Condo longwire Antenna help

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DonnieZ

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My wife and I live in a condo and I'd like to improve my antenna setup for my SWL.

I live on the top floor of a two story condo unit in the far southwest suburbs of Chicago. I have access to the attic which is built out of conventional trusses. My unit, and therefore my attic access is about 53 feet long and about 25 feet wide, with the long section going North/South. Right now I have single peice of coated solid 20 or 22 AWG wire running the length of the unit in the attic, and the feed line that goes down to my rig is soldered to the antenna wire right about the middle of the line. The feed line is more 22AWG Solid wire that goes down and over a few feet to my computer desk where the end is soldered to the center conductor of a a phono plug which connects to my Ten Tec RX-320.

Can anyone offer some ways I can improve my antenna to pick up more? Right now I can pick up most US and Canadian broadcasts on just about any band (>10MHz during the day, and <10MHz at night), and I can get Cuba pretty strong on 6000 and 6050 around 0300 - 0500 UTC. Occasionally I can pick up a few broadcasts from southern Africa, but they barely come in. Sometimes I can occasionally pick up stations that I think I can identify are broadcasting from Albania, but these barely come in. I'd like to try and pick up some broadcasts from the middle east. As I compose this at about 0200 UTC, my "noise floor" (am I using this term correctly?) on 60M is kind of high at S8 or so. It's about the same on 41M. Maybe I'm only hearing the strongest signals because there's too much noise?


Whatever I do in the attic is pretty much OK as I'm the only one who has access to it. I'm thinking about trying a wire that goes diagonally up one side of a truss and down the other might be a good idea to try, but it's kind of a PITA to wire up there so if someone can offer some solid advice before I poke and hope it would be great. I'd be willing to shell out a few bucks as well for some kind of antenna tuner or other gadgetry if that would help as well.

Any advice would be greatly appreciated!!

- Don
 

ka3jjz

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There are a couple of things I would suggest - I had a condo with an attic access, and you've got a good sized one, so there's no reason not to use it. I also had a RX320 for many years

However you have a few issues here. One is noise - it's quite possible you're getting nailed by something in the condo, with noise levels that high. You might not be able to get all the noise down, but at least do some homework and see what might be causing that in your immediate vicinity. I would say your PC is the first step - any loose cables are a possible radiator, as is your monitor. Using a cheap AM radio as a crude detector on an empty AM channel will suffice.

Next is the phono plug itself. It's not well known, but there's a small amp at the base of the screw in antenna. If the barrel of that plug isn't long enough, it might not disconnect the amp, making the external antenna act like it's not making a good connection. I used a PL-259 to phono plug adapter which I got from RS (when they still had lots of these) and it worked just fine.

As to the antenna - as I mentioned before you have a pretty nice sized attic. Use the entire area to hold an antenna. I had a roughly 25 foot square sized attic, and I made a loop running a wire (actually 4 conductor cable) around its perimeter and down to a switchbox; this is the Carpet Loop that I've mentioned here before (you have to build the switchbox but it's not difficult). It worked very well. Alternately you can wind that wire around the perimeter of your attic a couple of times (seperate each turn by a foot or two) then take the 2 ends to a 9:1 transformer (also called a Magnetic Longwire Balun), and from there feed that with coax to the RX320. This oughta work like gangbusters, and give you a small amount of noise isolation to boot.

You can build the transformer yourself - there are many plans floating around the web - or buy a commercial one. We have a few such commercial links in our HF antennas wiki, linked here (anything in blue is a link) - oh and by the way, there's a link for the Carpet Loop there as well..

HF Antennas - The RadioReference Wiki

Gotta go get ready for work...best regards...Mike
 
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ka3jjz

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Another thing with the antenna - try not to run the feedline anywhere near the PC, where stray pickup could cause issues. If it means a longer run of coax, that's fine - the loss on long runs for even cheap RG58u cable at HF is so small that it's not even worth mentioning. The more distance you can put between the noise source(s) and your 320, the better.

Don't forget to check all the appliances in your home. Do you have a Wii? Just recently a member here found that it's quite the HF noise generator. It's going to take a little persistence and you probably won't be able to quell all the noise, but hopefully you will be able to get it down to a bearable level

Mike
 

a29zuk

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If the loop doesn't help another option is the MFJ-1025 noise canceller. My neighbor's house is only about 10' on the other side of the the wall of my listening post. So I have to deal with the noises generating from his house along with the noise our TV emits while my wife is watching it.
It would require you to put up a second antenna but it looks as if you have plenty of room in your attic to do it. Two antennas parallel with each other about 15' apart would probably do the trick. My television emits a nice S9 signal to my receiver between 6 Mhz and 8 Mhz making it impossible to do any DXing. With the noise canceller I can null that noise down to S1 with no problem.
The noise canceller does come with a built in attenuator for signals below 2 Mhz but there is a simple mod to eliminate it. I don't remember the website offhand but it was easy to find in a google search. Now I can listen to broadcast DX again!

