|
Wellbrook question
Has anyone had a "bad", as in less then stellar performance, with a
Wellbrook ALA 1530 loop antenna? Given the almost sacred refference the Wellbrook is held in I have debated asking this question. I have a ALA 1530 that is part of a trade that I am looking at and guys I just don't get it. This antenna is reputed to be the cat's meow, but I have found it marginal at best. A north country active antenna is nearly it's match and the 3rd harmonic of a local MW (770KHz) is S3 on the Wellbrook. A Lankford Active Dipole stomps it in gain, IP2 and IP3 and for directivity. I am wondering if this antenna is defective or if it is a case of the Emperors New Clothes. I have tried loops several times in the last 30 years and always give up becuase I have never found the reported imunity against local QRM to be true. I am building a copy of the WL1030 (http://wl1030.com/), but I don't understand the fascination with loops. What am I missing? For MW DX "big" air loops make sense. Good directivity to null out an offending signal. I notice Ron Harding uses McKay 100E with a phaser to achieve good nulls. For HF the sky wave "smears" both the desired and unwanted signals making a null very iffy. Receivers used in this test: R2000 R8B R390 R392 The R390 and R392 where not tested at my home but at a friend's home where I have them stored. While I like both the R390 and R392, they are somewhat awkward to rapidly tune from one frequency to a wildly seperated one. Terry |
Wellbrook question
wrote: Has anyone had a "bad", as in less then stellar performance, with a Wellbrook ALA 1530 loop antenna? Given the almost sacred refference the Wellbrook is held in I have debated asking this question. I have a ALA 1530 that is part of a trade that I am looking at and guys I just don't get it. This antenna is reputed to be the cat's meow, but I have found it marginal at best. A north country active antenna is nearly it's match and the 3rd harmonic of a local MW (770KHz) is S3 on the Wellbrook. A Lankford Active Dipole stomps it in gain, IP2 and IP3 and for directivity. I am wondering if this antenna is defective or if it is a case of the Emperors New Clothes. I have tried loops several times in the last 30 years and always give up becuase I have never found the reported imunity against local QRM to be true. I am building a copy of the WL1030 (http://wl1030.com/), but I don't understand the fascination with loops. What am I missing? For MW DX "big" air loops make sense. Good directivity to null out an offending signal. I notice Ron Harding uses McKay 100E with a phaser to achieve good nulls. For HF the sky wave "smears" both the desired and unwanted signals making a null very iffy. Receivers used in this test: R2000 R8B R390 R392 The R390 and R392 where not tested at my home but at a friend's home where I have them stored. While I like both the R390 and R392, they are somewhat awkward to rapidly tune from one frequency to a wildly seperated one. Terry One thing you might do is check the cables connecting the different components of the Wellbrook. At one point I noticed that my loop wasn't performing as I thought it should and I discovered that the cable connecting the receiver to the antenna interface had a poor connection where it meets the interface box. The intermittent connection became obvious as soon as I jiggled the cable a bit. Also, where do you have the loop situated? In my experience the performance of the loop is seriously degraded when used indoors. |
Wellbrook question
Has anyone had a "bad", as in less then stellar performance, with a Wellbrook ALA 1530 loop antenna? Hi Terry, I have a homebrew version of the Wellbrook shielded loop 7' in diameter. It is in my woods on a short tower and rotator. On 160M and 75M it is the same as my 80M inverted vee. It's a good performer on MW/LW but not any real difference between it and a homebrew voltage probe antenna with a 4' whip. Loops are most useful where there is a single noise source that can be nulled with the loop- other than that, it's a toss up. There is still the wive's tale making the rounds that shielded loop are immune to the E field noise - rubbish and well disproven in the literature. So, in summary, I like mine for being a compact RX antenna for MW/LW, but at least in my environment, not sure I would go to the trouble next time. Dale W4OP for PAR Electronics, Inc. |
Wellbrook question
Steve wrote: One thing you might do is check the cables connecting the different components of the Wellbrook. At one point I noticed that my loop wasn't performing as I thought it should and I discovered that the cable connecting the receiver to the antenna interface had a poor connection where it meets the interface box. The intermittent connection became obvious as soon as I jiggled the cable a bit. Also, where do you have the loop situated? In my experience the performance of the loop is seriously degraded when used indoors. Calbe and connectors are good, and have been used to power the Lankford active dipole I am checking. I have tried it in a variety of locations. We even went so far as to drive to the Red River Gorge, an area well away from houses, power lines etc. The preformance just doesn't strike me as being worth the fairly high cost. The active dipole beat it every time. Terry |
Wellbrook question
