Mon 3rd Apr 2017, 17:02
First rig setup
Over the weekend I purchased most of the parts of a first rig. I got an Icom ic756 in basically mint condition, an Astron 35m power supply on nice condition and a dentron monitor Jr antenna tuner (I was planning on going automatic but the dentron came with the radio.)
I also bought the fixins for a 9:1 unun which I will be setting up on a carefully measured end fed antenna.
I'm very excited to get in the air!
I take my test next week and can't wait to get on the air.
Last edited by Kennylxix; Mon 3rd Apr 2017 at 18:32.
Mon 3rd Apr 2017, 18:15
Struggling a bit - uona? I got the balun. (I think?)
The one thing I learned a long time ago is that buying bits for aerials rarely works quite the way you expect. The ATU is a fairly standard type so what will the actual antenna design be - something resonant, or a random length of wire in the sky?
Mon 3rd Apr 2017, 18:36
Ok I fixed the typo but I actually did mean unun not balun. The aerial is just going to be connected in an end fed setup through the 9:1 unun using a table of best lengths for end fed antennas. I think 52ft is what I was looking at last night. According to what I saw that works for most bands with swr low enough for my built in tuner to handle. The purpose of the unun is to get the wire to a reasonable impedence so a few trials may be in order after getting the wire length sorted out.
Tue 4th Apr 2017, 07:58
If you have a tuner, the transformer is just duplicating what the tuner can do - and these things are always lossy - so with the radio tuner, the external tuner and the unun (which I have never heard as a term - maybe a US thing, as don;t know where you are?).
Do you need all these tuners if your radio has an internal one? Where did you get the idea the 9:1 transformers was needed, and did you buy it?
My experience is that if the VSWR is low enough for the built in tuner to handle, it's not that much good as a tuner? More of a final matching adjustment. The external tuner I have on my Icom can match almost anything - but this includes stupid things like 70cm verticals - which are hopeless at HF of course. Matching some random length doesn't mean it radiates or receives very well. Long wires of random length have a large capture area, so if you can match them, and all the weird lobes they have aim in useful directions, they are simple and great to use. Years ago, when I first passed, I ran a shortish long wire from the upstairs window to the washing line post at the end of the garden, tuned it with a tuner and discovered I could work Russia pretty well, and a bit of US/Canada - which was lucky, because 90 degrees to the wire points east/west. Pretty lucky. It did mean that scandinavia, France, Spain and countries southish were totally absent!
Tue 4th Apr 2017, 11:24
I've done a ton of research on end fed antennas and the one thing that is pretty much universal about them is the unun between the wire and the coax. Is it necessary? I'm not 100% sure but based on what I've learned it will allow the impedence to be close enough so my internal tuner can handle the matching on almost all bands.
I bought the ferrite core and a so239 bulkhead connector and am going to make the unun. The design is extremely easy to build. Plus where's the fun in buying premade things!
The external tuner was kind of a package deal I'm hoping to not need it.
That's awesome about the long wire contacts! If I didn't need to get clear from one end if the house to the other I'd be trying them (as a matter of fact I stuck about 20 ft of wire out my window last night a few heard someone who said they were in California. neat!
Im sure this antenna will not be the last or best it's just a good starting point for me.
Thanks for your input
Tue 4th Apr 2017, 11:44
The thing to remember is that electrical, you can make a device that gives a perfect match that is total rubbish at passing RF through it. These transformers can be efficient, or very inefficient. The idea being to simply convert a long wire, typically with a fairly high natural impedance, down to 50Ohms - but if you then have to use another tuner, the losses in both can easily add up. My tuner happily tunes a long wire, and to be honest, most tuners do. The only ones that have trouble are the ones that are physically small because the actual components can't cover the range of tuning required. I'd bet the tuner in the radio is going to cover perhaps 25-100Ohms I doubt much higher. They're a fine tuner really. Your Monitor Jr tuner almost goes to a 9:1 transformer ratio - so should do the job of the extra piece of kit. Using two transformers is usually destructive because neither will be absolutely perfect in the matching, making the losses add up.
Tue 4th Apr 2017, 11:50
Good info. I will definitely be trying all kinds of configurations as I'm rarely satisfied leaving well enough alone
Wed 5th Apr 2017, 17:52
with the unun, your internal tuner will do the job. An end fed works pretty well actually... I have used the exact same configuration you are discussing in my shop.
I used when when I was out playing at fixing something...I have my shack in the house but keep a few rigs (HF and VHF/UHF) in my shop out back for when I am out there playing around...one thing to watch is that at higher power, the end feds can produce some feedback into your shack...mine was fine up to about 300 watts but above that the feedback was noticeable...but if you are running just your rig with the internal tuner that will not be an issue, if you ever run an amp then the external tuner will come into play.
For our Brit friend the unun is short for unbalanced coax to unbalance load, where a balun is balanced to unbalanced.
oh and I did not find that a counterpoise made much difference in performance or feedback in my usage.
Thu 6th Apr 2017, 02:15
Good to hear. I'm really excited to get the antenna up but I'm still waiting on a few parts
Fri 14th Apr 2017, 14:11
I use a home brew 9:1 unun with 280ft end fed wire. The transformer is mounted outside and fed with coax from my external tuner, Yaesu FC-102. It tunes better with the unun than without. 52ft is a bit short. If you can get more, even if it is not in a straight line, your signal will be stronger.
Good luck experimenting.
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