Good Luck,
Jim
 

ridgescan

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There are a couple of things I would suggest - I had a condo with an attic access, and you've got a good sized one, so there's no reason not to use it. I also had a RX320 for many years

However you have a few issues here. One is noise - it's quite possible you're getting nailed by something in the condo, with noise levels that high. You might not be able to get all the noise down, but at least do some homework and see what might be causing that in your immediate vicinity. I would say your PC is the first step - any loose cables are a possible radiator, as is your monitor. Using a cheap AM radio as a crude detector on an empty AM channel will suffice.

Next is the phono plug itself. It's not well known, but there's a small amp at the base of the screw in antenna. If the barrel of that plug isn't long enough, it might not disconnect the amp, making the external antenna act like it's not making a good connection. I used a PL-259 to phono plug adapter which I got from RS (when they still had lots of these) and it worked just fine.

As to the antenna - as I mentioned before you have a pretty nice sized attic. Use the entire area to hold an antenna. I had a roughly 25 foot square sized attic, and I made a loop running a wire (actually 4 conductor cable) around its perimeter and down to a switchbox; this is the Carpet Loop that I've mentioned here before (you have to build the switchbox but it's not difficult). It worked very well. Alternately you can wind that wire around the perimeter of your attic a couple of times (seperate each turn by a foot or two) then take the 2 ends to a 9:1 transformer (also called a Magnetic Longwire Balun), and from there feed that with coax to the RX320. This oughta work like gangbusters, and give you a small amount of noise isolation to boot.

You can build the transformer yourself - there are many plans floating around the web - or buy a commercial one. We have a few such commercial links in our HF antennas wiki, linked here (anything in blue is a link) - oh and by the way, there's a link for the Carpet Loop there as well..

HF Antennas - The RadioReference Wiki

Gotta go get ready for work...best regards...Mike
Mike always has great advice- you should give his antenna idea a try
 

DonnieZ

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Joliet, IL
Thanks for the suggestions.

I'll probably go with the easier of the two, looping a single conductor around the perimeter of the attic. Running around the permiter of the attic is going to be a chore with the roof being pitched on the one side - it's pretty hard to get to plus there's a good amount of blown in insulation. What would you suggest the minimum distance be between the turns?

Does it make a lot of difference if I feed the antenna from one of the the ends of the loop or somewhere in the middle?

(I'm almost embarrassed to aske these questions.. I used to have an amateur radio license when I was 15, and I'm only 31 now.. I shouldn't have forgotten a lot of this stuff!)
 

ka3jjz

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Every layout is different, of course, but I would start your loop at the closest point to your access and string until you return to the access point at an opposing end. You could feed it in the middle if you wish - Being untuned and indoors, it's unlikely to make much of a difference - but you should experiment to see which works best in your environment.

Try to use as much area as you can. At 53x25, you have over 1300 square foot of space - even if you use 1/4 of it, that's still a whole lot of wire to string. In cases like these the shape is not critical.

Remember to do some homework on your noise issues - a good antenna is a start, but without quieting your environment, you're still going to be compromised with that level of noise you mentioned in your OP.

best regards..Mike
 

nspace01

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The "old" metal Slinky toys make great long wire antennas. I built one using 4 slinkys that runs the exterior roof line of my house, attached to a Icom IC-R75. It works better than any other I have used over the last 20 years.

Google "Slinky Antenna" for info.............
 

LtDoc

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Any particular bands you are interested in? An antenna(s) tuned for those bands would certainly help in some instances.
If I understood your explanation, you are using a single wire for a feed line. Why not end feed that existing wire? It will certainly make a difference in what you hear (radiation/reception pattern of the antenna).
Or, run a wire around the attic to make a loop as already suggested. Feed it with coax, or two single wires running to your receiver (parallel feed line). The larger the loop the better.
Will any of those suggestions make your reception better? I can't answer that, but it you try those suggestions you can tell me! From what you say you are hearing now, you aren't doing all that bad.
- 'Doc
 

DonnieZ

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Any particular bands you are interested in? An antenna(s) tuned for those bands would certainly help in some instances.
If I understood your explanation, you are using a single wire for a feed line. Why not end feed that existing wire? It will certainly make a difference in what you hear (radiation/reception pattern of the antenna).
Or, run a wire around the attic to make a loop as already suggested. Feed it with coax, or two single wires running to your receiver (parallel feed line). The larger the loop the better.
Will any of those suggestions make your reception better? I can't answer that, but it you try those suggestions you can tell me! From what you say you are hearing now, you aren't doing all that bad.
- 'Doc
I still haven't gotten up into the attic to string some more wire. (It's cold up there these days and moving around requires the right kind of patience..) Right now I've been using RadioShack solid 20AWG "hook up" wire. It comes in 100 foot spools, which I guess is twice as long as I have now, but I'd like to get a longer run if I can.

End feeding vs. center fed - You say there might be a significant difference? The antenna is center fed because my "man cave / radio shack / office" is pretty much in the center of the house. I'd have to run another feed line all across the attic to one end or the other, and I'd have to choose north or south.

