Longwire Shortwave Antenna Help

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StanStone

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I am looking for advice on getting the best reception for several different portable shortwave radios like the Grundig G-5 and Sangean ATS-803A. I am putting up a 100 foot 12 gauge insulated wire from a stationary post on the top of my house (25 foot high) out to a tree. I have used cable ties to wrap the wire to a 100 foot polypropylene rope. At the end of the run on the tree I have put a large door and gate spring on which I have attached a clothesline pully with a weight to the other end of the spring to a to keep it tight because of snow and wind. I was planning on using exterior RG 6 and wrapping the center solid wire around the stripped back end of the insulated wire (antenna wire) on the stationary post on the house, pulling back the shielded ground and ignoring it. I then run about 40 foot from the top of my roof into my basement where the radio is. One option I have is to use a 9:1 balun installed just before it goes into the house then using heavier coax ( LMR 400 I think) from outside the house into the radio. The other option is to use a antenna tuner. Not sure which is better for my application. I am not sure if I should use good heavy cable from the roof to the radio instead of the RG 6 either. I am also a little confused how I should protect this from lightning and grounding the antenna/radio. I have heard that it is bad to use too big of an antenna on a smaller portable and wondered if that should be addressed or corrected as well. If you can advise on any one item or all of this I would appreciate any advice that you can give me. Thanks very much. Stan
 

ka3jjz

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A couple of observations here...

a. Under normal circumstances, if you were on the East Coast, 100 foot of wire might be way too much for a portable, particularly for a Grundig (which often has a very sensitive front end to begin with). However, being in Iowa, you MIGHT get away with it. However, if you find you are hearing stations in odd places, a lot of signals mixing in with other things and other oddities, chances are decent you are overloading the radio, and would do better with a shorter wire. On MW that's a normal condition on certain graveyard frequencies...

b. A coax feed might not work well with these portables; they're probably set up to handle a hi-z input, and the coax is (generally speaking) low impedance. Using RG6 and any LMR just for a receiving setup is way overkill and hardly necessary. I would first try an inverted L setup, then feed the last few feet of the vertical feed into a 9:1 transformer, ground the transformer (if it has a lug for that) then use a short hunk of RG174u or 58u to the portable. A tuner really isn't really going to help here

An example of an inverted L (also called a random length antenna) can be seen at the bottom of...

Antenna Primer Part 1

c. Getting a good RF Ground is a tricky business - a simple rod in the ground isn't always the best way to go. In addition if there is no specific ground lug on the radios, you introduce the possibility of a shock hazard due to floating DC in and around the case. Some of these jacks are grounded at the lug or shell - check your owner's manual to be sure.

There are MANY articles on the web about proper grounding techniques, and you should be familiar with whatever rules are deemed necessary by your electrical code. I won't even try to cover those bases here - do some homework on the web to find this answer.

I would say that using a good lightning arrestor is a help, but should NEVER be taken as a guarantee. When there's lightning in the area, disconnect (and preferably ground) the antenna at a point AWAY from your receivers, and remove the AC power.

d. Wire ties are fine for a temporary solution, but exposure to the elements over time will eventually weaken them to the point where they will likely become brittle and fall off. The wire should be able to hold up to some abuse, even at 12 gauge

73 Mike
 
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prcguy

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I also think a random wire connected to coax is not the best practice and I would make it a 100ft center fed dipole with 300ohm TV twinlead run to my receiver. You will get less noise induced into the system from a funky ground and virtually no feedline loss at any HF frequency. A 100ish foot center fed dipole is also a good compromise for SW bands from about 3MHz on up.
prcguy
 

a29zuk

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Years ago, I used an 803 with about 100' of wire without any problem. The key was I didn't live near any AM broadcast band stations. That is something you may have to consider. I did have the shield of my coax connected to the outer prong on the 1/8" or RCA plug(I can't remember) going to the radio but it was left open on the antenna feed end. Back then I didn't own a computer so shutting off the TV eliminated most of the man-made noise.
The G5, on the other hand, may be a different story. The newer portables are more sensitive and are prone to overload and BCB interference. Fairly recently, I had a Grundig Yacht Boy 400 hooked to a 10' copper pipe on the side of a 40' mast and that was about all it could handle signal-wise without getting too much interference and overload. I did not have either end of the shield grounded in this case as it seemed to be acting as a noise antenna. It was basically using a single feedline from the radio to the antenna. Now days, having computers, modems, cable TV boxes, etc, cause a lot a noise on HF and hooking the shield of the coax to your radio and through your walwart to your home's ground system can pick up a lot of noise.
Ka3jjz mentioned that the coax you are using is "overkill". In overkill, he meant these coaxes are intended to be use for low loss on VHF and UHF feeds longer than 50'. At HF these coaxes will not make a notable difference in reception. Although the RG6 is fairly cheap and readily available at a local hardware.
Also using a dipole with twin lead is another good solution.

