Getting the most out of barefoot performance

[KEWB-N1EXA]

You will see much more than 2 or 3dB comparing horizontal to vertical. 20dB is a commonly used number for cross pol degradation but it depends mostly on reflective surroundings. If you remove that like an antenna pointed up to a satellite, mid 30dB and up to 40dB cross pol attenuation is normal. Slanting a dipole at 45 degrees will give you exactly 3dB degradation with no reflective surfaces around and that's what to expect from an inverted V dipole talking to a vertical.

27 Mhz Cb and A S band uplink are 2 different animals.
What ever guy...
Its a CB forum...
Just an answer to a question.

Peter N1EXA

 

[slowmover]

Let's take linear amps and mods out of the equation and assume that everyone ran barefoot. Where does that leave us?

In my non-technical experience with simply spending years around the practice of playing CB radio, I would think that leaves us leaning heavily on the antenna. That's where real performance begins.

So, if I want the best performance out of a good antenna, height is my best friend, right? So, what's a realistic expectation/estimation of range if I have an A99, Sirio 27 ground plane, IMAX or a similar omnidirectional antenna 35 to 50 feet in the air, communicating to mobiles and other stations with a similar setup, respectively?

Now, let's go a step further. Let's say I have something like a Moonraker with a "multiplication factor," and it's 35 to 50 feet in the air. With 4 watts, what kind of range could I reasonably achieve to another base station with an omni antenna in the air? Or another station with a similar beam?

I guess the nitty gritty here is, how effective can we expect 4 watts to be in different scenarios. Would love to hear your opinions, and stories of long-range barefoot communications.

Antenna, yes.

But “noise” is several chapters in itself.
With or without the antenna.

.

 

[WB9YBM]

So, is my takeaway lesson here that a single dipole will always perform best vertically, and in particular because most other stations use a vertically polarized antenna?

About 99% of my experiences with dipoles--both using them myself as well as what others tell me about their uses--they're horizontal.

 

[FPR1981]

About 99% of my experiences with dipoles--both using them myself as well as what others tell me about their uses--they're horizontal.

I put one vertically in an old oak tree in the late 90s. It talked like thunder. Prior to that, I had always done them horizontally. A ham buddy told me that horizontally wasn't the best way to go because most other stations are vertical. Not sure what science that's rooted in, but that's something I adopted and had okay luck with.

But they talked good horizontally for me too...

 

[merlin]

Im having a terrible time trying to setup a dipole on the balcony of my apartment located on the fourth floor which is also a dead spot.
Luckily i still dont have my new apartment furnished with nothing more than a tv a few milk crates and toats makes me want to ask the supervisor what are my chances of being switched to another unit preferrably on the 12th floor or highest available that i just might pay for the switch if the rent stays the same.
Ive had my cb/ham radio station since childhood better than 30 years its just significant me that cannot be without frequency.

No antennas where I am at the moment except dish and TV. My discone is funtionally a TV antenna and I can likely hide a dipole at the edge of the roof. Problem is nearby cables, conduits would seriously degrade performance so migrated to VHF/UHF. A pending move this spring, I will only take a place that will let me put up my 50' trapped dipole and room for my HF gear. A homebrew antenna tuner, and preselector, the dipole configured inverted V does an awesome job 1 to 32 Mhz. Setting up a 50 Mhz equivalent and back to SWLing, maybe some DX work under 100 watt.

 

[jonwienke]

About 99% of my experiences with dipoles--both using them myself as well as what others tell me about their uses--they're horizontal.

No. They need to match the orientation of the other antenna, which is almost always vertical for CB. Otherwise you're missing the main signal, and only picking up reflections that happen to have some oddball polarization.

 

[WB9YBM]

A ham buddy told me that horizontally wasn't the best way to go because most other stations are vertical. Not sure what science that's rooted in,

That's more of a general thing, nothing really to do with dipoles. For example from CB frequencies on upwards, the majority of ops use vertical antennas of different types (1/4 wave, 1/2 wave, etc) mounted to the car trunk or roof so vertical polarization is the de facto "standard". If someone wanted to be different and run a horizontally polarized antenna, yes there will be a "cross-polarization loss". It seems like for every one person I ask what that loss number is, I get two different answers (as a minimum), most often hearing a 6 db loss figure mentioned. That being said, though, I've experimented with a few different antennas, first holding them vertically and then turning them horizontal and didn't see a whole lot of difference on the signal strength meter--so either my meter's lying, or some people out there are exaggerating the problem.