As for what bands I'd like to listen to, that's a good question. My wire now seems do do well on 49M at night around 0000 but there's a lot of "local" stations (i.e. Canada, Cuba, US) that I pick up on, which is when this band seems to be open. During the day I don't get much of a chance to listen, unless it's on the weekend and I still havent' done much logging to see what exactly it's working best on. Ideally I'd like to be able to have reasonable performance no matter where I'm tuned.

I thought about making a few different V shaped antennas in the attic of varying lengths that would be somewhat tuned to whatever band I'm trying to listen to, though I'm not sure of the best way to do this aside from running a feedline down from each individual antenna.
 

DonnieZ

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One more question..

Should I get an antenna tuner or a Balun?

I understand that a balun in this case would still likely end up being un balanced on either end, as there's no real way to determine the impedence of my random length longwire. Would it help signficantly?

How about an antenna tuner in addition to or in place of the balun? Do antenna tuners really help that much on RX? Will I notice a significant difference with a tuner in place? I'd probalby pick up something older from eBay. I see some older MFJ units going for reasonable prices, probably because they don't handle large amounts of TX power, but that's not a concern for me.
 

ka3jjz

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If you look at my original reply, you will see that I had suggested a 9:1 transformer be used to terminate the 2 ends of the loop; you can then feed that with a decent (doesn't have to be super-expensive) coax to the 320. Ought to work like gangbusters. No tuner needed.

However this point needs to be repeated - you need to attack your noise issues. The loop will help some, but that will only take you so far. There are so many possible sources, you may need to use the old method of turning off everything in the condo, then reactivate one room at a time (along with all the appliances, one at a time) to see what the issue(s) might be. It's not out of the question that you might have more than one source, and it's also possible that the source might be outside your condo. It's going to take some detective work and a lot of patience. best regards..Mike
 

DonnieZ

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If you look at my original reply, you will see that I had suggested a 9:1 transformer be used to terminate the 2 ends of the loop; you can then feed that with a decent (doesn't have to be super-expensive) coax to the 320. Ought to work like gangbusters. No tuner needed.

However this point needs to be repeated - you need to attack your noise issues. The loop will help some, but that will only take you so far. There are so many possible sources, you may need to use the old method of turning off everything in the condo, then reactivate one room at a time (along with all the appliances, one at a time) to see what the issue(s) might be. It's not out of the question that you might have more than one source, and it's also possible that the source might be outside your condo. It's going to take some detective work and a lot of patience. best regards..Mike

Hi Mike,

I forgot to mention that I did a complete power off of the condo aside from the second bedroom / man cave / office. I unplugged the power to all the video game consoles, TVs, random chargers for random gadgets and it really didn't do much for my plight. I thought the use of CFLs throughout my place would have made a difference, but it didn't when I turned them all off.

I'm going to try and get the coax / balun going soon. After all the reading I've done on baluns I've done, I don't quite understand how the 9:1 figure was arrived at. As best I can tell, an Antenna tuner seems to be able to be described as a variable balun.
 

LtDoc

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No, a tuner isn't a balun. A 'balun' is a 'balanced' to 'unbalanced' traansformer. It can have almost any ratio of impedance transformation, the least would be a 1:1, the impedance you have on one side of it is the same on the other side of it. A tuner only converts/changed one impedance to another, so they can act the same in that regard, but that's it. A typical tuner can handle balanced to unbalanced situations, but that's usually because they have a balun inside them. There are also tuners that are normally 'balanced' tuners that can handle unbalanced situations (I'm aware of one being made commercially).
The problem with using a balun of some impedance ratio with a multiband antenna is that a single antenna seldom ever has the same impedance on more than one band. If that antenna has an impedance of 50 ohms and the receiver has an impedance of 50 ohms then a 1:1 balun should work just dandy. But if that antenna is used on a band where it's impedance is something like 1000 ohms, you'd need a 20:1 balun for it to be even close to 50 ohms. There's no telling what impedance an antenna may have on multiple bands without a lot of 'figuring' and -luck-. That balun would still 'do' the balanced to unbalanced conversion, but may put you way out as far as the impedance matching is concerned. 'Pot-luck' for baluns, in general. (And just to confuse it a bit more, an antenna with a single wire feed line isn't going to be balanced at all. :))
Ain't this stuff fun!
Also in general, the input impedance of any antenna just isn't that big a deal for receivers. It can make some difference in performance, but never as much as with a transmitting antenna. You can "fudge" a receiving antenna fairly 'far' in an impedance mismatch before it really amounts to an appreciable difference in what you hear.
- 'Doc
 

ka3jjz

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Re the noise issue - don't ignore the PC and any peripherals. Any loose cable should be considered a potential re-radiator of noise. That includes the audio cables going to/from the 320 due to common current issues. Sometimes you can reduce your issues by wrapping the loose cables into a loop - better to use some of those snap on chokes you probably have seen advertised about. Cheap cable modems are another possible source of RF junk. Put some space between the 320 and your PC if you can.

best regards..Mike
 
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