Dale Parfitt wrote: Has anyone had a "bad", as in less then stellar performance, with a Wellbrook ALA 1530 loop antenna? Hi Terry, I have a homebrew version of the Wellbrook shielded loop 7' in diameter. It is in my woods on a short tower and rotator. On 160M and 75M it is the same as my 80M inverted vee. It's a good performer on MW/LW but not any real difference between it and a homebrew voltage probe antenna with a 4' whip. Loops are most useful where there is a single noise source that can be nulled with the loop- other than that, it's a toss up. There is still the wive's tale making the rounds that shielded loop are immune to the E field noise - rubbish and well disproven in the literature. So, in summary, I like mine for being a compact RX antenna for MW/LW, but at least in my environment, not sure I would go to the trouble next time. Dale W4OP for PAR Electronics, Inc. I am begining to think that many people over rate a loop because it has lower over all gain and therefore is quiter. Based on my experience with improved detector and audio chains I have come to understand that the signal to noise is the only variable that really matters. I wish my fancy HiFer beacon/test source had not been fried by Thor. Even the 13.xxMHz crsytal was toast! It would be interesting to run some real experiments to compare antennas the way I compared detectors and post detection amplifiers. BTW I have completly ripped out all of my coax and pulled down my antennas. Since I got rid of my desktop PC and I have gone to a laptop I found I really needed to redesign my radio desk. Since my antennas and coax have been up for over 15 years, I decided to redo the whole mess. Fall is a very good time to errect new antennas and I am going to reroute all my coax through 1/2" copper tubing that will be bonded to my perimeter ground ring. An electrician friend used his mini Ditch Witch to dig me a couple of trenches. I hope to have the antennas back up by Monday evening. I typically research and build devcies in the summer, think about antennas in teh fall and do serious listening over the winter. Terry |
Wellbrook question
wrote in message oups.com... Dale Parfitt wrote: Has anyone had a "bad", as in less then stellar performance, with a Wellbrook ALA 1530 loop antenna? Hi Terry, I have a homebrew version of the Wellbrook shielded loop 7' in diameter. It is in my woods on a short tower and rotator. On 160M and 75M it is the same as my 80M inverted vee. It's a good performer on MW/LW but not any real difference between it and a homebrew voltage probe antenna with a 4' whip. Loops are most useful where there is a single noise source that can be nulled with the loop- other than that, it's a toss up. There is still the wive's tale making the rounds that shielded loop are immune to the E field noise - rubbish and well disproven in the literature. So, in summary, I like mine for being a compact RX antenna for MW/LW, but at least in my environment, not sure I would go to the trouble next time. Dale W4OP for PAR Electronics, Inc. I am begining to think that many people over rate a loop because it has lower over all gain and therefore is quiter. Based on my experience with improved detector and audio chains I have come to understand that the signal to noise is the only variable that really matters. I wish my fancy HiFer beacon/test source had not been fried by Thor. Even the 13.xxMHz crsytal was toast! It would be interesting to run some real experiments to compare antennas the way I compared detectors and post detection amplifiers. BTW I have completly ripped out all of my coax and pulled down my antennas. Since I got rid of my desktop PC and I have gone to a laptop I found I really needed to redesign my radio desk. Since my antennas and coax have been up for over 15 years, I decided to redo the whole mess. Fall is a very good time to errect new antennas and I am going to reroute all my coax through 1/2" copper tubing that will be bonded to my perimeter ground ring. An electrician friend used his mini Ditch Witch to dig me a couple of trenches. I hope to have the antennas back up by Monday evening. I typically research and build devcies in the summer, think about antennas in teh fall and do serious listening over the winter. Terry I'll match your dipole against my 70m full-wave horizontal loop for equal gain from 70M all they way up to 6M - can you say broadbanded? A dipole is not. |
Wellbrook question
Seeing-I-dawg wrote: I'll match your dipole against my 70m full-wave horizontal loop for equal gain from 70M all they way up to 6M - can you say broadbanded? A dipole is not. Can you rotate your "70M full-wave horizontal loop"? And at 70M, or about 230 feet in "diameter", it is a very different antenna then a 1M much touted miracle loop. I don't think I was attempting to compare 3' with 230'. One supposed advantage of the small, fractional wavelength, loop is the reported, or should I say reputed, highly directional charactoristics. That famous figure "8" pattern. The dipole to which I am reffering is an amplified, very high IP3 and IP2 unit with very good,as in flat gain and very directional, from 100KHz to above 28MHz. I will have to connect it to my scanner and see if I can receive any 6M ham comms, or more likely around here older 49MHz telephones. I suspect it will run out of steam somewhere just above 35MHz, but I haven't checked. It will be later next week before I can do any tests as my "shack" is in pieces and I am reduced to a DX398 coupled to a ~50 random wire out the kitchen window. Terry |
