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HoosierCardinal
| | Posted on Friday, September 13, 2002 - 7:52 pm: | 
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anyone use or have used one of these old antennas? I know a guy that knows were one is for sale for $150.00 that he claims is new in box. I will find out more and if it isnt sold yet and if it is new in box i might get one just to try out for kicks! |
Deadly Eyes
| | Posted on Friday, September 13, 2002 - 9:43 pm: |
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The Astro Beam was/is an astroplane groundplane mounted on a beam boom. It has a reflector and a director element. Think 3 element vertical Yagi but replace the loaded element with an astroplane antenna.
The primary handicap with these antennnas was that it was strictly a vertical antenna. The gain was decent enough though.
This by the way is a very old antenna design.
DE |
HoosierCardinal
| | Posted on Friday, September 13, 2002 - 11:04 pm: |
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DE.
I know they are a pretty "tight" antenna becasue i used to talk to a fella that ran one and he had to put it directly on me to be able for me to hear and talk to him. If he moved it even a little off of me well, I lost him! I guess guys that still have them will not let them go(ive tried to get 3 diff people try to sell me theirs!) and most of the ones i know of that are still up are in use and are over 25 years old. |
Bigbob
| | Posted on Saturday, September 14, 2002 - 5:24 am: |
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A friend of mine who's a tech has one in alba mich.same condition same price ,but when I produced the green a week later,said he sold it just 2 hrs. before.Said the front to back ratio was normal,but the front to side ratio was amasing!!! |
409
| | Posted on Sunday, September 15, 2002 - 5:14 am: |
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Those antennas were pretty good....a friend of mine a few miles down the road had a 4-element and i had an Astro-Beam. When we turned them back-to-back, we couldn't hear each other at all. The sides were pretty good also. For a 3-element beam, you couldn't beat them. |
HoosierCardinal
| | Posted on Thursday, September 19, 2002 - 2:47 am: |
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Gonna go and see the so called "new in box" astrobeam Friday. He says its an astrobeam but i dunno, i kinda think its not (astroplane maybe??) A guy in Ohio has it. I have a feeling its not what i think it is but ill see what it all amounts to. If its what i think it is well, ill probably get it!!!!
Ill keep you all posted!!!!! |
HoosierCardinal
| | Posted on Thursday, September 19, 2002 - 12:20 pm: |
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The antenna is NEW IN BOX! Never opened and never used!!
Pretty cool id say. I decided to by it so now i have something to tinker on!
Saw one go for 300.00 once on ebay.
Got mine for a LOT less than that! |
Dinker1
| | Posted on Thursday, September 19, 2002 - 1:13 pm: |
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Had one years ago, one of the best, if I could find one right ,I'd put it up and use it. The longer they are up the tighter they get on rejection and forward gain,,, DEAN-- |
409
| | Posted on Thursday, September 19, 2002 - 1:27 pm: |
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They originally sold for about seventy dollars . |
Scrapiron63
| | Posted on Thursday, September 19, 2002 - 2:09 pm: |
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I've run beams from 2 element to 16 element(8 each way), and I think the Avanti astrobeam had the most back-end rejection than any of them. I ran one and knew lots of others that did also back in the 1970s. They advertised it as 40 db front to back and I believe it was better than that. The rejection was comparable to stacked 3's or 4's, which I've ran also. The only negative I remember about the one I had, it was pretty narrow-banded, by the mid to late '70s, we were talking above and below the regular channels, it might could have been broadbanded, but I was ready for a moonraker anyway. I put a new moonraker 4 up and there went the backdoor by 50% or better, but the raker has other advantages, like hoz & vert, more gain, and widebanded. A really tight set of beams can be aggravating if thats your only antenna, it takes a lot of turning to hear the mud-ducks. |
Marconi
| | Posted on Thursday, September 19, 2002 - 5:10 pm: |
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Hey guys, I am real curious about the Astro Beam. Maybe one of you guys that had one can answer how it was made to match with the director and reflector added on to the basic AP?
As I recall the tune on my AstroPlane was pretty much fixed, like a center fed dipole. Maybe you could adjust the element length a bit or work with the cap hat elements at the top, but my old AP had no coil or tuning device on it at all and was a direct feed. The coax just attached to a SO-239 that was mounted on the hub and there was an insulator in the hub that supported the radiator and made the connection. How would this match if the it was just like the stand alone AP with a director and a reflector add?