Good luck with your set-up,
Jim P
 

k9rzz

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I'm in your corner, you know that! However, there's no use in running coax if the shield isn't connected on both ends. It's not 'shielded' anymore and therefore a waste of money. Just run wire to the radio, test it, and fix any problems you have from there. Don't worry about potential problems until you have them. Keep it simple.
 

jackj

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Faraday

I'm in your corner, you know that! However, there's no use in running coax if the shield isn't connected on both ends. It's not 'shielded' anymore and therefore a waste of money. Just run wire to the radio, test it, and fix any problems you have from there. Don't worry about potential problems until you have them. Keep it simple.
An ungrounded coax shield will act as a Faraday Shield, sometimes know as a Faraday Cage. It will make an effective shield even though it isn't grounded. But the impedance of the coax is no longer 50 or 75 ohms and the shield will act as a capacitive-coupled drain on the signal strength. Your best bet would be to do as others here have said and use a wire tied to one end of the antenna and leading to the radio, an inverted 'L'. A balanced feed line, like 300 ohm TV lead-in, will work well. It will be very low loss, compared to coax, and a lot more immune to noise pickup.
 

ka3jjz

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For your R600, it would likely work very well. But with portables - maybe not so much, since most of the low end portables aren't expecting a lo-z (low impedance) input such as a coax feed.

73 Mike
 

a29zuk

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I'm in your corner, you know that! However, there's no use in running coax if the shield isn't connected on both ends. It's not 'shielded' anymore and therefore a waste of money. Just run wire to the radio, test it, and fix any problems you have from there. Don't worry about potential problems until you have them. Keep it simple.
Sorry, I should have explained in more detail. Yes I agree, but I had the coax ran already from a previous installation and when I changed my receiver to the Yacht Boy(the R-390 went to the garage and the 803 was used at a different residence) I had noticed it received less noise without the sheild hooked to it. Having a crawl space instead of a basement I decided to leave the coax. I just wanted to make the point that hooking the shield to house ground would be creating more noise to his receiver. For the newer more sensitve portables a single wire most likely works the best.

Thanks,
Jim P.
 
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Ken_Allen

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Build a high pass filter. I did it for about $2 from radioshack and a schematic online. It works well on my Grundig G5 and I'm receiving things just as good as people I know who have been doing HF utilities for 30 years.

100ft wire dipole. 50/50
 

kb2vxa

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"An ungrounded coax shield will act as a Faraday Shield, sometimes know as a Faraday Cage."
Er, no, what you describe is a grounded metal enclosure used to shield equipment areas, rooms or entire structures from RF ingress/egress. The key word here is "grounded".
"It will make an effective shield even though it isn't grounded."
No again, unless grounded and terminated at both ends, due to common mode currents on the outer conductor it effectively becomes part of the antenna system. When these currents are locally generated RF hash they introduce noise into the signal.

The inverted L antenna has been around since the early days of wireless (before it was called radio) and may be of an extremely simple construction. You don't need a picture, just push the L over on its right side so the short stab is vertical and the long one horizontal. The simplest way of going about it is to use a single lead in wire all the way to the receiver so the whole shebang becomes the antenna system, as long as you don't run it past any of the well known hash generators you shouldn't have a problem with noise.

Usually a ground connection to the receiver helps give a better signal to noise ratio. If a ground terminal is not provided on the unit you may improvise by grounding something like the body of the headphone jack, negative battery terminal or just about any accessible item connected to the ground bus inside the unit. If you may be concerned about encountering a stray DC path and creating a short just connect a small DC blocking capacitor in series between the ground wire and whatever you connect it to, a .001-.01uF disc ceramic cap should do nicely.

So where do I find ground without driving a stake you ask? It's as close as the nearest wall outlet, the screw that holds the cover plate is grounded. I expect someone to object saying it will introduce noise but unless you have something in the house that screams with RF hash the electrical wiring is usually pretty quiet. I won't argue the point but rather sit back with a silly smirk on my face as I reflect on 50 years of experience with an inverted L and AC outlet ground beginning when an uncle gave me my first crystal set. (;->)

I leave you with this thought... in a word, experiment.
 

STEVIE39

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Shortwave Antenna restrictions

I will be moving into a retirement village as soon as we sell our house. Currently I am able to run a 60' longwire, but the new place I will be going into restricts the erection of any kind of antennae outside the house and especially on the roof.

Television is brought into the houses via a cable feed system from central array.

Is there anyone here who has a similar predicament?

The roof of the retirement house is a colorbond steel. I was wondering if a long wire placed inside the roof space will it receive as well? I know a loft antenna it works in houses with other types of roofs, but a corrugated powder coated may impede reception. Maybe the roof itself could act as an antenna???

