Comet CH-32 Miracle Baby - saved my 1040/500/106 !

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nanZor

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Long story short - I *should* have tried this long ago on my Whistler / GRE / RS handhelds here in strong-signal jungle of Los Angeles. I don't know why I waited so long. The antenna has been mentioned forever here, but I just wanted to reiterate how happy I am with it.

I just picked up a Whistler 1040, which as we know is basically the same as the GRE PSR500 and RS Pro106, have super hot front-ends. Can be a struggle in my location at times. I sold my other two, a PSR500 and Pro106 a few years ago and I guess had some seller's remorse. :)

Cut to the chase - I primarily wanted to monitor 927mhz amateur repeaters with it, but NO amount of custom antennas, long to short, resonant or not, with or without attenuation, made it possible. 800mhz reception was ok with some finagling of antennas and attenuator, but 900mhz? Nothing but trashy noise.

Pulled the Comet CH-32 out of a drawer and bingo! 800 / 900 mhz is nice and clean. Low/high VHF/UHF is good, but obviously strong signals are preferred.

Something is going on here that goes just beyond being small. Using a 3 inch paper clip didn't cut it either. Neither did the RS 800mhz duck with or without attenuation.

When you put the Comet on an analyzer, you'll see it has a **VERY** narrow bandwidth, much narrower than your average duck, and it is resonant at 900 mhz! I don't have the gear to analyze the 900mhz factors - if someone does, I'd love to know what it looks like!

I don't think resonance is all there is to the matter. I believe that the very very narrow bandwidth for amateur 2m / 440mhz (yet still usable in coverage overall in strong signal areas) is presenting a huge reactive impedance to whatever is driving the front-end amp nuts out of band. I suspect something in the VHF band actually.

I guess what I'm trying to say is that whatever the Comet CH-32 presents to the front-end of a Whistler / GRE / RS handheld is an effective tuned circuit - not just an attenuation factor with a small antenna.

While 800mhz wasn't my intended target, it sounds good. But primarily the 927mhz 33cm amateur band is really working now on it!

I can walk through hot-spots at 927mhz just like my Uniden 396 with a full-fledged Laird 900mhz half-wave duck and they sound similar.

Realistically, I'll be using the Comet CH-32 for 800/900 monitoring, and something a bit larger for my low/hi vhf and 440-485mhz UHF comms.

Just wanted to share my enthusiasm finding something that worked after all these years to tame the front end of a Whistler 1040 / GRE PSR500 / RS Pro106 here in L.A, beyond mere attenuation.
 

iMONITOR

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I've been promoting the Comet CH-32 Miracle Baby antenna for decades. I live in Macomb County, Michigan, surrounded my a 9-tower P25 simulcast system. The CH-32 solved the multipatch distortion issue very well!
 

nanZor

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iMonitor - YES! I had never used it for scanning, but just stealth amateur radio.

You'll love this testing I did - although you probably know it:

I have an absolute FLAMETHROWER data signal near me on 152.360. It finally dropped at 1am after going nonstop for who knows how long...

When the flamethrower stopped, the Whistler 1040's front end seems like normal on 927 mhz. No more crazy S-meter activity with no carriers, although the random spread-spectrum and other junk just *tickles* the s-meter to 1 bar very very sporadically. Actual signals sound much better, but once this flamethrower comes back up, I'm toast without the Comet.

TEST:
1) Entire drawer full of ducks from years of scanning. Short, long, multiband, even narrowly tuned airband, milair, classic RS 800mhz duck, even racing "bullets" smaller than the Comet.

2) *ALL* of my ducks provided full-scale reception of my local flamethrower on 156.320, including the racing bullet. Including just getting my pinky finger about 1/4 inch away from the bnc.

3) Only the Comet CH-32 attenuated the vhf flamethrower to absolute nothing!

4) Comet also made NOAA reception impossible. Except for signals very close to the 2 meter amateur band (144mhz), VHF hi was practically non-existent. Other antennas, even those resonant on 2 meters or even other bands like 220 mhz, was still able to produce relatively strong signals along with my flamethrower. Only the Comet stopped it.

5) On UHF (from about 420 to 460 mhz), the Comet had good reception. But going further, say 480 to the upper T-band like 512 was very attenuated.

