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Author Topic: Auto Tuner Recommendations for Inverted L  (Read 3691 times)
KC2NYU
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« on: March 16, 2011, 01:52:25 PM »

I  want to put up an inverted L to get on 160M, and possibly other bands. I plan to run RG 213 to base of tree and then put an Auto Tuner in a weather proof enclosure at the feed point. Several people have recommended the Icom AH-4 but at over $300 new that's a little more than I budgeted for this project. Right now I am using a LDG Z-11 Pro in the shack and have thought of putting one on the inverted L as an external auto tuner.
-- Looking for ideas on what other auto tuners that I should consider for this installation that aren't in the Icom AH-4 price range.

thanks and 73
Paul
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WB2WIK
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« Reply #1 on: March 16, 2011, 03:16:22 PM »

For this kind of thing at low power (<200W PEP) I use the SGC-230 "Smart Tuner," which I've had for about 15 years now.  It's an older design but very solid and comes in a weather resistant enclosure, so it needs no more protection.

It's bigger than the LDG but has more matching combinations and very sturdy antenna and ground terminals on opposite sides of the unit, making it really easy to connect all your radial wires to the ground stud while connecting the inverted L wire itself to the ceramic insulated output terminal.

http://sgcworld.com/Publications/Manuals/230man.pdf

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KC2NYU
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« Reply #2 on: March 16, 2011, 03:36:43 PM »

The SGC SG-230 looks like a fine tuner but the current price is > $500. Not quite what I had in mind  Wink, that more then the ICOM AH-4

73
Paul
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W5DC
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« Reply #3 on: March 16, 2011, 04:03:56 PM »

An alternative to a commercial tuner at the feed point is to use fixed sized components at the feed point.  Unless you have large losses in the antenna and/or ground, the feed point resistance should be lower than 50 ohms; for example, the feedpoint resistance on my 160 antenna is about 13 ohms at resonance.  You can match this to a 50 ohm line by using a inductance ( mine is about +j30 ohms reactance) and shortening the wire length slightly, assuming starting from resonance.

Dunc, W5DC
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WB2WIK
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« Reply #4 on: March 17, 2011, 10:26:43 AM »

An alternative to a commercial tuner at the feed point is to use fixed sized components at the feed point.  Unless you have large losses in the antenna and/or ground, the feed point resistance should be lower than 50 ohms; for example, the feedpoint resistance on my 160 antenna is about 13 ohms at resonance.  You can match this to a 50 ohm line by using a inductance ( mine is about +j30 ohms reactance) and shortening the wire length slightly, assuming starting from resonance.

Dunc, W5DC

Good solution.  I've used the remote tuner mostly to enable tuning on multiple bands, not just one.

Anyone who needs the antenna to load on only one band would be wise to create a fixed tuning network that works and just leave it there!
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W5DC
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« Reply #5 on: March 17, 2011, 01:22:17 PM »

If you don't mind the additional exercise, and don't change bands too frequently, clip lead matching network selection works.  I have one friend who is an avid 160 dxer who does this.  I do this to change from 80 to 160; unfortunately, I have to climb on a ladder to do this and my equilibrium and balance is poor.  Relays are in the works. 

Dunc, W5DC
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K3AN
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« Reply #6 on: March 17, 2011, 01:45:51 PM »

If you only intend to use the L on 160 and it's roughly a quarter wave of wire, then an autotuner in the shack will work fine because the SWR on the coax won't be that high. Using the same antenna on other bands WILL require an autotuner at the base of the antenna because otherwise coax losses will be significant due to the high SWR.

There have been recent QST articles, including one in the last issue or two, where the ham installed a less expensive indoor-type autotuner outdoors by using a large Tupperware container, and sealing all the holes with caulk.

