86" or 72"

[gunslinger338]

86" vs. 72"

i did a little comparison this past weekend... because i was bored........these are the results.
( Disclaimer ; your results may vary )
All test with Cobra 29 @ 12 RMS bird watts dead key with mic gain at zero
measured with Bird43 w/ 25 watt slug and Fatboy digital field strength meter
all test were from same suburban , same mounts , same location , same day , ect...ect...


2- 27 " 10ks at 72" --------------- 102 on the field strength
2- 27" 10ks at 86" ---------------- 82 on the field strength

2 FatBoy R4's at 72" ------------ 68 on the field strength
2 Fatboy R4's at 86" ------------ 99 on the field strength

2 adjustable 102's @ 72" ---- 123 on the field strength
2 adjustable 102's @ 86"----- 104 on the field strength

Ding , ding , ding
let the fighting commence !!!!

[gunslinger338]

NOTE


Yes.... when the spacing changes ,, So does the reflect

I wanted this test to show results of " Tuned " antenna systems

additional tuning was done to achieve "as close as possible" the same reflect watts when spacing was changed.

may be next weekend i will do the same test with out re-tuning and note the reflected watts also.

[Fluxmaster]

Good info thanks for posting, im planning 2 R4's at 86" on a suburban :)

[Marconi]

86" vs. 72"

i did a little comparison this past weekend... because i was bored........these are the results.
( Disclaimer ; your results may vary )
All test with Cobra 29 @ 12 RMS bird watts dead key with mic gain at zero
measured with Bird43 w/ 25 watt slug and Fatboy digital field strength meter
all test were from same suburban , same mounts , same location , same day , ect...ect...


2- 27 " 10ks at 72" --------------- 102 on the field strength
2- 27" 10ks at 86" ---------------- 82 on the field strength

2 FatBoy R4's at 72" ------------ 68 on the field strength
2 Fatboy R4's at 86" ------------ 99 on the field strength

2 adjustable 102's @ 72" ---- 123 on the field strength
2 adjustable 102's @ 86"----- 104 on the field strength

Ding , ding , ding
let the fighting commence !!!!

Interesting report 338. How would the FS number for a well tuned single antenna respond when compared to anyone of these setups?

What kind of FS meter and FS/antenna is used in this test?

In testing you have to move the antennas. So, when testing is the closest antenna to the FS antenna always the same distance apart in every comparison?

I have found in my 1/4 wave base antenna comparison work that neither the SWR nor resonance tends to make much difference due to tuning. In other word my tuning does not show me measurable difference in field strength that I can measure. Maybe the other follow up test you have in mind will indicate something similar to my results.

I know you measure the FS for the ultimate test, but when tuning---is the best value of reflected watts the only thing you have found necessary to consider with a competition type setup?

In my efforts with 1/4 waves, I have found that the ground plane is where I can make changes that show some remarkable results.

I don't generally comment on post about competition issues (no experience), but your report shows some effort, thought, and results. Personally, I do appreciate your good efforts.

[gunslinger338]

Interesting report 338. How would the FS number for a well tuned single antenna respond when compared to anyone of these setups?

What kind of FS meter and FS/antenna is used in this test?

In testing you have to move the antennas. So, when testing is the closest antenna to the FS antenna always the same distance apart in every comparison?

I have found in my 1/4 wave base antenna comparison work that neither the SWR nor resonance tends to make much difference due to tuning. In other word my tuning does not show me measurable difference in field strength that I can measure. Maybe the other follow up test you have in mind will indicate something similar to my results.

I know you measure the FS for the ultimate test, but when tuning---is the best value of reflected watts the only thing you have found necessary to consider with a competition type setup?

In my efforts with 1/4 waves, I have found that the ground plane is where I can make changes that show some remarkable results.

I don't generally comment on post about competition issues (no experience), but your report shows some effort, thought, and results. Personally, I do appreciate your good efforts.



1 . not sure about one antenna

2 . rear antenna is moved , truck was never moved

3. I use a digital fatboy FS meter.. and a skip shooter mounted to a 5 foot step ladder .... 200 foot of rg8 connects the skipshooter to the digital FS meter thats in the truck on the dash

4 . I tune for gain and reflect........... you can make alot of gain .. but 2 much reflect will end your day in smoke... and you lose any way:lol:

[BOOTY MONSTER]

200 feet of coax in a mobile ?
maybe i need to cut back on the :sifone: :punk:

[gunslinger338]

200' of coax connects the digital FS meter to its recieve antenna 200' away:confused:

[Marconi]

BM, I think 338 is using that much to reach out to his FS meter with a Skip Shooter antenna (whatever that is) attached.

[gunslinger338]

a skip shooter is an old fiberglass antenna with an adjustable stinger

Old Skool

[Marconi]

338, years ago I was involved with a group that build tuned co-phase harnesses. We use to see FS results like you are talking about, but that had much more to do with the actual phasing of the harness than with the tuning of the antennas. We use only 102"-106" SS whips in our setups, so there was no tuning for us. We got what we got and used phasing of the harness to make the gains we saw.

From a design viewpoint I think the ideas you guys use today make better gains however. Co-phasing never did prove to be very promissing, even with better harnesses.

Back then we did not really know that much about Velocity Factor. We did suspect that something was involved with the line that was not talked about too much. We later learned that our frequency tuning design accounted for the VF adjustment in these harnesses without our understanding.

[Marconi]

a skip shooter is an old fiberglass antenna with an adjustable stinger

Old Skool


Does that suggest that you have to tune the FS antenna also. I never tried that idea. I just moved around until I could get a mid range on my meter. The comparitive values of readings was all that we looked for. Actually we used a 1/4 of coax shorted at both ends and spiral wound on a 10' wooded dowel.

Thanks for the words. Keep us posted on you next report.

[gunslinger338]

some use these phase harnesses in a mobile set up
2 hots , end fire array ....are the tems these CB guys are using

all of these results are with a grounded rear antenna and coax going to the front hot antenna only

we have one guy around Houston that i know of playing with the 2 hot set-up on a Burban........ he is still tuning

he has been trying it out for the last few weekends
but not luck as of yet to make the gate and get past my grounded rear set up

[gunslinger338]

I dont tune the FS meter antenna.
it was tuned at some point on a truck .....

when used with a FS meter its only function is to recieve

[BOOTY MONSTER]

BM, I think 338 is using that much to reach out to his FS meter with a Skip Shooter antenna (whatever that is) attached.

cool , i thought i was missing something . now i can keep on :sifone: :hurray:

[Marconi]

You are OK BM, not missing out on anything. Without knowing the context of 338 statment, 200 feet did sound a bit long though.

Did you get my PM the other day? At least I intended to write you off forum about something. I was looking around and maybe someone has already posted something about that issue, not sure though.

Hang loose,

[BOOTY MONSTER]

no PM's here and non showing at the other forums i harass , ummm , i mean freequent . LOL
good to see you here though . :)

[Marconi]

BM, I can't remember stuff any more, so maybe I never wrote and then maybe it was Coolbreeze that came to mind.

Sorry,

[BOOTY MONSTER]

:yikes: dont let him know you got us confused !! :cuss: :willy_nilly:
he may never talk to you again !! :seeya:

[Marconi]

BM, it wasn't you guys that got corfused, I suggested that maybe it was me. But you are right, CB may still never talk to me.

[coolbreeze]

marconi, why would you say such a thing.



gun slinger good posting. I know sticks were best at 72. I always suspected 10k's were best at 72.

[Marconi]

I wasn't serious Coolbreeze. I was just carrying-on a bit and I think that Booty Monster was also. I think we got off of 338's issue a bit.

Are you still getting good reports on your Merlin? Are you getting any DX in your area yet? Since "Ike" hit Houston, I'm still without an antenna up. I have been ill and just recently got back on the Internet a little bit.

Thanks for the shout,

[coolbreeze]

yes I am getting good reports still and so is cotton mouth. He is a local here that since he put his merlin up he is talking farther and stronger then any antenna he had up.

[gunslinger338]

I wasn't serious Coolbreeze. I was just carrying-on a bit and I think that Booty Monster was also. I think we got off of 338's issue a bit.

Are you still getting good reports on your Merlin? Are you getting any DX in your area yet? Since "Ike" hit Houston, I'm still without an antenna up. I have been ill and just recently got back on the Internet a little bit.

Thanks for the shout,

i did not know you where around Houston area :confused:
I live on the East side.............. around LaPorte

[Marconi]

i did not know you where around Houston area :confused:
I live on the East side.............. around LaPorte

Yes 338, I live on the NW side. I'm not on the air since the storm. I have not put an antenna back up. I work only SSB and mostly on 38 or 39.

I go by Eddie or Grandpa. If you hang on SSB then you may hook up with Robert and the bunch he talks to over near Lake Houston. I used to talk to Charles in Baytown from time to time also. When times were good in the 90's and before, I talked with buds in East Texas to Bridge City and Orange up to the Lufkin area almost every day. I think Undertaker use to be down in your area somewhere too. When the skip starts back and if I can get well enough, I'll be back.

[duckkiller127]

i currently have a merlin and a I-10K up, they are not at same height yet.. but 10K at same initial feedpoint height as merlin to do some bleedover testing, after that complete then we'll raise the 10K up to the same height as the merlin and do side by side testing

[duckkiller127]

TYPICALLY..72 is best if you are only going to run a 2 antenna system

86" comes into play if you expand to 3,4,5 elements in the future

it also depends on how the antennas being used are designed

[Marconi]

I guess you are going to get the tip heights the same height to test, right? That will be interesting.

If you have a mobile field strength meter that works and you have the time, walk it around under each antenna and check the FS while someone keys up both antennas. Don't use any power except the radio. 5-10 watts should do it if they show anything. Set the meter to max and if both antennas push the meter to max, then back off about 1/2 way on the strongest one and make the test again. I use this test to see if I have any currents flowing on my feed lines.

You might have to get the FS antenna up close to the mast/tower or the feed line to get a reading, because some antennas show a lot of RF down below and others don't show any. You may also find that you have to set the meter down cause your body can effect the meter sometimes. I would be very insterested in what you find if anything.

Here is my Starduster up with my I10K some years ago. I will try to find some old signal reports with those two on it and post them.

http://img259.imageshack.us/img259/576/stardusterandi10kfromfrga1.jpg

[duckkiller127]

I guess you are going to get the tip heights the same height to test, right? That will be interesting.

If you have a mobile field strength meter that works and you have the time, walk it around under each antenna and check the FS while someone keys up both antennas. Don't use any power except the radio. 5-10 watts should do it if they show anything. Set the meter to max and if both antennas push the meter to max, then back off about 1/2 way on the strongest one and make the test again. I use this test to see if I have any currents flowing on my feed lines.

You might have to get the FS antenna up close to the mast/tower or the feed line to get a reading, because some antennas show a lot of RF down below and others don't show any. You may also find that you have to set the meter down cause your body can effect the meter sometimes. I would be very insterested in what you find if anything.

Here is my Starduster up with my I10K some years ago. I will try to find some old signal reports with those two on it and post them.



no FEEDPOINTS...antenna height is measured from the FEEDPOINT this puts the Merlin at a disadvantage, and so far is still showing a distinct advantage...it's all about the design...think outside the box

[gunslinger338]

:offtopic: :offtopic: you guys are killing my mobile antenna thread :D


WTF.........:lol: :lol:

just kidding !!!

[duckkiller127]

no, you are right, i wasn't paying attention to where i was
good results btw, always good to see that stuff

marconi, i have a Merlin thread up, feel free to continue there

[Marconi]

yea, of course. I misread your post.

