The Avanti Astro Beam antenna

[FPR1981]

Few of these are still on the air today, but if you find someone who set theirs up correctly, I've found they say they performed very well. This three-element beam utilized the Avanti Astroplane in the center as a driven element and was said to have some of the most potent front-to-back rejection out there, better than stacked 3's and 4's. It was advertised as 40dbi front to back rejection with a forward gain of 11dbi.

I have a chance to snag one off of a rental house here in town, and it's missing a hub and elements on one side. The rest of the antenna is fully intact. I see this as an antenna project in my future.

I've seen guys undertake a restoration on these antennas, only to complain about high SWR issues. This is likely the result of them not having a phasing harness. My research is telling me that some AstroBeams came with twin RG59U 75-ohm cables at 6' long, wired in parallel, for an outcome of 35 ohms.

Some other astrobeams came with a single length of RG83U, at 6' long, and this cable was 35 ohms to begin with. It is my understanding that without this phasing harness, optimal SWR could not be achieved.

Anyone ever have one?

 

[KB4MSZ]

It was advertised falsely. To obtain that kind of front to back ratio would require a very short element spacing, resulting in a low forward gain value. A 3 element beam with 9 db forward gain (here excluding the isotropic value) would be the outer limit possible (if possible) with a long boom Yagi.

 

[buddrousa]

They worked that good you could extend the reflector 3/4 inch top and bottom plus fill the reflector with steel wool to make it even better.
Back in the day I could drop most signals into white noise most of the time it was off the back corner not dead off the back. I went from astro beam to moonraker 4 then to a moonraker 6.

 

[FPR1981]

I read where one guy had an Astrobeam and said that he could drop a guy 7 houses down from 30 S-units to 6 with the rejection of this antenna. While it is likely Avanti exaggerated, most users agree the rejection was quite amazing for a three-element beam.

 

[buddrousa]

It was more like 7 blocks in the 70's
It took going to the moonraker 6 to get the same rejection my astro beam had.

 

[FPR1981]

So you're in agreement with the accolades people throw this antenna for its rejection?

 

[buddrousa]

Yes used this antenna for a couple of years before moving to the moonraker series made by AVANTI
The only gain in the moonraker series was the addition of horizontal.

 

[FPR1981]

I'm shocked by the split opinions on this antenna. Actual users loved them. theory experts seem critical.

 

[buddrousa]

Kinda like people that talk about a scanner that has never used the scanner they are talking down. All people have to do is try a astro beam and they become believers.

 

[prcguy]

I had an Astroplane but not an Astro Beam. I think the specs on the Astroplane were way inflated and a Shakespeare Big Stick was a little better. I also have a little experience with antennas in general and 40dB is not going to happen off any kind of Yagi or a Astro Beam or most any other directional antenna. I suspect the Astro Beam front to back didn't exceed 25dB and even that would surprise me.

 

[dispatch235]

I owned several beams back in the day and no matter what all the nay-sayers tell you the AstroBeam was an amazing antenna for it's size,
it was the only beam smaller than my Moonraker 6 that had as good rejection, if not a tad better. I ran several 3 element beams Hy-Gain, Mosley, Comet, and NONE had near the rejection the Astro Beam had.

 

[prcguy]

There is only so much front to back rejection you can achieve and you can't change the laws of physics. I could recall my 1970 stock VW bug did a 1/4 mile in 6 seconds flat, but reality says add 10 seconds to that.

I owned several beams back in the day and no matter what all the nay-sayers tell you the AstroBeam was an amazing antenna for it's size,
it was the only beam smaller than my Moonraker 6 that had as good rejection, if not a tad better. I ran several 3 element beams Hy-Gain, Mosley, Comet, and NONE had near the rejection the Astro Beam had.

 

[FPR1981]

I confirmed this morning that I can go and take down the Avanti Astro Beam and the tower any time I want. The beam needs elements on one side and the insulator hub. If anyone knows of where a hub might be, or has any pointers for me, I WILL be restoring this antenna, and I'm excited as hell.

This is such a cool old relic, and I am confident it will kill a Maco 3 element as long as I get the phasing harness correct. this is like living out my dreams as a CBer. I get to restore a Super Scanner and an Astrobeam. I'm so grateful for all the free CB gear I've gotten this year. I'm not sure why the universe is blessing me with so much, but I will take it, every bit of it.

 

[prcguy]

A MACO 3 element was not designed by engineers, so most any other 3 element should outperform it.

I confirmed this morning that I can go and take down the Avanti Astro Beam and the tower any time I want. The beam needs elements on one side and the insulator hub. If anyone knows of where a hub might be, or has any pointers for me, I WILL be restoring this antenna, and I'm excited as hell.

