Antenna Design help needed, please

[#1]

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 )

[#2 · Accepted solution]

@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.

[#3]

@Mr_Paul  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 !

[#4]

@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.

[#5]

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