Rattail for HTs - Page 1
Forum section: electronics / rf-microwave

author: @rt
author_rank: Super Contributor
timestamp: April 28, 2019, 06:30:07 am
content: HiIf the Rattail. or sometimes in the DIY arena, simply called a counterpoise, is a thing, then the antenna system at the bottom of the image is a thing.Does this antenna have a name?

author: ChristofferB
author_rank: Frequent Contributor
timestamp: May 05, 2019, 11:57:47 am
content: I guess that would depend on the topology of the counterpoise. With the tuned circuit I think its just a special case (electrically short) of many known antennas (dipole, gp).

author: radiolistener
author_rank: Super Contributor
timestamp: May 06, 2019, 04:34:14 am
content: it's the same antenna with extended ground (counterweight), it allows to decrease input impedance and makes antenna more balanced which reduces RF leaks on the outer side of cable braid, if you feed it through coaxial cable.Actually there is no antenna like your top picture, because handheld radio has metal chassis which works as counterweight. So, it is always bottom version. You're just adding second wire as counterweight. With good counterweight, antenna works better. But you're need to take into account that change counterweight length (or counterweight geometry) leads to change antenna resonance, so you're need to tune it again after adding better counterweight.Antenna always needs two wires - main element and counterweight. The same like capacitor always needs two plates.For handheld radio the metal chassis is used as counterweight.For GP antenna there is need counterweight, otherwise outer braid of feeding cable will works as counterweight.If your antenna counterweight is too short, your antenna impedance will be too high. And it will be too hard to push RF energy into such antenna. You will need to add antenna tuner which will be able to produce very high voltage. These inductor and capacitor on your circuit is nothing else than antenna tuner. It is needed in order to match your antenna impedance to output impedance of your transmitter.

author: @rt
author_rank: Super Contributor
timestamp: May 06, 2019, 07:02:35 am
content: That’s kind of my point. You can’t access the capacitor tap, as it’s inside the antenna.I’ve had no good result, in fact, it makes the received signal strength worse on any band I’ve tried, unless I actually make my own dipole, and not use the stock antenna at all.But people on YouTube propose we just tap a wire to the ground of the radio somewhere using the stock antenna.

author: radiolistener
author_rank: Super Contributor
timestamp: May 06, 2019, 09:39:47 am
content: adding extended counterweight shifts antenna resonance frequency. So it can make reception better or worse, it depends on your antenna tuning and exact frequency which you're used for test.you're needs antenna vector analyzer in order to see what is going on with antennaHere is picture how usual Baofeng UV5R pig-tail antenna works at 145 MHz band. This graph is individual for each antenna and depends on it's tuning:By adding additional counterweight you're shift this graph. The better reception is at minimum SWR value.As you can see, result will depends which frequency you're listening.With no measurement equipment you're blind and don't see what happens.