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**k6sti** · 08-18-2015, 09:03 AM

Compare forward gain and F/R for the Stellar Labs and FM-6 here:

http://ham-radio.com/k6sti/curves.htm

The gain curves do not include balun loss. Loss for the balun commonly used with the FM-6 is 0.85 dB. I don't know the loss of the integral balun in the Stellar Labs antenna. If it is as low as I've ever measured, the difference would be 0.35 dB. That would bring the FM-6 and Stellar Labs gain curves quite close at around 4.5 dBd. Except for the Winegard HD-6000, this is the lowest gain figure among all directional FM antennas modeled. The Stellar Labs antenna has the distinction of having the worst pattern among all antennas modeled.

I wrote a review of the Stellar Labs antenna that consisted solely of links to the antenna writeup and the comparison graphs with no comments. To submit the review, I had to select choices for value and quality. I checked poor for both and submitted the review last week. MCM has not posted it.

I tried various tricks to try to improve the performance of the Stellar Labs antenna, as I had done for the FM-6. Nothing worked.

I think this poorly designed antenna is a waste of time and money. Built something decent yourself. For example, a two-element circularly polarized cubical quad has a boom length of 25" and 1-2 dB greater forward gain for common right-circular signals. It will receive vertically polarized signals the Stellar Labs cannot, and it can attenuate multipath distortion. You can build it from cheap parts available at any hardware store.

And for those of you who think high-priced InnovAntennas FM antennas may offer exceptional performance, check this out:

http://ham-radio.com/k6sti/fmdx-9.htm

Brian

**mwdxer** · 09-07-2015, 10:46 PM

Brian, the overall gain on some of these are better than the FM6, but they have horrible F/B. I agree, our only choice to build one ourselves. I am thinking of trying to build 10 element yagi described on your site, if I can find the parts. The PVC idea is fine, but not in a windy area, too heavy. If I could find the boom on some old TV antenna, I could then get the aluminum or copper to build the yagi. Solid aluminum is less expensive than hollow at Home Depot, at least at ours. Can you use brass elements on an aluminum boom? I have not seen that mentioned. That could cost less. I have used the brass/copper piping for ground rods for year here. They last nearly forever. Much better than the copper-clad stuff Radio Shack sells and the brass piping is much cheaper.

**Damon Hill** · 09-23-2015, 03:22 AM

Channel Master has discontinued it's three-element Yagi, the CM-3026 and no longer offers any FM-only antennas.

Why doesn't FMDXAntenna offer a real FM antenna, like they apparently once did? Their name is an oxymoron. It's an opportunity for someone to pick up what's left of the market (assuming there is one beyond a handful of enthusiasts, like us).

**Guest** · 11-22-2015, 09:42 AM

My home brew FM antenna built from Mike B. specs of the CM stereo probe 9 has been taken down for repairs after a wind storm here last week. I ordered the stellar labs antenna to have something to replace it until I can get the supplies to rebuild my own. I agree, no one is producing a decent cheap fm antenna now. So I ordered last night from Amazon.com 50' of 3/8" aluminum auto fuel line tubing, a tubing bender able to do 180 degree curves, and 8 2"x3" plastic sheets to use as the boom insulators for the 4 folded dipole directive elements. Building (or rebuilding my own) seems the only alternative to the present market conditions.479923_10200483938210511_1735930526_n.jpg CM 4408_2.jpg CM 4408_3.jpg CM 4408_4.jpg

**k6sti** · 11-22-2015, 10:21 AM

The Probe 9 has decent forward gain but its pattern is poor. F/R barely rises above 20 dB at the center of the band and drops as low as 12 dB elsewhere. I'll bet the antenna was designed in the days when the FM band was uncrowded and co-channel or adjacent-channel interference wasn't much of an issue. You can compare the performance of the Probe 9 with that of other antennas here:

http://ham-radio.com/k6sti/curves.htm

That's a beautiful antenna you built! I'm sorry to hear that it requires repair.

Brian

**Guest** · 11-22-2015, 11:20 AM

Thank you Brian. Your site was a big motivator and probably the chief reason why I decided to build my own. Why not try it I thought 3 years ago.
Unfortunately the longest folded dipole DE (74" tip to tip) insulator cracked at the boom mounting point due to wind loading last week.
New design plans are in the works.
I am debating if I should keep the tubing round and not flattened at the elements-phasing interconnection points? Does it matter? I am thinking that uniformity is important for best impedance matching? Solid no seam tubing will be easier to drill holes thru than split seam elements.
Also... My original build has the spacing in between the dipoles at about 1 1/2". While Mike B.'s spec sheet said the original antenna elements were spaced about 2 1/4" apart. Again..does that matter?

