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 Post subject: Re: Long wire ( random wire) and ground proximity
PostPosted: Aug Sat 15, 2020 2:03 pm 
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SkyKing wrote:
I've been under the impression that using coax as a lead-in for a long wire antenna, with the outer shield grounded, would create a capacitor that would bleed your antenna signal off to ground. Is this not true?


The Short answer to this is Yes and NO. If you connect a long wire... we are talking about a wire that is at least 100 foot or more in length. If you connect that 400 to 600 ohm antenna to a 75 ohm piece of coax you have ? ballpark an 8 to 1 or more mismatch. Yes a bunch of your signal just disappeared at the entrance into the coax cable. Next you connect your 75 ohm cable to your antique radio's Ant and Ground connectors. You Old radio is looking for a 400 to 600 ohm antenna and you just handed it a 75 ohm signal. The already reduced by a large factor signal is now again totally mismatched to the receiver and therefore again 7 to 9 times the small signal is again reflected and you end up with a very very small amount of signal into your old radio. With a pair of Un-Un's one on each end of the coax you eliminate most of this double reflected signal. Un-Un is a transformer designed to be Unbalanced to Unbalanced matching unit. Yes most will just call them a Balun and let it go at that. There is a slight difference between ones that are designed to be BalUn Balanced to Unbalanced transformer and an UnUn.

A Long Wire Antenna will vary in impedance depending on length of the wire and the frequency your trying to listen to. If you connected up a very small transmitter and an SWR meter you could watch this happen as you tune across the band. You will see probably a variation of SWR from 1 to 1 perfect match up to 3 to 1 which is a 25 percent reflected signal level to your meter. I will say that for a receiver it is well worth trying the Long Wire direct to the old radio without the coax since the majority of the antenna is out away from the noise generators of your home and the signal should be much stronger than a simple 20 foot wire inside the house. This way the desired signal is a hopefully so strong that it will over ride the noise generators within your house. You should always try it this way to start with for a Long Wire antenna. Adding the coax with both shield and inside wire wired together as Curtis explained makes it look like just a FAT single wire with the outer insulator covering to keep it from shorting to anything metal that it passes in contact with.

If that doesn't work out for you then putting a pair of matching transformers on both ends of the coax and grounding the shield yes you will have perhaps a 25% reduction of signal level but you might have an 80 to 90% reduction in House Noise thereby allowing you to still listen to the desired signal.

John k9uwa

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 Post subject: Re: Long wire ( random wire) and ground proximity
PostPosted: Aug Sat 15, 2020 8:22 pm 
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hello John,
would be better just have the wire come in with out the coax like maybe use twin antenna lead as my lead in wire ?
Sincerely Rich
Right now I am using some 18 gauge speaker wire as antenna and lead in wire


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 Post subject: Re: Long wire ( random wire) and ground proximity
PostPosted: Aug Sun 16, 2020 12:18 am 
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John,

With this new conversation going...with a EWE antenna i assume i need the coax so as to not interfere with the termination/null part of the antenna i am trying to achieve. Correct?
Ie if i ran the end of the EWE back to the house without the grounded coax i would then in effect just have a very large U shaped long wire?

Also, am i better off with a 100' coax in a heavily treed area or a 200' coax in a sparsely treed area? What are my losses with doubling the coax if i use un-un's on both sides? Noise is not so much an issue for me now once its outside the house as evidenced my my 2 longwires now.

Thanks

Bill


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 Post subject: Re: Long wire ( random wire) and ground proximity
PostPosted: Aug Sun 16, 2020 9:05 pm 
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poulsbobill wrote:
John,

With this new conversation going...with a EWE antenna i assume i need the coax so as to not interfere with the termination/null part of the antenna i am trying to achieve. Correct?
Ie if i ran the end of the EWE back to the house without the grounded coax i would then in effect just have a very large U shaped long wire?

Also, am i better off with a 100' coax in a heavily treed area or a 200' coax in a sparsely treed area? What are my losses with doubling the coax if i use un-un's on both sides? Noise is not so much an issue for me now once its outside the house as evidenced my my 2 longwires now.

Thanks

Bill


Yes you need the coax. You want the whole works as far from the house and other metal objects as you can get it.
Trees are for the most part insulators. However limbs brushing against the wires of the EWE can cause noise into the antenna. I would put it out the 200 feet away from the house. Important probably is to not have the house in line with either the desired or undesired direction from the antenna. As to coax cable loss? The following is for quad shielded RG6 cable.

5 MHz: 0.6 dB/100 ft.
30 MHz: 1.1 dB/100 ft.
55 MHz: 1.6 dB/100 ft.
Losses at 1.8 MHz are virtually insignificant over several hundreds of feet of this coaxial cable. It can be used for low band receive antennas and arrays without the complications of using a preamp at the antenna.

