Dual Rubber Duckies?

[loumaag]

To loumaag, just because things are common in the amateur world doesn't mean they work correctly.

Doesn't mean they don't either. Face it, if it common feed to multi-band antennas doesn't work, then there are a lot of antenna manufacturers (making and selling) and a lot of ham radio operators (using) antennas that don't work correctly. Jeff, lets just say that your vision of possiblities is clouded by your perspective. As for the impedance mismatch, the mere fact that you are using a rubber duck and reach your hand towards it changes the impedance. Trust me when I tell you using the coupler as I described (oh so long ago) will work just fine as a receive antenna. It might even work as a dual band TX/RX antenna but I will reserve judgement on that until I get one in my hand to test.

This thread reminds me of the thousands of CB operators who used to trim their coax to get a 1:1 SWR not realizing that it had nothing to do with antenna matching (or effciency). Also those people who play with the mobile antenna whip length trying for the same thing, a mobile mind you! As soon as you start moving the antenna impedance changes. :lol:

 

[fourwd1]

1) Dual adapter with two handheld rubber duck style antennas: This will probably put your impedance (z) somewhere around 90-100 Ohms. This will work ok for rx, but it is hardly as efficient as a matched system where all of the received signal is coupled to the scanner.

The value would be less than 50 ohms, not more. Impedances in parallel behave like resistances in parallel for purposes of calculating combined effects.

Details, details. There would still be a mismatch. :wink:

73 de Dave, NF2G

Beat me to it, yeah, it would be closer to 25 ohms.

Also, each adapter you add into the mix will add a 3dB loss to the strength of the signal. It could attenuate a weak signal to nothing.

 

[N_Jay]

1) Dual adapter with two handheld rubber duck style antennas: This will probably put your impedance (z) somewhere around 90-100 Ohms. This will work ok for rx, but it is hardly as efficient as a matched system where all of the received signal is coupled to the scanner.

The value would be less than 50 ohms, not more. Impedances in parallel behave like resistances in parallel for purposes of calculating combined effects.

Details, details. There would still be a mismatch. :wink:

73 de Dave, NF2G

Beat me to it, yeah, it would be closer to 25 ohms.

Also, each adapter you add into the mix will add a 3dB loss to the strength of the signal. It could attenuate a weak signal to nothing.

Nope, A splitter in a matched network yeilds 3dB loss.
A "T" in an unmatched network yeilds an indetermanant amount of loss.

 

[unitcharlie]

with apologies.....

i don't use test equipment to determine whether what i hear is good or bad... i use my ears.... if i can take a rig such as the one under discussioin here and hear something i can't hear without it then it works.... i use a standard issue rat shack mag mount antenna that is now 20 years old and run the cable thru the door at the house, connect it to the scanner via a bnc tee adapter, put my optional rat shack 800 meg antenna on it and viola!... brings in one system i normally can't monitor and improves the voice recognition factor on another to the point i can understand what is said... i guess it works for me. to quote mr. murphy:

"If it sounds (or looks) stupid but it works, then it isn't stupid."