I'm not sure that percentage of expansion is the relevant consideration here. I would think that the gap between the cylinders (i.e., portion of the diameter) is the important part, and since the ex
Two observations: 1. 1500 watts would be about 335 volts RMS into 75 ohms, but peak voltage is about 475 volts. Presumably the F-connector specs have some margin built it, but still ... 2. I don't
His 16 element 20/15/10 tribander looks like an almost complete copy of my Optibeam OB16-3, except that SP6GXP claims about 2 db more gain on each band and uses lighter weight materials. Dave AB7E
I own an Optibeam OB16-3 tribander as well as an Optibeam OB2-40 shorty 40. I modeled both antennas in EZNEC+ using the published dimensions, as well calculating the impedance of the short square tu
If that's the case, they were clumsy on their website because it clearly states dBd. Dave AB7E 73... Randy, W8FN On 10/21/2021 10:38 AM, john@kk9a.com wrote: I have modeled some OptiBeam antennas a
That works, but if the problem is approximately short or an open, there is an easier way to achieve a kind of manual TDR: 1. Take readings with the FA-VA5 at three different frequencies chosen to re
Dave, Send me the FA-VA5 complex impedance measurements for these three frequencies taken from each end of the line (six readings): 5 MHz, 10 Mhz, 15 MHz If I can't determine where the faults are wit
If you want to make a 3 or 2 element array be bidirectional, tune the parasitic elements to the driven frequency. Don't make it shorter or longer. You can run that through EZNEC if you don't believ
I'd have to run it through EZNEC to see what the best spacing is, but the "best" spacing may vary depending upon things like bandwidth versus gain. I'll assume that you want maximum gain, but I won'
I just got the chance to play with this in EZNEC+. A 2-element version for 40m at 90 feet up in the air seemed to optimize at 67.6 foot element lengths spaced 20 feet apart. The main lobe was 10.65
Yup. It's the vertical equivalent of a hairpin match. 73, Dave AB7E If he removes the loading inductance and trims the wire for -j25 (and the R stays around 30) then a shunt inductor of 5.3 uH wil
That sounds like an urban legend. A Google search for "Congo fatal static charge" comes up with not a single reference. The physics of the idea doesn't make sense to me either. 73, Dave AB7E Supp
That's a different situation, of course, but certainly very true. I bet lots of people have multiple grounds connected to their homes, and most don't realize they do or the potential effect of it.
Thankfully for any of us that actually consider ham radio to be a technical hobby instead of just a wireless chat room, not everyone here shares your perspective. Dave AB7E On 1/21/2022 11:54 AM, S
Recent threads here have pointed out the adverse effect of poor ground conductivity on vertical polarization versus horizontal polarization, but as best I understand things there is some advantage to
I think I'll go with K2AV's take on the N4KG reverse feed idea: https://www.mail-archive.com/topband@contesting.com/msg21291.html 73, Dave AB7E Wayne W3EA Sent from Mail<https://go.microsoft.com/fw
I'm really surprised to keep seeing that comment these days, when everyone should by now know that antennas are more or less reciprocal for transmit and receive. The average ham on the other end is
I'm pretty certain the answer to that question depends upon more factors than you could possibly know or model, and if you can't model it anything else is a guess. 73, Dave AB7E Im not worried abou
I don't know why you would give enough credence to a poll like this to bother with it, but considering that a very high percentage of hams (at least in the U.S.) primarily use VHF/UHF handitalkies, t
I did this analysis for CW signals several years ago, but it should still be valid. I called it the "minimal discernible difference". It doesn't show how many QSOs an extra dB or two will give you,