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  #11  
Old 03-01-2011, 06:38 AM
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DaveInDenver DaveInDenver is offline
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You're such a geek Nathaniel. :-) I'm also horrible, I mean absolutely terrible, at copying call signs. I have to write them down as I hear them. I'm not sure what the problem is, but I'm pretty sure I'm getting dumber. Maybe there's something to this fluoride in our water thing afterall.
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  #12  
Old 03-01-2011, 08:22 AM
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Originally Posted by CO Hunter View Post
Just a thought based on your pictures. There is some rust and looks like powder coated or painted brackets. Are you sure you are getting good connections and they will stay good?

Funny, I was just up in Albany this past week. I flew in there anyway, meetings in Kingston.
And you didn't stop to say Hi?

I cleaned rust, powedercoat and/or paint underneath the ring.
I used the serrated washer under to dig into the metal.

That said, on the hood, one connection is 1/4" washer which I had, the other is 3/8" which I did not have the serrated washer for it. I since picked some 3/8 and 5/16 washers and I plan to install these soon. I know the hood is really important to bond well.
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  #13  
Old 03-01-2011, 08:23 AM
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Originally Posted by Groucho View Post
I would 2nd that idea of making sure you get metal contact...... Just throwing a piece of bonding on painted parts will not effectively do anything, except maybe keep the bonded part from falling off the vehicle.

Keep trying.
I am only sure about death and taxes.
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  #14  
Old 03-01-2011, 09:27 AM
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I know Dave will shoot me for this, but I also imagine that your particular antenna does not radiate efficiently enough to see huge gains from much of the mobile tricks to reduce noise and increase efficiency. I am not saying they can't make contacts, just that no one should expect it to perform awesomely, especially on the receive end.

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The popular ones tend to be the Hamstick®, and the various copycats. All are very low in efficiency, as their Qs are about 50 or less. A few of the 80 meter models have Qs less than 10! If you want a really lossy antenna, use one of the stubby 3 foot long versions!

Their only attributes are, light weight, low wind loading (some models), and low cost (≈$20USD, less mount). This means they can be attached by just about any type of mount, some of which add to their overall losses (i.e.: license plate mount). Efficiencies range in the .3% to 20% (80 through 10 meters), and they typically don't need matching as the system losses bring the input impedance to near 50 ohms.
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  #15  
Old 03-01-2011, 10:01 AM
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DaveInDenver DaveInDenver is offline
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Nah Nathaniel, I'm a nice fella. Really. ;-)

The Hamsticks are good for what they are, which are compromised mobile antennas. They are not really much worse than any other mobile antenna with the one main downside of having very small diameter coils. But even your Hi-Q antenna is a compromise and on the lower bands relies almost completely on the inductor radiating.

IMVHO the main downside to a Hamstick is they have very narrow bandwidth in general (this is a result of the coil form). They actually have a lot of radiating length, which is good. And they are electrically resonant, which is a good thing.

Don't fall into the assumption that low SWR or wide bandwidth makes an antenna any good at exciting electrons for a given frequency. It's about radiation resistance and uniform current distribution. There is no substitute for physical length and Hamsticks don't fall short there. Also the way they wind the antennas isn't too bad and this really distinguishes a decent antenna from a junk one.

I don't know what definition of radiation efficiency he's using (I assume it's KØBG), I'm not sure he is normalizing the measurement correctly to compare apples to apples. There's good reason why 'good' commercial engineering practice is a field of >120 tuned radials over a physical 1/4 wavelength radiator, this has been found to be what's necessary to guarantee a minimum efficiency over all conditions. Nothing about even a well bonded car is ideal and so they all rely heavily on the distributed stray capacitance to find a return. That's the real efficiency problem, the ground, not the radiating element so much.
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  #16  
Old 03-01-2011, 10:13 AM
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Dave, the fluoride's getting to you again!

I got my Hi-Q because I was convinced that their touting of a higher Q than other similar designs was attractive as a selling point. To each his own. I did, however, notice a dramatic improvement in my noise floor after doing the Same bonding as Rhyary. I did do my doors (all 4) and both upper and lower tailgate. I went from average S-6 noise floor to average S-3. Same location same time of day. No noticeable difference from day to day.

