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Author Topic: Improving Station for DX  (Read 3928 times)

Posts: 8911


« Reply #15 on: May 08, 2009, 08:26:28 PM »

"have not found a stealth antenna that appears to out perform a vertical - low radiation angle signal and S/N ratio. Please let me know if I have missed anything in that area. "

Keep reading and start experimenting.

Sometimes you will find strange things (and some not so strange things) about signal-to-noise ratio especially.  

I agree with the others that aside from maybe adding some more radials, a 22.5 foot flagpole with a tuner at the base is a pretty good stealth transmitting antenna.

But if you're having *artificial* noise problems, learning to get rid of them and design antenna installations to minimize them is one of the keys to a good DXing antenna farm.

I do pretty well with DX but I always have detectable artificial noise, probably sometimes keeping me from really hearing a DX station clearly.

So there's probably always something I could be doing to hear better.  At the moment, I've decided I hear "well enough" because it would be a real full time job to hunt down and eliminate all suburban noise sources, if it even were possible.  But it's just a slow development of noise troubleshooting and antenna learning skills.  The best S/N ratio antenna for you is going to be the one that picks up the least electrical noise while picking up the most DX signals.  That may sound a little stupid and trivial, but the only way you're going to find it is if you try something.

Don't discount some of the techniques some people use on the low bands.  I use a flag on 160m,80m, 40m and 30m (with maybe slightly less performance on the top two)

But I actually built a little high band flag for a special purpose, and there's no reason it wouldn't work up there.  Arrays of even smaller flag antennas might give some good results.  You can scale it down to something like 1.5 x 3 feet, turn it horizontally, mount it on a rotator on the roof, say it's your HDTV antenna, and be VERY VERY careful about common mode noise pickup, use a good preamp, and it will *hear* as well as if you had a two element yagi on your roof.  Wouldn't transmit worth a damn, but that's what your vertical is good for.

Arrays of really small verticals around the yard for receiving could be disguised as all sorts of stuff.

You could scale down W8JI's 160m eight circle to work on 20m and 17m with probably excellent receiving results:

These are *extreme* measures of course.

Otherwise, I think you're in good shape and I would not worry much about the station at that point.  Just go DXing.  When the bands are poor, you'll hear every bleep, bloop and buzzzz of everyone's electronic crap, but as you get confident in the fact you can work DX and as you find when the good openings are, you'll spend more time DXing and less time listening to junk noise.  

I would at least make sure your own nose is clean as far as your artificial noise problems.  If you can just unplug an air purifier or put some chokes on the TV for the kids' room or something, you'll be a much happier camper.

Back when I was N3UMH, starting out and living in my parents' place in high school, I had a little tower and tribander.  Every time I would point that thing toward Asia on 15m I'd get awful noise.  At some point it dawned on me that pointing to Asia was POINTING RIGHT AT THE HOUSE, and furthermore I realized that my bedroom shack was the closest thing to the heading I had the antenna on.  

I started unplugging stuff, and when I unplugged the switched off TV, *poof,* noise goes away.

Make sure you don't have any of that and then go find some DX.





Monkey/silicon cyborg, beeping at rocks since 1995.

Posts: 599

« Reply #16 on: May 09, 2009, 04:29:46 PM »

Consider using the Olivia digital mode as a way of working thru the noise.  It's not as fast as psk31 but is far more impervious to noise and fading.  Olivia is able to work 12 to 13 db BELOW the noise level.  

Posts: 62

« Reply #17 on: June 21, 2009, 01:33:02 PM »

Since I moving into a much smaller house and property, I've found myself dealing with many of the same problems. I have a similar setup, but have an inverted L disguised as a drop from the utility pole. That trick also allowed the use of a heavy,insulated wire that no doubt increases radiation efficency over 14 guage. The advice given here on the radials is very good. There's been a significant impovment to both the autotuner's performance and radiated signal with a greater radial field. I stopped being obsessive,trenching each new radial and used staples made from wire for the addtional radials. One or two added radials every couple of days doesn't attract much attention this way or causes problems with the lawn maintenance. Again as others here have mentioned, dealing with the noise finds that many of the problems can be localized by doing a noise audit of your own home. Greatest offender that I found was my wife's curio cabinet that has a touch dimmer. Even off, it generated a strong, broad spectrum noise. Other finds were our cordless phone base and a wall mounted hair dryer in our bathroom that has an automatic,dimming night light. Some early CFL's were notorious culprits too. You can find many surprises within your own house and property that can be corrected. A solution that I found to work reasonably well for external noise that I'm unable to resolve is the use of a JPS/Timewave ANC-4 noise canceller and an externally mounted marine active antenna. It's near worthless for a rx antenna, but excells as a noise antenna. This one is only an 18"x 2" pvc tube that was painted with some house paint for stealth. With a little practice, one of these units or perhaps similar MFJ units can make a big difference in many cases. Some judicious experiments with directional loops or polarity of a noise antenna can help too. Additionally, the choice of an external dsp unit can help. I've owned several from JPS,SGC,and Amcomm in place of the near worthless Icom DSP board option. The incredibly simple Amcomm with a single switch vastly outperforms the others using NCT's superior Clearspeach commercial firmware. Both Heil and West Mountain have continued the Clearspeach product and very well may have improved the product with more advancements since. How about your station speaker? Some simple,passive L/C filters can make the noise less fatiguing and improve intelligibility. It all adds up.

Posts: 242

« Reply #18 on: June 21, 2009, 04:47:01 PM »

Good advice from all.  I was always interested in the two element dipole installed on the roof.  Certainly the higher the antenna the better, but you are in a limited situation.  Make sure your station equipment is all connected together to a good Earth ground.  How close is your antenna to powerlines?

Do a little research on the net and take a look at comparisons between radios re lowest noise floors.  Consider finding a SCAF external filter or maybe an Autek QF-1A to use short term.  When I first started I did phone only, but after screwing up the courage to use CW, I found the the broad sigs on SSB made things much more chaotic.  The last time I tried to do a contest on phone, I was done after 10 minutes.  

I would look for a Ten Tec Corsair II or an Omni V, and put in both 500Hz and 250Hz filters.  These are non-DSP rigs that are very quiet. I can't say much about rigs for SSB, so maybe others can clue us in on that.
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