Venerable Omni “A”

newomni-a-rig Figure 1:  The new-to-me Omni-A, my Bencher paddle, and my homemade tablet computer, on top of my homemade operating desk.

Posted: 08/29/2015

I have always been a Ten Tec fan. As a kid I dreamed about the PM-1, but had to settle for home brew and (eventually) an old (even then) DX-40 transmitter / Lafayette-HA350 RX combo. When I was older, I purchased a Triton 4, and fell in love with the quietness of its noise blanker assisted audio, its filters, and its fabulous QSK. Some time ago, I decided to find another Triton (I’ve had and subsequently sold several, when I wish I’d kept them all). The prices have crept up, as the numbers dwindle, and ebay resellers have ascertained that hams will give blood for these units. They are made primarily of discrete transistors, with a smattering of commodity ICs, and so are relatively easy to fix in a pinch.

In recent months, these thirty five and forty year old gems have gone for as much as $400 (with the supply). After losing a number of auctions, I finally decided to pick up an easy Omni (they’re much more in supply because more of them were built). The first Omni (the A model) was sort of a Triton in a sturdier box. The sturdier box was really needed, as all Triton fans know. There were a number of changes made in the Omni, but the smooth feel of its ancestor comes through like silk, and now I’ve got that old-time CW-happy thing going on once again.

The Omni-A that I found is an analog version, so it mimics the original Triton more closely in its looks than do the digital models. The Triton IV had a few more differences in its looks than in its circuitry, relative to the first Omni. The Omni has a dark front panel, and some additional controls were added as well. As luck would have it, my (new to me) Omni arrived via USPS as clean looking as the day it shipped from Sevierville, TN. There’s not a scratch on it – not a defect at all. How did it stay that way for thirty five years? It must have had a good keeper.

When the Omni-A arrived, I was in a hurry to put it on the air, to run it through its paces. My only toroidal balun was already occupied by the forty meter dipole, so I cut a quarter wave section of coax to act as a balun for the twenty meter dipole I’d fashioned from pieces of old category 3 telco wire, so as to keep the coaxial feedline from radiating anything. I quickly strung the dipole across the attic and then fired-up the Omni, using CW on 14.035 MHz. Immediately I contacted VE2AJR in Quebec, who gave me a 569 report. “GM Henriot!” I tapped, with a grin across my face …

One of the nice things about the Omni (or the Triton, for that matter) – is how easily they can be adjusted to provide near-QRP levels of power. That’s exactly what I did, in deference to the proximity of the dipole. Switching the Omni into the dummy load, I attempted to find out how much was left in the output transistors.

I adjusted the MFJ 941D until the SWR was 1:1, and turned up the drive control on the Omni. Sixty watts is what I could muster, which was (only a little) deflating for me. The physical condition of the unit was par excellence, no contest, so I’d live with a little bit of ding on the output transistors. The output turned out to be a bit better on one of the other bands, but nevertheless I’m happy as a pea in a pod with the Omni. Having had a number of Triton IV rigs, I knew how the output transistors worked, and so the low output was a non-issue. The output transistors are damaged when under adverse conditions for too long. The good part is that the damage (at least with the Triton output pair) – is always incremental. So, as long as they’re not abused again, they keep on working. Of the Tritons I have purchased over the years (other than the first one, which was perfect) – none had full output. The last one had only about 70 watts on the best band, but I was able to continue to use it for years. I typically run a tad less than full capability, as a matter of caution.

omni-pic-with-tt-keyer-1

Figure 2:  The original (recommended by TT) keyer, with the model “A”.

Ten Tec is a subsidiary of Dishtronix, Inc, and trademarked is held by them.  They are not affiliated with this site or author in any way.

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