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Old 05-24-2011, 04:15 PM   #1
TXiceman
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Default Comet CHA-250B

Has any of this group used a CH-250B antenna for portable us with the RV?

it gets a lot of mixed reports.

Ken KE5DFR
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Old 05-24-2011, 06:41 PM   #2
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I would avoid any antenna that covers the entire HF spectrum without using a tuner or some other means of matching. The Comet must have a very lossy matching network inside it that allows a short vertical (especially on 80/40) to have an SWR less than 1.5:1.

Will it radiate a signal- absolutely, but you will lose much of your signal in its matching network. It is better than nothing, but probably not nearly as good as a screwdriver with a 108" whip or a 24' vertical run thru a tuner.

They claim that no radials are needed, but say that it should be mounted 10' off the ground, with 33' being optimal. Basically the mast it is mounted on is acting like the ground side of the antenna (think a vertically oriented dipole).

There are no ways to cheat the laws of physics...

Doug
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Old 05-24-2011, 07:26 PM   #3
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I have never tried one on the MH, But have played with one here at home and can't say that I'm anywhere near impressed with it .
Yes it would load all bands spected but was a bit narrow banded.
Doing a side by side with my old 18 AVT (with only a ground rod) the 18 AVT out preformed it (except for 6 of course).
I'd call it better than a dummy load, but not much better.
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Old 05-24-2011, 09:34 PM   #4
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OK. I'm the exception to what a lot of other folks have to say about the CHA 250. I have used one on my motor home for the last couple of years and it has worked very good. IT IS NOT A YAGI. IT IS NOT A VERTICAL WITH 30 GROUND RADIALS. As soon as folks stop expecting it to be something it's not and actually use one, they find it does what it's supposed to do. It does work well without a tuner. It is super simple to put up and take down. Less than 5 minutes each way. I have a Tarheel 200 also mounted on my rig and the Comet has better ears. The Tarheel is mounted to the rear ladder with the whip above the roof line. The Comet is attached to a telescoping pole that is 16 feet long, extended, and attached to the rear ladder. I have a Gap Titan at my stick house that I would gladly trade for a Comet CHA250B. I'm not an engineer but I've been involved with Ham Radio since 1961, off and on, and I know what I expect from my equipment.
Just my dos centavos worth.

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Old 05-25-2011, 06:59 AM   #5
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Our Manchester, CT EOC/EmComm QTH uses 2 Comets. They are on the flat, metal roof about 25' above the ground. There are 100' high HV tension lines about 75yds to our north. We use Kenwood TS-2000s which have built in tuners. That provides a better bandwidth on each band. We have 68 confirmed LOTW countries including Australia, Indonesia and India on SSB. We have 45 confirmations on eQSL. The confirmation to QSO ratio is about 1:20. So, for what it physicaly is, I think the 250B does a good job. It is easy to erect and take down if needed. It may not be as good as other antennas, but for camping and other situations that require portability, it's pretty good.



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Old 05-25-2011, 08:24 AM   #6
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Next question is the 41' S9 antenna?

I am not looking for an antenna that is wonderful, just easy to set up and works to make some contacts while on the road.

I was looking at a short push up pole anchored to the tongue of the trailer with the comet mounted some 10 to 15' above grade.

At home I mostly use my Carolina Windom 80 at 50'. The Butternutt HF9V is ground mounted with 12 radials. I do not expect a compromise vertical to be nearly as good as the base antennas.

I also carry a fan dipole I built for 20 and 40m with a push up pole to mount it as an inverted V. It takes up a lot of room which a lot of the campgrounds do not like.

Ken
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Base unit...Kenwood TS480HX, LDG AT200 Pro tuner, Eagle One Vertical and Windom 80 meter dipole.
Standard Schnauzer..her call is K9WOOF
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Old 05-25-2011, 09:28 AM   #7
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I have a Kenwood KAT-1 auto tuner.. A open "Eye bolt" near the roof line of my motor home, a 12 foot painter's pole, some nylon cord and 2 pound weights.

Just now I'm in an open field, no trees, no poles no ... anything.

I pass one length of cord over the eye, it's tied to a 100' wire a few feet out, the short end goes to the KAT (Kenwood Auto Tuner) The far end hooks to another length of Nylon, it (the cord) loops through a hole in a triangular piece of plywood that is screwed on the painter's pole instead of a roller. Two more lengths of cord, which go through colorful "Fun Noodles" for visual enhancement go from the other two corners of the wood to tent stakes.

I get good signal reports.

If I'm in among trees.. I leave the pole in the pass through compartment (it gets shorter fast) and hook a 2 pound weight to the far end of the cord on the far end.

I do a "David and Golaith" type sling of the weight over tree limbs.. I can easily hit 20 feet. Again I get good reports.

I have one park won't let me put it up.. So I mde a very ugly Slinky type antenna,, ANd put it up instead, it hangs above the motor home on a ladder at one end and a 25 fot flag pole at the other.
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Old 05-28-2011, 10:27 AM   #8
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I use the Comet for our MARS trailer, but not by choice, it was issued to me. It works "ok" but it is clearly a compromise. Also, it does not collapse into itself for portability very well at all. I currently have one section wedged 3' into the lower section and it's not coming out without a hacksaw--still transmits though! I am going to replace it with a multiband hamstick dipole very soon. The hamstick dipole will give me some directionality and can be lowered for NVIS work as well.
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Old 05-28-2011, 05:06 PM   #9
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"I currently have one section wedged 3' into the lower section and it's not coming out without a hacksaw"

Hopefully you haven't used the hack saw yet !
Before you do, try two stout pieces of rope one each double half-hitched around each section with the lower section tied to something solid, the rope on the upper section rope loose end tied into a loop and that hooked to a come-a-long , apply tension and tap the telescoped sections gently with a rubber mallet or wooden base-ball bat, keep applying tension and tapping as they separate.
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Old 05-28-2011, 05:53 PM   #10
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You're right. The Comet will not telescope into itself. The sections, except for the top section, all have screws that hold them in place. The top section telescopes into the section below it and I have a mark at the correct level so there is no measuring. BTW, the rope trick works. Just takes a little patience.

Doc
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