eHam

eHam Forums => Mobile Ham => Topic started by: KH6AQ on October 27, 2012, 05:05:49 PM



Title: Little Tarheel II installation
Post by: KH6AQ on October 27, 2012, 05:05:49 PM
I'm installing a Little Tarheel II and plan to use a lip mount on an SUV hatchback. What is the better mount for this? A Diamond K400 or a Comet HD-5?


Title: RE: Little Tarheel II installation
Post by: KH6AQ on October 27, 2012, 08:21:13 PM
Now I'm thinking the Tarheel 75A or the 40A-HP would be much better but that might looks like too much antenna for a single K400 mount. Perhaps a support tube from the antenna to the hatchback 16" up from the K400 would stabilize it. Any ideas?





Title: RE: Little Tarheel II installation
Post by: W9MMS on October 28, 2012, 04:11:23 AM
Any ideas?

The best suggestion I can offer is ...... www.k0bg.com

Be ADVISE... Lip mounted Antenna of any substantial size do put stress on the sheet metal.

 http://www.k0bg.com/antmount.html

Interesting Pics .....  ::)

http://www.k0bg.com/gallery2/main.php?g2_itemId=2220


(((73))) Milverton.



Title: RE: Little Tarheel II installation
Post by: KH6AQ on October 28, 2012, 07:38:26 AM
Thanks, I did look at Alan's fine website and poked around the web looking for other ideas. I found one installation method that might work for me without too much trouble. What with air bags, plastic body parts right were I would like to place a bracket, and not wanting to drill many holes where they would be seen makes it a challenge. Using the aluminum plate method from one website and Alan's info on Breedlove ball mounts has directed me to a tentative solution with two visible screws in the vehicle body.  

I have narrowed the antenna choice down to the Tarheel 75A mounted with the base at roof level. That puts the top of the lower mast section just low enough to make it in the garage with the whip off.


Title: RE: Little Tarheel II installation
Post by: M6GOM on October 28, 2012, 12:43:23 PM
I have a Little Tarheel II with a 72" whip mounted on a Diamond K400. It hits a tree twice a day when I go out, goes under low height barriers at drive-thrus and it has survived 70-80MPH headwinds with me doing 70MPH into them.

You WILL need to do bonding between the hatchback and the rest of the car.

Here's my install: http://s300.photobucket.com/albums/nn9/computershack/Amateur%20stuff/Icom%207000%20install/


Title: RE: Little Tarheel II installation
Post by: AC4RD on October 28, 2012, 04:34:20 PM
I have a Little Tarheel II with a 72" whip mounted on a Diamond K400. ...
Here's my install: http://s300.photobucket.com/albums/nn9/computershack/Amateur%20stuff/Icom%207000%20install/

Very interesting!  Did you reinforce the roof of your car to help support the antenna?


Title: RE: Little Tarheel II installation
Post by: M6GOM on October 28, 2012, 05:45:16 PM
The Little Tarheel II is actually on the tailgate - there's a 5" or so metal strip going from left to right above the glass. No strengthening.  So far it has been on there for 10 months and there has been no warping although I had to bend the little tag on the mount that sticks out slightly to prevent it pushing the mount over to the left as the tailgate sits just very slightly below the edge of the rear quarter panel. It would've been in the middle of the roof except they use some gloop for sound deadening that you can't get off so I couldn't re-enforce it and guarantee a good "ground" connection. On the MK3 Mondeo I had, the previous version, I didn't reinforce the roof and although it didn't bend, if you removed the mount you could see where the clamp underneath had pressed into the roof. Didn't warp the roof at all although I suspect it was thicker.

The 5/8 wave 2m antenna that is on the roof doesn't have any strengthening and again has been on about 10 months.

After having it installed through the roof on the previous car, I'd have preferred to do it the same way again. I use a BetterRF screwdriver/tune controller for my Icom 7000 which is sensitive to common mode and there was a fair bit on it with the K400 install which wasn't there at all on the previous car.

Whilst it seems to work OK and I've had no problem getting to VK on 20m it is always in the back of my mind that it probably isn't working as well as it could do using that method of mounting. Sometimes it just seems harder to make contacts than it used to do in the previous car but as I changed from a Kenwood TS480 as well at the same time I'm not sure how much of that is the poorer TX audio. I used to get people who'd say "wow I can't believe you're mobile" and that seems to have been lacking a bit.


Title: RE: Little Tarheel II installation
Post by: KH6AQ on October 28, 2012, 05:55:43 PM
Thanks for the great information.

On my Kia Soul there is a stout lip on the side of the hatchback that a K400 could attach to. Everyone seems to do quite well mounting the Little Tarheel II on a K400. I'd like to use the heavier 75A though (5.5 lbs. vs 1.9 lbs.). The 75A lower mast length is the same as the Little Tarheel II but with a larger coil diameter. With the lower mast being mounted below the car roof level it is shielded from direct wind force and the K400 might work.

