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Author Topic: Little Tarheel II installation  (Read 8083 times)
M6GOM
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« Reply #15 on: October 30, 2012, 01:34:29 PM »

I thought that but when I bonded the hood to the strut top, the resonant point dropped almost another 100kHz.
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WX7G
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« Reply #16 on: November 01, 2012, 10:00:44 AM »

The antenna choice is narrowed down to the Tarheel 40A-HP or the Scorpion SA-680S (shorty). It all depends on if I want 80 meters or not. On 40-10 meters I believe these two antennas perform the same. These two antenna are both rated for 1500 watts.

I had considered the Tarheel 75A but the photo shows what looks to be close-wound enameled wire. And it needs no base matching inductor, which says it is lossy on 80 and 40 meters. And it is rated for only 250 watts. The Tarheel 40A-HP has a base matching coil and that says it not as lossy.
« Last Edit: November 01, 2012, 10:05:21 AM by WX7G » Logged
M6GOM
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« Reply #17 on: November 01, 2012, 02:05:51 PM »

I would say that is an accurate assessment of the situation in regards to choice and efficiency.   Grin

I don't think I'd really get too hung up with 80m. Any contacts you make on that band are literally proof QRP works even though you're throwing 100/200W into the antenna.

I don't think I'd want the Scorpion on a K400 or any other lip mount. At 13lb it is over two and a half times the weight of the Tarheel and at 28" retracted, almost twice the length.
« Last Edit: November 01, 2012, 02:36:50 PM by M6GOM » Logged
WX7G
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« Reply #18 on: November 02, 2012, 08:51:07 AM »

The Hi-Q Piranha antenna looks good too. It uses silver plated coil wire while the Scorpion uses tin plated wire. The RF resistivity of tin is four times that of silver. I can mount this in the middle of the hatchback using a Breedlove mount and a bracket at the top of the hatchback.

The antennas in the running are:

Hi-Q Piranha
Tarheel 40A
Scorpion 680S

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WN2C
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« Reply #19 on: November 02, 2012, 09:25:23 AM »

680s. You won't be sorry!
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WX7G
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« Reply #20 on: November 03, 2012, 05:47:41 PM »

I have the Comet antenna mount on the top of the left rear door, the power cables installed, and the 17 meter HF Stick tuned. The TS-480HX is mounted near the top of the dash and the paint is drying on the keyer paddle holder. Now to bond the doors, hood, and hatchback. And there's no noise ignition noise.  

Given my 6.5' garage opening, and wanting to simply remove the whip (quick disconnect) and keep the screwdriver on when parking, the antenna choices are the short Tarheels. They are 18" tall when fully retracted. The Tarheel 40A-HP and 75A are in the running.
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WX7G
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« Reply #21 on: November 06, 2012, 12:14:48 PM »

OK, the Tarheel 40A-HP is on order. My calculations show that in my installation it will be about 2 dB better on 40 meters than the Tarheel 75A. And better 40 meter performance is the primary goal of this antenna and transceiver installation.
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M6GOM
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« Reply #22 on: November 07, 2012, 04:50:00 AM »

I'll be ordering one myself soon as well to replace my Little Tarheel II after discussing the same options with Robert @ Tarheel.
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WX7G
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« Reply #23 on: November 07, 2012, 05:58:43 AM »

That should be a nice improvement over the little Tarheel.

For 80 meters I will use a loading coil attached to the top of the Tarheel 40A. That will work much better than the Tarheel 75A.
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K0BG
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« Reply #24 on: November 07, 2012, 06:21:21 AM »

It may be advertised as silver plated, but it isn't. And all of the metal mass within the filed of the coil, places the HiQ near the bottom of the list.
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WX7G
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« Reply #25 on: November 07, 2012, 09:50:27 AM »

Alan, yes I recall you saying before that the Hi-Q has large metal end caps that reduce the Q.

With the Tarheel 40A the coil is tin plated copper and that's not good for Q. The Q might be only 100. For 80 meters the added top loading coil will be #14 copper and about 3.5X the inductance of the Tarheel 40A coil. In my installation that should make it a better 80 meter antenna than any of the Tarheel or Scorpion antennas. The antenna will be mounted at the roof line of an SUV, putting the top 13.5' above ground. The only improvement from there is a top hat 6' above the loading coil.
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WX7G
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« Reply #26 on: November 07, 2012, 11:57:47 AM »

But how thick is the tin plating on Tarheel and Scorpion coils? At 3.5 MHz unless the plating is over 5 mils the copper under the plating carries the RF current and the coil Q is set by the copper and not the tin. With thin tin plating the Q would be 300-400 rather than 75-100. If that is the case my Tarheel 40A plus homebrew 80 meter copper loading coil will be equivalent to the Scorpion 680S.

What is the plating on the Hi-Q coils? Whether silver or tin if it is thin enough the coil is essentially copper on the lower HF bands.
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WX7G
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« Reply #27 on: November 07, 2012, 07:04:02 PM »

I did some research and for the tinned copper bus wire types I found the plating thickness is less than 300 u inches. One skin depth of tin at 28 MHz is about 2000 u inches. So, if the tin plated coils in the screwdriver antennas use this kind of tinned copper wire most of the RF current flows in copper and not tin. The coils are essentially copper.
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WX7G
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« Reply #28 on: November 13, 2012, 08:24:36 AM »

The Tarheel 40A-HP arrived yesterday and is installed.

Based on impedance measurements performed without the base matching coil the Tarheel 40 meter radiation efficiency is 5 to 6 dB better than the ATAS-120. Add to that the new 200 watt transceiver and my 40 meter signal is improved by 8 to 9 dB.
« Last Edit: November 13, 2012, 08:43:26 AM by WX7G » Logged
KF7NUA
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« Reply #29 on: November 13, 2012, 11:48:12 AM »

That should be a nice improvement over the little Tarheel.

For 80 meters I will use a loading coil attached to the top of the Tarheel 40A. That will work much better than the Tarheel 75A.

Will this be a home brew loading coil or ?
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