I am also going to consider buying a loop antenna, but I need to look at ALL alternatives before spending money on equipment that would be useless.

I own a small Degen portable with SSB. Its isn't a big expensive radio, but it picks up HF Aviation traffic over the south east Pacific on good evenings. The village I am moving to is on the side of a hill facing east, so I am optimistic that reception will be good with HF and VHF.

I have enjoyed the hobby for about 40 years and I do not want to give it away because of antenna restrictions in my new place.



Any advice will be appreciated.
 

RadioDaze

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Stevie, I'm in a very similar situation to yours, excluding the retirement part. I'm in a very restrictive HOA that I tolerate because of the ocean view. But it's a metal roof as well, underneath the composite tiles. I'm on the 3rd floor with a vaulted ceiling, but I can't take advantage of it like the "lucky" people who get great results from attic antennas. I've had to be creative with scanner antennas, and if you go to my earlier post in this same thread, you'll see I was considering a PAR longwire antenna. I did pull the trigger on the purchase, and expect it here before Wednesday. I read a review in which a fellow loosely unfurled it inside his house, ungrounded, and already had an improvement over his longwire antenna, with lower noise. I can keep you posted on the results. PM me if I forget to follow up here.

I considered a Wellbrook loop antenna, but the thought of paying 300-400 bux to acquire it just seemed out of my budget.
 

jackj

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Shielding

"An ungrounded coax shield will act as a Faraday Shield, sometimes know as a Faraday Cage."
Er, no, what you describe is a grounded metal enclosure used to shield equipment areas, rooms or entire structures from RF ingress/egress. The key word here is "grounded".
"It will make an effective shield even though it isn't grounded."
No again, unless grounded and terminated at both ends, due to common mode currents on the outer conductor it effectively becomes part of the antenna system. When these currents are locally generated RF hash they introduce noise into the signal.
The ground isn't needed for an effective Faraday Cage, Warren. I worked for Indiana Bell Telephone back in the early '60s. They had an early paging system that operated somewhere around 35 mHz AM. The pager receivers were small, super-regen receivers. One of my jobs was to repair the receivers. There was a transmitter about a block away from me running 500 watts. I worked inside of a Faraday Cage on the 19th floor, no way to get an effective RF ground up there. The cage didn't give 100% shielding but it did work.

This is a quote from Wikipedia: "A Faraday cage's operation depends on the fact that an external static electrical field will cause the electrical charges within the cage's conducting material to redistribute themselves so as to cancel the field's effects in the cage's interior. This phenomenon is used, for example, to protect electronic equipment from lightning strikes and other electrostatic discharges."
 

kb2vxa

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Picky, picky, picky... and you're expecting an argument?

Stevie, while a metal roof will severely impair VHF reception it will have limited effect at HF due to the much longer wavelengths involved. Go ahead and string a wire in the attic only I wouldn't put it close to the metal and/or wiring as to avoid as much interaction (capacitive coupling) as possible. All things considered a loop in addition to the wire is a good idea, whichever works better at the time (conditions change) will do the trick. BTW, building is fun in itself, buying skips over it. All you're looking at here is some wire and in the case of a loop maybe a balanced tuner, if you lack the skills you can by one separately but the antenna itself is still just a wire. Indoors you don't need insulators, the building materials being non conductive BTW.
 

k9rzz

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Kind of ironic, but that metal roof may act as a Faraday shield to some extent, kind of like listening to the AM radio when you drive into a parking garage, or short tunnel. However, that beautiful flag pole that you've always dreamed of to proudly display the great red white and blue could be a great antenna (hint!). How can they deny your right to express your patriotism? Google that option.
 

MarMatthias

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Hi,

I live in Nebraska and have a Luke Dynamo/Solar SW radio (2 switches/8 bands each). I use a 100 foot long wire (14 gauge) antenna with an alligator clip. It works well and I'm able to receive quite a few short wave frequencies. I left mine ungrounded and insulated and unroll it as needed. For me, it works out well for me as I can take it with me and hang it on a tree and such.
 

CLynch7

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I have one of these I use with portables pretty often. One lug is connected to the antenna, usually with a short piece of 18ga bell wire and alligator clips. Ground is connected to the other lug, and the pin goes into the ext ant jack. Quick and dirty, I've used this setup with a G5 connected to a 300' Beverage on Ground. Seems to be good above 500kc. No images or intermod noted. Also the only way I can receive anything with the laptop on, cross referencing with the NASWA list. I've considered getting a project box and adding an audio taper pot between the antenna and the balun lug to use as a poor mans attenuator control.

VCR Parts: Accessories from Studio Sound Electronics
3.5mm Balun to Screw Terminal Transformer p250
 

MarMatthias

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With the Luke, I don't need a balum... I do very well without one... I went simple and just clip mine to the antenna. Quick and dirty was the perfect way to go.
 
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