Wellbrook question
I'll match your dipole against my 70m full-wave horizontal loop for equal
gain from 70M all they way up to 6M - can you say broadbanded? A dipole is not. Apples and oranges. The current discussion is about electrically small, rotatable loops. Dale W4OP |
Wellbrook question
In article VD8Tg.9636$422.6849@trnddc03,
"Dale Parfitt" wrote: Snip There is still the wive's tale making the rounds that shielded loop are immune to the E field noise - rubbish and well disproven in the literature. Snip Old "wives tale" is a rec.radio.amateur.antenna trash talk phrase. Were have you been reading that an electrically small shielded or unshielded loop is sensitive to E field? -- Telamon Ventura, California |
Wellbrook question
|
Wellbrook question
" That was a self defeating test. The idea here is that you will have a lower noise floor in a locally noisy area with a shielded loop than a dipole antenna. There is going to be no advantage to using a loop over a dipole in an electrically quiet area. A shielded loop is not better at picking up a distant signal than a dipole but is less sensitive to local noise generators so in an area with high local noise you would have better signal to noise than a full size dipole antenna. Please see: http://www.w8ji.com/magnetic_receiving_loops.htm Dale W4OP |
Wellbrook question
In article kImTg.111$pS3.23@trnddc01,
"Dale Parfitt" wrote: " That was a self defeating test. The idea here is that you will have a lower noise floor in a locally noisy area with a shielded loop than a dipole antenna. There is going to be no advantage to using a loop over a dipole in an electrically quiet area. A shielded loop is not better at picking up a distant signal than a dipole but is less sensitive to local noise generators so in an area with high local noise you would have better signal to noise than a full size dipole antenna. Please see: http://www.w8ji.com/magnetic_receiving_loops.htm A nice page written by some amateur drawing wrong conclusions. Following his logic coax cable would not shield the center conductor either for example since the coax has to be open on both ends. He quotes a lot of good information and then spouts conclusion that don't follow. I don't have the patience to read the whole page but I scanned through it and for starters he does not seem to distinguish between far and near field energy. Far field has equal energy in the E and H fields so two antennas, example dipole and loop, that are strongly couple to one field and not the other generate the same power. No real difference then between antennas that are strongly affected by one field and not the other to far field signal or noise. Near field is a different story. Near field is what the local noise makers generate the most of and the electric tends to propagate farther than the magnetic from the source so you want to use an antenna that is sensitive to the H field for the same reason you try to get an antenna as far away from local noise sources as possible. You can see the logic in that right? And let's not forget about that very handy null in the loop pattern. I use that all the time on the AM portable with its built in loop stick antenna that is not even shielded. -- Telamon Ventura, California |
Wellbrook question
wrote: Has anyone had a "bad", as in less then stellar performance, with a Wellbrook ALA 1530 loop antenna? Given the almost sacred refference the Wellbrook is held in I have debated asking this question. I have a ALA 1530 that is part of a trade that I am looking at and guys I just don't get it. This antenna is reputed to be the cat's meow, but I have found it marginal at best. A north country active antenna is nearly it's match and the 3rd harmonic of a local MW (770KHz) is S3 on the Wellbrook. A Lankford Active Dipole stomps it in gain, IP2 and IP3 and for directivity. I am wondering if this antenna is defective or if it is a case of the Emperors New Clothes. I have tried loops several times in the last 30 years and always give up becuase I have never found the reported imunity against local QRM to be true. I am building a copy of the WL1030 (http://wl1030.com/), but I don't understand the fascination with loops. What am I missing? For MW DX "big" air loops make sense. Good directivity to null out an offending signal. I notice Ron Harding uses McKay 100E with a phaser to achieve good nulls. For HF the sky wave "smears" both the desired and unwanted signals making a null very iffy. Receivers used in this test: R2000 R8B R390 R392 The R390 and R392 where not tested at my home but at a friend's home where I have them stored. While I like both the R390 and R392, they are somewhat awkward to rapidly tune from one frequency to a wildly seperated one. Terry I use the ALA 100. The smaller loops may not be as good on MW. It is a good idea to insure the amplifer is actually doing something. The fuse could be blown, the wall wart bad, etc. Unplug the power connector and make sure the signal strength drops. You will get reception from the loop even if the amp is off since some RF will leak. Some of the Wellbrook amps were positive ground. The unit is fused and I would guess there is a reverse biased protection diode. If the wrong wall wart was used, it would pop the fuse. In my portable set up, I have red shrink wrap on the connector that goes to the Wellbrook, just to make it clear the ground is backwards. As far as the 1530 goes, it may not have a good resale value since they released the "plus" version, which has response in the FM BCB. |