Source of this coax. https://www.dxengineering.com/parts/dxe-rg6uq-1000 thats $185 for a 1000 foot roll of the coax. Shorter pieces...
https://www.dxengineering.com/parts/dxe-rg6uq-ctl They want 24 cents per foot. Duffy is making money off selling the stuff. Home Depot offers Southwire QUAD shielded RG6 500 feet for $57 plus sales tax. https://www.homedepot.com/p/Southwire-500-ft-18-RG6-Quad-Shield-CU-CATV-CM-CL2-Coaxial-Cable-in-Black-56918445/202316309?modalType=drawer

you get to put the connectors on the stuff. Get the tools to cut and prepare the coax ends as well as buying the proper F connector plugs for that coax. Something around 20 bucks for the tools and plugs. I also tape the plugs and connections outside with Scotch 33 or Scotch 88 black tape ... you don't want water into the plugs.

John



so the Broadcast band loss isn't an issue. Large Metal anythings are an issue they would perhaps mess up the pattern of the antenna.
John k9uwa

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 Post subject: Re: Long wire ( random wire) and ground proximity
PostPosted: Aug Tue 18, 2020 6:05 am 
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radiorich wrote:
hello John,
would be better just have the wire come in with out the coax like maybe use twin antenna lead as my lead in wire ?
Sincerely Rich
Right now I am using some 18 gauge speaker wire as antenna and lead in wire


Rich for your reasonably short 50 feet or so long wire probably best to just continue the wire all the way to the radio. It will all be antenna rather than a feedline so that makes it longer. As long as you don't pick up lots of house noise no need for a coaxial feedline. As to the antenna itself longer is always better height is not near as important as length. Even if the antenna is not in a straight line length still helps.


If you guys want to see a REAL antenna farm take a look at Tom W8JI's website showing his receive antennas. I think his total property is around 300 acres.
https://www.w8ji.com/w8ji_rx_ants.htm

The rest of us only wish we had this much room for antennas.
John k9uwa

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 Post subject: Re: Long wire ( random wire) and ground proximity
PostPosted: Aug Sun 30, 2020 1:53 am 
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Location: Poulsbo, Wa
Update:

No real good news. I built the ununs like on your website the earchi type ones 9:1.
I used a 16' high vert and approx 64' horizontal EWE with 4 foot ground rods.

As i adjust the ohms on the terminated side from 0 -2000 i get a very very small change. No real
directionality or null at at all and a fair amount of static. Signal strength isnt bad.

I checked my wiring on the ununs. I had some problems soldering the coax shield to the ground wire of the ununs. I did not use fittings on this test, So i have a mechanical connection

Any ideas to check? Or expect to hear as i adjust the var resistor? Any other ideas?

Thanks

Bill


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 Post subject: Re: Long wire ( random wire) and ground proximity
PostPosted: Aug Sun 30, 2020 5:53 am 
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poulsbobill wrote:
Update:

No real good news. I built the ununs like on your website the earchi type ones 9:1.
I used a 16' high vert and approx 64' horizontal EWE with 4 foot ground rods.

As i adjust the ohms on the terminated side from 0 -2000 i get a very very small change. No real
directionality or null at at all and a fair amount of static. Signal strength isnt bad.

I checked my wiring on the ununs. I had some problems soldering the coax shield to the ground wire of the ununs. I did not use fittings on this test, So i have a mechanical connection

Any ideas to check? Or expect to hear as i adjust the var resistor? Any other ideas?

Thanks

Bill


Possibly not a great ground rod system with the 4 foot rods. Try this connect the two ground rods with a wire between them. Yes a wire on the ground turning the antenna into what is known as a "flag" instead of a EWE. And then adjust the variable resistor. Let us know if that helps.
John k9uwa

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 Post subject: Re: Long wire ( random wire) and ground proximity
PostPosted: Aug Mon 31, 2020 2:50 pm 
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OK will do. Another question.

Where i have hung the unun vertical leg of the EWE is from a tree, I need to run the coax back up that tree to get across a driveway. IS this ok? I have read that long stretches of ground are not good parallel to antenna wire,
I can get the coax about 2 feet away putting it around the other side of the tree and as it crosses the horizontal antenna wire as well above at a right angle . Right now it is on the ground but cant stay that way.

Thanks

Bill


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 Post subject: Re: Long wire ( random wire) and ground proximity
PostPosted: Aug Mon 31, 2020 6:59 pm 
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poulsbobill wrote:
OK will do. Another question.

Where i have hung the unun vertical leg of the EWE is from a tree, I need to run the coax back up that tree to get across a driveway. IS this ok? I have read that long stretches of ground are not good parallel to antenna wire,
I can get the coax about 2 feet away putting it around the other side of the tree and as it crosses the horizontal antenna wire as well above at a right angle . Right now it is on the ground but cant stay that way.

