The ARRL Compendium 7 has a very detailed article on how to make a 160M base loading coil for mobile operation. The very old ARRL Antenna Anthology also has an article by Barry Boothe, W9UCW (The Min
PVC and PBT and other such plumbing pipe plastics are very lossy for RF. Best to stick with some of the better plastics such as Lexan (polycarbonate), Plexiglass, etc. or even Teflon stock if you can
The traditional test for lossy plastic is to put a section of about six inches in the microwave for 20 seconds or so and see if it gets hot under full power. To protect the magnetron, also put a smal
From: Bill Turner <w7ti@ispwest.com> To: topband@contesting.com Subject: Re: Topband: 160 Meters Mobile Antenna Date sent: Wed, 07 May 2003 20:06:06 -0700 Send reply to: w7ti@ispwest.com <mailto:topb
I haven't actually tried heat shrink as a means of preventing rain from detuning, but I suspect it might not work as well as one might think. Since the heat shrink would be right next to the coil tur
The largest effect of dielectrics (insulation) on 160-meter mobile loading inductors is the insulation noticeably increases unwanted stray capacitance between turns and across the coil. Any increase
Bill brings up a good point. Heatshrink not only won't help much with detuning, if you do get water between the coil and the shrink it will stay a long time. Heatshrink will noticeably reduce Q in a
_________________________________________________________ Quite correct. My approach is that any material that passes the microwave oven test should be excellent at HF. -- Bill, W7TI
_________________________________________________________ Really? You're saying there is a material which passes the "microwave oven" test but is *not* suitable for HF coil forms? What would that mat
forms! Yes, that is what I am saying. It is HOW we use the material that is important! Pure Teflon will significantly de-Q a coil if placed in an area of strong electric fields because the dielectri