An Old Kit’s Second Chance at Life in the Shack

tentec

An old RF “Artificial Ground” Tuner sold as a kit in the 90s(*) (the Ten-Tec Kit 1251) can help improve the tuning of a long-wire by a modern remote auto tuner.

The best HF multiband antenna in the shack is a 50+ Ft. wire in an elongated “C” or inverted “L” shape hanging quasi vertically some 40 Ft. up one of the maple trees in the yard. Counterpoise wires (abt. 1/4 WL, one for each HF band) run along the inside of the yard wooden fence, in a horizontal “L” shape elevated about one meter from the ground. The whole is end-fed “remotely” via an auto-tuner and a 4:1 unun. The “remote” tuner is an LDG RT-100 with its corresponding controller, the LDG RC-100. The connection diagram is as follows: Rig (IC-703+ or IC-706MKIIG) –> Elecraft WII Watt & SWR meter –> RC-100 –> Coaxial Cable –> RT-100 –> 4:1 unun –> antenna and counterpoise wires.

One of the problems detected with the LDG RT-100 is that in some cases it tends to lock at SWR values close to 2.0:1. This happens even after it flashes lower values during its search for the best match. In the case of the above setup this mainly happens when tuning in the 20m band.

Recently, I read a 14-year old (!) review in eHam.net on the TenTec T-Kit 1251 ground tuner (by Damon KC5CQW), indicating that the 1251 could work “with any ATU” (http://www.eham.net/reviews/detail/2657).

The Ten-Tec Kit 1251 was one of the first kits I put together years ago, and I remember to have been quite impressed with the quality of the materials and in particular with the inductor, for which Ten-Tec provided a pre-drilled plastic clamshell and a long piece of silver clad wire:

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It was hard work to wind but worth the effort. I was less impressed with the meter provided with the kit, which was the main reason for the 1251 to have remained dormant in a shelf this many years. However, having now the benefit of the LED’s of the Elecraft WII to assess SWR, I decided to resurrect the 1251 and see if it could help to finely tune the counterpoise cables of the above antenna.

Connected between the unun and the counterpoise wires, and using the AM carrier to both trigger the RT-100 and visualize the SWR in the WII, I noticed that, adjusting mainly the inductance in the 1251, the SWR in the 20m band could be further reduced from 2.1:1 to 1.3:1 and that incoming signals were enhanced as much as 2 units in the S-meter of the transceiver. Similar results were obtained in the other HF bands (10m to 80m). How much of an improvement this may represent during regular operations remains to be determined, but for the time being the old Ten-Tec 1251 is enjoying a second chance at life in the shack.

See also: https://thewakesileave.wordpress.com/2016/11/15/further-data-on-the-kits-second-chance-at-life/


(*) http://lists.contesting.com/_tentec/1996-11/msg00062.html

 

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