Re: Topband: VO1HP FCP Inv L and Kitchen Oven
When I first installed my 3/8 over FCP here, it was PRE isolation transformer. Given the unfortunate 424' length of elevated Wireman #554 "450" ohm window line back to the tractor shack for conversion to 50 ohm coax into shack, it was very heavily coupled, as explicit modeling would later reveal. That degree of common mode current was exceptionally lossy. For all practical purposes, well over half my power was going to a 160 meter endfed 3/4 wave wire 8 feet above ground more or less grounded at the far end. If you have that much loss pre-conversion, you have a certain lowered field strength from the antenna. When you fix the loss the field strength is going to jump up, just the same as if you raised power. Anything that was close to interference, but not yet, may now be interfered with. As I found out when the massive common mode loss in my system was solved. I now blew away both my and my neighbor's AT&T Uverse gateway boxes with anything over 400 watts out from the amp. Various local experiments proved that it was just the new higher field strength from the antenna and nothing else. Previously 1.5 kW to the feedline did not even cause pixelation that we were aware of, and afterwards over 400 watts would cause the gateway to shut down. As AT&T would verify, the remainder of the problem was entirely an issue with AT&T that was well known, and they had fixes for. Frank, if I remember correctly, you previously had short and irregular 160m radials in a relatively thin poor soil layer over bedrock. That might as well have been an attenuator in your feedline, which you have now removed. And, unlike my house, your antenna is very close to the house. I hope you have as good luck on other issues that may pop up as with your stove. I am not sure I have anything useful to add about the insulators. The stuff that is used for electric fence support in the US obviously has the voltage rating. The complaints about them I have heard are entirely mechanical in nature. 73, and keep working 'em! Guy K2AV On Thu, Aug 30, 2012 at 9:00 AM, VO1HP wrote: > The Inv L FCP continues to perform. > > After a nice long hot summer here which is unusal here I was on last night > around 0230 and worked K6ND, WJ3A, G4EIM. LY2OU, UY0ZG. > > While operating I started hearing at regular intervals somewhere of in the > distance "beep beep" pause "beep beep" ...upon investigation I found the > kitchen oven had turned itself on and was awaiting further instructions > from the keypad. I was running about 600w and the flat-top of the L runs > more or less over the kitchen area. > > I reread the RFI article re kitchen ovens in May 2012 QST and my first > reaction was to try and place by-pass caps as described in the artcile. > Howevere I thought I would try the simplest thing first. This morning I > was able to place two snap on chokes of #43 material over the 240V wire > inside the access panel at the back of the stove. The 1/2inch hole in the > cores is not big enough to snap over the cable as it enters the stove. So > I removed the plug from the wall and removed the access panel of the stove. > There was enough room in the area to accommodate two snap on chokes -- i > ran two wires through one core and one through another. There was just > enough space to accomodate the cores. > > Upon testing at 600-700W the oven appears to be unaffected now. hopefully > it remains thus. > > The old inv L and on the ground non-uniform and erratic radial system did > not cause this issue so do I conclude that the effective radiated field > from the FCP Inv l is that much stronger? Yesterday I also did some more > work on the FCP ...when I initially built it I used 1/2inch pressure > treated wooden spacers and tie wraps. Yesterday I replaced the those > spacers with 1/2inch "PEX" (HDPE material) water pipe painted black. > These spacers appeared to cause a slight shift in the SWR curve for the > L...raising somewhat away from 1800khz. I am wondering about this material > and whether its the right stuff to use? > > By the way the oven model Jenn-Air JES8850ACB ( same number for Maytag) > > 73 Frank VO1HP > __**_ > UR RST IS ... ... ..9 QSB QSB - hw? BK > ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: VO1HP FCP Inv L and Kitchen Oven
> The old inv L and on the ground non-uniform and erratic radial system > did not cause this issue so do I conclude that the effective radiated > field from the FCP Inv l is that much stronger? Hi Frank, When we confine a counterpoise to a small area, especially if we cancel the magnetic induction field, voltage and resulting electric induction field levels go way up. There just isn't any free lunch, no matter what the sign on the door says. When convenient, we often attribute increased problems to better performance without regard to 20 other bad things that could be at work. My wife does that with her occasional crispy blackened casseroles. > Yesterday I also did > some more work on the FCP ...when I initially built it I used 1/2inch > pressure treated wooden spacers and tie wraps. Yesterday I replaced the > those spacers with 1/2inch "PEX" (HDPE material) water pipe painted > black. These spacers appeared to cause a slight shift in the SWR curve > for the L...raising somewhat away from 1800khz. I am wondering about > this material and whether its the right stuff to use? Like the increased RFI, no one really knows what causes what without some reasonable testing or evaluation. What we do know, without a doubt, is the less spread out the counterpoise (or antenna) the more concentrated fields become. I would expect any change in spacing or dielectric to have an exaggerated effect on stub tuning (the folded counterpoise is a stub with common mode current) compared to cases where there isn't such an intense electric field. It all makes sense for multiple reasons. The question is, how much of what. If we took a big antenna and made it into a 20 foot long antenna, no matter how we did it, we would expect more sensitive tuning and higher voltages and/or currents. We would expect increased sensitivity to close surroundings. Why would we expect anything different in this case? The very fact it needs an isolation transformer with high voltage insulation tells us we have very large localized electric fields. Logically, we should expect all that comes with those voltages. 73 Tom ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Topband: VO1HP FCP Inv L and Kitchen Oven
The Inv L FCP continues to perform. After a nice long hot summer here which is unusal here I was on last night around 0230 and worked K6ND, WJ3A, G4EIM. LY2OU, UY0ZG. While operating I started hearing at regular intervals somewhere of in the distance "beep beep" pause "beep beep" ...upon investigation I found the kitchen oven had turned itself on and was awaiting further instructions from the keypad. I was running about 600w and the flat-top of the L runs more or less over the kitchen area. I reread the RFI article re kitchen ovens in May 2012 QST and my first reaction was to try and place by-pass caps as described in the artcile. Howevere I thought I would try the simplest thing first. This morning I was able to place two snap on chokes of #43 material over the 240V wire inside the access panel at the back of the stove. The 1/2inch hole in the cores is not big enough to snap over the cable as it enters the stove. So I removed the plug from the wall and removed the access panel of the stove. There was enough room in the area to accommodate two snap on chokes -- i ran two wires through one core and one through another. There was just enough space to accomodate the cores. Upon testing at 600-700W the oven appears to be unaffected now. hopefully it remains thus. The old inv L and on the ground non-uniform and erratic radial system did not cause this issue so do I conclude that the effective radiated field from the FCP Inv l is that much stronger? Yesterday I also did some more work on the FCP ...when I initially built it I used 1/2inch pressure treated wooden spacers and tie wraps. Yesterday I replaced the those spacers with 1/2inch "PEX" (HDPE material) water pipe painted black. These spacers appeared to cause a slight shift in the SWR curve for the L...raising somewhat away from 1800khz. I am wondering about this material and whether its the right stuff to use? By the way the oven model Jenn-Air JES8850ACB ( same number for Maytag) 73 Frank VO1HP ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
