Dipole Antenna

[skippydiesel]

Attention Radio Guru's - Is a dipole antenna inherently "tuned" and suitable for any transceiver?  or does it need the attention of a SWR meter like a conventional antenna?

[RFguy]

unless the antenna, any antenna  is in free space, or effectively free space, or is inherently wideband and not affected too much by nearby objects or installation, the answer is yes, tuning is often required.

 

I've seem some 'no tune' aircraft antennas and they have a lossy resistor as part of the antenna.  you might as well have just used lossy cable and acheived the same result.

 

 

[Old Koreelah]

3 hours ago, skippydiesel said:

Attention Radio Guru's - Is a dipole antenna inherently "tuned" and suitable for any transceiver?  or does it need the attention of a SWR meter like a conventional antenna?

Skippy my 20c worth- I guess most people know this, but I didn’t (I’ll blame crook advice): install it vertically.

 

So it would fit inside the plywood fuselage behind me, I installed my dipole antenna about 30 degrees off vertical.

After years using it like this, an air traffic controller told me my signal was very weak while coming straight in. 

Turns out the damned thing needs to be vertical, as the strongest signal propagates at right angles.

 

Since it’s now vertical, people 20nm away can hear me clearly.

[RFguy]

what are you trying to acheive skip ? base antenna? road  vehicle antenna? aeronautical mobile antenna ?

 

there are some antennas I can give you a recipe for that wont need tuning for a frequency (range).

Edited April 29, 2021 by RFguy

[skippydiesel]

Dipole antenna  has been "glassed" into a composite airframe. It runs to the tail and then rises almost vertically (tail fin slightly swept).

 

Should my SWR meter suggest modification (long/short) might be appropriate, there does not appear to be any facility for changing anything on the existing set up.

 

The only alternative would be to fit a conventional antenna  or another dipole.

 

Conventional antenna would spoil the look of this very "clean" aircraft but clear comms is more important.

 

 

[Jabiru7252]

If your SWR is below 2 to1 it's not worth dicking about with, unless that dicking about is easily done. Believe me, I have spent a lot of time playing with antennas, from 1.8Mhz through to 470Mhz. 

[RFguy]

what cable is it fed with ?

does it have feedline chokes ?

you'll find that the fibreglass will tend to length the antenna , so it may appear a bit low in frequency.

Best VSWR you will get will be 1.5:1 with that setup, so if its it between 1.5  and 1.8 in the middle of the band, and less than 2:1 at the ends, that will be fine

 

bandwidth of the dipole is proportional to the width of the elements.

A dipole built with flat strip 1/2" wide will have superior bandwidth to an antenna made from 1mm wire.

glen

 

 

[skippydiesel]

3 hours ago, RFguy said:

what cable is it fed with ?

does it have feedline chokes ?

you'll find that the fibreglass will tend to length the antenna , so it may appear a bit low in frequency.

Best VSWR you will get will be 1.5:1 with that setup, so if its it between 1.5  and 1.8 in the middle of the band, and less than 2:1 at the ends, that will be fine

 

bandwidth of the dipole is proportional to the width of the elements.

A dipole built with flat strip 1/2" wide will have superior bandwidth to an antenna made from 1mm wire.

glen

 

 

From visual inspection, I think the "wire" is about 5mm 

 

9 hours ago, Jabiru7252 said:

If your SWR is below 2 to1 it's not worth dicking about with, unless that dicking about is easily done. Believe me, I have spent a lot of time playing with antennas, from 1.8Mhz through to 470Mhz. 

Thank you both - GREAT INFORMATION ! Have just signed the sales agreement. Will let you know (the fine detail) what I find when I actually have the aircraft in my possession.

[Thruster88]

We need a pic of your new machine 

[RFguy]

Jabirus have antennas in their tails, I bet he's got a Jab !!!  (not 'The Jab')

Edited April 30, 2021 by RFguy

[skippydiesel]

22 hours ago, Thruster88 said:

We need a pic of your new machine 

Europa Classic