusader, I would be interested to see what effect covering the foamy centre element with the outer shell of "network cable waterproof sheathing" has on the swr when it gets wet. I understand the principle now of water getting into the coax. I would really like to use the T2LT on my 10m pole all through the winter to participate in the nets as an alternative to my trusty Tank Whip.

So, I am going out to the car right now to retreive the T2LT as the Mrs has said I am allowed to lay it out on the front room floor in front of the telly to make some adjustments.

Thank you all for helping me out.

Next projects are an Inverted dipole and then a Mag Loop once I find a suitably priced air capacitor and a friendly plumber who will bend my copper pipe.
I really have got a bad antenna bug, that's the beauty of this hobby tho'.

Thanks again all.
Kind regards.
Simon.
26CT2379
M7SMN
santa santa


Last edited by Dogfish on Sun Dec 08, 2019 7:06 pm; edited 1 time in total (Reason for editing : Couldn't get the quote to show, ametuer eh!)
Back to top Go down
Pappy Nick



Posts : 27
Reputation : 0
Join date : 2019-09-26
QTH or Location : Bristol, UK
Call Sign : 26SW1919
Equipment Used : CRT SS6900 N, CRT One N, Baofeng UV-5R, Alinco DJ-X3

Tuning and balun on home made T2LT Empty
PostSubject: Re: Tuning and balun on home made T2LT   Tuning and balun on home made T2LT Icon_minitimeYesterday at 8:57 am

Dogfish wrote:


once I find ... a friendly plumber who will bend my copper pipe.


Ooh Er Missus !!! Laughing Laughing Laughing
Back to top Go down
Sponsored content




Tuning and balun on home made T2LT Empty
PostSubject: Re: Tuning and balun on home made T2LT   Tuning and balun on home made T2LT Icon_minitime

Back to top Go down
 
Tuning and balun on home made T2LT
Back to top 
Page 1 of 1

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