Wellbrook question
|
Wellbrook question
|
Wellbrook question
A nice page written by some amateur drawing wrong conclusions. Following his logic coax cable would not shield the center conductor either for example since the coax has to be open on both ends. He quotes a lot of good information and then spouts conclusion that don't follow. The author of the page is one of the most respected amateurs, an active consulting engineer, designer of the DX engineering Low band line of active antennas, and widely published. I have read identical conclusions in the IEEE Journal on EM. The null of the loop is its best feature. We agree there. Dale W4OP |
Wellbrook question
Very interesting post's on this subject so far. Sure is nice to have
some topics that are about DX & radios. I did a bunch of CW contesting back some years ago & am very familiar with W8JI's station. All of the best ops in the country wanted to run his station during the ARRL 160 cw contest. BIG signal & could work stations most could not even hear. My point is I am sure he "knows his stuff". With that said....I have 2 hf antennas up right now. A wellbrook K9AY & a wellbrook ALA 1530. The 1530 is mounted at 6ft off the ground strapped to a wooden fence. The K9AY always has a signal that shows more s-units. However many times the 1530 will give a better s/n ratio. It took me a while to "get over" the lower s meter reading & realize I was hearing the signal better because of the better s/n ratio. My location is in a housing project with several houses within 300 ft of me so the loss in gain was not hurting me since my noise floor was higher. Now If I were located out in the wide open spaces with no man made noise for miles then the 1530 would have no where near enough gain. All of these are my opinions of course Ken KG4BIG Dale Parfitt wrote: A nice page written by some amateur drawing wrong conclusions. Following his logic coax cable would not shield the center conductor either for example since the coax has to be open on both ends. He quotes a lot of good information and then spouts conclusion that don't follow. The author of the page is one of the most respected amateurs, an active consulting engineer, designer of the DX engineering Low band line of active antennas, and widely published. I have read identical conclusions in the IEEE Journal on EM. The null of the loop is its best feature. We agree there. Dale W4OP |
Wellbrook question
Ken Wilson wrote: Very interesting post's on this subject so far. Sure is nice to have some topics that are about DX & radios. I did a bunch of CW contesting back some years ago & am very familiar with W8JI's station. All of the best ops in the country wanted to run his station during the ARRL 160 cw contest. BIG signal & could work stations most could not even hear. My point is I am sure he "knows his stuff". With that said....I have 2 hf antennas up right now. A wellbrook K9AY & a wellbrook ALA 1530. The 1530 is mounted at 6ft off the ground strapped to a wooden fence. The K9AY always has a signal that shows more s-units. However many times the 1530 will give a better s/n ratio. It took me a while to "get over" the lower s meter reading & realize I was hearing the signal better because of the better s/n ratio. My location is in a housing project with several houses within 300 ft of me so the loss in gain was not hurting me since my noise floor was higher. Now If I were located out in the wide open spaces with no man made noise for miles then the 1530 would have no where near enough gain. All of these are my opinions of course Ken KG4BIGY Perhaps my local noise floor is "good enough" that whatever benifit the Wellbrook offers is lost. I am trading the newly aquired ALA 1530 to an acquaintance who lives in downtown Lexington for a Datong AD370 that was only used for a few weeks. He is aware of my doubts about the ALA1530's ability but says he has nothing to loose. When I get a copy of the WL1030 built we will test it at his condo. Terry |
Wellbrook question
Ken Wilson wrote:
Very interesting post's on this subject so far. Sure is nice to have some topics that are about DX & radios. I did a bunch of CW contesting back some years ago & am very familiar with W8JI's station. All of the best ops in the country wanted to run his station during the ARRL 160 cw contest. BIG signal & could work stations most could not even hear. My point is I am sure he "knows his stuff". With that said....I have 2 hf antennas up right now. A wellbrook K9AY & a wellbrook ALA 1530. The 1530 is mounted at 6ft off the ground strapped to a wooden fence. The K9AY always has a signal that shows more s-units. However many times the 1530 will give a better s/n ratio. It took me a while to "get over" the lower s meter reading & realize I was hearing the signal better because of the better s/n ratio. My location is in a housing project with several houses within 300 ft of me so the loss in gain was not hurting me since my noise floor was higher. Now If I were located out in the wide open spaces with no man made noise for miles then the 1530 would have no where near enough gain. All of these are my opinions of course Ken KG4BIG Dale Parfitt wrote: A nice page written by some