How say you?
BTW, I would love to have the documentation on this one. If you can copy same, let me know.
Marconi |
Bigbob
| | Posted on Thursday, September 19, 2002 - 5:19 pm: |
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PUT a rotor on the boom also then you can go flat side,hehe. |
Taz
| | Posted on Thursday, September 19, 2002 - 7:27 pm: |
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yeah, dual rotators are cool |
Mack
| | Posted on Thursday, September 19, 2002 - 10:20 pm: |
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one of the most directional beams ever, you get 10% of center and forget being heard by it, my dad ran one in the 70's. |
Tech833
| | Posted on Friday, September 20, 2002 - 12:54 am: |
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Marconi,
Adding parasitic elements to the AP lowers it's resistance and has almost no effect on reactance. The driven element on the Astro Beam is a little longer than a standard AP.
Yes, the Astro beam is a very good directional antenna. No, it is not better than an 8 element yagi or quad. That is a fishing story. |
409
| | Posted on Friday, September 20, 2002 - 5:13 am: |
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The tune was on the driven element. It was mounted on a stud and had room to slide a little for best SWR's. |
HoosierCardinal
| | Posted on Friday, September 20, 2002 - 4:31 pm: |
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How broadbanded is the astrobeam?
I have a Avanti sigma 5/8 and it is not as broad as say a I max 2000 but it seems to go about 25 or so channels above and below the reg 40.. |
Tech833
| | Posted on Friday, September 20, 2002 - 8:22 pm: |
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The Sigma 5/8 is not as broadbanded as the Astro Plane Radiator. The A.P. is under 1.5:1 from 26.0 to 28.0 MHz. |
HoosierCardinal
| | Posted on Friday, September 20, 2002 - 8:27 pm: |
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Tech 833......I know the sigma 5/8 is not as broad i have found out. So the AP radiator reply you made will apply to the astrobeam? |
HoosierCardinal
| | Posted on Friday, September 20, 2002 - 8:44 pm: |
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As a sidenote how do i know weather i have the older 23 channel version of the newer 40 channel version? |
Tech833
| | Posted on Saturday, September 21, 2002 - 1:32 am: |
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The Astro Plane Radiator works about the same when it is configured into the Astro Beam.
23 or 40 channel version? I don't understand. |
Marconi
| | Posted on Saturday, September 21, 2002 - 8:49 am: |
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Hey 833, I just looked at some internet docs on the beam and noticed that it uses a 6' foot, 75 ohm, line transformer to solve the issue of matching.
I also noticed that the driver on the beam does not have the cap hat or the horizontal section above the cap hat. With all that missing it would seem that the antenna is shorter than the grounplane, but I guess the radidator could be adjustable and longer if fact. I hope someone can tell us about all this.
Marconi |
HoosierCardinal
| | Posted on Saturday, September 21, 2002 - 12:18 pm: |
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You dont understand what?
Avanti made 2 version of antennas back then the 23 channel version that were tuned to the 23 cahnnels and the laters ones that were tuned for the newer 40 channels. Think about it.. |
HoosierCardinal
| | Posted on Saturday, September 21, 2002 - 9:18 pm: |
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One question i do have concerns the "matching pigtail". It is made of RG 83U and what exatly does it do for the antenna? I built the antenna today ( I was bored) and tested it out. I couldnt get the SWR below a 2.5 but i didnt have it away from any surrounding things (trees, bushes, my other CB tower with the moonraker 4 and vehicles and the house) and only had the bottom of the antenna like 2 foot off the ground. I think if i had it up and away from anything id get a better SWR. Also what is the likelyhood of the matching pigtail going bad from sitting in a box over 25 years and if it is bad can i replace it with something of the kind? I checked the pigtail on my swr meter with a dummy load and my ranger 3500 hooked inline with about 3 watts carrier and the pigtail had a 1.5=1 swr. I hope the coax is ok but then again who knows after sitting for 25 years maybe its dried out! :-( |
Marconi
| | Posted on Sunday, September 22, 2002 - 12:47 pm: |
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HC, the tuning harness is what I was asking you guys when I questioned what matched the AP GP element in the beam version with the director and the reflector present. I thought the driven element was just a AP GP on a boom, but I find out it is a bit different than I thought.
