A ham seeking to optimise his station based on some measurements with a VNA and some modelling of a matching network posted the results of a test in the process.
The radio is an Icom IC-7300. I bypassed the built in tuner, transmitted a tone into my external tuner, adjusted it for SWR=1. I then disconnected the tuner from the radio, and measured the impedance looking into the tuner with a VNA. Surprisingly, (to me anyway) the result was a pretty good 53-j3 Ohms at 14 MHz.
What should we / have expected? It is an interesting case to study. Continue reading Some pretty woolly thinking on measuring Thevenin equivalent source impedance of a ham transmitter
After a lot of grief with Excel trying to open and fix some 10 year old spreadsheets… finally…
I was recently asked about FT-8 on the Colling 30-L1 linear amplifier considering my article Collins 30L-1 and AM.
The first thing to note is the Colling 30-L1 manual cautions against AM and FSK:
That said, what are the reasons for such a prohibition? Continue reading Collins 30-L1 on FT-8
RF Power Meter 2 is a logging RF power meter based on AD8307 and ESP8266.
The project was used as the basis for a new project, and during that development work some improvements were made and ported back to RFPM2. Continue reading RF Power Meter 2 (RFPM2) – update 04/21
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
The Baofeng UV-5R is a U/V portable FM transceiver. The battery supplied is labelled BL-5 and rated in this case at 1800mAh.
Supplied charger adapter
Above is the supplied USB adapter to supply power to the CH-5 charger cradle. The adapter is rated at 9V and indeed, it delivers 9.01V no load. Continue reading Baofeng UV-5R battery and charging experience
In recent articles, I flagged that on some of John’s VNWA plots he showed flawed impedance calculations using VNWA’s t2s inbuilt function.
The function t2s is documented in the VNWA help.
t2s is a VNWA built in function intended to solve the so-called s21 series through fixture for impedance measurement of two terminal Zx connected between Port 1 and Port 2.
None of John’s test fixtures were equivalent to the circuit above required for valid t2s transformation. Continue reading Comment on KN5L on balun CMRR – series through impedance fixture
The article Comment on KN5L on balun CMRR dealt with model and measurement of John’s coaxial choke in fixture, dealt with first because it is a simpler model. This article builds on that and models the balun wound with a pair of wires.
Above is the subject balun in fixture.
John’s schematic shows the balun as coupled coils, but that does not capture the transmission line transformation that occurs in the actual device. Again the test fixture is used without explanation. Continue reading Comment on KN5L on balun CMRR – two wire line example