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 Winter 11m Challenge - from December 1st 2023 to 31st March 2024
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
» W3EDP, what kind? Or simple alternative.
Short circuit in 1/2 wave Sigma Venom Icon_minitimeToday at 8:16 am by karelgol

» PS-LM40 Power Supply cooling fan mod
Short circuit in 1/2 wave Sigma Venom Icon_minitimeToday at 7:00 am by Victor

» HF Contacts 20m
Short circuit in 1/2 wave Sigma Venom Icon_minitimeToday at 6:13 am by Ivy Mike

» JT65 on 10m
Short circuit in 1/2 wave Sigma Venom Icon_minitimeToday at 6:07 am by Ivy Mike

» FT8 on Freeband Frequencies?
Short circuit in 1/2 wave Sigma Venom Icon_minitimeToday at 3:19 am by N4DLT

» Amateur Radio (In fact any radio) - Measure your own successes
Short circuit in 1/2 wave Sigma Venom Icon_minitimeToday at 2:26 am by Coyote

» MCHF V0.6.3 HF SDR QRP Transceiver
Short circuit in 1/2 wave Sigma Venom Icon_minitimeToday at 1:46 am by VanRougeT4

» New Member (Issued)
Short circuit in 1/2 wave Sigma Venom Icon_minitimeToday at 12:07 am by SuffolkRaider

» calling channel.
Short circuit in 1/2 wave Sigma Venom Icon_minitimeYesterday at 10:55 pm by andy66

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

 

 Short circuit in 1/2 wave Sigma Venom

Go down 
+2
Alan Pilot
7576Dave
6 posters
AuthorMessage
7576Dave
New Member
New Member



Call Sign : 26-CT-3382
Posts : 3
Times Thanked : 0
Join date : 2020-03-13
QTH or Location : Macclesfield
Equipment Used : Amstrad 901 Fidelity 2000

Short circuit in 1/2 wave Sigma Venom Empty
PostSubject: Short circuit in 1/2 wave Sigma Venom   Short circuit in 1/2 wave Sigma Venom Icon_minitimeMon Aug 09, 2021 6:28 pm

Hi guys,

I’ve been setting up a Sigma Venom 1/2 wave silver rod bought new from eBay a few years ago. Checking with a multimeter shows continuity between the mounting bracket/outer thread of the connector and the radiating element.
I’m not overly knowledgable about the subject, but this surprised me. I’d be grateful for your comments as to whether this is normal for an aerial of this type, or whether it’s a possible fault.
Many thanks in advance for your comments.
Regards from Dave Smile

Victor likes this post

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


Call Sign : 163-CT-220...MW7TTA
Posts : 2504
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 : 150

Short circuit in 1/2 wave Sigma Venom Empty
PostSubject: Re: Short circuit in 1/2 wave Sigma Venom   Short circuit in 1/2 wave Sigma Venom Icon_minitimeMon Aug 09, 2021 6:34 pm

You will find that with most aerials.
You need to check with an SWR meter in between the radio and aerial coax.

Victor likes this post

Back to top Go down
Markone
Senior contributor
Senior contributor
Markone


Call Sign : 26-CT-3433
Posts : 160
Times Thanked : 6
Join date : 2020-04-06
QTH or Location : Hull
Equipment Used : Midland Alan 88s + crt 9900+5/8 gain master
Age : 55

Short circuit in 1/2 wave Sigma Venom Empty
PostSubject: Re: Short circuit in 1/2 wave Sigma Venom   Short circuit in 1/2 wave Sigma Venom Icon_minitimeMon Aug 09, 2021 6:42 pm

I THINK THAT HOW IT SOULD BE, the  multimeter does register a short(dc ground)check SWR and I'm sure if I am wrong someone will give better advice
take care 
mark

Victor likes this post

Back to top Go down
Victor
CT Directors
CT Directors
Victor


Call Sign : 26-CT-3228 / M7VIC
Posts : 5697
Times Thanked : 349
Join date : 2019-11-10
QTH or Location : Bedford
Equipment Used : Various

Short circuit in 1/2 wave Sigma Venom Empty
PostSubject: Re: Short circuit in 1/2 wave Sigma Venom   Short circuit in 1/2 wave Sigma Venom Icon_minitimeMon Aug 09, 2021 8:20 pm

Hi Dave,

As already said it's not unusual and nothing to worry about.

There's a matching coil or actually an inductor in your antenna which measures as a short on a multimeter at DC or Direct Current but at RF or radio frequencies it appears as a 'reactance', so along with capacitance, (either added or part of the antennas capacitance which also has a 'reactance'), it gives you a RF 'impedance' which should be about 50 ohms to match your coax and radio.

I know, all sounds complicated. Wink

You should see the maths involved!!  Shocked


Again, as mentioned by our helpful members, you should only really worry about getting a good SWR.

I wouldn't worry either, catches everyone out the first time and as they say 'every day is a school day', as in we always learn something new. Short circuit in 1/2 wave Sigma Venom 1f44d 


It's when you delve into antenna design or a better understanding of antennas and feed lines that it all gets interesting....you can have a good SWR but a terrible antenna! (For example a 'dummy load' has a great SWR reading but won't get your transmissions out very far. Very Happy)


There's always someone happy to provide help here at Charlie Tango so you're in the right place for any questions you have.