Can anything else be done to improve front to back ratio numbers? I ask because I am in between 2 FM stations on the same frequency and the one I want to receive (furthest one away of course) is drowned out by the local one. Of course they are 180 degrees apart.

**k6sti** · 11-22-2015, 11:54 AM

Bill, I have repaired broken antenna mounts with PVC or ABS cement (I forget which), the stuff that melts plastic. At other times I have held broken mounts together with additional parts like old perfboard screwed into the mount. That was a thorough kludge, but it worked. Currently I have a broken reflector reinforced with a popsicle stick. Whatever works.

If you want a better pattern, the best option is to use the parts you have to build a different design. Check my website for several that use 3/8" elements, the diameter of the tubing you already have.

Flattening tubing shouldn't matter electrically. I'm not sure about the folded dipole spacing. My guess is that it's not that important for the Probe 9.

I checked the FCC database and 19% of the FM stations in Colorado use vertical polarization. That's an unusually high percentage. Before you settle on a new antenna design, you might check that the stations you want to receive transmit either circular or horizontal polarization.

Brian

**Guest** · 11-23-2015, 05:13 PM

Brian, my target FM station of choice is KBCO 97.3 Mhz Boulder, 92 miles north at 340 degrees from my site. (Via FM Fool web site.) The interference is 20 miles south, Pueblo at 160 degrees (transmitting circular polarization). I checked with the FCC database but cannot find KBCO's transmitter polarization info. Where / how can I find it? Probably a futile effort anyways, given my situation and distances involved, right? I am right smack in between them. Bill

ps...Guess I should have read your write up on Quads first! Thanks for the background, you are a wealth of information. I will contact the station engineer at KBCO for details. Bill

**Guest** · 11-23-2015, 05:27 PM

Brian, my target FM station of choice is KBCO 97.3 Mhz Boulder, 92 miles north at 340 degrees from my site. (Via FM Fool web site.) The interference is 20 miles south, Pueblo at 160 degrees (transmitting circular polarization). I checked with the FCC database but cannot find KBCO's transmitter polarization info. Where / how can I find it? Probably a futile effort anyways, given my situation and distances involved, right? I am right smack in between them. Bill

**k6sti** · 11-23-2015, 05:31 PM

Look at the horizontal and vertical powers in the FCC listing. KBCO is mostly horizontal, transmitting 94 kW at that polarization. Though closer, K247BP, the Pueblo station, is only 250 W. Unless you're shadowed to KBCO, I would think you have a good chance of receiving it if your antenna has reasonable rear rejection.

I see that KBCO runs HD Radio. You might be able to receive it that way even if K247BP is stronger. I've done it here.

Brian

**John Wilke K9RZZ** · 05-07-2016, 08:47 PM

I just put mine up today and I think it's working okay for a 4 element beam. My space is very limited (I've got it indoors!) and there isn't much selection on the FM beam market, so I figured I'd give it a whirl. It's currently on a 3 ft tripod in a spare, second floor room ... far from optimal, but pointed towards Chicago 75 miles away, shooting through a wooden roof, I've got good copy on all the powerhouse stations, and most of the medium powered ones. At my old house I had a stacked pair of Winegard 6055p's, and I know there's no comparison, but at least I have some directivity to work with.

**k6sti** · 05-08-2016, 08:05 AM

p.gif

This compares the Stellar Labs antenna with a 4-foot wire loop, both 12 feet above ground.

http://ham-radio.com/k6sti/stellar.htm

http://ham-radio.com/k6sti/cploop.htm

Brian

**John Wilke K9RZZ** · 05-09-2016, 06:35 PM

Wonderful. I'm hearing what I want to hear. I'm happy.

**k6sti** · 07-11-2016, 12:37 PM

I have tried several times to improve the miserable performance of the Stellar Labs Yagi by shortening elements (not lengthening them, so that you can still use existing elements), but nothing ever helped. Today I found that adding an element to the existing boom improves both forward gain and the pattern. This still does not turn the antenna into a decent performer, but it helps. Take a look at the curves to see if you think it's worth the trouble. Note that the gain curve includes an estimated loss of 0.75 dB for the integral 75:300Ω balun, the value I typically measure for small ferrite baluns.

http://ham-radio.com/k6sti/stellar.htm

Brian

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STELLAR LABS 30-2460 FM "YAGI" Antenna

STELLAR LABS 30-2460 FM "YAGI" Antenna

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