You may recall that the AP ground plane antenna's top radiator had 2 wires that made a 4 element cap hat with a single short horizontal L shaped element out the top of the cap hat. These parts are missing in the beam.
There are some continuity checks that need to be run on this antenna. There is a warning in the docs that suggests that parts can be broken and affect the tune. This thing appears to be fixed tune, I see no way to tune anything. The tuning harness should probably be RG 59, 75 ohm coax. I don't know about 83U. Where did that # come from?
BTW, I talked to the guy near me about his beam. We measured the driven element and electrically it appears to measure about 23 feet long. It is fed off center, which is typical of a 5/8 wave antenna, so I now believe it is a 5/8 wave antenna. It looks like part of the lower section is turned back on itself sort of like a folded dipole does.
I am not sure but I seem to recall that this beam came out during the 40 channel era when 5/8 wave antennas were getting hot also, so I am not sure there was a 23 channel verson. Maybe someone has a real old one that shows some differences.
Marconi |
HoosierCardinal
| | Posted on Sunday, September 22, 2002 - 10:00 pm: |
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That coax says RG 83 right on the cable. I removed the jumper today and viola'! My match went down to a 1.2! I asked my tech and he told me that back in the late 1970s he helped install several astrobeams and he told me he always removed the coax jumpper because he said it didnt work on the antenna and it wasnt needed. |
HoosierCardinal
| | Posted on Sunday, September 22, 2002 - 11:14 pm: |
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Marconi;
I can remeber seeing an old avanti catalouge at a local CB shop that the owner let me look at that was dated from the fall of 1974 and the astrobeam was new that year so that was well before the 40 channel boom of the late 1970s. |
Marconi
| | Posted on Monday, September 23, 2002 - 5:28 pm: |
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HC, I find in my coax table that RG 83/U is 37 ohm coax. Maybe there are two pieces of coax in your cables harness that are connected in parallel, producing a 74 ohm line. How are the ends made up, with 259's? I took a copy of the AstroBeam docs off CB Tricks site and it refers to this cable as Dual 59-U. Are our docs different?
The Dir & Ref hubs shows to be plastic. Each aluminum element is made up of 4 pieces of tubing, two pieces of are mounted on top and two on the bottom of the hub, making one element. Looks like the hub insulates the top from the bottom in each case. It also looks like that the hub insulates the element from the boom. Are these parts connected electically, or are they all insulated?
The boom is mounted on a rectangle hub (boom hub) made of several pieces of metal & plastic that bolts the pieces together securing the boom to the top of the AP's mast bracket. As in the AP, this bracket includes the feed point SO-239, supports the lower section of the antenna with the two radials and the hoop, and provides a insulated connection to the lower supporting mast. This part, the mast bracket, looks just like the one used in the ground plane. The stinger, however, is not mounted in this mast bracket, like it is in the GP. With the beam, the upper part of the stinger is located on a stud that screws into the top plate of the boom hub. How does the stinger that is attached to this stud connect, electrically, to the rest of the antenna? From the docs, I see no way that the SO-239 can make contact with what is referred to as the driver stud. Also, is the top part of the driver made up of two pieces of tubing?
I mentioned some continuity checks that are recommended in my docs, did you check yours? |
409
| | Posted on Monday, September 30, 2002 - 3:20 am: |
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The top and bottoms of the elements are connected on the inside by a metal strip which connects the two. There is a small cover on the hub which allows access to the jumper bar(connector). The top of the driven element is fed through the plate and bolts that hold the assembly together.It is connected to the bottom or mounting point for the hoop assembly. |
Marconi
| | Posted on Monday, September 30, 2002 - 9:23 am: |
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409, you are describing the strap inside the hubs that hold the reflector and the director at the ends of the boom. That is correct and is obvious from the documentation.
The question is, what is going on with the top section of the driven element, the part that sits on the driver stud on top of the boom bracket.
I see how the lower section with the hoop attached works. This section mounts inside two insulators located on both sides of the main bracket which insulates it from the main hub, the boom bracket, and the mast that supports the antenna.