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W5DC
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« Reply #7 on: March 17, 2011, 02:36:03 PM »

How well an autotuner in the shack works is somewhat dependent on the dimensions of the inverted L.  I once had an inverted L for 160 that was 65 feet vertical and 65 feet horizontal and matching was no problem; I wish I still has the antenna but not the location.  If my current matching network had higher Q coils instead of the MFJ air inductor that it currently has, without a matching network at the feed point, it would probably have a swr at resonance in the 5 to 10 range.

Dunc, W5DC
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KC2NYU
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« Reply #8 on: March 17, 2011, 05:48:04 PM »

My primary intention is to get on 160M , BUT if I can why not try to get on other bands also. That is why I am thinking of an auto tuner at the feed point of the Inverted L. I am planning about a 60ft. vertical run and than about 80-85 ft horizontal. The only recommendations so far have been quite pricey. Looking for something < $200 range.

73 Paul
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NA0AA
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« Reply #9 on: March 17, 2011, 06:06:02 PM »

If you are running 100 watts, then you could mount the z-11Pro at the bottom of the L.  You can battery power it.

An SG-230 is an ideal solution, but they are rather dear even when used.

MFJ is selling a less expensive coupler for this application as well.

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K6SI
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« Reply #10 on: March 19, 2011, 12:52:04 AM »

I have an Icom AH-2a tuner, unused, in the box, $259 plus shipping. Same as AH-4, except made for 160 meters. AH-4 factory specifications 80-6 meters. AH-2a Icom factory specifications 160-10 meters. A4 will work if 160 meter wire long enough, but not built for 160 meters, see AH-4 specifications. Also of course you should have Icom rig, as Icom tuners need the Icom rig 'tune' interface. K6SI.  kclm217@gmail.com
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W4VR
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« Reply #11 on: March 19, 2011, 12:48:03 PM »

If you don't want to spend a lot of money you can do as I did several years ago.  I bought a surplus motorized 10-1000 pF 3kV vacuum variable capacitor from Fair Radio Sales for $75.  I built my own inductor and used this L network on my 160 meter inverted L.  To power it I used a Radio Shack wall-plug-in 12 volt power supply and a toggle switch so I could forward and reverse the motor from my shack.  Total cost was under $100.
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KO7I
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« Reply #12 on: March 20, 2011, 09:30:30 AM »

You-all can save a few bucks by installing a auto tuner inside a surplus military ammo can. The MFJ tuners can be operated by a bias tee feeding 12VDC operating voltage down the transmission line to the remote tuner. Not sure if LDG has an internal bias tee.
I found the flexibility of being able to use the tuner "remotely" or on the desktop to be very convenient.
73, Don KO7i
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W3HKK
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« Reply #13 on: March 29, 2011, 03:16:59 PM »

Ive used an SGC 230 tuner on 160m and 80m ....theyre well  considered. 

But  the one you have should be fine also.   Qtr wave inverted Ls , one for 160 and one for 80m work fine on 60m as well.  Use a single  coax feed and solder the two wires at the base. then trim the length and add radials as space permits.

The higher the vertical portion of your wires the better for DX but its not critical  from an operational standpoint. 
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K0ZN
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« Reply #14 on: March 29, 2011, 09:03:31 PM »


Hi.

On 160 M the losses are so low in good coax that it seems unnecessary to put the tuner at the base of the antenna if it is just a 160 Antenna.

Again, if it is a mono band antenna for 160, the "correct" thing to do is build a matching network to be placed at the base of the antenna.

You could also run TWO pieces of coax in parallel which would give a 25 ohm transmission line, which is likely very close to the base impedance
of the 160 Inverted L.....certainly a lot closer to 12 to 18 ohms (the estimated feedpoint Z) than 50 ohm coax would be. That would yield a pretty
reasonable SWR for the tuner to deal with.

My experiences have always been that it is much easier to put the matching network IN THE SHACK, rather than out at the antenna....and the way to
make that work is to use a good low loss transmission line to the antenna, with the matching network ("Tuner") in side.

Some time spent with the ARRL Antenna Book would be well worth the effort and time.

73,  K0ZN
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