Anyone have experience doing a GABLE mount instead of eave mount for the MA-550? This would be on my workshop / ham shack, so noise is not my concern. Any problems getting a building permit for the g
Several reference on lightning control recommend using some type of flexible grounding contacts to ensure continuity between the telescoping sections of a tubular tower. I'm considering using stainle
There is only about a 2% difference between the two sizes of mast you listed, with the 2" x 0.25" being the stronger. Assuming 87,000 psi yield strength, they would handle a max of about 3900 ft-lbs
Try http://www.k7mem.150m.com/Electronic_Notebook/inductors/wire_strip.html For a strip not over a ground plane, just set the height/thickness to some large distance (like 36 inches). Select the Indu
I received several inquiries off-list, so I'll summarize some of the answers here, instead of replying individually: No, you can't just multiply the inductance of one foot of wire by ten to find the
Jim, A good approximation is to consider a right angle bend as a 1/4 turn coil with the same radius of the bend. But the typical coil inductance calculators make too many simplifying assumptions to h
A free-space inductor is first cousin to an isotropic antenna and a free-space dipole -- useful theoretical models, but not much use in the ham shack. The "characteristic impedance" of a stripline tr
That's why I posted some actual measurements early on in this thread. I couldn't find a model for a inductance of "straight wire over lossy earth". The absolute accuracy of my quick tests probably ar
One of the best technical presentations on NVIS propagation and antennas is at: http://groups.yahoo.com/group/wl2kemcomm Look in the files section for NVIS_Presentation_R1-4-8a.pdf by WA5BEN. You nee
The gain at a 90 degree take off angle isn't a very reliable indicator of NVIS performance! 40-75 degrees is more useful. Having done very controlled testing of different antennas and different heigh
Rather than rely on gut feelings and others' anecdotal experience, calculate the mast load. There is a fairly simple spreadsheet in the companion files section for the Physical Design of Yagi's book
David, Use MicroDEM to extract the Digital Elevation Model for your area. There is an "HFTA-changes.pdf" document that updates how to get 1 arc-second data, although you may have to settle for 3 arc-
We used a Butternut HF6V on a large metal roofed county building successfully. The base loading coil had to be stretched out really long (per the manual's hints regarding a metal roof) and we elimina
I use Google Earth (GE) as a visual aid for many RF programs such as Radio Mobile Deluxe and HFTA. If you have high res imagery for your area, you can add Placemarks visually. Otherwise you can enter
Your model of the 8-element LPDA was apparently done from a formula and wasn't optimized at all. Although I do agree that 6 & 8 element logs are sub-optimum. But an optimized design for a 9 element 1
Jim, As it said -- it's free space gain. It's the same antenna I sent you the direct reply about earlier. This antenna design is still being tweaked and is an example of optimizing it for the higher
Since the Tennadynes that I've seen have a 50 ohm nominal feed point Z, not 200 ohm, the issue is a little different. Having a balun at the front of the boom isn't a problem if it's constructed corre