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The war against NOISE
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wrote:
(snip) It made a big difference. But, alas it is a far cry from the quite I had for a few days. Given the omnipresent man made electrical noise around most American cities, I suspect that very few of us get to see just how sensitive our receivers really are. On the flip side, one could say that the receivers, especially tabletops, HAVE to be sensitive in order to deal with all the noise. ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
wrote About 15 years ago we hasd a nasty ice storm. Knocked out the AC mains, telephone, and cable TV for 3 days. I was amazed at how quite it got. I was operating from a couple of GellCells, kept charged off by a a small PV (solar cell) array. Other then freezing my but off, it was great fun. Since I normally only go on camping/mine DX-epditions in the late summer and early fall, it was much wquiter at home then I had ever exeprienced in the deep woods. I could hear the igniton noise from the highway about 1 mile away! I had very mixed feelings when they brought our power back on. I was tired of the cold, but reslly enjoyed the quite. I have done all that I can to reduce the RFI that I produce. I have bypassed all the AC mains outlets, bypassed teh AC mains where it enteres the breaker box, used lots of RFI suppresion ferrite "beads" on all the active electronics, imporved my ground system as much as I can, and use the best (lowest noise) antenna that I can currently afford. Since I had a glimsp of what true radio quite conditions were, I had the incentive to do what I could. It made a big difference. But, alas it is a far cry from the quite I had for a few days. Given the omnipresent man made electrical noise around most American cities, I suspect that very few of us get to see just how sensitive our receivers really are. Terry Roger that, in Virginia Beach every couple years or so we get a summer week-off from the grid after a hurricane blows by. The reception is phenomenal. I wonder what it would be like in the winter? Jack |
You can sometimes get rid of noise with the ANC-4, but it has been my
experience the noise needs to be really local, such as your damn PC. I use a Wellbrook ALA-100, which is their basic amp with a roll it yourself loop. I will never go back to a long wire. I've built a DC adapter for the Wellbrook (as discussed before, the thing is postive ground so use caution.) Taking the Wellbrook out in the boonies, you can experience low noise. At my house, forget it. This is the small loop, about 3ft on a side. http://www.lazygranch.com/images/radio/loop1.jpg http://www.lazygranch.com/images/radio/loop2.jpg http://www.lazygranch.com/images/radio/loop3.jpg http://www.lazygranch.com/images/radio/loop4.jpg http://www.lazygranch.com/images/radio/loop5.jpg I have a similar set up that is 7ft on a side. That is about as large as this single hub design can handle. The thing with the Wellbrook loop (supposedly) is that as you make it larger, the signal to noise ratio increases. It's not like a long wire where the longer length boosts both the noise and the signal. Here is what Wellbrook says about this: ----- The large aperture of the ALA 100 improves the signal pickup to optimise the signal to noise ratio and also reduces fading at HF, this is a very important advantage compared to small active antennas http://www.wellbrook.uk.com/ALA100.html -------- I run the ala 100 with a loop about the size of a hoola (sp) hoop. That is about as small as you should go. |
"Jack Painter" wrote in message news:h0cVd.37530$%U2.35335@lakeread01... wrote About 15 years ago we hasd a nasty ice storm. Knocked out the AC mains, telephone, and cable TV for 3 days. I was amazed at how quite it got. I was operating from a couple of GellCells, kept charged off by a a small PV (solar cell) array. Other then freezing my but off, it was great fun. Since I normally only go on camping/mine DX-epditions in the late summer and early fall, it was much wquiter at home then I had ever exeprienced in the deep woods. I could hear the igniton noise from the highway about 1 mile away! I had very mixed feelings when they brought our power back on. I was tired of the cold, but reslly enjoyed the quite. I have done all that I can to reduce the RFI that I produce. I have bypassed all the AC mains outlets, bypassed teh AC mains where it enteres the breaker box, used lots of RFI suppresion ferrite "beads" on all the active electronics, imporved my ground system as much as I can, and use the best (lowest noise) antenna that I can currently afford. Since I had a glimsp of what true radio quite conditions were, I had the incentive to do what I could. It made a big difference. But, alas it is a far cry from the quite I had for a few days. Given the omnipresent man made electrical noise around most American cities, I suspect that very few of us get to see just how sensitive our receivers really are. Terry Roger that, in Virginia Beach every couple years or so we get a summer week-off from the grid after a hurricane blows by. The reception is phenomenal. I wonder what it would be like in the winter? I've never had that scenario happen for very long; usually for me the power goes out for a while during a thunderstorm, but I'm not inclined to fry my electronics and hook up the big antenna at that time. The two biggest changes I had to clean up noise we move to a house where the electrical and phone lines are underground, and to take the Sat 800 off of the same breaker used by the Dell laptop for work and put it on a separate one. In the case of the Dell, noise coming through the AC/DC transformer was absolutely horrible; my trusty home computer never had that issue. --Mike L. |
Can I say "perfect"?