In the picture the SD'r is about 3" shorter to the tip than the I10K. I did not get as remarkable results as you did, but it was about 50/50 for the most part. Some times it's hard to really tell though, cause guys turn amps off and on sometimes and then the get new stuff at times. If I did the testing today I would try to spend more time doing it and I would do as your suggest, put the feed points equal. I wish I had recorded more info about the stations I checked and distance between.

I try to avoid talking antenna testing on the air. Some don't like it and start to mess with the signals if they can. So most of my comparisons are recording the RX signals I see. If TX information comes in, I record that also or make a note.

Good luck,

[Marconi]

sorry 338, I got carried away and I just commented in another post about that. Shame on me.

[coolbreeze]

338 just report them to the swamp

[coolbreeze]

gunslinger. when you did this test, how did you tune each antenna, by max gain or lowest swr?

[The Shadow]

gunslinger. when you did this test, how did you tune each antenna, by max gain or lowest swr?

Having the lowest (or least amount of) reflected wattage does not mean the selected "antenna" is an efficient radiator of the RF signal being applied. A 50 ohm dummy load is the perfect match for most of the modern day Amateur and CB radio (type accepted) equipment, but it does not make a good antenna as we all know.

In my experiments with multi-antenna arrays the most FWD gain has been achieved on the array with some compromises in the reflected wattages. As an example, 2500 watts FWD with 5 watts REF is only 1.09:1 VSWR. Does that mean that antenna is "optimized" for the best vswr, no. But if 1 or 2 more DB gain can be achieved by allowing the 1.09:1 VSWR to occur then I would accept those losses due to the increased gain from the antenna array.

A 1.09:1 VSWR (example given: 2500 watts FWD and 5 watts REF) is still 99.8% efficient (Rho = 0.04) the -0.2% in efficiency is normally not measurable on the receiving stations side of the communications. Higher losses (meaning more then 0.2%) normally occur from the coaxial cable and connectors on it, all by themselves.

Although this may mean nothing to some, I thought it might be worth posting as an informational notation for those that actually understand it.

[duckkiller127]

Shadow is 100% correct, if vswr was an indicator of how well a antenna works my cantenna dummyload would be the best antenna out there

[gunslinger338]

gunslinger. when you did this test, how did you tune each antenna, by max gain or lowest swr?


check out the second post.........


I understand that you can tune a little more reflect and show a greater forward gain.

In this case I tuned the antennas as close as possible to the same reflected watts .
When the spacing was changed.......... i tuned the antenna right back to the same reflect watts.
When the antennas where changed.......... i tuned the antenna right back to the same reflect watts.

when i got as close as possible the same reflected watts ..... i checked the field strength meter.

[drdx]

Cool comparo. Did you by chance take readings with single antennas on there? I wonder what the difference would be between say one 102 inch whip, then on to the whip and a back door, grounded, then some data on a true 2-hot, fed with a phase delay? I'd guess the phase delay 2 hot(90,135, whatever you use) would be best but don't know for sure. The phase makes a big difference there, and it is something you don't have to fool with on a single hot but I wonder if there is a price for that simplicity in the form of signal? The main benefit I see of the true 2 is that both elements are nicely tuned. With a grounded back door you have a nice tuned antenna for the hot one but the grounded one has a wildcard- the vehicle is adding the other half ++ length to give it reflector quality, and who knows how close it is to being optimum or not. I guess some front to back ratio measuring would help there to determine that.

-drdx

[coolbreeze]

gunslinger, not to argue with your results by any means. The comparison was with spacing and mission acomplished.

I dont have 6ft spacing on the van to do the test you did. I would be interested in seeing what the results would be if each antenna was set for max gain rather thn equal reflection. Reason I ask is just for seeing what happens.

[gunslinger338]

gunslinger, not to argue with your results by any means. The comparison was with spacing and mission acomplished.

I dont have 6ft spacing on the van to do the test you did. I would be interested in seeing what the results would be if each antenna was set for max gain rather thn equal reflection. Reason I ask is just for seeing what happens.

YES....

Tuning any of the above listed antenna sys. for maximum gain may result in a completely different outcome. :yesnod: