Morning Rick I'll have to read your email after I get back to the from the
back...You probably already know this but just in case did you know there is a
Omni Vll group on YAHOO?. A lot of good info flowing in there to. Good Luck
With The Vll and I hope it turns out to be a great rig for you, 73 Mac
----- Original Message -----
From: "Rick, NJ0IP / DJ0IP" <Rick@DJ0IP.de>
To: "'Discussion of Ten-Tec Equipment'" <tentec@contesting.com>
Sent: Thursday, March 01, 2007 7:19 AM
Subject: [TenTec] OM7 on 40m in Europe
> Yesterday afternoon the OMNI VII arrived.
>
> My XYL had committed me to being the designated driver for her and her
> girlfriends' "night out", so that highly limited my time for playing with
> the new OMNI.
>
>
>
> I currently only have a 40m vertical (full size) and no other rigs to
> compare the OM7 to (except a 20+ year old Argonaut 515 without any narrow
> filters). Next weekend I will take the OM7 to one of our BCC contest
> stations, DL1A on the west side of Munich. There we have beams on all bands
> except 160. For comparing we have an FT-1000 MK5 FD, FT-2000, and Orion.
>
>
>
> Being a 40m fanatic and living in Europe, I have become accustom to
> disappointments when testing new rigs.
>
> We have a multitude of shortwave broadcast stations which play havoc with
> most receivers' front ends, beginning in the early evening, getting worse at
> dusk, then slowly getting better towards midnight. Attenuation in the front
> end helps, but it also attenuates the desired signal. This can be
> significant if the desired signal is only S1 or S2. That's why the use of
> an external preselector is popular over here.
>
>
>
> Although I had no other "good" radios here to compare it to, I have recently
> owned (within the last 2 years) two Orions, two K2's, an Omni VI+, and a
> TS-480 (and tried a TS-850 but it fell over with intermod problems). The
> comparisons shown below are based on memory, not on side by side comparison,
> so take them with a grain of salt, your mileage may vary, etc.
>
>
>
> Testing was done last night from 5pm until 6pm local, from midnight until
> 1am local, and again from 7:30 until 8:30 local this morning.
>
> I was mostly just receiving and trying hard to find intermodulation problems
> on the OM7.
>
> The external preselector connected to the OMNI VII is a home brew bandpass
> filter (not tunable), similar to the famous Braun preselectors, but not
> quite as good.
>
>
>
> Results:
>
>
>
> * There was no blanket of noise across the 40m band (even without the
> external preselector), like there are with so many other rigs. Even
> switching the preamp on did not produce this adverse effect. THIS IS
> SIGNIFICANT! For comparison, on this antenna:
>
> * The newest K2 (S/N 4606) had about an S1 to S2 blanket of noise
> across the entire band with preamp on. It was generally clean without the
> preamp, except for peak problem times (dusk) where the attenuator or the
> external preselector eliminated the intermod entirely.
> * The TS-480 SAT had about an S5 blanket of noise across the entire
> band with preamp on. With the AIP (preamp off) the radio was also pretty
> clean, except for peak problem times (dusk) where I needed the attenuator.
> I never tried the preselector on this rig. Of course the attenuator also
> attenuates the desired signal but not as much as it attenuates the intermod.
>
> * The OMNI VI+ was generally clean with perhaps an S1 blanket of noise
> at peak problem times. The attenuator, but better yet, the external
> preselector always eliminated it.
> * The ORION was always clean in all circumstances on my antenna, and
> on DL1A's 3-el beam at 100 ft., exhibits similar light intermod problems to
> what I experienced with the OMNI VII using my vertical. These are completely
> eliminated (on the ORION) by turning back the RF gain to 95%.
>
> * OMNI VII Intermod: There were a few instances where there was a
> strange carrier (obviously intermod) on the order of S2 to S5, but usually I
> could eliminate it with 6dB (occasionally 12 dB) of attenuation. Of course
> switching the external preselector in also eliminated it without reducing
> the strength of the desired signal. These carriers would go on and off, and
> I have no idea what was causing them, but it was clearly intermod because
> just 6dB of attenuation would drop it several S-Units. Something somewhere
> was mixing with something else. There were 4 or 5 frequencies where I
> experienced this. The rest of 40m was clean, even with preamp switched on.
> DO NOT INTERPRET THIS TO BE BAD. IT IS EXCELLENT. Most receivers are much
> worse under these conditions.
> * There was no pumping on strong signals like we experienced on the
> FT-2000. To be fair, that was on DL1A's beam and I haven't tried the OM7
> yet on that antenna (update next week).
> * While I was on 40m, my neighbor ham (Freddy) was on 160m trying to
> work the VK9NDX-pedition. He was running a healthy kilowatt (using my old
> linear amplifier) and our two antennas are about 200 yards apart. When he
> transmitted, the noise level would go up about an S unit or 2, but modulated
> according to his SSB signal or to the cw signal - he used both modes. The
> noise sounded a bit raspy. The preselector eliminated this. For
> comparison:
>
> * The TS-480 had about an S-8 increase in noise under these conditions
> (in the past of course)
> * I never noticed this on the OMNI VI (over a period of 4 or 5 years)
> unless Freddy was on the same band as I was. Often he was operating SSB
> while I was on CW on the same band. In that case I used my home-brew
> tunable preselector which pretty much eliminated the problem.
>
> * This morning I heard our BCC boys currently activating VK9NDX and
> worked them first call (cw), barefoot, through a mini pileup.
> * And to my pleasant surprise, the old Argonaut 515 could hear
> everything the OMNI VII could, unless it was disturbed by strong QRM.
> However I had to back off the 515's RF gain and play with its own built-in
> preselector to avoid intermod.
>
>
>
>
>
> Bottom Line: This radio is a true Ten-Tec!
>
>
>
> There has been a lot of speculation on the reflector as to whether the term
> "Distributed Roofing Filters" is real value-add or just marketing hype.
> Coupled with careful management of amplification (signal strength) from the
> antenna input through to the second mixer, it becomes very effective, but
> one needs to understand this. It's a slightly different approach. It
> clearly gets the job done, but I think Ten-Tec will have some missionary
> work ahead of them.
>
> Their main problem is, they did too good of a job in selling the industry on
> the concept of "roofing filter" when they brought out the ORION.
>
>
>
> Next update will be after testing on "real antennas" at DL1A.
>
>
>
> 73
>
> Rick
>
> DJ0IP (NJ0IP)
>
>
>
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>
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