Terry |
More sensitivity then the local noise floor doesn't do you any good
and might add to your problems. Think about it. If you have 100uV of noise then a receiver with a 10uV threashol will need to have a signal that is above 100uV to be heard. A 90uV signal will be 10uV below the noise floor and lost. It is much better to remove your local noise to the point where yoy can use better sensitivity. Terry |
wrote:
More sensitivity then the local noise floor doesn't do you any good and might add to your problems. Think about it. If you have 100uV of noise then a receiver with a 10uV threashol will need to have a signal that is above 100uV to be heard. A 90uV signal will be 10uV below the noise floor and lost. It is much better to remove your local noise to the point where yoy can use better sensitivity. Terry I meant to say selectivity. I get the two confused sometimes (because I'm a tard, right, Ace?). ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
Even selctivity will not help all that much in the case of most
noise. Which by nature is broadbanded. When fightening someforms of digitalnoise, a real narrow IF fitler can sometimes help. But unless you are trying to dig CW out frm the man made noise, super narrow filters are really much use. Much better to work to reduce you local noise. A low noise antenna can really help. From what I have read the Wellbrook loop,is great at reducing "point source" noises. I have played with home made shielded/balanced loops, but the results weren't worth the added trouble. I am currently playing with a sycnhronous noise blanker that "slices"/mutes the antenna output for an adjustable number of mSec with a 60Hz line locked "switch". It almost works. Some of the Lowfers swear by this. The "swicth" has to go ahaead of the radio's front end. I am strting to think that my 9:1 matching transformer is "ringing". Terry |
For those interested in looking at looks to be a very
well thought out "line noise blanker", check out: http://www.mods.dk/mod/kenwood/ts-950_syn_blank.pdf#search='synchronous%20line%20noi se%20blanker' I hadn't checked back in a few months and tehre is a correction that might just solve my problems. Terry |
The antenna shown uses fiberglass tent poles. They are 2ft each. The
larger version uses fiberglass rods from Tap Plastics. They are cut to fit the back of my suv, something like 65 inches. I'd love to use the antenna with the amount of wire indicated on the Wellbrook site. I suspect someone could roll their own Wellbrook. I believe they use a very wideband transformer and a low noise JFET amplifier. You can find wideband transformers on ebay (North Hills). JFET amps aren't that hard to build. The transformer lets you float the loop and does the double to single ended conversion. |
I have read that in several ham antenna sites, but mine has been
in use and outside for at least 4 years. Last spring a lightning bolt took out an Chineese Elm tree about 30' from the "long" wire feeding it. When the tree fell it took the wire antenna, and our fence, with it. I was concerend about the transformer and was mildly shocked to find it unscathed. Somewhere I have a link for a "multi-set coupler" that disusses the commercial and roll your owns and mentions the techniques used by mincircuits give a "flatter wider bandwidth with less loss". The last line is a parphrase of their conclusion. It isn't that we can't wind good low loss, wide bandwidth transformers, to me being able to buy one for a few (my 9:1 cast less then $4 US) dollars will help get the project done that much faster. And in a situation where a JFET amplifier is under consideration, I supect that the FETS will get fried many more times the the tranformer. Terry |
wrote in message oups.com... The antenna shown uses fiberglass tent poles. They are 2ft each. The larger version uses fiberglass rods from Tap Plastics. They are cut to fit the back of my suv, something like 65 inches. I'd love to use the antenna with the amount of wire indicated on the Wellbrook site. I suspect someone could roll their own Wellbrook. I believe they use a very wideband transformer and a low noise JFET amplifier. You can find wideband transformers on ebay (North Hills). JFET amps aren't that hard to build. The transformer lets you float the loop and does the double to single ended conversion. The Wellbrook is definitely a balanced amp, but I've not heard of someone who's either reverse engineered it or built an approximation of one, as the demand would be pretty good, I'd imagine. --Mike L. |
The Wellbrook is great, but not a big seller, especially the ALA 100,
which is just the amp. Based on serial numbers, they sold 3 in 9 months in the US market. Other than size, the wellbrook beats out any of those loops like the Kiwa or Quantum. The Kiwa might be of some advantage if you don't have narrow band filters in you radio, but anyone forking out the $400 for a Kiwa probably has a decent rig. I suspect the US market doesn't like the hoops you need to go through to buy the Wellbrook. No secure internet website for instance. No toll free numbers. |
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