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Transplants: Are We Missing Something Here?
John H. Bryant <bjohnorcas@...>
When I went to Easter Island last year, I took with me a Ramsey active antenna based on a 5/8" x 6" ferrite rod. The Ramsey PR bragged about its Faraday shielding and the fact that the antenna operated in the magnetic realm, isolated from most urban, man-made noise. I bought the thing to use during my time in Santiago, Chile, knowing full well the reputation of older Latin American cities as being RF noise swamps. Santiago was a wonderful city (I want to go back) but the radio dial was just as advertised.... constant S-9 noise from the power grid and other stuff. The Ramsey antenna was a real revelation.... it worked like a bandit and I was able to DX, almost noise-free.
On the way home, I had to tear the antenna apart to rid myself of the PVC housing (another story). The shielding was simply a rectangle of aluminum foil laid on the coil and bar, with a 1/8" gap running longitudinally down the bar. An electrical connection to the ground plane of the little amp/control box and thence to the radio was made by a paper clip inserted under the foil, with the ground wire soldered to the paper clip. There was probably a piece of paper as insulation between the foil and the bar.
That was my first experience with a shielded loop antenna and there was a lot to love about it in an urban environment. Are we missing a bet by not shielding our external bars, even if they are a Booster Bar??????
John B.
John B.
Stillwater, Oklahoma, USA
Rcvrs: WiNRADiO 313e, Eton e1, NRD-535(kiwa-mods)
Antennas: 700' NE/SW mini-Bev, Wellbrook Phased Array (pre-production version)
On the way home, I had to tear the antenna apart to rid myself of the PVC housing (another story). The shielding was simply a rectangle of aluminum foil laid on the coil and bar, with a 1/8" gap running longitudinally down the bar. An electrical connection to the ground plane of the little amp/control box and thence to the radio was made by a paper clip inserted under the foil, with the ground wire soldered to the paper clip. There was probably a piece of paper as insulation between the foil and the bar.
That was my first experience with a shielded loop antenna and there was a lot to love about it in an urban environment. Are we missing a bet by not shielding our external bars, even if they are a Booster Bar??????
John B.
John B.
Stillwater, Oklahoma, USA
Rcvrs: WiNRADiO 313e, Eton e1, NRD-535(kiwa-mods)
Antennas: 700' NE/SW mini-Bev, Wellbrook Phased Array (pre-production version)
John,
Ultralight radios, by nature, are plastic-enclosed
electronic devices subject to RF noise issues. Shielding the leads to
external ferrite bars wouldn't accomplish much, since the RF hash would still
strike the external loopstick (or booster bar), as well as the internal
circuitry (plastic usually doesn't shield anything).
DXpeditioners desiring great Ultralight reception either
need to have an RF-hash free room (like the famous Room 15) or get out of an
RF-hash area, and walk toward the beach.
During the last fruitless DXpedition to Westport
with Guy Atkins (May 4), our room in Westport was full of RF hash, TV
heterodynes, etc. We ended up driving to the beach at Grayland (4 AM),
only to find a steady stream of clam diggers proceeding to the beach in their
RF-hash producing beater cars, hi.
73, Gary
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John H. Bryant <bjohnorcas@...>
Gary,
I understand what you are saying - that with a small plastic radio and noise hitting the circuitry, shielding the loop stick is unlikely to improve rejection of noise from the local environment - and I think that you are likely correct. However, when I used that Ramsey unit that worked so well in Santiago, it was running my Eton E1, which is a plastic case crammed with circuitry, of course..... That being the case... this is one test that I've just gotta try.
I think that I'll go "whole hog" as usual and use RG-174 mini-coax for the run between the circuit board and the bar... connecting the shield of the coax to the ground plane of the board and to an aluminum foil shield on the bar. The other reason that I gotta try this one is that the material costs are near zero and its an easy + very reversible test. As you say, probably won't work, but I just gotta try.
ON ANOTHER ISSUE:
Gary, great catch on the influence of the whip antenna on the bar of the E100. The easiest fix in the world, of course, is to unscrew that little Phillips screw at the antenna base (back side of the radio) and just lift that puppy outta there. It leaves `a hole in the case and destroys FM and SW, but if the radio is dedicated to MW DXing, it seems a winner all around. Of course, to get back to factory specs, all you do is put the whip back in place and tighten the screw. I know that you are aware of all of this, Gary, but folks who haven't opened the back of the E100 may not be .
Is there something that I'm missing that is a problem with removing the whip... other than the loss of FM and SW??? Removing the whip gives me a perfect-sized hole to run those two pieces of mini-coax thru, of course.
John B.
At 03:38 AM 5/15/2008 -0400, you wrote:
toggle quoted message
Show quoted text
I understand what you are saying - that with a small plastic radio and noise hitting the circuitry, shielding the loop stick is unlikely to improve rejection of noise from the local environment - and I think that you are likely correct. However, when I used that Ramsey unit that worked so well in Santiago, it was running my Eton E1, which is a plastic case crammed with circuitry, of course..... That being the case... this is one test that I've just gotta try.
I think that I'll go "whole hog" as usual and use RG-174 mini-coax for the run between the circuit board and the bar... connecting the shield of the coax to the ground plane of the board and to an aluminum foil shield on the bar. The other reason that I gotta try this one is that the material costs are near zero and its an easy + very reversible test. As you say, probably won't work, but I just gotta try.
ON ANOTHER ISSUE:
Gary, great catch on the influence of the whip antenna on the bar of the E100. The easiest fix in the world, of course, is to unscrew that little Phillips screw at the antenna base (back side of the radio) and just lift that puppy outta there. It leaves `a hole in the case and destroys FM and SW, but if the radio is dedicated to MW DXing, it seems a winner all around. Of course, to get back to factory specs, all you do is put the whip back in place and tighten the screw. I know that you are aware of all of this, Gary, but folks who haven't opened the back of the E100 may not be .
Is there something that I'm missing that is a problem with removing the whip... other than the loss of FM and SW??? Removing the whip gives me a perfect-sized hole to run those two pieces of mini-coax thru, of course.
John B.
At 03:38 AM 5/15/2008 -0400, you wrote:
John,
Ultralight radios, by nature, are plastic-enclosed electronic devices subjehis is one that Ict to RF noise issues. Shielding the leads to external ferrite bars wouldn't accomplish much, since the RF hash would still strike the external loopstick (or booster bar), as well as the internal circuitry (plastic usually doesn't shield anything).
DXpeditioners desiring great Ultralight reception either need to have an RF-hash free room (like the famous Room 15) or get out of an RF-hash area, and walk toward the beach.
During the last fruitless DXpedition to Westport with Guy Atkins (May 4), our room in Westport was full of RF hash, TV heterodynes, etc. We ended up driving to the beach at Grayland (4 AM), only to find a steady stream of clam diggers proceeding to the beach in their RF-hash producing beater cars, hi.
73, Gary
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