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Random wire question
- Thread starter Singularity35
- Start date
Like the title says, a random wire straight into the tuner. Im concerned with lengths to avoid or go for and grounding the system.
I will make or buy an end fed at some point but right now its a pain as I will have to import it to DU land.
Chameleon Antenna
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Here is the problem with a wire going straight into the tuner:
When you put a wire straight into the tuner and run it out of your shack to go outside, a portion of that wire if currently inside your home (shack).
The SWR that you see BEFORE tuning is more important than the SWR that you see after tuning because a tuner only make your radio happy (close to 50 ohms). The closer is your initial SWR to 1.1:1 the higher will be your radiating power AFTER tuning. A wire installed directly into your antenna tuner will show VERY high SWR BEFORE tuning thus reducing the amount of radiating power AFTER tuning.
This is exactly why that this kind of antenna products (CHA EMCOMM II and all the other Chameleon Antenna products) exist!
Carl
When you put a wire straight into the tuner and run it out of your shack to go outside, a portion of that wire if currently inside your home (shack).
- That portion of the wire will actually radiate inside your shack and might create all sort of RFI all around your equipment.
- A substantial amount of RF output will be lost and you'll lose performance. The first 30% of the wire coming out of your tuner has the highest amount of current which is the portion of the wire that radiate the most. The rest of the wire is high in voltage which radiate the less.
- The SWR might fluctuate and hard to stabilize because you won't have anything to equalize the impedance of the wire coming out the tuner.
- It will probably going to be hard to actually configure the antenna to the desired elevation and angles to achieve desired results.
The SWR that you see BEFORE tuning is more important than the SWR that you see after tuning because a tuner only make your radio happy (close to 50 ohms). The closer is your initial SWR to 1.1:1 the higher will be your radiating power AFTER tuning. A wire installed directly into your antenna tuner will show VERY high SWR BEFORE tuning thus reducing the amount of radiating power AFTER tuning.
This is exactly why that this kind of antenna products (CHA EMCOMM II and all the other Chameleon Antenna products) exist!
Carl
If you only have one piece of wire terminated at the tuner, you only have one half of an antenna. You have to provide the other half; otherwise the antenna will have no way to radiate. Google "counterpoise". That's a word meaning "the other half of your random wire". And by the way, if you're trying to avoid certain lengths, it's not entirely "random".
All valid points... But if you are going to use random length straight into the tuner avoid 1/2 wave , impedance will most likely be to high, also you will still need a good earth. Move the tuner as far as possible away from radio preferably outside at bottom of antenna and fit a choke in the cable going to the radio .if you can find the materiel's it would be far better to make a 9 to 1 balun and use an end fed.
I guess it wont exactly be a random wire, so what do I call it? Maybe how I call it will make the difference between it performing well or not. 
if the tuner "will mostly see 50 ohms throughout the entire HF band", then it is not needed.
I thought max power transfer occurred at resonance, which is usually not the min VSWR.
Maximum power transferred from the feedline to the antenna occurs at resonance however overall maximum power is transferred when ALL impedances are equal. IOW when the transmitter that has a 50 ohm output feeding a 50 ohm feedline attached to a 50 ohm antenna. If the antenna has an impedance of 75 ohms then max power is transferred when the feedline is 75 ohms however there is a loss where the TX is connected to that 75 ohm feedline.
So this setup that many people have used successfully (and I have personally seen work multiple times at multiple locations) can't work? How odd...
The DB
I guess I'll have to find another solution then. I cant seem to figure out the proper way to do it. Thanks for all the replies guys.
It seems like there are more issues with a random wire than Im willing to handle. All your replies are much appreciated.
It seems like there are more issues with a random wire than Im willing to handle. All your replies are much appreciated.
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