Today, with DEMs available to generate the "tiles" for a full 3d model would be straightforward. That was one of the challenges when Breakall did his work. There are commercial (and non-commercial)
"Today, with DEMs available to generate the "tiles" for a full 3d model would be straightforward. That was one of the challenges when Breakall did his work." Jim, the data I would need are measured
Can you post an example? (I can run an example on nec4 and see what it looks like. Yes, Id expect dielectric to have the most effect where the E-field is biggest) I've been using EZNEC Pro/2 to try
No, I think it would be independent of that. But I have to think a bit to come up with the analytical basis. Given that the field strength of that traveling wave follows current, would that mean that
I'd definitely terminate the shield at one end. You don't want it floating. And terminating at both ends might be a way to get an inadvertent loop. Jim will probably weigh in - shielded twisted pa
I doubt you need much power here, what about a resistor with a suitable value for whatever voltage so that it dissipates, say, 1/4W. If you're feeding 12VAC, 560 ohms is pretty close to a quarter
I've got a DX Engineering AVA-3 preamp here. It's designed to work with a short monopole and supersedes the other preamps that they used to sell (e.g. Clifton labs, etc.) for low frequencies. The in
I'd suggest looking at crane rental companies in the area - they usually will rent the crane with an operator. A big use in SoCal is moving HVAC stuff on and off the roof of a building. Another po
True, but I think that's also, to a certain extent, an artifact of the simple phasing, switch network (BIP, BOP, Top, Bottom): which sort of gives you 4 different patterns in the elevation axis. If
There are plenty of examples of concrete bases that are formed and backfilled. Think of it this way - if you built a huge concrete base that was sitting on the surface, that was sufficiently large t
This is where modeling can help you tell if it's a big deal or a little deal. The DX engineering box is a L network for phase and you have 1/4 wave transmission lines to the elements - so that's e
They are "exactly" like Yagi antennas... They're both phased arrays, just one has all driven elements, and the other has elements that are passively coupled to a single driven element. yeah, a few
putting numbers on it.. consider a 3dB gain: you divide your power into two signals with the same power sum up to the 3dB. If the phasing is off by say, 20 degrees, that means the current is down t
These QFHs are great for LEO satellites in general, because they can be designed to have more gain at the horizon and less and less as you get close to zenith, so you have about the same link prope
UL listed coax protectors are none-to-common either (well, for cable TV, they're pretty common). It depends on why Martin needs this. Typically the requirement (e.g. from the county building dept) i
This is all good stuff, BUT, if he's looking for regulatory compliance, he'd have to get his relay box signed off by someone (either a test lab, or in some jurisdictions, a Professional Engineer). Th
Just checked the Polyphaser page - none of their antenna products are listed. They *could* make one for you and get it certified. (as someone in the thread noted, this would be expensive). I've not
Yes, of course. And that would probably mean your relay box wouldn't need to be listed or stamped or whatever. Depending on what the AHJ is worried about. Realistically exceedingly few hams build a
If it's a low power or receive only application that might be ok. Also, one should assume a worst case mismatch, so double the voltage. And that's a kW CW (or constant envelope - FSK RTTY, for insta
i found a copy of ANSI/UL-452 Can't be adjustable gap. DC resistance between antenna terminal(s) and ground has to be >=75k measured at 6V Current carrying components shall be corrosion resistant mat