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LDG Z-100 or T1? Or homebrew auto ATU?

LDG Z-100 or T1? Ive read the reviews on eham but i wonder who uses a LDG Z-100 or T1? I wonder who uses either ATU on SOTA summits and how do they rate them?

I have been playing around with some ideas for aerials to experiment with while its winter but im finding the use of an ATU is almost unavoidable for the amount of bands i wish to cover.

Anyone who has homebrewed there own auto ATU i would like to hear from them also as this would be a nice project for me. Sean / M0GIA

You’re quite interested in the antennas side of the hobby, aren’t you Sean?!


In reply to M0GIA:

I used a MFJ-902 travel tuner for a while with great success Sean, but opted to use a multi-band linked dipole instead. The atu is not an auto atu, more info on this link.

If you want to borrow it for a month to have a play, you’re welcome, I could post it to you.


In reply to GW0DSP:
Hi Mike I have also now started to use a linked dipole.After being shown one by Mike G4BLH. I tune each section with a MFJ-259j Antenna analyser.No atu needed as each section is resonant as near as posible to the nearest popular SOTA frequencies.ATB Geoff.

In reply to GW0DSP:
Ehhhhh yes you could say that Tom! To me its the last tuned circuit and then its the Ether so i think paying plenty of attention here should and mostly does pay off.

The use the ATU here is just to tidy things up so i know im getting full 5w forward, its not for doublets so i do not need a balanced ATU.

Mike thats very kind of you and im very aware of that ATU and i have built a manual “L” match ATU http://homepage.ntlworld.com/s.amesbury/M3FVB/lmatch.htm that will match almost anything. I have now decided to go for the push of a button for convienence … getting lazy in my old age!

                                               Sean / M0GIA

In reply to M0GIA:

No probs Sean.


In reply to M0GIA:
The ATU only fools the rig in to thinking the antenna is ok it does not mean that all your five watts are goig out some of it is being lost in the atu ATB Geoff

Hi Sean

FWIW I use an LDG AT 7000 with the 706. It’s relatively light and compact… it hasn’t met anything it cant tune yet and has so many memories it’s almost ready before you’ve pressed the tune button!

73 Marc G0AZS

In reply to G6MZX:
Thanks again Mike, and thanks Geoff for the info and your right the ATU is a matching unit not a tuning unit. Im not going to ramble on here about what im going to try as it just might not work and that wouldnt be the first time.

ATU’s being manual or auto are passive devices meaning they need power to work and that power is in the way of RF. General rule of thumb is the greater the mismatch the more RF is used in the ATU to correct it.

I might be wrong in my thinking here and that wouldnt be the first time either! But back on track im looking at 3:1 worst case on any one given band so min losses in the ATU with the aerial singing at max power (qrp) at any location. Sean / M0GIA

In reply to G0AZS:
Marc do you use that ATU on summits? Sean

Hi Sean

I’ve used both the LDG Z-100 and the Elecraft T1.
Both ATUs met my requirements but the T1 is smaller, run from internal 9V battery and interface with my FT-817. The Z-100 I used to own was the model with no internal battery.

Most of the time I use a 7m wire vertical on a telescopic fishing pole with a 7m counterpoise on 20m and 40m. I also use it to tune a 2 * 13,4m doublet fed with 300 ohms feeder via Elecrafts switchable 4:1/1:1 balun on 20m, 40m and 80m.

I run QRP SSB only.



In reply to M0GIA:

Marc do you use that ATU on summits? Sean
Yes Sean… if I’m using the 706 and my 88ft doublet… not with the PFR-3 though.

Bear in mind it only works with Icom TX/RX 's. Anyway I’m very pleased with it.

73 Marc G0AZS

I use this ATU with my FT-817ND and it works a dream.


73 Chris 2E0FSR

In reply to M0GIA:


I have used the T1 for sometime now with a longwire and counterpoise (Sotabeams) though am in the process of building a linked dipole at the moment. I found the T1 excellant for use with the 817 as it has a link cable to the TX allowing the memory in the T1 to detect band changes in the rig and automatically retune the ant. The T1 one is very small, light and runs on a PP9 battery. The down side is the cost though.

Hope this helps


In reply to GM4CFS:
Thanks for the replys and i think its going to be the LDG Z100, a link dipole is a great idea but for what i have in mind i need an ATU.

Just had a look at your site Mad and well done on the QRP DXCC very impressive and i must get out more HI! Sean

In reply to M0GIA:

When using the T1 ATU it is useful to check the output power by pressing one of the buttons (I do not remember which now) before starting to transmit. Just in case that there might be a problem in the transmitting circuit or the batteries could be almost death. If the QSO fails while the receiver still picks good signals, the propagation conditions must be very bad or there is nobody listening.

An other useful feature of T1 ATU is its ability to report the matching inductance and capacitance values. These could be compared to the values calculated by antenna modelling programs or to estimate values needed for a manual tuner. Unfortunately I have not made any systematic book keeping of these values so far.

73, Jaakko OH7BF/F5VGL

In reply to F5VGL:

Used to take my Z-100 but got fed up with batteries going flat or not working because of the cold temperatures and rendering it inoperative. So I spent some time trimming my link dipole properly and now I don’t take an ATU. But if I did it would be the manual MFJ portable one I think.

In reply to GW8OGI:

No experience on Z-100 here. I was talking about the transceiver batteries. The T1 ATU manual does not specify operation temperature range, so I can not comment on that. The link dipole is a good antenna anyway.

73, Jaakko OH7BF/F5VGL

In reply to F5VGL
Thanks Jaakko for the info i do take an ATU but its a 300w one and is too big really, i have to say i enjoy all bands and like to be able to use the whole band so an ATU for me is a must especially on 80m and 160m.

For now i will keep thinking on my next project for use on the SOTA summits. Sean / M0GIA

In reply to M0GIA:

Perhaps a small TIP about the T1.

I have made a small cirquit in SMD with 7809 on a cold plate and built these in the T1 at the normally 9 V battery place. I can use now an external 12 V battery or the internal 9 V battery of FT817 via a DC connector on the backsite of the TxRx.

Btw I have and use both ATU’s for /P use. T1 Elecraft for QRP with the FT817 and the LDG Z100 for the Alinco DX70 at 100 W.

Ant.: For the Alinco DX70 --> Inv.V dipole for 40 and 20 m or a multiband 40-20-17-15 at 7 m up.
For the QRP FT817 --> Inv.V dipoles for 40 or 20 or 17 or 15 or 10 m band at 3 m up.