102 whippers
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What frequency(ies) are you trying to use? T junction aside...
The reason to use a displaced set of antennas is to increase gain in a given direction and/or reduce gain in given direction. If done correctly, then across a limited set of frequencies you get a directional pattern (ex North and South) and reduced gain elsewhere (ex East West). Maybe this is what you want or maybe it isn’t. As the frequency is increased the antenna spacing becomes electrically long and you get multiple lobes of higher and lower gain along the horizon. That’s never a good thing and you are better off with a single antenna.
Accordingly, it’s not a good solution for wideband reception and it gets harder to get things right for higher frequencies where the spacing and cable lengths are more critical. It is relatively easy to pull off for HF and maybe VHF Low. The max spacing not to exceed is usually around one wavelength.
Whether this is a good path to take depends on what you are trying to do (frequencies, do you want a more directive pattern, can you just go higher with what you have, etc).
The reason to use a displaced set of antennas is to increase gain in a given direction and/or reduce gain in given direction. If done correctly, then across a limited set of frequencies you get a directional pattern (ex North and South) and reduced gain elsewhere (ex East West). Maybe this is what you want or maybe it isn’t. As the frequency is increased the antenna spacing becomes electrically long and you get multiple lobes of higher and lower gain along the horizon. That’s never a good thing and you are better off with a single antenna.
Accordingly, it’s not a good solution for wideband reception and it gets harder to get things right for higher frequencies where the spacing and cable lengths are more critical. It is relatively easy to pull off for HF and maybe VHF Low. The max spacing not to exceed is usually around one wavelength.
Whether this is a good path to take depends on what you are trying to do (frequencies, do you want a more directive pattern, can you just go higher with what you have, etc).
n0nhp
Member
Using all 50 ohm cable (assuming equal lengths of legs and perfect cable and a bunch of other things) Your antenna system would show 25 ohms impedance to the radio.... bad SWR.
Using specific lengths of 90-100 ohm cable, you could make a bi-directional antenna system at broadsides to the antennas.
Co-phasing antenna systems is a project in physics with a side of black magic.
Bruce
Using specific lengths of 90-100 ohm cable, you could make a bi-directional antenna system at broadsides to the antennas.
Co-phasing antenna systems is a project in physics with a side of black magic.
Bruce
So I did it. Two 102 whippers. One on the North side and one on the South East side of the house. 1.0 SWR. T hook up on the back of the radio and both antennas hooked up like the truckers do but for a base set up. Havnt had it up long enough to see if itll cover more ground or its just a waste of time. In any case I set the new one up higher and was just gonna use that but decided to try em both out since I had the other coax in the house etc ...
There's a specific length of coax required between the "T" and each antenna (if memory serves, I think it might be called a "phasing harness"). Unfortunately I don't have the formulae memorized to calculate the required length but a search on the Internet will probably give you either the formula you need or mention an antenna reference book that might help.
What is the loss over the cable? If this is standard 50 ohm cable, you are just warming a lot of wire.
not sure ... its not something im trying to achieve, it was just an experiment since i had two whips. i will more and likely just use one at a time. my north antenna talks pretty far for being barefoot. the other one shoots east good. i will try em both together and see what it does. doent seem to be a lot of info about how to do a base set up. they are the basic rgx5. one is a mini 8
If you ran the calculator, it shows a loss of 33% depending on what brand of RG8X. The calculator doesn't have the Mini 8, but if it is the mini I am familiar with, it would actually be worse for the distance.
... not to mention that if the phasing between the antennas is off (and it will be unless the correct coax lengths are used) there will likely be out-of-phase loss, up to as much as 180 degree mismatch. Meaning 100% total signal cancellation.
n0nhp
Member
At 27MHz usually not a problem.
Not so good at VHF
and horrible at UHF up
Bruce
Not so good at VHF
and horrible at UHF up
Bruce
prcguy
Member
At CB frequencies 100ft of RG-8X has about 2dB loss, so if your radio puts out 4 watts there will be 2.5 watts that make it to the antenna. I think that's excessive and I would go for a lower loss cable.
Calculators and charts are okay for a general guess, but nothing beats measuring power than a good quality power meter. For example when I did a test of 50' of RG-8 at 220 MHz, the power lost measured was a lot less than the charts told me it would be (and just to make sure I wouldn't have any squirrely effects cause by a less-than-perfect antenna at the far end, I used a 50-ohm dummy load).
Here are a few items I found:
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Phasing Harnesses Archives - Amphenol Antenna Solutions
Phasing and matching harnesses can be used to combine multiple antennas into one output or to split antenna signals into multiple paths.
amphenol-antennas.com
jonfinley.com - jonfinley Resources and Information.
jonfinley.com is your first and best source for all of the information you’re looking for. From general topics to more of what you would expect to find here, jonfinley.com has it all. We hope you find what you are searching for!
www.jonfinley.com
Phasing harness for antenna array
I understand that certain antenna designs (particularly phased arrays) require feeding each radiating element with a certain number of degrees of phase separation in order to achieve a desired radi...
ham.stackexchange.com
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