All the best,
Victor
Back to top Go down
https://www.qrz.com/db/M7VIC
Markone
Senior contributor
Senior contributor
Markone


Call Sign : 26-CT-3433
Posts : 160
Times Thanked : 6
Join date : 2020-04-06
QTH or Location : Hull
Equipment Used : Midland Alan 88s + crt 9900+5/8 gain master
Age : 55

Short circuit in 1/2 wave Sigma Venom Empty
PostSubject: Re: Short circuit in 1/2 wave Sigma Venom   Short circuit in 1/2 wave Sigma Venom Icon_minitimeMon Aug 09, 2021 9:12 pm

Yes it does catch us all out victor ,I had a right royal wobble. But its all part of the learning curve.PS just been on 20m and heard OSCOR OSCOR OSCOR,did a double take. Short circuit in 1/2 wave Sigma Venom 1f602  Short circuit in 1/2 wave Sigma Venom 1f602  Short circuit in 1/2 wave Sigma Venom 1f602 
take care 
mark

Victor likes this post

Back to top Go down
Victor
CT Directors
CT Directors
Victor


Call Sign : 26-CT-3228 / M7VIC
Posts : 5697
Times Thanked : 349
Join date : 2019-11-10
QTH or Location : Bedford
Equipment Used : Various

Short circuit in 1/2 wave Sigma Venom Empty
PostSubject: Re: Short circuit in 1/2 wave Sigma Venom   Short circuit in 1/2 wave Sigma Venom Icon_minitimeMon Aug 09, 2021 9:28 pm

Ha! Ha! 
Did he shout out "ONE KEELO-WATT!" at the end too? Very Happy


I've heard all sorts on 20m Mark including CB club call signs. Rolling Eyes


As for the antenna question and pretty much every discovery they aren't always heralded with the word "Eureka!" but usually by the words "Woah! That's weird!?!" Wink

Markone likes this post

Back to top Go down
https://www.qrz.com/db/M7VIC
43CT016
Major contributor
Major contributor
43CT016


Call Sign : 43-CT-016
Posts : 353
Times Thanked : 22
Join date : 2019-11-17
QTH or Location : Perth
Equipment Used : iCom IC-7610/IC-9700/IC-705
Age : 54

Short circuit in 1/2 wave Sigma Venom Empty
PostSubject: Re: Short circuit in 1/2 wave Sigma Venom   Short circuit in 1/2 wave Sigma Venom Icon_minitimeTue Aug 10, 2021 9:49 am

If you have a look at most antennas of that type (I've popped a picture up of a very common one used over here below, as it's easy to visualise what we're saying on this model) you'll see the centre conductor goes to a tap on the coil, and the outside of the SO239 and one end of the coil connect to the chassis, with the other end of the coil going to the radiating element.  So in effect, you have a DC short through part of the coil from the inside and outside of the SO239, as you have noticed.

However, at RF frequencies, as others have said, what you really have is a simple matching network as that coil appears as an inductive reactance, and helps to tune the antenna for a 50ohm impedance match with the other variables involved. 

Short circuit in 1/2 wave Sigma Venom IMG_2031_1024x1024@2x

Victor, Alan Pilot and SangueG like this post

Back to top Go down
Victor
CT Directors
CT Directors
Victor


Call Sign : 26-CT-3228 / M7VIC
Posts : 5697
Times Thanked : 349
Join date : 2019-11-10
QTH or Location : Bedford
Equipment Used : Various

Short circuit in 1/2 wave Sigma Venom Empty
PostSubject: Re: Short circuit in 1/2 wave Sigma Venom   Short circuit in 1/2 wave Sigma Venom Icon_minitimeTue Aug 10, 2021 10:03 am

Nice one Jeff. Short circuit in 1/2 wave Sigma Venom 1f44d 

As they say a picture is worth a thousands words.
Back to top Go down
https://www.qrz.com/db/M7VIC
Northern Crusader
Major contributor
Major contributor



Call Sign : M0GVZ / 26CT1760
Posts : 526
Times Thanked : 35
Join date : 2019-11-13
QTH or Location : IO94SA
Equipment Used : Icom 7300, TS480, President McKinley, Albrecht AE6110, CRT Mike
Age : 53

Short circuit in 1/2 wave Sigma Venom Empty
PostSubject: Re: Short circuit in 1/2 wave Sigma Venom   Short circuit in 1/2 wave Sigma Venom Icon_minitimeWed Aug 11, 2021 9:22 pm

Many a perfectly working antenna has been thrown in the bin by people testing them with a DC multimeter and seeing continuity between inner and outer.
Back to top Go down
Sponsored content





Short circuit in 1/2 wave Sigma Venom Empty
PostSubject: Re: Short circuit in 1/2 wave Sigma Venom   Short circuit in 1/2 wave Sigma Venom Icon_minitime

Back to top Go down
 
Short circuit in 1/2 wave Sigma Venom
Back to top 
Page 1 of 1
 Similar topics
-
» Sigma Venom Silver Hot Rod 5/8 wave (tinkering)
» Venom 1/2 wave SWR Issue
» VENOM 1/2 WAVE SILVER ROD HI GAIN AERIAL
» Sigma 2011 Skip Master 5/8 wave
» 1/2 Wave at Low Level Vs 1/4 Wave Up High?

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: