capacity hat expert needed

[BOOTY MONSTER]

BM, excepting that slanted radials do tend to affect the feed point impedance for such setups in a positive way, I disagree with your understanding here. Can you describe the basis for your thinking or experience?

im thinking the amount of loss between 50 ohms and 30 something ohms isn't detectable by human ears on the CB band . when i was a teen i had a radio shack 1/4 wave ground-plane with three horizontal ground elements . the guy that help me put it up had a meter and he said the meter said it was below 1.5 and that was plenty good . i knew absolutely nothing about meters then , it was my very first setup . it did very well just having a old johnson 23 channel tube base on it with the stock johnson desk mic that looked like a green turner +2 but didn't use a battery .

i certainly cant compare results from over 30 years ago to today , but i lived behind the airport outside of roanoke rapids towards littleton and could talk to folks im emporia va pretty consistently . i also didnt keep track of signal strengths , but that was a respectable trip on any stock radio with omni back then so i know a 1/4 wave with horizontal ground elements can be a very effective antenna . i also know there are better antennas . i've read hams say that if both antennas are at the same feedpoint that no vertical omni can beat a vertical dipole unless the dipole is made or installed wrong . and honestly it's not something i care about as its much cheaper and easier to get a 30 ft antenna to a 50 or 60 ft tip than a 1/4WGP . its a moot point to me .

can you explain why you disagree ?

 

[Marconi]

FWIU the ground elements on a 1/4wgp only have to be sloped to get a 50 ohm tuning . they can be horizontal and still get to 1.3 which is still very good , even 1.5 is still quite adequate with a amp .

id try a 36 ft mast with a 108 on top and see if anyone notices , if they do then put a 4 FG mobile on it or try a dual coil 10K ........

BM, I agree with what you say about slanted radials, but I totally disagree with your idea regarding horizontal radials...assuming I'm understanding your setup correctly. Do you know if the old RS 1/4 wave you described had a matching device? Even if it didn't, you might have still seen some reasonable results on your SWR meter. IMO that was probably because you were using a long feed line, which is OK...but such results can also be misleading.

Back in the day I tried to test using similar setups to what other's might use. Such results can be all over the map with a reactive system, and a long feed line can mitigate such responses. I tested using a feed line too. IMO horizontal radials on such a setup will not produce near as good of SWR as you indicate. The antenna will work in a fashion, but this is an example of the problems noted above.

I'll post my old 2006 notes below. This real testing is so we can compare with the models I will make later and post here. These notes are a mess to look at, so don't get all excited. What I did was mount a 102" whip on a 10' foot mast using a mobile mirror mount with a A99 GPK hub for the radials right below the mount. I used a 50' foot RG8u coax to do the real world test. The model for this one is at the bottom.

The first test was without radials,
the second was with one 102" whip radial horizontal,
the third was with one radial slanted down,
the fourth was 2 radials slanted down,
the fifth was with 3 radials slanted down.

The analyzer readings for each test shows the values for frequency, R, X, and SWR at 27.200 mhz, and the another reading is taken at the frequency with the best match I could find. I wish I had done the test for the two and three horizontal radials, but I didn't. I am modeling them however.

I contend that the feed line allows even the analyzer to show results that are better than the models will show. That is the nature of a reactive load with a feed line, and this is why your SWR readings show good results.

View attachment 1_4 wave notes 2006.pdf

I hope you can read and understand these notes. The models are a lot of work, but I'm working on that now and I'll post them soon. Hopefully you'll at least look at the patterns and gain figures for both the 3 radial antennas. I think you'll see the gain, for these models, is not what I disagree with. In fact the horizontal radials show a better gain and angle than the slanted down radials do. The issue for me is the match is far worse than you indicate and suggest will result.

Per you last comment about a 1/4 wave on a mast, I also post here a model for a 102" whip on a 10' mast without any radials, so you can see why that won't work at all, for gain, angle, or match.

View attachment BM's idea for a no radial .25 wave radiator..pdf

 

[BOOTY MONSTER]

BM, I agree with what you say about slanted radials, but I totally disagree with your idea regarding horizontal radials...assuming I'm understanding your setup correctly. Do you know if the old RS 1/4 wave you described had a matching device? Even if it didn't, you might have still seen some reasonable results on your SWR meter. IMO that was probably because you were using a long feed line, which is OK...but such results can also be misleading.

im pretty sure i just had 50 ft of cheap radio-shack coax . the meter wasnt mine , it was a friends . i have no idea about the matching circuit or lack of on the RS 1/4 WGP .

if you're disagreeing with me saying 1.3 should be obtainable with flat ground elements , im ok with that . if you're saying i didn't have good results with it that's ok too . it was maybe 8 or 10 ft off the ground on a piece of old very rusty pipe ..... i certainly didn't make all the contacts others did with better and higher antennas (not to mention a good many had tubes behind the radio) but i recall it doing pretty well . when i moved and got a penetrator up on the roof it certianly did better , but the lil 1/4 wave pulled its weight .