amateur drawing wrong conclusions. Following his logic coax cable would not shield the center conductor either for example since the coax has to be open on both ends. He quotes a lot of good information and then spouts conclusion that don't follow. The author of the page is one of the most respected amateurs, an active consulting engineer, designer of the DX engineering Low band line of active antennas, and widely published. I have read identical conclusions in the IEEE Journal on EM. The null of the loop is its best feature. We agree there. Dale W4OP Thanks to all for the most interesting and relevant thread on this group I can remember. I have a North County antenna in an apartment community and hope someday to have a way and means to install Dale's antenna but right now The North County will hafta' do, and I am amazed how well it works here in central Florida Yodar w/RX 320 |
Wellbrook question
In article oZuTg.1266$753.664@trnddc05,
"Dale Parfitt" wrote: A nice page written by some amateur drawing wrong conclusions. Following his logic coax cable would not shield the center conductor either for example since the coax has to be open on both ends. He quotes a lot of good information and then spouts conclusion that don't follow. The author of the page is one of the most respected amateurs, an active consulting engineer, designer of the DX engineering Low band line of active antennas, and widely published. I have read identical conclusions in the IEEE Journal on EM. The null of the loop is its best feature. We agree there. I'm sure he is a great guy and knows a lot but that does not mean he is right. What he states is against theory and experience. I will go with what practical experience supported by theory over someone's preeminent opinion. His opinion is contrary to the theory of operation of electrically small shielded (or unshielded for that matter) loops compared to electric field probes (example single wire or dipole). You possibly misconstrued what you read in the IEEE journal. We just had a discussion about inductive noise probes for trouble shooting problems. Maybe you missed that. It was discussed here about using a small shielded loop to distinguish between magnetic fields and a short wire probe to pick up electric fields. Now this past discussion relates to very close local induction fields. This is the very situation the author you refer to claims the shielded loop probe would be useless as it would be no different than the voltage probe response. Well sorry, these probes really work as advertised because I used them professionally and successfully. My experience building and using antennas also run contrary to what the author you refer to states. My experience in antenna building is also predicted by theory. Most other people have had similar experiences using loop and dipole antennas. Again I will mention that there is a difference between an inductive field and a far field that is a propagating wave and that theoretically there will be a significant difference in response between E and H field sensitive antennas to the inductive but not the far field. -- Telamon Ventura, California |
Wellbrook question
Dale Parfitt wrote: A nice page written by some amateur drawing wrong conclusions. Following his logic coax cable would not shield the center conductor either for example since the coax has to be open on both ends. He quotes a lot of good information and then spouts conclusion that don't follow. The author of the page is one of the most respected amateurs, an active consulting engineer, designer of the DX engineering Low band line of active antennas, and widely published. I have read identical conclusions in the IEEE Journal on EM. The null of the loop is its best feature. We agree there. Dale W4OP Interesting. I just checked out the DX Engineering website and it's worth a look: http://www.dxengineering.com I learned, among other things, that they'll soon be marketing a very expensive phasing unit. If it's worth that much, it'll be really interesting. |
Wellbrook question
In article .com,
"Ken Wilson" wrote: Dale Parfitt wrote: A nice page written by some amateur drawing wrong conclusions. Following his logic coax cable would not shield the center conductor either for example since the coax has to be open on both ends. He quotes a lot of good information and then spouts conclusion that don't follow. The author of the page is one of the most respected amateurs, an active consulting engineer, designer of the DX engineering Low band line of active antennas, and widely published. I have read identical conclusions in the IEEE Journal on EM. The null of the loop is its best feature. We agree there. Very interesting post's on this subject so far. Sure is nice to have some topics that are about DX & radios. I did a bunch of CW contesting back some years ago & am very familiar with W8JI's station. All of the best ops in the country wanted to run his station during the ARRL 160 cw contest. BIG signal & could work stations most could not even hear. My point is I am sure he "knows his stuff". With that said....I have 2 hf antennas up right now. A wellbrook K9AY & a wellbrook ALA 1530. The 1530 is mounted at 6ft off the ground strapped to a wooden fence. The K9AY always has a signal that shows more s-units. However many times the 1530 will give a better s/n ratio. It took me a while to "get over" the lower s meter