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Old 12-07-2012, 07:26 AM   #1
N8CXX
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Default Stumped by my Tarheel II 100A-HP

I'm struggling to get this antenna to resonant on any frequency UNDER LOAD. I'll try to supply all the info on this installation.
The 100A-HP is mounted on a 3' tripod on the roof of my garage. Garage structure is wood and asphalt shingles. There are 9 - 9' radials mounted to the bolt on the bottom of the Tarheels mount.
The Antenna Controller is a Ameritrom SDC-102. Rig is an Icom 751A. Rig is grounded.
I used a SWR Analyzer to find the lowest swr for a given frequency. (analyzer shows 1 to 1 across its range into a dummy load)
These are my readings:
freq = turns on counter
28.300 = 342 (1.3 to 1)
21.100 = 515 (1.4 to 1)
14.100 = 873 (1.4 to 1)
7.05 = 244 (1.7 to 1)

Now when I hook up the rig and use a 50 watts load, the swr is 3 to 1 on every frequency.

I've adjusted the matching coil. Nothing changes. I called Robert and he suggested I disconnect the the matching coil. Still the same high swr.

Obviously I'm missing something. What is it??
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Old 12-07-2012, 08:50 AM   #2
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Had that problem with radials. Check your coax connectors and remove the radials and give it a try. Also my matching coil was not making good contact under load. BTW, I currently have 2, 26 ft radials attached and everything grounded.
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Old 12-07-2012, 08:51 AM   #3
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Wow some thing sounds wrong with the turns counter. Doesn't it bottom out in the setup procedure? Mine at the very bottom (highest freq) reads 0 turns and goes up as the antenna rises. Maybe it is different with the (Lil Tarheel) but it should start at 0. You absolutely have to have a choke on your control wires or it will not tune, the bigger the better. The treads are 20 to the inch on the motor drive so 20 turns will give you a 1 inch rise in the height and the 40 meters to 10 meter turns are way too close. I use no matching coil on mine and it tunes from 10 to 80 meters with a 56" stinger. The manual is pretty vague but power on +6 should get you started then step your way through and zero the counter. I set mine with a Bird AT 100 antenna tuner but a good SWR meter should work.
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Old 12-07-2012, 09:15 AM   #4
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I will go with double check connectors.. But 9' radials might work on 10M but on lower frequencies you need longer wires. Run an assortment of radials ranging from 9 feet to well, 80 meters is what 62.5 feet, If you can't go that long don't worry but I'd try assorted length radials, go at least out to the corners of the garage with them.
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Old 12-07-2012, 09:15 AM   #5
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Thanks for the insight.
Counter start at zero with the antenna fully collapsed. It has a 8' whip. I bought the std 100a-HP kit. I wrapped the control wire as specified with the ferrite core they supplied.

I would try the suggestions, BUT, we're done. The 751A no longer puts out an power.

Pretty disappointed.
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Old 12-07-2012, 05:35 PM   #6
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Update!

Fixed the radio - shot the operator. Split vfo's does it everytime. Still lost 40 meters. This is what happens when you take 20 years off.

Checked the coax connectors - OK
Removed the radials - OK
Reinstalled the matching coil.

Now the readings are closer to the manual
10m - 32 on counter
15m - 56 on counter
20m - 200 on counter
Still need to work on 40 / 80

Directional correct.

Feel better.

Thanks for the suggestions.
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Old 12-07-2012, 06:08 PM   #7
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Oh good that looks a lot more like it the numbers are higher then mine but you have a good deal longer whip. You just got to be quick when tuning the motor does coast after you let it go so when your close just a touch with the up and down.
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Old 12-07-2012, 06:38 PM   #8
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I seem to remember that I had to stretch the coil until it looked like a horseshoe to get 80m right. But I have terminal CRS, so it could be something else.
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Old 12-08-2012, 11:47 AM   #9
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You know,,, I've had occasions where I just did not seem to be geting out.. Split VFO did it every time
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Old 12-10-2012, 08:09 AM   #10
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Another update.
Took two 32' piece of 5 strand rotor wire and cut each wire for a seperate band. Attached them and swr went up. Disconnected the wires and the matching coil. No help. Reassembled per instructions with the matching coil about stretched about 2" and it works OK.
I spent a little time on 10m:
33 contacts
11 countries
10 states

Definately not like the days from my old station.
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Old 12-10-2012, 07:27 PM   #11
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Tarheel says 10, 9' radials at ground level with the antenna just above them. I'm using no coil and it,s mounted to the rear of my truck and the truck bed is plastic! I have made contacts on every band but 160 pretty much every day to Europe and beyond I don't get it, it should tune up fine.
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Old 12-12-2012, 01:43 PM   #12
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Quote:
Originally Posted by N3LYT View Post
You just got to be quick when tuning the motor does coast after you let it go
You can probably reduce the coasting markedly by modifying the control system to short the motor when you're not powering it in either direction. This ought to be fairly easy to do with an additional relay. Shorting a DC motor is a standard technique for braking its motion when unpowered.
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Old 12-12-2012, 02:46 PM   #13
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Here's the installation.

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Old 12-12-2012, 07:48 PM   #14
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Quote:
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You can probably reduce the coasting markedly by modifying the control system to short the motor when you're not powering it in either direction. This ought to be fairly easy to do with an additional relay. Shorting a DC motor is a standard technique for braking its motion when unpowered.
It's not real bad but they tune quickly and it's easy to miss it as it coasts by. I found the only effective way is with a antenna analyzer.
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Old 12-12-2012, 07:51 PM   #15
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Here's the installation.

Your going to need some type of ground plane even radials connected to the 3 legs of the tripod would help, you maybe be better off at ground level with a series of radials.
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Old 12-13-2012, 10:36 AM   #16
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Your going to need some type of ground plane even radials connected to the 3 legs of the tripod would help, you maybe be better off at ground level with a series of radials.
All of my previous post described the radials installed / tried. The radials didn't help. I was trying to simulate mounting to the top of my 5th wheeler. I'll probably try re-installing on the ground with radials.
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Old 12-13-2012, 02:44 PM   #17
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Quote:
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All of my previous post described the radials installed / tried. The radials didn't help. I was trying to simulate mounting to the top of my 5th wheeler. I'll probably try re-installing on the ground with radials.
Install it on the fifth wheel and ground it to the frame. The 5th wheel frame then becomes the ground plane just like on my MH.
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Old 12-13-2012, 05:56 PM   #18
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I agree the camper does a good job as a ground plane but I think he wants to use it at the house during the off season. I went all over my camper and tightened screws and checked all the grounds with a mega ohm meter and mine does an out standing job on 10 to 80 meters. Maybe he should mount it on the camper and run a coax to the house shack!
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Old 12-14-2012, 11:33 AM   #19
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Maybe he should mount it on the camper and run a coax to the house shack!
Its about 9 miles away.

I'll try it on the ground today just to see if it works better.
I'll beat in a piece of copper pipe and then set out the 9 radials.

Have you guys noticed any motor noise? I have to turn mine off once I get it to the best position.
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Old 12-14-2012, 07:23 PM   #20
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Well with ladder line the loss might not be too bad The only motor noise I hear is when it's tuning. Are you talking about noise in the radios? I had to put a choke on my VHF/UHF remote head control cable to get rid of the processor noise the controller makes though.
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