Based on your description, I just ran your "T" in 4Nec2 with the NEC/4.2 engine. Your T should have a base Z near 21+j110 at 1825 kHz and will be resonant at 1620 kHz which will help to push the max
Good point, Jim. Or, go the extra distance and add L too and make it a complete low-pass L as was mentioned. Then, the ATU on the shack table can breath a sigh of relief when needed with reasonable
of 2 to 1. Good job in getting the X value down -- even if it wasn't planned that way! What device did you use to measure base Z? Paul, W9AC _______________________________________________ UR RST IS
To Joe's point, I don't think we want the feedline to become a radial. It also seems that placement of the line should occur under the radial field and not on top of it, but I have not seen any stud
Dave, What complex Z value do you get after running NEC at 1835 kHz? Can you attach the .NEC input file? Phil, Does your MFJ analyzer give you complex Z results in a R+jX format, rather than just Z m
I believe Rich Fry pointed this out a couple months ago. The effect can be seen when using the surface wave modeling tool in 4Nec2. At first, it surprised me since nearly all base-fed, vertical radi
As Richard points out, the surface wave plot in 4Nec2 is a key analytical tool when focusing in on what's happening at very low elevation angles. Otherwise, when only observing the elevation profile
In the early 1930s, both WSM and WLW had spent a considerable amount of time optimizing their Blaw-Knox tower heights by monitoring skywave at a distance of a couple hundred miles. By trial and error
I ran a 4Nec2 (with NEC/4.2 engine) surface wave plot for a 160m 1/4-wave vertical radiator over a field of 60 radials with average ground conductivity. Input power = 1.5KW. 4Nec2 was first set to a
And that's the piece that probably not been underscored in this discussion. Some have probably concluded that the surface wave plot in NEC only includes ground wave conduction. An interesting exerci
Adding to Joe's suggestion, NM3E and Chuck Martin RF Supply are good sources for used Bird and Coaxial Dynamics product. I've been pleased with both suppliers. http://www.nm3e.com/ http://www.chuckma
It's generally two inductors wound on a single core for common-mode choking. The result is that total common-mode inductance is 2*L while differential-mode inductance cancels and equals zero. The 22
Tom, Run it in any SPICE variant as proof that in CM, total apparent inductance is 2*L. For example, two 0.1H inductors: subckt CommModeChoke InA InB OutA OutB L1 InA OutA .1H L2 InB OutB .1H K1 L1
What I think is missing from the discussion is that any benefit from using a CM choke between shack hardware can be undermined by necessary parallel paths. Consider a CM choke placed on the RF cable
connectors." I agree for the most part, but in the case of using "UG" reducers with a PL-259, I believe there's a better method over the "proper" procedure supplied by Amphenol and the ARRL Handbook
Makes sense to me, Jim except in the context of any RF current that could exist on the outside of the coaxial interconnect cable (e.g., between rig and amp) which when using the audio demonstration
Right. I think Joe, W4TV, was one of the first to identify that problem back around 2008. Many of us quickly jumpered the handful of RFCs used on shield leads of the RS232 I/O Board. Until revised b
Steve, What was the length of the horizontal "T" section? Paul, W9AC _______________________________________________ UR RST IS ... ... ..9 QSB QSB - hw? BK
On the surface this seems to agree with what I find. There are dozens of ways to have about the same results. I wonder what Grant has in the book? I recently purchased a copy from the ARRL and it's w
I have a flat-top T transmit antenna as well. I modeled it with EZNEC, found its feed resistance/reactance, fed these into a L-match program. I'm another fan of the TLW program. After modeling a "T"