Another idea is to use a Breedlove Ball mount with a 4-1/2 inch backing plate mounted to the hatchback sheet metal. That is rather "bendy" though and I have to drill five holes in the hatchback.

The Little Tarheel II looks good but the specified power rating isn't high enough for the 200 watts CW I will be running. The 75A is rated for 250 watts while the II is 200 watts PEP and 50 watts in all other modes. On the other hand the II power rating is with the 34" whip and with the 72" whip should be higher (radiation resistance is higher, coil current is lower, and less coil is used which means less loss). So maybe I can get away with 200 watts CW to a Little Tarheel II. Now it comes down to radiation efficiency. How much better is the 75A vs the II?

I'm looking for better 40 meter performance than I am getting with 100 watts to an ATAS-120. While I can work Asia from Utah on 40 meters it could be better. And I would like to give 80 meter mobile CW a try. If not for 80 meters I'd go for a Tarheel 40A-HP rated at 1.5 kW.





Title: RE: Little Tarheel II installation
Post by: AC4RD on October 29, 2012, 04:18:24 AM
On my Kia Soul there is a stout lip on the side of the hatchback that a K400 could attach to.

Ah!  I just bought a Kia Soul a month ago.  I've had an HF antenna (Hustler system) on the hatchback until this weekend.  I wasn't satisfied with the hatch for long-term mounting, though; it's awkward and I was concerned about warping the hatch.  It also cost me some antenna length.  Since I'm already limited to 8.5' above ground (due to the parking garage where I work), I wasn't pleased having the antenna begin so high off the ground.

On Saturday I made an antenna bracket out of aluminum angle stock and bolted it to the towing eye on the right side of the frame at the rear.   It's a tinkertoy arrangement, and it'll need to be replaced with something stronger, but it works quite nicely for now. 


Title: RE: Little Tarheel II installation
Post by: KH6AQ on October 29, 2012, 05:30:31 AM
Thanks for the Soul information. I decided to try a Comet HD-5M lip mount with an MFJ HF Stick. I'll test the mount with the $15 antenna rather than a $430 Tarheel.


Title: RE: Little Tarheel II installation
Post by: WN2C on October 29, 2012, 08:55:43 AM
Why not go w/ the Scorpion 680s? Weld a mount to the frame and you will have a great antenna.
Good luck with your install and maybe will hear you on the air from the mobil.

73 de wn2c  Rick


Title: RE: Little Tarheel II installation
Post by: AC4RD on October 29, 2012, 09:09:39 AM
I decided to try a Comet HD-5M lip mount with an MFJ HF Stick. I'll test the mount with the $15 antenna rather than a $430 Tarheel.

That sounds like a good idea!  Good luck on the installation!


Title: RE: Little Tarheel II installation
Post by: KH6AQ on October 29, 2012, 09:11:13 AM
I had considered the Scorpion 680S and consider that to have better performance (compared to the Tarheel 75A) on 80 meters, about 1 dB on 40 meters and the same on the high bands. But at 13 lbs that is a lot of antenna to mount. I'll see what I learn mounting the Hamstick on the hatchback and take it from there.


Title: RE: Little Tarheel II installation
Post by: M6GOM on October 29, 2012, 01:10:49 PM
When you install it, use an antenna analyser. Before you start doing any bonding, note the frequency of the resonant point of the antenna (x=0 or as near as it'll go). As you add bonding you should notice it dropping as you improve the RF "ground". Mine dropped around 300kHz from start to finish.


Title: RE: Little Tarheel II installation
Post by: KH6AQ on October 30, 2012, 01:05:17 PM
M6GOM, I'll do that with my MFJ-259. Hopefully the only bonding needed is the hatchback to the body panel above it.


Title: RE: Little Tarheel II installation
Post by: M6GOM 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.


Title: RE: Little Tarheel II installation
Post by: KH6AQ 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.


Title: RE: Little Tarheel II installation
Post by: M6GOM 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.   ;D

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.


Title: RE: Little Tarheel II installation
Post by: KH6AQ 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



Title: RE: Little Tarheel II installation
Post by: WN2C on November 02, 2012, 09:25:23 AM
680s. You won't be sorry!


Title: RE: Little Tarheel II installation
Post by: KH6AQ 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.


Title: RE: Little Tarheel II installation
Post by: KH6AQ 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.


Title: RE: Little Tarheel II installation
Post by: M6GOM 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.


Title: RE: Little Tarheel II installation
Post by: KH6AQ 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.


Title: RE: Little Tarheel II installation
Post by: K0BG 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.


Title: RE: Little Tarheel II installation
Post by: KH6AQ 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.


Title: RE: Little Tarheel II installation
Post by: KH6AQ 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.


Title: RE: Little Tarheel II installation
Post by: KH6AQ 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.


Title: RE: Little Tarheel II installation
Post by: KH6AQ 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.


Title: RE: Little Tarheel II installation
Post by: KF7NUA 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 ?


Title: RE: Little Tarheel II installation
Post by: M6GOM on November 13, 2012, 12:45:42 PM
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.

You'll notice that, especially on RX.  ;D