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Alsworld
| | Posted on Saturday, October 18, 2003 - 1:58 pm: | 
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Tech 833,
Being I got so caught up in another thread trying to split hairs between mobile antennas, it perked a curiosity in me to try and perform a “side by side” comparison between two different antennas.
I would like your opinion on how to most effectively/realistically test two different CB antennas in a real world environment based on the details I am suggesting?
I would like to add some disclaimers to protect your professional reputation in your expertise:
- You are not conducting this test, but requested to assist with “best guess” advice only under a non-scientific circumstance, beyond your control, within a limited and sole source test (me, my antennas, and my vehicle) based on the information I provide.
- Your advice would pertain only to me during this test and my setup as I describe. Not as a general test for others to base similar testing to.
- You are not to be held accountable to, support, agree to, or even accept whatever results I conclude.
- Everyone who reads this thread realizes that Tech 833 is an antenna expert, and that I am not. Tech 833 is a professional Engineer designing, building, and testing antennas and like systems. I am not any of those, but performing an unscientific test and no more.
This test would be based in a real world environment and not under controlled circumstances. There is no calibrated or measuring equipment involved beyond what is mentioned below.
Okay, here’s what’s up. I want to compare my Monkey Made MM5 antenna to a ¼ wave 102” stainless whip (with spring) during some local testing. I plan to reach out as far as possible (miles) using my base station as the “S” meter registering signal strength between these two antennas. I want to test from various places (North, South, and East) at differing elevations (local terrain is rocky and hilly), but miles apart is the key point. I cannot test West due to the ocean unless I spend lots of time and Ferry $ to Canada. For this test, being it’s not that important, I’ll defer the Western testing.
All of the testing would be from the same antenna mount mount on the vehicle (although the ¼ wave whip would have a spring installed), in a non-moving environment. I will simply do a number test as described, then remove the antenna and replace with the other one and re-perform the exact same steps, documenting each result. Once completed, I will drive to another predetermined area and repeat the same steps.
No power input fluctuations would be allowed going in to the antennas (I have variable power on the President Lincoln in my truck. Same power applications for both antennas apply, no additional power allowed or anything else to skewer the results). I will perform SWR checks prior to going anywhere with these antennas and post them along with results.
This test is not designed to say positively what is the better antenna (unless obvious for my application), but to see how each best fits my truck and my situation concerning performance. Basically to see if one far outperforms another, or if closer results are found
I agree to:
- Perform test as described.
- Will not falsify results posted here on this forum or anywhere else.
- Will give a fair and honest evaluation. If my results seem unreasonable or unrealistic, I will (upon request) forward both antennas to Tech 833 so he can test himself under controlled environments at my cost (2 way shipping only). Sorry Tech 833, I can’t afford what you cost per hour to test CB antennas.
- I will NOT adjust the volume on my power microphone to skewer results.
Here is my plan in a nutshell.
1) Sit a person behind my radio at home to read results. All readings (RF Gain at maximum, squelch at minimum) will be set and left untouched throughout the duration of testing).
2) I will utilize some type of recorder to perform ALL modulation into the truck CB microphone. This should eliminate any variance in voice inflection or octave differences into the microphone, and be equal through all testing. I do not have a tone generator, so am thinking of recording certain tones from an electronic organ that I can play for an extended time to give the person at home time to read each reading. I want to record average signal strength when modulating, not a peak swing.
3) My partner at home recording readings will have no idea what antenna I am using except by “A” or “B”.
4) I had planned to use AM mode only, but am now throwing in FM as well. With the way FM does not swing, it will also be another way to test the dead key.
With luck, I plan on covering many miles and differing locations just to see what pans out without prejudice. It should have interesting results for all to think about, or “prove” well established theories concerning two CB antennas (impossible to actually prove anything based on this test, but suggest maybe based on my setup).
I do plan on using a handheld GPS to measure distance between each reference point to give exact distance from the home base antenna. I would use my own GPS but it’s hard wired into my boat, so I will borrow a friends handheld GPS to measure true distance as the crow flies, and as signals travel (between antennas). I will post that statistic along with results.
I realize that these meters in my CB radios are junk at best, uncalibrated, etc. But at least it will be consistent on the receiving end. I could also get real detailed measuring dead key signal strength, then a modulated signal strength which I just may do. I will create a spreadsheet with all information laid out so during testing, it’s fill in the blank under each category.
I will not be testing/documenting the receive “S” units in the vehicle as it will be based only on the person who I am communication with, but will annotate in my notes if one antenna appears to be noticeably better or worse at one or more locations.
I cannot predict weather, or know if it affects anything related to this test, but will annotate the conditions at the time of testing.
Okay, under this non scientific test, what am I missing? Any advice?
Alsworld |
Kc0gxz
| | Posted on Saturday, October 18, 2003 - 3:42 pm: |
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Hey Al
You could probably make a living at writting disclaimers when and if you deside to retire from the service. You're good at it.
And one more thing. You have a knack for answering your own questions and instructions more than anyone I've ever seen.
For your non-scientific and non-controlled enviroment test, about the only thing I would suggest is....
1- Be far enough away so the receiving station is receiving about 3-5 S-units from the test site.
2- Use a frequency that is dead quiet. And preferably at nite.
3- Make sure every antenna you are going to test is tuned for the lowest possible SWR for the test frequency.
I'm sure Tech833 has some better ideas than mine. We both know that he's Thee Man when it comes to antennas.
Personally Al, I'm looking forward to your end results. Lol. I really enjoy reading your posts. You're just so darn thorough. It must be from your 20+ years in the service. The military has ways of effecting people in strange ways sometimes.
Respectfully and 73s for now.
Jeff, kc0gxz. |
Alsworld
| | Posted on Saturday, October 18, 2003 - 9:52 pm: |
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Roger that on the disclaimers. I do this especially for Tech 833 because I'm asking him to "shoot from the hip" and give his professional advice on something that he has no control over, and is about the farthest thing from the standards he upholds. Here, we are talking CB antennas, and asking him to wing it really seems unfair to even ask given the circumstances under which I have proposed the question.
The reason I have is being he test antenna systems for a living, maybe there is a big step I have overlooked. With such so many variables to consider, no proper testing equipment included, how can someone who has so much expertise in this area respond to such a amatuer and primitive test? Well, I can only hope he steps back and takes a look from my perspective. How much more thorough can one be from this side of the fence?
Beside, it's really pretty basic, and will prove pretty much nothing except what works best on my vehicle between these two antennas. Quite possible it will mirror our thoughts on the 102" whip, or maybe it will surprise us both. Let's see.
Thorough? You bet man. My job requires it full blast. Always thinking cause and affect, what are the "if's", what can go wrong and what is the risk involved? Is the risk worth the outcome? blah blah blah I could go on forever but yes, I try to be thorough and yes my job demands it.
I do want to note something here. I have no idea of the outcome, but suspect the 102" whip will prevail based on antenna theory. Now before you start freaking out, I would like to stress that I am not back peddling nor backing off the fact that I really like my Monkey Made antenna. It performs wonderfully for me. Remember the old thread, I had to compromise my antenna height so I went with the next best thing (or a variant of that, opinions vary). I am not backing off the fact that I really like the antenna, even the looks  , but I still do back my claims of it being a solid performing antenna. You can do a search on this forum and see I have never claimed it would beat out a whip, but I will bet it beats out some other brands. Depending on when I can do this, I would like to try more than just two antennas. I have always had great success with Francis antennas (long ones), and might even throw in the Anttron 1700 if Copper can get me one soon enough? Forum Master? Why not, easier to do a bunch at once instead of redoing this all over again in the future. With my base antenna so high and sitting on an island, this test will cost me most in gasoline and mileage for my truck than anything else. I can easily reach 45 miles north on AM, and 95 miles south on SSB (I'm talking barefoot), so at some point I'm gonna quit without driving into an additional oil change if you know what I mean.
My test will be done as close to the CB frequencies as possible, but just outside the 40 channels for quietness.
I performed SWR checks earlier on both antennas;
102" whip about a 1.2:1, MM5 1.3:1. The later will not go lower so I'll run with these.
Enough said.
Alsworld |
Kc0gxz
| | Posted on Sunday, October 19, 2003 - 12:08 am: |
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Al
I thought you had a couple of Firestiks and a Wilson of some kind.
If you still have them, compare them all to the 102. Start with the 1/4 waves, then any 1/2 waves you may have on up to the 5/8 wave.
Why am I telling you this? You know what you're doing.
Later Al.
Jeff. |
Alsworld
| | Posted on Sunday, October 19, 2003 - 10:54 am: |
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Nope. Gave away my K40 to a friend who needed it. Bought my brother a Wilson 1000 but he's now 2500 miles away. Never owned a Firestick. Had a Francis 8ft'er that I loved but somebody needed it more than I did so I gave it to them. My other whip is cut down for 10 meters so hence the new one. I've got a Shakespeare marine 8 ft CB antenna on the boat opposite the VHF antenna but is okay on the water, would waste my time here. Non tuneable, no ground, high SWR (even advertised as such).
Oh, I do have a Wilson Little Wil for the wifes car when we travel. It's good for that, but pretty much only that. I doubt I'll try it here. If it were a 1000, then I'd do it. I used to listen to guys flouder with those baby's in FL, even on top of a van they had little range.
Alsworld |
Pig040
| | Posted on Monday, October 20, 2003 - 10:19 am: |
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Al,
Wow, sound like an attorney! I tried a wilson 1000, and a 5000 on my pickup, I swear the 1000 had better ears, dont know why. But then I tried one of those double coil antenna about 5' tall, and it outperformed both wilsons both on transmit and recieve. Then I melted the mag mount, and when I tried another mag mount never could get the same results. I think if I drilled a hole and mounted the coil, it couldn't have been beat. |
Tech833
| | Posted on Monday, October 20, 2003 - 9:29 pm: |
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Al, you make me laugh!
O.K., I would perform your tests as follows:
1- Make sure both antennas are tuned similarly.
2- Make sure and use the same mount, cable, radio, etc. ONLY change the antenna.
3- DO NOT change locations when changing antennas. Do the comparison test without moving the vehicle and within 15 minutes of each other.
4- Make sure the receiving station uses some sort of non-gain antenna. No beams, no 5/8 wave ground plane, no trick anything. I suggest a 1/4 wave ground plane, or better yet, a discone.
5- No power. Do your test with legal power (for many reasons).
6- Do your tests with no modulation. FM would be great, but it is not a legal mode on CB. Dead carrier would be better.
7- Do it at night on a clear channel! If there is ANY skip at all, the receiver meter readings will be skewed greatly.
8- Attach a digital voltmeter to the receiver's S meter for signal strength readings. Sometimes, you will find a situation where both antennas provide the same S reading to the analog eye, but a digital voltmeter will tell you one has 5.78 volts and the other 5.92 volts. This will also give a no-error measurement that is not dependant on viewing angle of meter.
9- Stay keyed for a minute or two each time a reading is made. Have the receive station note any fluctuations in signal (which would indicate multipath) and throw out readings that move. Adjust your location slightly (a few feet or so) to remove any multipath from the equasion.
10- Make sure the vehicle engine is running while the radio is transmitting. This will remove any voltage fluctuations/power output differences from the tests. A 12 volt battery will be 13.6 or more volts for a minute or two after you shut off the motor and will slowly drop to 12.5 or so volts.
11- In addition to static (still) tests, drive the vehicle in a circle (if room allows) while transmitting and have the receiver record the high and low and average (this is subjective).
833 |
Alsworld
| | Posted on Tuesday, October 21, 2003 - 11:35 pm: |
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Tech 833,
thank you for responding. That was very informative and I appreciate the time you put into that answer.
I will follow as closely as possible your advice. Sure enough I knew you would have things that I had not thought of, or was not even aware of (imagine that). Multipath, cool beans, I never knew about that. Working legal power makes sense, without modulation and working dead carrier only will shorten my trip, which is okay by me. Probably a much truer reading on signal strength. That saves me much travel and fuel.
I had thought about the vehicle running and reduced battery voltage once off. I will let the vehicle/battery "settle" for a few minutes after driving while I set things up (performing a non-documented rough draft, looking for multipath and a no-noise environment).
