This article is a desk study of the CirroMazzoni Baby loop.
Above, the Baby loop is a small transmitting loop with a novel remotely controlled loop tuning capacitor and tuning mechanism, and gamma match. Continue reading CirroMazzoni Baby small transmitting loop – a desk study
A recent video explained how to use a Smith chart to solve a series single stub match using coax.
The diagram above from the video shows the topology of the series stub match. Continue reading Pitfalls of series stub matching with coax
A reader of A common scheme for narrow band match of an end fed high Z antenna commented:
…if the coil is tapped at 1/3, surely then the coil is a 1:3^2 or 1:9 transformer and the capacitor simply ‘tunes out’ the coil reactance, what is the input impedance when it has a 450+j0Ω load?
That is very easy to calculate in the existing Simsmith model.
Above, with load of 450+j0Ω, the input impedance at 50MHz is 8.78+j34.36Ω (VSWR(50)=8.4), nothing like 50+j0Ω. Continue reading A common scheme for narrow band match of an end fed high Z antenna – surely it is a 1:9 transformer?
This article discusses the kind of matching network in the following figure.
A common variant shows not capacitor… but for most loads, the capacitance is essential to its operation, even if it is incidental to the inductor or as often the case, supplied by the mounting arrangement of a vertical radiator tube to the mast. Continue reading A common scheme for narrow band match of an end fed high Z antenna
A correspondent asked about the difference between two small untune loops mentioned in two of my articles, this article explains.
Firstly lets set the context, a small loop means less than λ/10 perimeter, and untuned is to mean that the loop is loaded directly, in this case by a receiver which we will assume has an input impedance of 50+j0Ω.
Let’s look at the two cases. The key difference is in the connection at the gap:
- the first has a short circuit coaxial stub of half the perimeter between the inner conductor at the right side of the gap and the outer surface of the outer conductor at the right side of the gap; and
- The second directly connects the inner conductor at the right side of the gap and the outer surface of the outer conductor at the right side of the gap.
Above is a diagram of the loop. Continue reading Differences in two similar simple untuned small loop configurations
A chap recently posted some advice on construction of a dual ratio transformer for EFFHW antennas, advice with an informative pic, but without measurement evidence that it works well.
Pictured is a dual UnUn. I made this for experimenting. It’s both a 49 and 64 to 1 UnUn.
The 49 to 1 tap uses the SS eye bolt for the feed through electrical connection and the SS machine screw on the top is the 64 to 1 connection. If I want to use the 49 to 1 ratio, there’s a jumper on the eye bolt that connects to the top machine screw where the antenna wire is attached. The jumper shorts out the last two turns of the UnUn. Disconnect the jumper from the top connection and now you have a 64 to 1 ratio.
Continue reading Shorting winding sections of a ferrite cored EFHW transformer
N6THN’s novel balun presented measurement of the Insertion VSWR of the subject balun, and N6THN’s novel balun – an explanation gave explanation that included mention of flux leakage as a contributor to the quite high inductance per unit length of the transmission line formed by the two windings.
A correspondent suggested that with a ferrite core, flux leakage is insignificant. This article calculates the coupled coils scenario.
The balun as described
Above is the ‘schematic’ of the balun. Note the entire path from rig to dipole. Continue reading N6THN’s novel balun – flux leakage
N6THN’s novel balun presented measurement of the Insertion VSWR of the subject balun, this article presents an explanation of why it is so poor.
The balun as described
Above is the ‘schematic’ of the balun. Note the entire path from rig to dipole. Continue reading N6THN’s novel balun – an explanation
One sees lots of articles and videos on how to make a current balun suited to a low VSWR antenna. This one was recommended in an online discussion on QRZ.com. N6THN might not have invented this balun, but he made a video of it.
In this case, it is described in the referenced video as part of a half wave dipole antenna where you might expect the minimum feed point VSWR to be less than 2.
Apologies for the images, some are taken from the video and they are not good… but bear with me.
The balun as described
Above is the ‘schematic’ of the balun.Note the entire path from rig to dipole. Continue reading N6THN’s novel balun
Since the nanoVNA got real traction a year or so back, lots of online experts have sprouted new found secrets of VNA use… and the classic is “phase is paramount”. A recent quote:
Take a look at the antenna with a VNA and sweep with the Phase function.
Let’s do that! Continue reading Phase nonsense