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Hi Maynard Electrical modelisation is appreciated as a first approche of computing in the history, after what we procede with computers simulation last twenty years, in present time there is no

I would say that L remains constant (it's mostly determined by the physical construction, and the length), as long as it's not one of those funky delay line coaxes where the center is a spiral wrapped

If you need to calculate the characteristic impedance over a range of frequencies that overlaps the curved segment of the figure and, if you can assume that G=0 for all frequencies of interest, a

The only adjustment the antenna will affect is L2. Here's an alternative to measuring and averaging the impedance of several antennas: Put a short whip on your signal generator and radiate a signal

I've forgot to add AM is sadly out of the picture. There are no audio AM broadcasting left in France, we still receive BBC very well but not for long. So this is 100% an FM matter. Most use the AM amp

I assume that you will be aligning this antenna in the broadcast band. So be careful about strong signals from nearby stations. 73, Maynard W6PAP

That antenna looks like a 100k reactance capacitor at 1 MHz. (about 1.5 pF) The coax probably is something like 50 pF, so even without the radio in the mix, you're looking at a 1:30 voltage divider.

It will let you align the front-end more accurately. Check the radio alignment instructions. If there are no adjustments for the front-end, then it doesn't matter. Just connect the generator directly

Thanks for answering my post guys. Some additional information: here's a photograph of the whole antenna network. The antenna is about 43cm in length from the central stud of the base to the tip of

True! The three expressions in the figure represent the exact formula, a low frequency approximation, and a high frequency approximation. On the logarithmic scale of the figure, the low frequency

It's best to measure the antenna with the VNA as the antenna will be used. Mounted on the car, outside, doors closed, away from large metal structures, etc.

The impedance presented to the front-end can affect tuned-circuit tracking and Q in the RF amplifier, which can affect receiver sensitivity. It can affect receiver selectivity if the tuned circuits

If you need to do an alignment on an FM radio you need an RF signal generator not a VNA. In my case I used the TinySA to generate the IF frequency, probably 10.7 MHz in your case, and the RF

I remember a form of low loss cable that was popular in the 1980-90's the size of rg-8 (can't remember the brandname). It had a spiral plastic dielectric and I used a run of it for a UHF antenna.?

exactly. You want low epsilon of the dielectric and foam tube or a spiral of plastic meets the requirement nicely. To that extent it's like minimizing dielectric losses in microwave cables, but for

Maybe that explains an automobile antenna I found once in the past.? I was surprised that what looked like coax was actually a piece of plastic tubing, maybe 1/4" I.D., with a thin wire running

The big requirement for coax on voltage probes is low capacitance - you generally don't worry about impedance. That's because the antenna is largely capacitive (so it looks like a voltage in series

What I would do is use a NanoVNA to measure the impedance over 88-108 MHz right at the connector that plugs into the radio. Average the measurements for several cars. Then design a network that

The high-Z coaxial cable is more for the AM portion of the radio. On AM frequencies, especially the European version, the "stinger" antenna is nothing but a capacitive probe. Consequently, it

Hey everyone, True beginner in RF here for a classic alignment question. Sorry if this is inappropriate or the wrong group, I'm not sure where to ask such question. I suppose the NanoVNA would be a