Fun with cavity filters

Рет қаралды 14,995

3 жыл бұрын

Some experiments with a 430 MHz cavity filter made in a biscuit tin. More background info here:
www.repeater-builder.com/anten...
vk6uu.id.au/warg2mduplexer.html
www.radioexperimenter.us/rm-1...
pa0nhc.nl/homemadeDuplexfilte...
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Пікірлер: 30

@bendunselman Ай бұрын

Your infant will love this when grown up.

@MoTown44240 3 жыл бұрын

While in my early learning days about VHF, 1986, I built a poor man's cavity filter for 2m. Like Peter says, it works but not very efficiently. Great video Peter. 72 de KB8AMZ

@MakeDoAndMend1 3 ай бұрын

I've just made a Cavity Filter from an old gas bottle. Works a treat. Cheers from old George ps cost to make about a UK pound.

@markhonea2461 Жыл бұрын

OMG I am so going to get involved with that, this, the most fascinating information I have found in the sea of KZfaq.🤓👍

@artemisdefcon 3 жыл бұрын

Nice jobs dude.

@markhonea2461 Жыл бұрын

I will now watch this again 👍

@dereklassen4841 8 ай бұрын

A few words... The frequency is determined by the length of the inner (not mass, it can be (usually is) hollow). It should be 1/4 wavelengthll long. The Q is set by the ID of the outer (bigger is better), and the conductivity of the inner surfaces (mostly). You want the Impedance to be 50 Ohms - set by the ratio of OD / ID. The end where the connector(s) are (is) must be shorted. The other end needs to be closed only to preclude corrosion. It could be a removable plastic cap. Your milage may vary. 73 de Derek, KN6TD.

@markg6jvy135 3 жыл бұрын

Very creative thinking Peter 👏👏👏

@terrybondy1948 3 жыл бұрын

Wow! Suffered 5 adverts to get through this, most of them mandatory.

@mabselves 3 жыл бұрын

That's not great. I didn't have to suffer one.

@bigpimp347 3 жыл бұрын

then install an ad blocker like most people with sense do.

@terrybondy5458 3 жыл бұрын

@@bigpimp347 can you give me a link describing how that is done for the KZfaq app on a phone or iPad?

@bigpimp347 3 жыл бұрын

@@terrybondy5458 aaaaah, yes, don't use an app, get a PC.

@scimitar123 3 жыл бұрын

Free tube on pc or newpipe on android

@coblecam 3 жыл бұрын

Are there general rules about the diameter of the cavity used? GREAT video! 73!

@vk3ye 3 жыл бұрын

I believe that it gets more efficient/sharper as you increase the diameter, but there's a point where the diameter is excessive for proper operation.

@chronobot2001 Жыл бұрын

Would adding additional mass at the end of the internal tube change the filter frequency?

@chronobot2001 Жыл бұрын

What if the internal tube was a coil? Longer tube coiled to fit into a smaller space.

@markhonea2461 Жыл бұрын

Would large bore copper pipe work?

@MakeDoAndMend1 3 ай бұрын

Many thanks for the inspiration to make filters. I used discarded steel gas bottles. Work a treat. I have posted on here. George 🇬🇧

@ssubaihi 3 жыл бұрын

How it's work , Why Loops ? Still a lot to tell ...

@vk3ye 3 жыл бұрын

Loops are needed to couple the signal to the main resonating element. See links in the description for more background.

@Max-kn9yi 2 жыл бұрын

Does it matter what end you attach a filter to the antenna?

@vk3ye 2 жыл бұрын

Sorry I don't understand your question.

@thomasmaughan4798 Жыл бұрын

As shown, it does not matter; the device is symmetrical and bi-directional. Either port can be the input with the other as output.

@SirsenduGhosh1989 3 жыл бұрын

Is it possible to build cavity filter for HF? Just curious 73 de VU3WTJ

@antennafarmer7380 3 жыл бұрын

Possible yes, practical no, especially since other types of filter are more effective at lower frequencies.

@SirsenduGhosh1989 3 жыл бұрын

@Paweł Hadam thank you for info

@thomasmaughan4798 Жыл бұрын

You can build cavity resonators for pretty much any frequency but they become very large below VHF.

@gillywild 3 жыл бұрын

I wonder if that was what someone was doing in the cuban embassy? The cricket noises and brain damage always sounded like microwaves to me. I should think a Theremin resonator for microwave frequencies would be quite compact.