topic Re: Antenna Design help needed, please in Tech Help - Software/Hardware etc

Antenna Design help needed, please

shutter — Mon, 17 Jun 2024 14:04:19 GMT

I am experimenting with different types of antenna on a project, and would like to make a smaller version of this type of antenna.

I have worked out the actual lengths of the elements for the frequency I want to use it at, ( receive and transmit, at very very low power ) .

The element lengths should be around 40 mm each. (40mm is equiv to about 1.57 inches.)

The picture shows 45 feet equivalent to 13,716 mm !..

The "techy bit" is ...... what would be the best value of the resistor between the two elements.... ? at 40mm to 45 mm f

( the distance between the antenna lead, and the two elements joined by the resistor would be about 14 mm )

Re: Antenna Design help needed, please

Anonymous — Mon, 17 Jun 2024 20:50:01 GMT

@shutter

What frequency are the dimensions in the diagram designed for?

It is many, many years since I have experimented with antennas, but even if you are scaling the aerial for a different frequency, I would have thought that the resistor value stays the same, ie 1000 ohms?

One thing to bear in mind that I do remember from my experimenting days of 40 years ago, is that the resistor must present a purely resistive load. Some carbon film resistors have their resistive track etched in a spiral, which has inductance that will upset the aerial design. Wirewound resistors are definitely out of course! Also, keep the resistor's leads as short as possible.

Re: Antenna Design help needed, please

shutter — Mon, 17 Jun 2024 21:04:19 GMT

@Anonymous Thanks for responding......Not sure what frequency it was designed for, but the total wire length says 82.3 mtrs... so assume it was for the 80 mtr band, but could also be tuned for the 40 and 20 mtr bands, (probably!)

Thanks also for the info about the resistor.... I`ll see how it works out with a 1k resistor... will be interesting to see how it compares with other stuff I am messing about with..

Case closed !

Re: Antenna Design help needed, please

Baldrick1 — Tue, 18 Jun 2024 06:44:06 GMT

@shutter

Eons ago when I was an Electronics Development Engineer we found that metal film resistors were also inductive. Carbon composition resistors were used for applications that required very low inductance.

Re: Antenna Design help needed, please

shutter — Tue, 18 Jun 2024 06:47:25 GMT

@Baldrick1 ok... Thanks for that... appreciate the interest.