Thanks

Bill


I doubt it makes any difference Bill. Maybe tune the variable for your REJECTed station and then put the coax up in the air and retune the variable again to see if it makes any difference. But normal is wires and coax that cross at or near right angles don't effect the other wire.
John k9uwa

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 Post subject: Re: Long wire ( random wire) and ground proximity
PostPosted: Sep Fri 04, 2020 2:03 am 
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Success!! A long story....

So i tried the 2 grounds together for a "flag" and got no improvement. I was kinda stumped as you, and everything i read say what a great antenna this is. I had been testing the antenna directly to the screws on the back of the set, but it takes times to compare say to the long wire (unscrewing old , re screwing new wires etc) and didn't feel like i was getting a good read on it.

I had built a box a few weeks ago with switches so i could turn on my 2 long wires (random ) and a ground separately. I am able to go back and forth between antennas ( or together) and grounds quickly so its easy to compare the sound of each combination. I wired it so each random wire could go to the antenna screw and also separately to the ground screw ( like a counterpoise) i suspect. I did this as i have had improvement in static by using one long wire attached to the ground screw and one to the antenna screw. I also wired the switches so that the long wires could also actually be grounded so that could pull the ground to the set as a center tap (about 3/4 the way). So a 200' wire and a 40' ground become a 240' grounded wire with a tap at the 200' mark. Sounds screwy but it does work. I have found all different kinds of combinations of grounds and random wires get the best signal and least static.

That's the odd thing, seems every day a different combo works. But i have had much luck with these combos.

So i attached the EWE to my box so i could rapidly compare combos and well no change when i switched the EWE on. WHAT? Yup nothing. hmmmmmmm. Like it wasn't connected. I rechecked the wiring diagram on the unun and it was correct.


So i turned on the set really loud, opened the front door and started twisting the coax looking for a broken wire or ? and finally at the unun location in the yard all of a sudden the sound got louder and the static went away.

The unun wire (B2) that goes into the coax feed had broken inside its insulation. That's why no changes at the var res or anything else but i couldn't tell until i was able to compare directly with another antenna.

So, so far i have left the var resistor at about 1200 ohms since i just figured this out and i had to try this. With just the n/s random wire i still get the offending station to the south but when i switch to the EWE the vol does come down a little but the offending station is almost gone.

When i get a chance i will re tune the var resistor to tune it all out. I hope. I dont hear the offending station all the time just when all the stations are strong...but the EWE does seem to work!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

I also have a 150' well casing into the earth near the termination resistor i may try and attach to. Now that's a ground!!! lol

I will report back....
Thanks again!!!!!!

Bill


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 Post subject: Re: Long wire ( random wire) and ground proximity
PostPosted: Sep Wed 16, 2020 1:59 am 
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So after testing for a few days i now have the resistor value pretty close. What an incredible difference vs the long wire
where there is 2 stations close by.

Is a carbon film resistor ok? Or do i need a carbon resistor. I see a lot of metal film resistors out there as well.

I am thinking about making a bigger one. I still do get some signal from the southern station, and
am wondering if there is anything i can tweak on the next one to get it to null it more. Ie what's more important,
vertical, horizontal, total length, direction ( i see the lobe is forward and off to the right, i have yet to find the null
area anywhere...is is directly opposite the lobe of just directly "south" of the wire?

Thanks

Bill


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 Post subject: Re: Long wire ( random wire) and ground proximity
PostPosted: Sep Wed 16, 2020 4:40 am 
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Film resistors are OK... just don't use wire wound ones. I would hook up a Pot... Carbon Volume Control 100 ohms up to 10,000 ohms perhaps. It should be in the low end of a pot like that and quite critical in adjustment in place of the resistor. Then listen to the UnDesired station... requires two people who have walkie talkies so one can turn the resistor pot while the other one tells them where the NULL is... adjust for minimum signal on the undesired station. And yes it may not be perfect of the rear of the antenna. House and any metal object within a couple hundred feet or more will effect the pattern of the antenna. I am not sure that longer length or higher vertical would effect the pattern enough to be useful. Due to other stuff close house etc.. perhaps you get instead of a single near perfect null right off the back you get a small ball on the rear and off a bit from each side of that the deep nulls. Anyway try the plain old carbon volume control as a temp to test with and find the exact deeps null on the undesired station. Then measure the pot with your ohm meter and get a film or carbon resistor of the same value and replace the pot with it. It will probably be critical enough that your hand on the pot or you standing close to it may change the pattern a bit. So tweak the pot then get away and have the person inside say yes or no you lost a bit and need to readjust a bit more or less to get the deepest null possible on that UnDesired station.

John k9uwa

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