 

[WB9YBM]

No. They need to match the orientation of the other antenna, which is almost always vertical for CB. Otherwise you're missing the main signal, and only picking up reflections that happen to have some oddball polarization.

Sounded to me like we were discussing the vertical mounting of a dipole . Actually the signal you're referring to is not a "reflection". It's still the primary signal at a different phase or polarization. When two antennas are differently polarized (like one vertical, the second horizontal), there's a cross-polarization loss.

 

[jonwienke]

That's more of a general thing, nothing really to do with dipoles. For example from CB frequencies on upwards, the majority of ops use vertical antennas of different types (1/4 wave, 1/2 wave, etc) mounted to the car trunk or roof so vertical polarization is the de facto "standard". If someone wanted to be different and run a horizontally polarized antenna, yes there will be a "cross-polarization loss". It seems like for every one person I ask what that loss number is, I get two different answers (as a minimum), most often hearing a 6 db loss figure mentioned. That being said, though, I've experimented with a few different antennas, first holding them vertically and then turning them horizontal and didn't see a whole lot of difference on the signal strength meter--so either my meter's lying, or some people out there are exaggerating the problem.

Your signal meter isn't accurate. Attenuation at 45 degrees is 3dB, at 90 degrees attenuation is theoretically infinite, but in practice isn't usually much more than about 20 dB due to reflections, antenna elements not being perfectly vertical/horizontal, and so on.

 

[jonwienke]

Sounded to me like we were discussing the vertical mounting of a dipole . Actually the signal you're referring to is not a "reflection". It's still the primary signal at a different phase or polarization. When two antennas are differently polarized (like one vertical, the second horizontal), there's a cross-polarization loss.

What I said is correct. Reflections are polarized based on the orientation of the reflecting surface, not the polarization of the original signal. That's how polarizing filters work to filter out reflections--the reflections are polarized, even though the original light source isn't.

 

[WB9YBM]

What I said is correct.

just sounded a bit off-topic. Valid point, though (in addition to what I originally said).

 

[WB9YBM]

Attenuation at 45 degrees is 3dB, at 90 degrees attenuation is theoretically infinite, but in practice isn't usually much more than about 20 dB due to reflections, antenna elements not being perfectly vertical/horizontal, and so on.

Yeah, that speaks to my point mentioned elsewhere in the thread.

 

[prcguy]

This post below is about what you should expect. For some terrestrial and all satellite signals, they actually have two completely different channels of video, audio or data running on the exact same frequency and its the polarization that separates the two channels and allows them to work independently. This requires more than 20dB isolation and ideally over 30dB which is a minimum goal for satellite downlinks.

Some vertical CB antennas radiate a little energy in the horizontal plane like most with a circular tuning ring at the bottom. The old Avanti Sigma 5/8, the Maco copy of it and the Cushcraft Ringo are some examples. It would be impossible to approach 20dB cross pole isolation using those antennas, if for some reason you wanted to.

If you are really curious about this you could set up a pair of CB dipoles across town with choke baluns at the feedpoint so the coax doesn't radiate, then get them a 1/2 wavelength or multiple of a 1/2 wavelength high with one vertical and one horizontal. You could then carefully tweak one of them in polarity until you get the absolute most attenuation and I'll bet it will be close to 20dB unless there is a huge water tank or metal building in the path between the antennas. A major portion of the cross pol isolation happens within the last 2 degrees or less of being perfectly 90 degrees different in polarity. If the horizontal dipole in this test is perfectly horizonal but the vertical dipole is bent over a few degrees you may only get 10dB or so cross pol isolation.

Your signal meter isn't accurate. Attenuation at 45 degrees is 3dB, at 90 degrees attenuation is theoretically infinite, but in practice isn't usually much more than about 20 dB due to reflections, antenna elements not being perfectly vertical/horizontal, and so on.

 

[jonwienke]

For some terrestrial and all satellite signals, they actually have two completely different channels of video, audio or data running on the exact same frequency and its the polarization that separates the two channels and allows them to work independently. This requires more than 20dB isolation and ideally over 30dB which is a minimum goal for satellite downlinks.