This is such a cool old relic, and I am confident it will kill a Maco 3 element as long as I get the phasing harness correct. this is like living out my dreams as a CBer. I get to restore a Super Scanner and an Astrobeam. I'm so grateful for all the free CB gear I've gotten this year. I'm not sure why the universe is blessing me with so much, but I will take it, every bit of it.

 

[dispatch235]

I confirmed this morning that I can go and take down the Avanti Astro Beam and the tower any time I want. The beam needs elements on one side and the insulator hub. If anyone knows of where a hub might be, or has any pointers for me, I WILL be restoring this antenna, and I'm excited as hell.

This is such a cool old relic, and I am confident it will kill a Maco 3 element as long as I get the phasing harness correct. this is like living out my dreams as a CBer. I get to restore a Super Scanner and an Astrobeam. I'm so grateful for all the free CB gear I've gotten this year. I'm not sure why the universe is blessing me with so much, but I will take it, every bit of it.

Super Scanners were also a great antenna if assembled correctly. I don't have any degrees, just a lot of on hands experience since I was a young boy when I was fascinated with my Grandpa's Ham and CB radios, and have worked with quite a few old times on antenna projects. Theories and equations don't always have the answer... just as the Dr's don't have an answer how I survived Stage 4 cancer... love to see someone enthused about restoring and experimenting with the classic's, you will love them.

 

[FPR1981]

A MACO 3 element was not designed by engineers, so most any other 3 element should outperform it.

Don't say that in the wrong crowd. I've encountered quite a few Maco 3 element lovers that think the sun rises and sets with their beams.

But, replying further, they probably were designed by engineers, that worked elsewhere, for other companies who brought their products to market and Maco just ripped them off.

Just because Maco didn't design them doesnt necessarily make them junk, but I get what you're saying.

 

[prcguy]

Look at a MACO catalog and the boom length and number of elements. Its the boom length in wavelengths and proper used of elements that maximizes gain. MACO has crazy inflated gain figures and usually way too many elements for a particular boom length. Like most people they THINK more elements is better so they stuff more in. That's how someone with a hobby mentality and no formal training goes about antenna design.

Here is an example with hard facts. M2 antenna company is well known, its owner is an antenna engineer and they are known for the latest in computer design antennas, wringing the absolute most out of them. Their flagship CB antenna has a 46' 3" long boom and 7 elements properly spaced along the boom. You can see the typical and proper design where the driven element has a closer spacing to the reflector then the directors are wider spaced. This antenna is rated at 12.4dBi gain or 10.26dBd gain with a 26dB front to back ratio. That is spot on and if you look at any other VHF/UHF 10dBd gain antenna from a real antenna company they are 7 element and a very long boom looking identical to this one but smaller. Here is its spec sheet: 11M7, 27.10-27.80 MHz

Now look at the largest MACO, the Flat 8 with 40' boom and 8 elements. Its a shorter boom than the M2 by 6 feet but they had to stick another element in there for some reason. MACO claims 18dB gain and "up to" 46dB front to back ratio. They don't specify dBi or dBd gain but even if it was dBi how did they squeeze 5.6dB more gain on a 6ft smaller boom? The answer is they didn't and they lied. I don't know why they didn't just claim 24db gain or 32dB gain and 60dB front to back, its all the same lie. Here are some MACO lies, I mean specs. Maco Antenna Specifications

Don't say that in the wrong crowd. I've encountered quite a few Maco 3 element lovers that think the sun rises and sets with their beams.

But, replying further, they probably were designed by engineers, that worked elsewhere, for other companies who brought their products to market and Maco just ripped them off.

Just because Maco didn't design them doesnt necessarily make them junk, but I get what you're saying.

 

[FPR1981]

I don't doubt that they're BS artists, not one bit. But a basic 3-element beam is tried, true and been around for ages. I'm not an engineer and I could build a 3-element beam that would perform at commercial-levels.

You don't need an engineer title or degree to build a good antenna with tons of design history.

I will give you credit, you successfully talked me out of buying a Maco antenna several months ago. I wanted their PDL-2 knock off but then researched the differences. I'd rather search for a broken old PDL-2 and rebuild it.

 

[WB9YBM]

This three-element beam...was advertised as 40dbi front to back rejection with a forward gain of 11dbi.

Based on the beams I've seen, dealt with, and/or operated so far 40dbi (especially with only three elements) seems a bit far-fetched. Like the old adage says, "if it looks too good to be true, it probably is".

 

[FPR1981]

They all inflated their figures in that era.

Avanti claims 11dbi of forward gain with this beam. Do you find that claim believable?

I mean, Solarcon tries to claim the A99 is 8db when we all know thats total bullshyt.

But, former users of the Avanti say the rejection was as good as a Moonraker 4.