HFU HF Underground
Technical Topics => Equipment => Topic started by: radioreddz on July 08, 2012, 0245 UTC
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i have a 200' long wire and was wondering what i could do to get better performance from my receiver's. i'm using a RS dx394,RS dx302 and a icom R71a
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Years ago I used to use an MFJ-16010 random-wire tuner to connect a 40' long wire to my DX-440. I think it made a significant improvement to just connecting the long wire directly to the radio. It might be worth a try; the tuner is not that expensive. http://www.mfjenterprises.com/Categories.php?sec=220
Another possibility is to put a pre-amplifier at the antenna feedpoint; this might help if the feedpoint is at a significant distance from your radios.
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Yes, an antenna tuner can help, especially with anything Realistic (I've owned pretty much them all fro DX-60 to DX302).
Peace!
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Thanks Fansome and cmradio. I had a MFJ-948 sitting in front of me these past 3 years, and didn't realize it could help for rx. It is hooked up now and helping somewhat (more on some bands than others.)
Another possibility is to put a pre-amplifier at the antenna feedpoint; this might help if the feedpoint is at a significant distance from your radios.
Does anyone know where might one obtain such a thing? I have looked around and found several preamps for use at the radio, but not at the feedpoint. (I don't guess the cheap TV signal booster that I noticed at the local ex-rat shack would work?)
Radioreddz: Placing the antenna as far as possible from your house and a well shielded/grounded feed can eliminate most household electrical noise. This design http://www.iw5edi.com/ham-radio/?low-noise-antenna-connection,45 (http://www.iw5edi.com/ham-radio/?low-noise-antenna-connection,45) has worked well for me. It is a low-noise design, so don't expect strong signals. But the signal/noise ratio is good. (I have heard IDs from stations without seeing the needle move.)
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I'd be a little leery of using a pre-amp, only because most modern HF radios, even portables, are fairly sensitive, and usually noise levels dominate at HF. A pre-amp will just amplify everything signals and noise, and add some more noise of it's own. Plus possibly some images and mixing products.
If you can get a sky loop type antenna up, I think you will see a dramatic improvement in reception. Since you have a 200' longwire now, I imagine you should have room for one that is a few hundred feet in perimeter? Another good choice would be a T2FD, although I think the sky loop would end up being easier to build, and probably work better.
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Ill back chris up 100% i had a long wire up and i switched to a loop huge difference mines only around 400ft but it still amazes me.And a tuner helps to i got around 4 s-units more signal on the loop and also my wire was directional out the sides the loop is almost omni.
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Thanks guys. I'll have to try that one.
Cheers, Terry
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I see that Universal Radio sells antenna pre-amps, but I am not familiar with any of the brands they stock.
Wellbrook sells an antenna pre-amp that is specifically for the feedpoint. I have not used it myself, but I did own a Wellbrook active loop antenna for a while, and it worked pretty well. It had a pre-amp at the feedpoint.
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thanks for the info, i just may have to try a sky loop i'm blessed to have enough room for any type of antenna. i may just go rent a lift and hang a loop. great info from all
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Thanks Fansome. But, upon reflection, I think bringing a power source close to my antenna would be counter-productive.
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If you really like to DIY, Clifton Labs has some interesting and well documented components and assemblies for feed-point amps. An example of a very nice high level Norton amp is here: http://cliftonlaboratories.com/z10042a_norton_amplifier.htm
IIRC, Clifton makes components and assemblies for some antenna manufacturers. I think I remember reading that Clifton supplies amps for the Pixel Technologies loops. They also make gain and phased matched short amplified verticals which from all appearances seem to be the ones used in the DX Engineering receiving arrays.
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I wrote up another blog post about sky loop antennas, this time with an emphasis on construction tips: http://www.hfunderpants.com/?p=1097 (http://www.hfunderpants.com/?p=1097)
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Thanks Chris. A very well written article. (I have to get one of those EZ Hangs!)
Cheers, Terry
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Thanks Chris. A very well written article. (I have to get one of those EZ Hangs!)
Cheers, Terry
The EZ Hangs are not cheap (I think around $100) but they work very well. I have had one for 10 or 15 years, I forget how long. The rubber bands do seem to fail every few years, possibly because I leave it out in the shed in the winter and it gets cold. But they're cheap. And of course you need to stock up on fishing weights and line, due to antenna eating trees. I recently switched to steel sinkers, and they work just as well as the lead ones, without the lead. I feel better about losing them in the woods.
I've seen the pneumatic launchers, and while they look cool, they also look scary to me. I'm not a huge fan of lots of psi of compressed air, and PVC pipe.
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Try a 9:1 balun at the feedpoint. It's the traditional solution to improving longwire performance. Several vendors sell them,or if you're handy,you could wind one,it's fairly straight forward and easy to do.
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Chris - I notice that your profile says you use a 670' horizontal loop. Do you have & would you be willing to share a schematic? How is it terminated (if it is....) and what type of feedline do you use? How high is it mounted? I have the room and currently use a 300' LW - works well but I'm always looking to improve!