reading & realize I was hearing the signal better because of the better s/n ratio. My location is in a housing project with several houses within 300 ft of me so the loss in gain was not hurting me since my noise floor was higher. Now If I were located out in the wide open spaces with no man made noise for miles then the 1530 would have no where near enough gain. All of these are my opinions of course And this is the experience of most people with loop antennas. Things are a bit more complicated with electrically small loop antennas because amplifiers come into use. Now you have to consider amplifier design along with antenna design to predict performance. Larger loops require less amplification so the amplifier performance becomes less of an issue. Full size loop antennas are a little different dimensionally and depending on your house lot you might be able to fit a loop on your lot where you can't fit a full size dipole. This difference in dimensions may allow you get the full size loop farther away from a local noise source. -- Telamon Ventura, California |
Wellbrook question
In article . com,
wrote: wrote: I use the ALA 100. The smaller loops may not be as good on MW. It is a good idea to insure the amplifer is actually doing something. The fuse could be blown, the wall wart bad, etc. Unplug the power connector and make sure the signal strength drops. You will get reception from the loop even if the amp is off since some RF will leak. Some of the Wellbrook amps were positive ground. The unit is fused and I would guess there is a reverse biased protection diode. If the wrong wall wart was used, it would pop the fuse. In my portable set up, I have red shrink wrap on the connector that goes to the Wellbrook, just to make it clear the ground is backwards. As far as the 1530 goes, it may not have a good resale value since they released the "plus" version, which has response in the FM BCB. This ALA 1530 requires a reversed, is shell positve and inner negative, wall wart. But the center conductor of the coax was positive. I left the original power injector/diplexer intact and built my own. I verified the problem with the stock wall wart/diplexer before trying my own. With out power I get virtually no signals. A few very strong MW and SW at way less then S1. So the amp is working. The original owner says it always behaved like this. OK, but clearly not the do all end all of antennas. What you are calling a "power injector/diplexer" would probably be best described as a bias-T. This is a three port device: Sample schematic: http://www.smelectronics.us/biast.htm 1. DC voltage. (DC input) This is connected to the power supply. 2. AC voltage. (RF output) This is connected to the radio. 3. DC + AC voltage. (RF input, DC output) This is connected to the antenna/amplifier. Port 3 to 2 is connected with a capacitor of very low reactance (zero) to the signal you want to pass through these two ports. Port 1 to 3 are connect with an inductor, which passes DC voltage from port 1 to 3 but blocks RF (high Z) going from 3 to 1 so the RF only sees a path from 3 to 2. Port 3 and 2 are coax cable and port one could be two terminals. One terminal is common grounded with the coax shield grounds. Using a ground independent power supply to the terminals on port 1 allow you to have either a positive or negative power supply to the remote amplifier. -- Telamon Ventura, California |
Wellbrook question
I have a Datong AD-270 = very noisy antenna.
My DX pals have ALA1530's and I would exchange the Datong for a Wellbrook anyday. -- John Plimmer, Montagu, Western Cape Province, South Africa South 33 d 47 m 32 s, East 20 d 07 m 32 s RX Icom IC-756 PRO III with MW mods Drake SW8 & ERGO software Sony 7600D, GE SRIII, Redsun RP2100 BW XCR 30, Braun T1000, Sangean 818 & 803A. GE circa 50's radiogram Antenna's RF Systems DX 1 Pro, Datong AD-270 Kiwa MW Loop http://www.dxing.info/about/dxers/plimmer.dx wrote in message ups.com... Perhaps my local noise floor is "good enough" that whatever benifit the Wellbrook offers is lost. I am trading the newly aquired ALA 1530 to an acquaintance who lives in downtown Lexington for a Datong AD370 that was only used for a few weeks. He is aware of my doubts about the ALA1530's ability but says he has nothing to loose. When I get a copy of the WL1030 built we will test it at his condo. Terry |
Wellbrook question
|
Wellbrook question
In article ,
"John Plimmer" wrote: wrote in message ups.com... Perhaps my local noise floor is "good enough" that whatever benifit the Wellbrook offers is lost. I am trading the newly aquired ALA 1530 to an acquaintance who lives in downtown Lexington for a Datong AD370 that was only used for a few weeks. He is aware of my doubts about the ALA1530's ability but says he has nothing to loose. When I get a copy of the WL1030 built we will test it at his condo. I have a Datong AD-270 = very noisy antenna. My DX pals have ALA1530's and I would exchange the Datong for a Wellbrook anyday. What do you mean by noisy? Since this is an amplified antenna the amplifier will add its own noise, which can be a little or a lot or maybe you mean the antenna/amplifier has a lot of gain where the atmospheric noise is loud or maybe you mean it picks up a lot of local noise sources. Since you are comparing it to a loop I am guessing you mean you expect the Wellbrook to pick up less in the way of local noise sources? -- Telamon Ventura, California |