6) 800 - 930+ reception on the Comet was just great. I even tried it on my Uniden 396xt, and lo and behold, even with that, background noise which was tolerable, was gone! So the Comet is also going to be used with the Uniden's with their included sma to bnc adapter.

Conclusion: A GREAT antenna for reception of 800/900 with scanners, regardless of whether you are an amateur or not. The very narrow tuning provides much needed attenuation of VHF and UHF crud outside of the amateur bands, nailing common troublemakers like NOAA, pagers, and others on both vhf and uhf, vhf especially. Amateur who need a small antenna, and plan to stick to the amateur bands will like it, but man, it really shines as a natural filter for broad-band scanner front ends if you just want to listen to 800/900.

It seems that there is much more going on other than tuning, but I just don't have the gear to analyze it properly, other than making bench observations. Again, it beat out a "bullet" antenna that I got with a racing scanner that is actually smaller (and doesn't even seem to be resonant anywhere), which heard the flamethrower just fine!

I'm stoked. Had I tried this sooner years ago, I wouldn't have sold the Pro106 and PSR 500. I was surprised that it even improved the Uniden too. Not as much as the Whistler to be sure, but I'm sure going to use them on them now! At least for 800/900 reception. More common ducks will be used for my hi-vhf, and uhf stuff until I find a very narrowly tuned duck that is a tad longer. Or until we find out why 152.360 seems to be running 5kw to an 8-bay array a few miles from me. :)
 
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jonwienke

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Your 152.360 "flamethrower" is a pager transmitter, and they are notorious for running high power. If one of them is nearby, you either need a receiver with good filtering, or to attenuate the freq with an antenna or filter to hear anything else.
 

nanZor

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Precisely!

Since the Comet CH-32 is basically a very narrowband 2m/70cm amateur dual-bander for tx (up to 10w), and 900mhz resonant rx, it is doing a GREAT job filtering / attenuating anything much outside the amateur bands, with full 800-960mhz reception on rx-only as an added bonus. But yeah, only an inch high we're talking local comms, or scanning high-powered stations.

So unlike other ducks, even ones that are resonant elsewhere (like my airband Icom duck, or even 220mhz ducks), the extreme narrow tuning of the Comet is acting like a very broadband filter allowing the front-end of the Whistler to cope at 800/900.

Other small amateur dual-band ducks don't seem to have the extreme narrow tuning that the CH-32 has. It's not just the small size. Would love to cut one open and/or put it on a REAL analyzer up to 1ghz.

A lot of antennas tout their "reception only" ranges, but like a paperclip, it too is broadband with a lot of ranges. :) I think Comet's spec for it's ranges is pretty close to reality.

At least now I know the freq to order for say a PAR filter for my desktop scanner with it's wide open front end. :)
 

jonwienke

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I have one about 1000 feet from my house, and my 436 handles it pretty well connected to an ST-2, except for a few adjacent frequencies.
 

nanZor

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scanmanmi - wow, that is fantastic!

I had done the simplistic 1/4 w open stub hanging off a tee-connector at the back of the rig before, but never thought about using two or more separated by a half-wavelengh.

I was totally surprised by the measurements - I had always assumed that when two stubs are used, that in reality the 2nd stub only provided 3db or so improvement of the notch. BUT this measurement of about 10db blows my mind.

Holy cow - may have to cobble up some tee-connectors, spare coax, and a sharp pair of dikes to try this out. Awesome.
 

KB7MIB

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How well does this antenna work at 700 MHz? I'm using a PSR-500 myself.

The Phoenix metro area has two 700 MHz LSM systems that carry the majority of city police and fire communications. The IR sites have limited usefulness in allowing people to listen to what most people want to hear, with most of the comms of interest being on the simulcast sites.

John
Peoria, AZ
 

nanZor

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I don't do any 700mhz monitoring, but all things being equal, taming the front end amplifier overload on vhf/uhf should do well.

But stay tuned - I was so happy with the very narrow tuning that I took a chance on it's bigger brother - the Comet SMA-3.

In a word - FANTASTIC. Same narow response calms the front-end, but the slightly larger element provides enough exposure so that I can listen to other out-of-band comms like airband, and so forth - albeit with reduced sensitivity as compared to a broader-band duck, but at least they are there, whereas with the small miracle-baby they are just gone.

I'll be writing up a report on it and posting it here shortly.
 
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