Wow, that voltage meter to the RX "S" meter threw me for a loop. I swear I cocked my head sideways like a confused dog, stared at the wall, and after an unknown period of time, muttered the only thing my Texas school of public education brainwashed mind could think of. I think it was....."huh?". Took me a few tries but it slowly sank in. I'll have to figure that out on this radio, as a digital reading would be foolproof. I'll play with that for sure. Man I never would have thought of that! If I can get it, another block to add to my spreadsheet, cool.
My receiving antenna might be a problem. It's an IMAX 2000 which you know well. Being it's a 5/8ths wave which you said don't use, I'll have to see what else is available. I do have a 1/2 wave omni as a spare antenna, workable? I cannot mount it where my other antenna is, so it would be much lower in elevation. Hmmm, I'll have to either find a solution, or that may be my weak spot in reference to my results.
I had thought about your last comment, testing the omnidirectional characteristics of the antennas (on my vehicle). I had actually done this on my MM in Florida with a base station about 20 miles away, I worked about eight compass variants then just drove in a very slow circle modulation all the time. I found it seemed pretty darn omni, but that was about the roughest and primitive test I could do. If I can (I will see if I can perform this depending on time and location), I will try to incorporate a much more thorough version. Maybe, if this is designed to find a directional, or lackthereof radiation pattern (without using any testing equipment), if I have a few good areas, I may make a few runs and see if I can obtain similar results with each antenna.
Thanks tremendously again for your help. I have planning to do, and must work on shortening up my post. Time to go play Mr. Mom some more.
Alsworld |
Scrapiron63
| | Posted on Wednesday, October 22, 2003 - 9:23 am: |
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Alworlds, the idea of using a digital voltage meter on the signal meter threw me for a loop also, that will certainly show the differences. When we checked antennas before just using the signal meter on a radio, most would show about the same, it takes a lot of gain to make just a nettle's width difference. scrapiron |
Kc0gxz
| | Posted on Wednesday, October 22, 2003 - 3:14 pm: |
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Al
Like you, I was looking forward to Tech833s answer to your post. I just KNEW I was going to learn something new.
Oh yeah, he's the (antenna) MAN, no matter what flee bitten Third World country he happens to be standing in at the time. We sure are fortunate to have him on Coppers Forum.
Jeff. |
Alsworld
| | Posted on Wednesday, October 22, 2003 - 8:56 pm: |
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Yes indeed that's a new one. I hope I can make that happen, as the meter in the radio is so small. Splitting hairs on what is an "8 s-meter reading" vs a 8.25 is almost impossible to really make out.
I'll pull out the schematics and look for voltage going to the meter, then play with it a bit when I can. If I can duplicate his intentions listing to skip and local talk, I can make a few dry runs and check stability. Not sure when I can get to that but I'll let you know if I am successful pulling it off.
Alsworld |
Kc0gxz
| | Posted on Thursday, October 23, 2003 - 1:13 am: |
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Take your time Al.
I'm looking forward to you results.
Jeff. |
Bullet
| | Posted on Friday, October 24, 2003 - 10:29 pm: |
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alsworld,
this is, with the exception of 833's # 8 and #11
exactly how i performed my comparisons of mobile antennas a few years back. "i'll be darn i guess i might just know alittle somethin after all"! LOL
i like the multi meter idea, thats a better way to compare them by voltages.
if you could do this for the recieve stations as well it would take alot more guess work out of witch is the best on tx.
then you could get an average and your data would be a bit more accurate than by using s meter readings alone.
good luck and let us know how it comes out.
and if you happen to have one that beats the 102 whip you might consider keeping it to your self and friends.
or "video the event at all stations" so youll have a date time group for each reading and anounce and show each antenna on film durring testing.
i know this sounds abit over board but thier are those that need it i guess.
later man. |
Alsworld
| | Posted on Saturday, October 25, 2003 - 1:07 am: |
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Bullet,
great idea for sure, but I got to take it one step at a time LOL!
It will be neat to see what comes out and fill this curiosity on antenna A vs B, etc.
Man I got to get busy soon, my life just took a left turn and time just got much shorter for my testing window or else I may have to put it off for months, and that is not what I want to do.
I may have to just do it with the Imax 2000 due to my new time constraints. We will see.
Video proof, now wouldn't that be worth a 1000 words?
Alsworld |
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