Wellbrook question
John Plimmer wrote: I have a Datong AD-270 = very noisy antenna. My DX pals have ALA1530's and I would exchange the Datong for a Wellbrook anyday. -- John Plimmer, Montagu, Western Cape Province, South Africa South 33 d 47 m 32 s, East 20 d 07 m 32 s RX Icom IC-756 PRO III with MW mods Drake SW8 & ERGO software Sony 7600D, GE SRIII, Redsun RP2100 BW XR 30, Braun T1000, Sangean 818 & 803A. GE circa 50's radiogram Antenna's RF Systems DX 1 Pro, Datong AD-270 Kiwa MW Loop http://www.dxing.info/about/dxers/plimmer.dx I mounted the AD370 on a tree and connected it to the R2000 on the kitchen table. With the PS side amplifier in the off position there is minimal noise. Compared to "North Country" or the AMRAD it is very close. With the never to be cursed enough MW station on 770KHz and another local on 1240KHz I have some very constant signals for IMD. The AMRAD is imune, no mix products, the NC has some minor mix + and a very weak 2nd and 3rd harmonic that is internal to the antenna under test. The AD370 has a very slight, as in right at the noise floor, mix + (770+1240) and maybe a weak 3rd harmonic of 770 (2,310KHz). Hard to be sure as it is right at the noise floor. I can only find it with a FFT window. With the additional amplifier the noise floor really jumps up. A better amp would likely be the Lankford "ultra linear amp" at http://www.kongsfjord.no/ At this point I have NO regrets about the trade. Terry |
Wellbrook question
The Datong is mounted next to my DX-1 and generates considerably more noise
Firstly from a poor amplifier and secondly It is prone to magnifying the local suburban electrical noise which the DX1 doesn't do. The Datong consists of two five foot whips which can be mounted horizontally, when it then exhibits the characteristics of a dipole, or it can be mounted vertically when it performs like a typical vertical whip antenna. I use it in the vertical position for best results (but noisy). The Datong is rather poor on MW, but as the frequency gets higher it performs considerably better. So by 27 megs it outperforms any other antenna I have used. I do not own a ALA1530, but two of my pals do, one of whom lives in an inner city urban environment. It is considerably quieter than his longwires. -- John Plimmer, Montagu, Western Cape Province, South Africa "Telamon" wrote in message ... In article , "John Plimmer" wrote: I have a Datong AD-270 = very noisy antenna. My DX pals have ALA1530's and I would exchange the Datong for a Wellbrook anyday. What do you mean by noisy? Since this is an amplified antenna the amplifier will add its own noise, which can be a little or a lot or maybe you mean the antenna/amplifier has a lot of gain where the atmospheric noise is loud or maybe you mean it picks up a lot of local noise sources. Since you are comparing it to a loop I am guessing you mean you expect the Wellbrook to pick up less in the way of local noise sources? -- Telamon Ventura, California |
Wellbrook question
Telamon wrote: 1. DC voltage. (DC input) This is connected to the power supply. 2. AC voltage. (RF output) This is connected to the radio. 3. DC + AC voltage. (RF input, DC output) This is connected to the antenna/amplifier. Port 3 to 2 is connected with a capacitor of very low reactance (zero) to the signal you want to pass through these two ports. Port 1 to 3 are connect with an inductor, which passes DC voltage from port 1 to 3 but blocks RF (high Z) going from 3 to 1 so the RF only sees a path from 3 to 2. Port 3 and 2 are coax cable and port one could be two terminals. One terminal is common grounded with the coax shield grounds. Using a ground independent power supply to the terminals on port 1 allow you to have either a positive or negative power supply to the remote amplifier. -- Telamon Ventura, California It is clear you work in the microwave satellite part of electronics. In the "good old days", circa 1990, most text and other refference sources reffered to them as "power injectors" or "diplexers". Your discription of it's function is correct. A power source is isolated from the RF with an inductor, or strip line version, and a capacitor blocks the DC from the receiver. MiniCircuits has very nice, as in wide band, inductors. Since I may use the same coax for VLF. LF, MW, HF, or VHF my power inject, bias "T" or diplexer has different inductors in series because I couldn't find a single inductor to cover from 10KHz through ~500MHz. I found that by using smaller chokes that were effective at UHF, with larger chokes for each decade decrease in frequency. One of the changes I am making is to use the MC wide band inductors to allow a smaller package to be used. Space is at a premium in my "shack". My shack is the 2nd bath with the plumbing removed and covered. It is 5' by 10'. I prefer the word cozy over cramped. Terry |
Wellbrook question