How does the top element connect to the center conductor and the bottom of the antenna with the hoop? The way I see it, the two plates, four bolts, and driver stud, make up the metal parts of the boom hub. This metal hub is directly connected via another bracket to the main bracket at the bottom plate. This is all attached directly to the antenna supporting mast, which I note above. This is all on the ground side of the antenna.
Thanks for your reply,
Marconi |
Marconi
| | Posted on Monday, September 30, 2002 - 11:37 pm: |
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833, I need some help understanding the Astro Beam. A few days ago you made the following statement, "The Astro Plane Radiator works about the same when it is configured into the Astro Beam." That was a pretty positive statement, so I figure you have had some experience with the AP and maybe the beam also. You may not have the docs but they are available on CB Tricks main page. If you click on Antenna Info at the top of their main page you can select these docs. If you get a chance and have time, see if you can help me out on this one.
I believe the beam's driven element is really not what it appears, and this may warrant some discussion.
If you get a chance to respond I will tell you why. I figure most of the guys could probably care less about this much detail, so I won't waste the space now.
Marconi |
409
| | Posted on Tuesday, October 01, 2002 - 3:56 am: |
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You are correct about the driven element being on the ground side. The antenna is at DC ground for lightning protection. The top element is connected through the plate mount and is at the end of the circuit. The RF is fed into the antenna at the other end of the hoop at the bottom. I have the specs. on the astrobeam if i can locate them. It's been a few years since i have looked at them. |
Marconi
| | Posted on Tuesday, October 01, 2002 - 1:11 pm: |
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409, that is not exactally what I was saying.
You may be right, but I don't see that at all. Look at the troubleshooting tips and note the pictorial continuity checks for the beam. It shows the top stinger and the lower radials and hoop are connected and it should show a short on an OHM's meter. The two down radials and the hoop are set into insulators in the main bracket so they do not touch the ground side at all. However, according to Fig 12, & Fig 13, the driver stud and the top element that sits on top if it, are just siting there. The docs show no connection to the bottom at all. The top part appears to only be connected to the ground side of the antenna, which does not look like a part of the radiating element. So how do you get continuity between the top and bottom of this antenna?
The two piece boom is also totally insulated from the ground and the two ends are insulate from the other. The whole boom looks insulated from the ground. So what does that tell you about the idea that the antenna is at DC ground for lightning protection. The director and the reflector are not at DC ground either based on what I am able to see in the documents.
I understand what you are saying, it makes sense. I just don't see all this with the documents I have. Look again and let me know what you see.
Marconi |
Tech833
| | Posted on Tuesday, October 01, 2002 - 11:40 pm: |
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Marconi,
Feel free to drop me an email. I have no idea what you are asking. I will gladly email my office phone number to you for voice communication if you prefer that to email. |
409
| | Posted on Wednesday, October 02, 2002 - 2:41 am: |
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You are right about the boom , reflector,and director. But the driven element and the hoop are at DC ground. Those other elements don't have to be grounded. The driven element on top is connected to ground also through the mounting plate. |
Marconi
| | Posted on Wednesday, October 02, 2002 - 4:50 pm: |
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409, I know you are correct. My curiousity came about because 2990 got an Astro Beam. It has been years since I saw one and I only recalled that generally it was an AstroPlane with a boom and two elements. However, in looking at the doc's, I noticed that the driven element only looks similar to the old GP, but it is different in ways.
I have one of the GP's so I started checking things out on it. Again, I found it different than the beam. I knew it was direct fed and that is why I always thought it was just a funny looking dipole and I was for sure it was a shortened 1/2 wave if it was direct fed. The AP-GP is reported to either act like or actually be a 5/8 wave antenna and I didn't believe it could be successfully fed directly and still be resonant.
I also discovered that it is a grounded element. That surprised me also, considering it is direct fed with no matching device. I also discovered that the stinger, with the cap hat, has an insulated stud in the bottom end, where it screws into the insulator on the main bracket. It is not electrically attached to the rest of the antenna and that really took me aback. I did not tear it apart to check it, however.
409, what do you think?
Marconi |
Marconi
| | Posted on Saturday, October 12, 2002 - 7:37 am: |
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Hey 409, if you have time maybe you could follow up on this thread. I still have questions and just today 10/12/02, I note another thread about this good old antenna.
I still have questions and few answers.
833, you suggested I email you for you phone number, but your provile has no address. How?
Marconi |
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