Some say my butternut vertical at ground level is a pile of junk, too, but with 4 radials I was able to hit Japan on 100W, and my house is in the way for that QSO. Make do with what you have, I say. I just didn't want Rhyary feeling the bonding he did was a waste of time.
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  #17  
Old 03-01-2011, 10:44 AM
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No man, I don't think the Hi-Q or Butternut are bad antennas, far from it. But in the Hi-Q example, it's not 20 times better than a Hamstick to justify their price solely on performance. Is it 2 or 5 or maybe 10 times better? Probably somewhere in there. But in electrons excited per dollar, the Hamsticks are clear winners over the expensive stuff. It's the law of diminishing returns. Your rig is about as good as it gets from a mobile standpoint.

Caveat emptor: My ATAS-120A was $250 and is mostly universally hailed as a pile of crap. I don't disagree. I know it'll never win me exotic mobile call signs. It does the job I ask of it and is much better than anything I could build similar to it. Works seamlessly with a minimum of hassle with my radio, for example. All I had to do is run a coax to get wall-to-wall 40m to 6m. In the tight confines of my truck that outweighed a lot of other variables.

You also know anecdotes are not proofs... :-) Someone else with the same conditions that you had to make a 100W contact might have done the same with 2W into a highly efficient dipole. Just hypothetical, but you get the line of reasoning.

I don't think bonding is a waste of time, it's something that you must do if you want any chance of mobile HF. BTW, I forgot to ask about the connection between the battery, 12VDC return, antenna and radio grounds. How are they done? I assume you ran the power supply return all the way to the battery, same routing and length as the 12VDC supply. Then the ground connection between the battery and frame (the frame is your common bonding point, right?). Just the stock battery negative to the engine block? If that's the case, you need to run a decent RF ground, a wire braid for example, to the frame from the battery negative.

Also the radio itself should be connected to the same common point as all the bonding. I ran a short braid from my radio ground lug to the cab floor (my radio body is mounted under the passenger seat). The cab itself is grounded to the frame and exhaust, so any secondary bonding I do, like the bumper, is done to the frame and does not need to run all the way back to the radio. Imagine the truck frame as your earth when comparing it to a stationary QTH. It's good enough electrically to consider it that way, as are large sheet metal panels. Never assume RF can make it past bolted connection, so if you are using a fender or door as a bond point, then that bond must be extended to the common 'earth'. RF can flow over a fender very well, but it will get stymied at the painted, bolted or isolated (like body mounts) connections and become a fantastic capacitor even if it looks like a DC connection.
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Last edited by DaveInDenver; 03-01-2011 at 11:21 AM.
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  #18  
Old 03-01-2011, 11:40 AM
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Groucho,
I don't want to make you feel bad, but my noise level is between S1 to S3.
Are you sure you have it mounted on/in a Landcruiser? :-)

(without the PRE amp. When I click in the pre amp (+12dB) the floor noise level go to 4 or 5.

I just got in a 1"x0.46" x 100 feet tinned copper strap. So I will be doing some more bonding to appease the RF Gods. :-)
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  #19  
Old 03-01-2011, 11:44 AM
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Quote:
Originally Posted by rhyary View Post
Groucho,
I don't want to make you feel bad, but my noise level is between S1 to S3.
Are you sure you have it mounted on/in a Landcruiser? :-)

(withought the PRE amp. When I click in the pre amp (+12dB) the floor noise level go to 4 or 5.
Is that with the engine running? If so, you're pretty much golden. I get that level of noise sitting still with the engine off from the atmosphere, power company and city even with the IPO on. I run with the pre-amp off on 40m and sometimes 20m, doesn't make enough difference in signals to make it worth it.
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  #20  
Old 03-01-2011, 11:52 AM
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Originally Posted by DaveInDenver View Post
Is that with the engine running?
Oh Gowad. You guys are relentless :-)

No, it was not with the engine running. Ran out side to the parking lot to test with engine running. No apparent difference with engine running or not. Same floor level. The only difference is that you hear the pulsing, but it does not change the floor noise.
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