There are a few exceptions to this. GPS signals are circularly polarized, so that a terrestrial antenna oriented in any direction will still receive an acceptable signal level. I believe EPIRB and other signals that need to get through, regardless of the orientation of the antenna on the ground, are the same. Requiring rotational alignment of the antenna within 2 degrees would impose a serious usability issue for that sort of stuff.

Some vertical CB antennas radiate a little energy in the horizontal plane like most with a circular tuning ring at the bottom.

Antennas with loading coils will do the same--rotate a bit of the antenna output ~90 degrees from the main orientation of the antenna.

 

[Bologna_sammiges4me]

I think i had an obsession for antennas long before i got involved in the cb/ ham radio hobbie that began when i was 9 years old with my fist cb i had mounted to a milk crate that also contained an old car battery inside an old metal wheel barrel with a 102 inch whip mounted to the side of it.
Every day when my battery was fully charged i would push this old wheel barrel radio up and down the hills and ridge lines of southeastern appalachia where i covered several miles of non stop each day as i talked to everybody streight shot upto 3 or 4 countys away and shot skip allover the world.
I learned alot about shooting skip on 4 watts from a wheel barrell Lol.
A hot spot for shooting skip will never be that 1 stationary location of antenna placment that guarantees world wide communication during such conditions provided by mother nature in never ending waves of unpredictability.
I made contact with australia from inside my garage on my 4 watt wheel barrel station that was a dead spot for all my locals over a mile away.

 

[prcguy]

Aah, but with circular polarity you have the other polarity as in right hand vs left hand. You can easily get 30dB or more cross pol isolation with circular polarization. If you have a dual horizontal/vertical cross Yagi on CB you can configure it using a delay line and create circular polarity. That can reduce fading when receiving skip signals.

There are a few exceptions to this. GPS signals are circularly polarized, so that a terrestrial antenna oriented in any direction will still receive an acceptable signal level. I believe EPIRB and other signals that need to get through, regardless of the orientation of the antenna on the ground, are the same. Requiring rotational alignment of the antenna within 2 degrees would impose a serious usability issue for that sort of stuff.


Antennas with loading coils will do the same--rotate a bit of the antenna output ~90 degrees from the main orientation of the antenna.

 

[Bologna_sammiges4me]

Nagoya 771 ht antenna used as a base antenna has taken place of my old 4 foot tall tram dual band base antenna

Does anybody have any input on the use of a dipole without coax ??? Lets say i want to use 102 to 106 inches of copper wire strung streight from the antenna jack on my radio ?

 

[merlin]

So my RG6 75 ohm is bad ? Seems to work just fine...Now I would not put 100 Watts down it !
The guy is running 4 watts on CB.

Peter N1EXA

RG6 will easily handle 100 watts, I have used it in series section matching. The typical CB radio has 50 ohm impedance so the 75 ohm coax will have some loss. Your 4 watt radio may only be getting 1 1/2 watts to the antenna.
50 foot runs or less, any good RG58 would be better. Use RG8 up to 100 foot.

 

[jonwienke]

Aah, but with circular polarity you have the other polarity as in right hand vs left hand. You can easily get 30dB or more cross pol isolation with circular polarization.

Yes. The advantage to right/left circular polarization is that the antenna alignment isn't critical the way it is with horizontal/vertical polarization. As long as the antennas are pointed directly at each other, their rotational alignment along the line between points A and B doesn't really matter. They don't need to be aligned within 2 degrees of each other to get the desired isolation.

GPS is only right-hand circularly polarized, though, so that the receiving antenna doesn't have to be aligned to the satellites to get a usable signal, and dual antennas are not required.

 

[prcguy]

Most RG-6 at 27Mhz will handle a good 750 watts continuous under matched conditions, meaning the antenna is 75 ohms and heat buildup is the limiting factor for continuous operation. 500 watts is probably a safer number when using with a 50 ohm antenna. For short duration pulsed applications it will easily handle tens of thousands of watts under matched conditions.

RG6 will easily handle 100 watts, I have used it in series section matching. The typical CB radio has 50 ohm impedance so the 75 ohm coax will have some loss. Your 4 watt radio may only be getting 1 1/2 watts to the antenna.
50 foot runs or less, any good RG58 would be better. Use RG8 up to 100 foot.