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Chris - I notice that your profile says you use a 670' horizontal loop. Do you have & would you be willing to share a schematic? How is it terminated (if it is....) and what type of feedline do you use? How high is it mounted? I have the room and currently use a 300' LW - works well but I'm always looking to improve!
I have a short article about it here: http://www.hfunderpants.com/?p=1097 (http://www.hfunderpants.com/?p=1097)
There's no termination, I just feed it with 100 ft of RG-6 into a 12:1 balun (which may not be the ideal ratio). The height varies but is around 25 to 50 ft, depending on what trees I could make use of.
It is by far the best antenna I have had in 35 years of DXing.
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I wrote up another blog post about sky loop antennas, this time with an emphasis on construction tips: http://www.hfunderpants.com/?p=1097 (http://www.hfunderpants.com/?p=1097)
Perhaps a naive question...would a 58 meter perimeter loop (stretched along the edge of a roof) have any utility?
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Perhaps a naive question...would a 58 meter perimeter loop (stretched along the edge of a roof) have any utility?
You mean where the gutters are (or would be if you don't have any)?
If you've already got the wire and it's easy to install it, it might be worth a try. My main concern is that you're putting the antenna around (and close to) your house - a major source of potential QRM.
I suspect it would be better than an indoor antenna, though.
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As Chris says, it may be worth a try to sting it around your house. But if your house is like my house, Its a noisy RF Killing zone. I try to keep my antennas more that 30 ft from the house to keep away from the "zone of radio death." Even then, I still have trouble from my neighbor's Super Trashmaster 500kW atom smasher....or the plasma TV he has. I am guessing its an atom smasher however.
If thats you only choice, its better than nuttin.
If you have any space some sort of "loop", pendant, or other 'closed loop' system fed with a balun you will experience much quieter reception. (The antenna wire comes from one side of the balun, and then returns on the other side of the balun. I am using a cheap Cable TV coax to twinlead balun. It probably is nowhere near perfect, but it is remarkably quieter vs a longwire.
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Not sure it counts as a long wire...but if I wrap 600+ feet of wire around a 12x12 room, any chance of improving signal/noise? Or would I be better off wrapping the equivalent around the house? OR....heh heh hehhhhhh...burying it around the perimeter of my property.....
I'm also curious....how does one pick a balun when looking for broadband HF performance?
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As Chris says, it may be worth a try to sting it around your house. But if your house is like my house, Its a noisy RF Killing zone. I try to keep my antennas more that 30 ft from the house to keep away from the "zone of radio death." Even then, I still have trouble from my neighbor's Super Trashmaster 500kW atom smasher....or the plasma TV he has. I am guessing its an atom smasher however.
If thats you only choice, its better than nuttin.
If you have any space some sort of "loop", pendant, or other 'closed loop' system fed with a balun you will experience much quieter reception. (The antenna wire comes from one side of the balun, and then returns on the other side of the balun. I am using a cheap Cable TV coax to twinlead balun. It probably is nowhere near perfect, but it is remarkably quieter vs a longwire.
You should try and get a blood sample from your neighbor after the next superbowl and see if he has elevated 24Na levels from his personal LHC.....
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I used to be interested in tropical band dx,so I put a dipole for the 90 meter band around the eaves of the roof,as you mentioned. As I put it up in early winter,it worked like gangbusters. Come March,when the thunderstorm season started kicking up in the region,the antenna became a giant noise collector. It stayed that way until November,when it reverted to being a great antenna.
Loops are generally quieter than dipoles,give it a try,you've got nothing to lose.
I once wrapped 150 ft. around a 12x12 foot room. Crap results. I did better stringing 30 feet of wire out the window to a tall bush.
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Loops are generally quieter than dipoles,give it a try,you've got nothing to lose.
This is something that has become very apparent to me over the last few years. For a given size antenna, a loop provides a much better signal to noise ratio than a dipole. I really can't stress this enough to anyone in the hobby. If you have a dipole now, make putting up a loop antenna your next project. You will almost certainly be impressed with the results.
I once wrapped 150 ft. around a 12x12 foot room. Crap results. I did better stringing 30 feet of wire out the window to a tall bush.
Yep, getting an antenna outside has at least two benefits - you get further away from RFI producers (TVs, computers, etc) and you get stronger signals, since RF tends to get attenuated by the structure.
If you're "not allowed" to have an antenna, be creative. If you have a fenced in yard, run the antenna wire along the top of the fence (that plus the house should let you make a loop). Disguise your antenna, make it appear to be something else.
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In the days of the uber-dipole,I found I could use the chain link fence around the backyard as a low noise antenna. I clamped the center conductor of my coax to the fence and let the braid float.
I still use the fence-tenna when the noise levels get ridiculous. It does well as a general receiving antenna down to about 1400 khz,give or take.
