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

[Jerry Volpe <kg6tt@tomorrowsweb.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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