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 <fda...@nfld.net> 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