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Soldered 40 ft of 22GA wire to the center connector of 30 ft of coax and ran it out the window and down the deck bannister. It's a bit of overkill...lots of intermod, etc but the attenuate function on the PCR1000 gets it down to something reasonable. Here's a scan from 6MHz to ~14MHz this evening starting at around 0010 UTC or so...
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I also tried various popular indoor wire-around-the-room loops. None of 'em fared any better than a hank of random wire strung along the ceiling.
The only homebrewed indoor loop that's been consistently better for me is a shielded coaxial cable loop based on a design from Joe Carr's 1990s receiving antenna handbook. It's pretty similar to the popular KR1ST loop (http://www.kr1st.com/swlloop.htm), just using coax instead of copper tubing. I hang it near a window and twiddle the orientation just enough to null out the worst local RFI. It's directional on MW but not HF, although the directional characteristic does help null out some household RFI.
Sometimes I'll sneak 30' or so of magnet wire out a window and up a nearby tree, but usually one my apartment building's maintenance guys will spot it and tear it down. No great loss since magnet wire is cheap. I'm more concerned about safety - don't want anyone to get snagged on it while they're up a ladder doing their jobs.
I don't have access to a proper ground so I just use odd lengths of magnet wire as makeshift counterpoises. It works pretty well on some frequencies, not at all on others. I just experiment with the lengths until I get it right for the 6800-7000 kHz range.
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The PA0RDT mini-whip (google for more info) gets a lot of good reviews. The webSDR in .nl uses one, and gets pretty good reception. AFAIK there is no commercial version, but it doesn't have a huge number of components.
The key, as always, is to get the antenna outside. The difference between an indoor and outdoor antenna is huge. The mini whip is pretty small, I'd imagine that most folks could easily disguise one.
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i have a 200' long wire and was wondering what i could do to get better performance from my receiver's. i'm using a RS dx394,RS dx302 and a icom R71a
200 ft. is a fair chunk of wire, especially on shortwave, where an antenna that long can start to become directional (you can get a cloverleaf pattern when the length of the antenna is over a wavelength long).
Maybe re-orienting the antenna you already have would bring in more stations from the areas of the world you want to hear.
I've never tried a large loop but have read about them and there are people who swear by them. That also sounds like a good idea.
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If you don't want to shell out the $$$ for an EZ Hang, just get your hands on a cheap slingshot and some 1 oz steel sinkers (please don't use lead). Get a big spool of 20lb-ish test monofilament fishing line, and some masonary line (from Home Depot).
Lay out a zig zag pattern of the fishing line on the ground in front of you. Estimate about what you would need to get it over the tree in question, but don't cut it from the spool, just let the spool lie there on the ground too. But the zig zag pattern on the ground is important, so that it easily (and with minimal friction) flies up into the air. Tie a sinker to the end of the fishing line.
Hold the slingshot with a gloved hand (the hand you use to pull the sling back can be bare) and, wearing goggles, fire that sinker up to were you want the line to go. It almost always pays off to aim higher than where you really want it. With some practice this works well. Next, use the fishing line that has been launched over the tree to pull the masonary line up over the tree. Masonary line is much stronger than the fishing line you just used, and is also "slippery" and doesn't knot. Finally, use the masonary line to pull your antenna rope over the tree, which really should be the good UV resistant dacron type stuff they sell on eBay or at Ham Radio Outlet. Rope from Home Depot will not work well at all for antennas. Use real antenna rope, it's worth the money.
The slingshot, fishing line, sinkers and masonary line is probably a $40 initial investment. Good antenna rope is not all that expensive either; I've found the Davis RF stuff on eBay to be excellent and I believe this is also the stuff that Ham Radio Outlet stocks. It lasts forever, doesn't kink, and is really is easy to work with.
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I've used a similar system,a Zebco 202 and Wrist Rocket for years,Beerus. One ounce egg sinker on the end of the the line to get it over the branch,and most importantly back down as mono can cut into wet bark,especially in broadleaf trees.
I've launched and erected antennas in the middle of nowhere in the soggiest of conditions with that thing. An enclosed spincasting reel like the Zebco 202 makes the launching tangle free. You lay the reel on the ground,press the bail button,load the sling and let it fly.
Be very careful when using a one ounce weight,it can be lethal to someone downrange of you. It can also ricochet off of the trunk of the tree and come sailing back at your head. (Trust me on that one.)
The reel,wrist rocket,mono line and uv-resistant dacron "crab line",can all be found at that one stop pirate shop,Wal-Mart,for about 20-25 bucks before taxes.
The mono line and sinkers are the only things you'll ever replace regularly.
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As an alternative to fishing sinkers, I use small white pill bottles made of HDPE - the kind over the counter analgesics come in. They're flexible enough to resist cracking. Fill 'em with coffee, sugar or sand. Snug a fishing line around the neck and I sling 'em over our trees with handheld fishing line, bolo style. Our trees are only 20'-30' tall so it's easy. If I miss, the plastic pill bottles won't break anything.