 

[Marconi]

im pretty sure i just had 50 ft of cheap radio-shack coax . the meter wasnt mine , it was a friends . i have no idea about the matching circuit or lack of on the RS 1/4 WGP .

if you're disagreeing with me saying 1.3 should be obtainable with flat ground elements , im ok with that . if you're saying i didn't have good results with it that's ok too . it was maybe 8 or 10 ft off the ground on a piece of old very rusty pipe ..... i certainly didn't make all the contacts others did with better and higher antennas (not to mention a good many had tubes behind the radio) but i recall it doing pretty well . when i moved and got a penetrator up on the roof it certianly did better , but the lil 1/4 wave pulled its weight .

BM, I don't know if you'll get anything out of this, but here goes. I've tried to find someone with the matching information or a drawing for the RS 1/4 wave and 1/2 wave for years, to no avail. I also believe the Hy Gain 1/4 wave had no matching device, and thus the antenna could respond just as you described..workable even though I consider it to show too much mismatch. I doubt very seriously anyone would buy one if they knew that the antenna feed point match was as I describe being problematic, however. I don't have any way of knowing the performance results you saw, excepting for your words, which I can't question. I can only guess the performance was so mediocre that antenna just never caught on, working good or not. And if it did catch on, I've never heard a soul say a word, except for you.

So, my disagreement meant to say that such an antenna would not show the 1.3-1.5 match you described at the feed point (a distinction). I noted why, when saying that a long feed line is capable of covering up much of the mismatch that was sure to occur. I've seen this in the real world testing I posted earlier. Were you able to make any sense out of the notes? Could you see what I saw in the match for the antenna with only one horizontal radials while I was using my analyzer, albeit I was using a long feed line too? Sorry I didn't test it with two and three horizontal radials, but like I said earlier, I have modeled them.

Now the models below will also show similar trends as I noted in the notes above, but the matching results will be much worse. And that is because Eznec indicates its matching results at the source, which represents the feed point. So, don't expect to see the same differences with my real world test vs these models. You should, however, be able to note that the results are across the board worse than my real world results using my analyzer and the trends are similar. Again, IMO this is due to my using a long feed line, which is the difference between the end of the coax and the feed point.

Note that all of these antennas tested and modeled were using 102" x .125" whips. No effort was done to tune these antennas for resonance, but that would not fix the mismatches for the antennas with horizontal radials anyway. Also take note of the current magnitude (in red) for each antenna element. The distance from the element gives some indication of the amount of current flowing in the element. So, when the space is large the current is large and visa-versa. I included a few free space patterns as I checked the Average Gain for each model, but take notice of how bad the model with three horizontal radials looks, it is less than unity gain while the one with slanted radials shows about 2.44 dbi in free space.

View attachment 5943

View attachment 5944

I hope Needle Bender don't mind my Shanghaiing his thread.

 

[Needle Bender]

the apt hes in is shaped strangly so we have to hide the antenna and shape it to fit the under roof.
what if he uses the coax sheild for the down radial like the gainmaster and wiinds a coil choke at 9 feet down?

 

[BOOTY MONSTER]

the apt hes in is shaped strangly so we have to hide the antenna and shape it to fit the under roof.
what if he uses the coax sheild for the down radial like the gainmaster and wiinds a coil choke at 9 feet down?

like this ?

The Vertical Bazooka Antenna - Ham Radio Library

its not a bazooka FWIU .

 

[Needle Bender]

FWIU

fwiu? for what its uorth?

 

[BOOTY MONSTER]

from what i understand

 

[Needle Bender]

from what i understand

ah ok, for what its worth, i didnt understand:blink:

 

[W5LZ]

No, that's not a vertical bazooka antenna. It's a 'sleeve dipole' antenna. It's a fairly old design, been around for a lot of years. The only suggestion I'd make is that a coaxial choke be wound just at the bottom of the thing. there's a lot of voltage on the ends of a dipole and that will tend to cause CMC on the feed line.
They work. Are easier to string up since you basically only need one sort of high support instead of two of them.
- 'Doc

(Call it a "PBA" or a 'Perverted-Bazooka' antenna is you'd like, it's just a perversion of a 'name'.)