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[TenTec] Omni 6 sensitivity, DSP, SDR, and general rants!

To: wf2u@starband.net, tentec@contesting.com
Subject: [TenTec] Omni 6 sensitivity, DSP, SDR, and general rants!
From: Jerry Volpe <kg6tt@tomorrowsweb.com>
Reply-to: kg6tt@tomorrowsweb.com, tentec@contesting.com
Date: Sun, 19 Dec 2004 08:32:55 -0800
List-post: <mailto:tentec@contesting.com>
It is 5am and I am not able to sleep so you are all in for it! :(

I recently did a bit of revamping of my shack placing two more HF rigs on line with my Omni-6+ (I also have two Scouts but they are a different breed) and subsequently I have been doing a lot of listening comparisons between my three main rigs. Certainly not scientific evaluations nevertheless I have gained some personal perspectives. Recently I have worked several contests with my Omni-6+ and I am very pleased with its ability to separate the 'wheat from the chaff'. I have all the standard Ten-Tec filters including the 1.8 and 500 hz roofing filter options. The Omni can zero in on a sideband signal slicing it out of the QRM and QRN but it really isn't a pleasant rig for general armchair listening. I had a Jupiter before and although an SDR (with bad along with the good) it sort of set some expectations as to what is possible, but that is another story.

A few weeks ago I added a really nice 9+ Paragon to my station. It too has all the standard Ten-Tec filters. On listening tests I would say that the Paragon is characteristically similar to the Omni just not as sensitive overall. This is especially noticable on 15 and 10 meters. The difference is mostly in how much s-meter deflection you see as generally if you can hear it on the Omni it is there on the Paragon... well almost. For me the difference is certainly moot. Now on CW I truly prefer the Paragon's Tone/Fade/BP analog controls to the lack of same on the Omni. I can peak in on a CW station much faster. On sideband I definely give the nod to the Omni's spartan but effective DSP. Turn that baby on and back off the RF gain control and enjoy the ride. For some reason doing this seems to open up the audio a bit.on the Omni.... I am sure this is just a perception effect and not a reality.... and of course you get that 'DSP' mungled audio... certainly NOT natural but you get use to it pretty quickly. In contrast, I did not like the DSP-based noise reduction on the Jupiter that I owned earlier. The audio gain on the Jupiter simply dropped toooooo far resulting in an apparent lack of gain when listening to a group of stations with some being appreciably weaker than others. The Paragon's AGC seems to operate similar to the Omni and both rigs seem to have comparable levels of residual background noise levels. I am always on the hunt for that infernal 'Phase Noise' demon as I know it is out there somewhere. Audio-wise the Paragon and the Omni sound much alike... this is not a bad thing.

Last week.... and don't ask me why.... I accepted a Kenwood TS-940SAT in trade for my old faithful Omni-C station. Now my original intent was to sell the Omni-C to pay for the Paragon, but the trade was offered to me and I talked myself into it. It has been nearly 20 years since I last owned a non-Ten-Tec HF rig although I have used many that belonged to other hams. Aside from the fact that the TS-940 has some intermittent issues (this particular example was fairly heavily used and apparently in a cool/damp environment as can be witnessed by the high amount of oxidation on the internal aluminum and steel... blah, blah, blah) the Kenwood has a very nice receiver overall as it should as it was an Expensive transceiver in its day. My particular TS-940SAT has INRAD and Fox Tango filters rather than stock Kenwood filters (good or bad I have no direct way to verify). In general listening tests between the Omni, Paragon, and Kenwood, and using a Kenwood HS-5 headphones or my SoundsSweet external speaker, I definely give the Kenwood a better overall grade. It is just more listenable to my 53 year old ears... more open sounding. The Kenwood's AGC seems a bit smoother and with a tough better dynamic range. Sensitiviy and selectivity wise the Kenwood is definetly somewhere in between the Paragon and the Omni, but it is very difficult to quantize the differences here. On the other hand I can make personal judgements on 'creature comforts'. When operating CW I prefer the Kenwood's Pitch/RF Tune and CW VBT control functions to the lack of which on the Omni. I also like the Paragon's Tone/Fade/BP/PBT contols when compared to the Omni.... The Paragon is more intuitive though so I like using it most in CW. Kenwood's controls take a bid of getting use to but for a rig pushing nearly 20 years in age it isn't half bad.

All three transceivers have very quiet receivers. If I have to give the nod to one over the others then I guess the Kenwood is generally quieter. This is purely subjective on my part BUT when I change antennas from rig to rig I never have to turn the Kenwood's audio down as I simply don't hear it but I DOOO have to turn the Paragon and the Omni's volume down as they produce a noticable audible 'rushing' sound with no antenna attached. Now for an unusual observation which I am still trying to figure out... and which has a lot to do with what I just wrote.....

In my setup the Omni, Paragon and Kenwood have their antenna terminals going directly to a venerable Heathkit coax switch which is of the 'shorting' variety (shorts out un-used connectors). If the Paragon and Omni are turned on, but the Kenwood is off) changing the coax switch from one rig to the other doesn't result in much residual background noise from the non-selected rig. HOWEVER, if the Kenwood is also ON AND selected with the antenna switch both un-selected Ten-Tec's produce rather dramatic and objectionable audible noise levels getting worse on the higher frequency bands. The reverse is not true. An unselected Kenwood does not respond audibly to either or both of the Ten-Tec's being on regardless of what band and is tuned to. What this means in practical terms I am not sure. I just turn the volume controls on the Paragon and Omni down when I am listening to the Kenwood. Oh, and I have tried several different coax switches with the same results.

On the discussion of DSP and SDR...... Though I have a frairly technical background and tend to naturally appreciate and welcome technical advances 'as they mature', my general feeling is that DSP and SDR is not yet ready for prime time. I bought a new Jupiter last year but traded it off rather quickly. Bought a new JRC NRD-545 and sold it within months! Of course DSP and SDR technologies are not going away.... the scale of economies and the need to reduce part counts and manufacturing costs dictates that manufactures replace hardware with software But like any fairly new and radically different technology it takes time to 'get there' and just because you can doesn't always mean you should. And to 'get there' will probably require far more capable microprocessor/DSP combinations than what are currently being offered.... and far more complex firmware. For now, absent the 'gee wizz' effect, give me a good old descrete design. AND give me KNOBS to TWIST and buttons that LIGHT UP! And real MECHANICAL meters. And sharp florescent or LED-based displays with just the essential information PLEASE! don't build in any operating modes like RTTY, PSK and CW receive... just built in obsolesence waiting to happen and never implemented nearly as well as what can be done externally.AND MOST OF ALL I don't want to wade through menus except for an incredibly rare functions.

OK, I've ranted long enough. :) And someday I will own an Orion, but probably not till there it is an Orion III.

73 All,
Jerald, KG6TT
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