I agree 100% on all counts, and even if this is "old hat" it bears repeating every once and a while. I did the same kind of modeling exercise (no measurements) when someone on eHam was asking if thi
I think "velocity factor" coaxial antennas are a perfect example of the dangers of viewing antennas from the feedpoint only! A field strength measurement, a quick spin of the antenna while capturing
Matching networks for my 60 foot vertical wire should work on a 65 foot vertical with some adjustment: http://n3ox.net/projects/sixtyvert/matching_networks_18m.pdf That might give you a starting poi
For what it's worth, for matching antennas that are less than 50 ohms, I favor shortening the vertical a tad to show some capacitive reactance and using a *shunt* inductor to step the feed impedance
Yeah, quite possible. I do like motor-drive tuning. But you don't *have* to go out to the 50+jWhatever point to do that... though you do tend to need a pretty huge capacitance if you want to tune an
You also have to consider the routing of cables "inside" the room. Depending on where you put your wiring inside, even if it doesn't "break the plane" of the mesh, it will pick up more or less signa
Much more efficient than a design with total trap losses of 0.24dB? There's this assumption that paralleling has zero extra loss and that traps have big losses... but if you are talking about 0.025d
I was looking for small diameter black dacron for guying my Spiderbeam pole vertical and happened upon www.kitebuilder.com. In particular, check out this stuff: http://www.kitebuilder.com/catalog/pro
For gain vs. height stuff, I'd rely more on the models, honestly. The models really tell you what you need to know. Why? Because the differences in ground clutter, soil conditions, noise sources, av
The exception to this is if you have some concrete, testable prediction about what the antennas under comparison or test *SHOULD* do. This is ideally what we might want to shoot for with modeling. M
" I wonder WHY NOT worry about trying to cover the bands with good antennas?" Because it's very easy to make ham radio *frustrating* instead of *fun* if you try to do too many bands in a small space
I'm fond of VK1OD's *calculator* http://vk1od.net/tl/tllc.php It's good for calculating mismatch losses too. VK1OD is pretty rigorous about his work. Dan _____________________________________________
Why would you have 3dB loss in your matching scheme?! Bolt a 750 watt electrical heater to a decent-Q tank coil sometime and see how long you want to hold it. Then make a parallel tank circuit with
A coax just a little bit shorter than a quarter wave shows a VERY quickly changing inductive reactance ... so you can change the stub length +/- a few centimeters and find the exact value of reactan
It does work, in a way. The radiating elements are the *outside* of the coax shield. The *inside* of the coax shield and the center conductor form a coaxial stub that's in series with the outside. I
Yep, mismatched line loss. Coax can be surprisingly awful when badly misterminated. I brought home a fresh roll of RG-6 from Home Depot and stuck a connector and a 1.5:1 unun on it just for kicks. S
protection against such a condition. Do any of you have any good Some of the ceramic and metal insulating flexible shaft couplings have the shaft bushings just press fit into the metal spiders and k
"What if i use lower 40-50' portion of their 60-footer? Is it gonna say straight?" Guyed? Unguyed? You won't be able to put much balun up very high, in any case, honestly. You might consider running
"It doesn't seem right that these could stand 1000 lbs.+ of pull." They don't. They withstand 1000lbs+ of push ;-) Look for compression guy insulators. Ceramic is much weaker under tension than under
Huh, that should get along well with my antenna tuner: http://www.n3ox.net/projects/servo and the position sensor for my homemade rotator http://photo.danzimmerman.com/webimage/rotator_lg.jpg I was a