Morning all.
Just bought myself an Icom 7300 and I am looking to set up a dipole antenna.
One of the problems I'm facing is making up an RG58 connection to the antenna, quite a few instructional video's on Youtube similar to this
https://www.youtube.com/watch?v=k7Jxi1G-OpE&t=200s however a trip to the local Bunnings was unsuccessful, seems pvc fittings of the type I need are not available in Oz.
My question, can one of the forum members suggest an alternative connection using materials commonly available in Australia.
Any other suggestions re my antenna project would be appreciated.
In case you haven't guessed, I'm pretty new to the world of Amateur Radio.
Jon.
VK5WRJ
Jon
You CAN use plumbing caps from Bunnings - the white PVC high pressure series - and a short length of the pipe they are designed to fit as a joiner. eg Holman 50mm Press PVC Cap End but use the smaller BNC connector series at/up to 100W in lieu of SO239 sockets /PL259 plugs (also known as UHF series). eg Jaycar BNC PANEL Socket - SINGLE HOLE MOUNT PS0658, and use PP0650 clamp plug so you don't require a crimp tool. Alternatively a box like a Jaycar HB6120 will do the job, and gives two options - either a toroidal core or just plain connecting wires inside.
Ideally you should use a 1:1 BALUN at the centre point so that there is less likelihood of radiation from the coax feeder - which does happen as a matter of course when a BALUN is not used. These can be fitted into one of the sealed ABS boxes like the HB6120 (above) available from Jaycar or the heavier duty similar boxes available from electrical outlets.
Visit the web pages of VK6YSF for suggestions about BALUN and HF dipole projects :
https://vk6ysf.com/projects.htm
Doug VK4ADC
Hi Jon,
You probably want a Jaycar HB6216 for a balun. They fit toroids nicely and have room for connectors n such.
I recently used one for a common mode current filter for my fan dipole, see pic.
cheers
Tim
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attachment=530]
(12-01-2022, 03:04 PM)VK2XAX Wrote: [ -> ]Hi Jon,
You probably want a Jaycar HB6216 for a balun. They fit toroids nicely and have room for connectors n such.
I recently used one for a common mode current filter for my fan dipole, see pic.
cheers
Tim
Thanks, Tim I think the HB6124 will do the job, plenty of room for a balun at a later stage, right now I just want to get on the air.
As a matter of interest can you suggest a supplier of balun cores?
Cheers,
Jon.
(12-01-2022, 04:01 PM)VK5WRJ Wrote: [ -> ]Thanks, Tim I think the HB6124 will do the job, plenty of room for a balun at a later stage, right now I just want to get on the air.
As a matter of interest can you suggest a supplier of balun cores?
Cheers,
Jon.
Hi Jon,
I get all my ferrites from Mark - VK5EME,
https://www.minikits.com.au/
cheers
Tim
Thanks for the replies people.
I'm leaning toward making up my first antenna sans balun, will probably include one at a later date once I have gained a greater understanding of what I'm doing.
Seems many don't see any need to include one in the setup, I don't live in an uban area, so neighbours are not a real problem.
Will roll the dice and see what comes up.
I would suggest rethinking that strategy - RF on the outside of the coax and in to the shack can do nasty things.
Jon
This detail might help you tune your antenna to frequency a little quicker / easier than otherwise :
https://www.vk4adc.com/web/index.php/hf-...na-lengths
When you don't use a balun then it becomes a little trickier to tune a(/each) dipole as the feedline causes interaction with the polar pattern due to interaction with the dipole half that the braid-side connects to. The inclusion of a balun largely removes that interaction.
A 'ray dipole' consists of multiple frequency dipoles connected to a common feed point BUT the dipole sections must be spaced apart physically as they expand from the feed point to make them easily tune-able.
Doug VK4ADC
(14-01-2022, 10:10 AM)VK5WRJ Wrote: [ -> ]Thanks for the replies people.
I'm leaning toward making up my first antenna sans balun, will probably include one at a later date once I have gained a greater understanding of what I'm doing.
Seems many don't see any need to include one in the setup, I don't live in an uban area, so neighbours are not a real problem.
Will roll the dice and see what comes up.
Yeah - don't do that!
If you want a dipole to behave like a dipole then you must have a balun. Even a perfectly symmetrical dipole over good ground will not have a good pattern without the balun.
Fundamentally you are going from a balanced antenna to an unbalanced feed line. A balun transforms
BALanced to
UNbalanced. Hence the name.
Without the balun one side of the coax becomes part of the antenna and you will get radiation from that coax and potentially RF in the shack as Doug has pointed out. It will also be a pain to tune.
A balun can be made simply by wrapping coax around an appropriate ferrite core - see pic. This balun forms the feed to my multi-band fan inverted-V dipole that covers 160m through to 6m.
regards
Tim
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attachment=533]
Thanks again for the interest.
Looks like the jury has spoken unanimously, a balun it shall be.
Now another request, physically wiring the balun into the connection box, can someone provide a simple drawing illustrating the connections, I'm sure it's old hat to most of you but all new to me, and, obviously I would like to get it right.
By simple drawing/illustration, that's what I mean, not a schematic.
I appreciate your superior wisdom.
Note that the parts list in that manual specifies an F14 material toroid.
The Jaycar toroid is on L15 material and really only suitable for frequencies below ~15MHz.
Depending on what you have to hand and Ugly Balun may be a suitable stop gap to get you going while building a ferrite based balun.
https://www.instructables.com/Air-Choke-...Ham-Radio/
A bit of pvc pipe, zip ties and some coax. Probably not as pretty or efficient but it's better in the interim than no antenna system.