Incidentally, the 160m "T" I discussed below was deliberately resonated to 1.4 MHz -- not to 1.8 MHz. At 1.4 MHz, Z was 85+j0. At 1.8 MHz, Z was 50+j200. A low-pass L network then transformed that va
Sometimes VSWR does change significantly along a line -- and not always for reasons of loss nor common-mode RF current on the outside of a coaxial line. Consider this example: At the operating frequ
Not needed. Nor is any math involved in reaching the correct answer. So, which is the correct answer? If math or a 600-ohm VSWR meter is needed to answer the question, then the concept isn't underst
Yes, if the characteristic Z of the line is 50 ohms. Not true for lines of other characteristic Z terminated into that antenna. True when a non-reactive load value equals the characteristic Z value
Jim, As an alternative, I open/close the line outside the house with a pair of 75A/10KV vacuum relays. The relays are controlled from inside the shack. Although there's no guarantee that lightning c
You can with some "Brand X" Asian imports... I recently made a set of precision OSL loads for use with a vector network analyzer. The 50-ohm load was made using a 0.1% SMD resistor precisely fitted
Probably a more relevant test is not to string a bunch of connectors together in series. Rather, take the same number of connectors and place them at random points on say, 100 feet of low-loss line.
That ties in with why we have a 50-ohm coaxial line standard for most 2-way communications purposes and it probably dates back to the Quackenbush era. 50-ohms represents the mean value between 30-oh
That's about ten decades of research reading to catch up on -- starting with short Marconi base-fed vertical radiators, then moving on to the shortened, but optimized "T" used at 1BCG for the transa
Gary, K9AY, presents an interesting hypothesis that combines theory and some evolutionary practical developments: http://www.highfrequencyelectronics.com/Archives/Jun07/HFE0607_Editorial.pdf Paul, W
This may be of interest for folks thinking about purchasing a NEC/4 license for use with 4Nec2. The one-time license fee is now $300 though Lawrence Livermore National Labs. This is a lot less than i
The currently available radial plates are mechanically flawed. Now, if someone designed a radial plate that allows use of 2-hole lugs, perhaps that too would meet today's lax novelty test. The plate
Dave, Good point, especially if single-point connections are used. I brought up the example of using 2-hole lugs as being a better plate alternative, but if I were to create a radial field tomorrow,
That attribute is not a strength - but a weakness. Any accidental counter-clockwise lateral force applied to a single-hole lug causes it to loosen from its mounting bolt. No matter how good the crim
Gary, you can vary the impedance at the input end of the line, but not the SWR. The SWR on the 450-ohm section will remain nearly constant over your 150 ft run, even with length trimming. In EZNEC,
Another thought... Although you cannot vary the 450-ohm SWR, you can vary the line's 50-ohm SWR by changing line length to possibly reach close to 50+j0 at the line input, and perhaps without the nee
Gary, I imported the same model into 4Nec2 and scaled the frequency to 7.0 MHz. Feedpoint Z is 4.6-j17.7. Your Z values look quite extreme (also see notes below about feed Z for the 8JK). Using Zo=45
Dave, The 8JK EZNEC input file is for 0.466 wavelength elements and 1/4-wave spacing. That is going to produce the results shown. Going back to Gary's first post, he does indicate 44 ft elements at 7
I agree with Dave's loss numbers for 44 ft element length. However, before giving up and using a shortened 44 ft. dipole, you may want to see if there's a way get the elements lengthened close to a
Perhaps one day an HFTA "wizard" can be developed where the program simply inputs geographical coordinates from the user, searches the geography based on the USGS database, compiles the radial inform