wrote: wrote: I use the ALA 100. The smaller loops may not be as good on MW. It is a good idea to insure the amplifer is actually doing something. The fuse could be blown, the wall wart bad, etc. Unplug the power connector and make sure the signal strength drops. You will get reception from the loop even if the amp is off since some RF will leak. Some of the Wellbrook amps were positive ground. The unit is fused and I would guess there is a reverse biased protection diode. If the wrong wall wart was used, it would pop the fuse. In my portable set up, I have red shrink wrap on the connector that goes to the Wellbrook, just to make it clear the ground is backwards. As far as the 1530 goes, it may not have a good resale value since they released the "plus" version, which has response in the FM BCB. This ALA 1530 requires a reversed, is shell positve and inner negative, wall wart. But the center conductor of the coax was positive. I left the original power injector/diplexer intact and built my own. I verified the problem with the stock wall wart/diplexer before trying my own. With out power I get virtually no signals. A few very strong MW and SW at way less then S1. So the amp is working. The original owner says it always behaved like this. OK, but clearly not the do all end all of antennas. Terry If you throw it on ebay, please post the auction here. |
Wellbrook question
|
Wellbrook question
|
Magnetic Loop Antennas Receiving "Small Receiving Loop Antennas" [Was : Wellbrook Question]
Dale Parfitt wrote: " That was a self defeating test. The idea here is that you will have a lower noise floor in a locally noisy area with a shielded loop than a dipole antenna. There is going to be no advantage to using a loop over a dipole in an electrically quiet area. A shielded loop is not better at picking up a distant signal than a dipole but is less sensitive to local noise generators so in an area with high local noise you would have better signal to noise than a full size dipole antenna. Please see: http://www.w8ji.com/magnetic_receiving_loops.htm Dale W4OP Dale [W4OP] - Thanks for the very informative link. http://www.w8ji.com/magnetic_receiving_loops.htm Magnetic Loop Antennas Receiving "Small Receiving Loop Antennas" http://www.w8ji.com/magnetic_receiving_loops.htm * Small Loop Antennas are often referred to as "Magnetic Radiators". Folklore claims a small "Shielded" Loop Antenna behaves like a sieve, sorting "good magnetic signals" from "bad electrical noise". http://www.w8ji.com/magnetic_receiving_loops.htm * Nothing is further from the truth! At relatively small distances a small Magnetic Loop Antenna is more sensitive to Electric Fields than a small Electric Field Probe type Antenna. http://www.w8ji.com/magnetic_receiving_loops.htm * Field Impedance of the Loop Antenna http://www.w8ji.com/magnetic_receiving_loops.htm Loop Antenna Fields - Short Dipole or Vertical Fields - Radiation * Loop Antenna Shielding and Balance http://www.w8ji.com/magnetic_receiving_loops.htm * Examples of Small Loop Antennas and Analysis of Loop Antenna Construction http://www.w8ji.com/magnetic_receiving_loops.htm * Typical Magnetic Loop Antenna (found on Internet and other places) http://www.w8ji.com/magnetic_receiving_loops.htm * Circuit Representations of Shielded Loop Antennas http://www.w8ji.com/magnetic_receiving_loops.htm |
Wellbrook question
wrote in message oups.com... Seeing-I-dawg wrote: I'll match your dipole against my 70m full-wave horizontal loop for equal gain from 70M all they way up to 6M - can you say broadbanded? A dipole is not. Can you rotate your "70M full-wave horizontal loop"? No need to. It essentially receives equally well in all directions on all bands, unlike a dipole. And at 70M, or about 230 feet in "diameter", it is a very different antenna then a 1M much touted miracle loop. No, the circumference is 70 meters = full wave horiz. loop @70M If you were to transmit into this loop you would see a flat swr from 70M-6M. No tuner required. Just need to match the ladder line to your tranmitter. A dipole can't do that without a tuner. I don't think I was attempting to compare 3' with 230'. One supposed advantage of the small, fractional wavelength, loop is the reported, or should I say reputed, highly directional charactoristics. That famous figure "8" pattern. The dipole to which I am reffering is an amplified, very high IP3 and IP2 unit with very good,as in flat gain and very directional, from 100KHz to above 28MHz. A dipole, any dipole, is cut/tuned for a single band. Any signal outside that band and its harmonics are attenuated. Not so with a large loop - equal gain to dipoles at any frequency. I will have to connect it to my scanner and see if I can receive any 6M ham comms, or more likely around here older 49MHz telephones. I suspect it will run out of steam somewhere just above 35MHz, but I haven't checked. It will be later next week before I can do any tests as my "shack" is in pieces and I am reduced to a DX398 coupled to a ~50 random wire out the kitchen window. Terry For your perusal: http://www.cebik.com/wire/hl.html http://www.cebik.com/fdim/atl1.html http://www.cebik.com/wire/horloop.html |
Wellbrook question
For your perusal: http://www.cebik.com/wire/hl.html http://www.cebik.com/fdim/atl1.html http://www.cebik.com/wire/horloop.html Here is a nice horiz loop program from http://www.smeter.net/antennas/rjeloop4.php "This program is self-contained and ready to use. It does not require installation." Click this link http://www.smeter.net/software/rjeloop4.exe then click Open to run from the web or Save to save the program to your hard drive. After you have entered the initial values you can vary the frequency up or down. Then watch how the efficiancy and loss characteristics barely vary. |
| All times are GMT +1. The time now is 01:55 AM. |
Powered by vBulletin® Copyright ©2000 - 2025, Jelsoft Enterprises Ltd.
RadioBanter.com