I've used a series of DownEast Microwave transverters {144 MHz & 432 MHz}
with my Omni VI Plus and now with my Omni VII with a great degree of
success. I can hear 2M signals off of the moon with a single 10 ele yagi
and the DEM without a mast mounted preamp. That speaks well for the
performance of the DEM transverters and the Omni series of receivers as the
10 meter IF.
73
Bob, K4TAX
----- Original Message -----
From: "Steve Berg" <wa9jml@tbc.net>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Sunday, January 20, 2008 6:12 PM
Subject: Re: [TenTec] Omni VII on 50 mHz
>I have never seen an Omni VII. I went the transverter route, starting
> out with the Ten Tec kits, with my Argonaut II transceiver as the IF
> radio. They worked well, but were not spectacular. Recently, I built
> up two of the Elecraft transverters, one for 6 and one for 2 meters. I
> am using them with the Omni V and made some contacts during the contest
> this weekend. I tried using the Corsair II as the IF radio to allow
> cross mode contacts, but wound up having problems with drive level. It
> required different settings for the drive control on CW and on SSB, so
> it was not just a matter of flipping a switch to change modes. I tried
> several different settings of the ALC control, and it still would
> overdrive the transverters on voice peaks. Besides, I am having a ball
> with the Corsair II on 80 meter CW right now. I may go back to using
> the Argonaut II as the IF radio. Like the Omni V, it is not easy to
> make cross mode contacts, but the noise blanker is infinitely better
> than the ones in the Omni V and Corsair II. The Elecraft 2 meter
> transverter just got back from their excellent service staff, and is
> properly aligned. I noted that K9NS, who is a local contest effort
> would overload the 2 meter transverter, but not the 6 meter one. Those
> guys are LOUD. My limited experience is such to tell me to continue to
> use a transverter stack. I may add 222 and 432 MHz transverters as time
> and finance permit. The Elecrafts are nice in that they are easily
> bandswitched. They have some shortcomings on setting LO frequency when
> not used with Elecraft IF radios, but so far I am satisfied.
>
> Steve WA9JML
>
> Dr. Gerald N. Johnson wrote:
> snip...
>>>
>>> 73.
>>>
>>>
>> Without test data, I can't judge the radio. But I don't think Tentec
>> understands weak signal VHF receivers. Their 6N2 has a receiver
>> sensitivity MDS on the order of -132 dBm. More than 10 dB worse than the
>> state of the art. Not an unusual value for rice boxes either. 2m rice
>> boxes have had poor sensitivity for decades. I blame that on lots of
>> Japanese 2m activity and that backing off the RF gain is the easiest way
>> to get away from intermod.
>>
>> I have a Tentec 6m transverter (2m IF) that uses a nice double gate
>> MOSFET that ought to do better than 1 dB NF, but with their almost PIN
>> diode (1N4007) switching that loads the incoming signal with the PA all
>> the time, achieves about 7 dB NF. Yah, in the cities that's good enough
>> but out here that's not all that good. Tolerable for 10 watts but not
>> for higher power.
>>
>> Recently someone on a VHF list commented they had measured a modern 2m
>> rice box NF at 10 or 12 dB and so needed 20 or 30 dB preamp gain to make
>> the best use of the fractional dB NF preamp in an EME station. That sure
>> makes intermod a sure thing. I'm beginning to think its time to toss the
>> rice box VHF radio and go back to transverters. I had a 3 dB SYSTEM NF
>> using a 6CW4 2m converter and my 75S3B back in 1965. I'm sure one of the
>> converter's I've inherited from estate sales using a 417A will do a
>> little better for NF, though it may not handle the local FM BC station
>> (at a mile) or the inband APRS stuff at about that distance.
>>
>> But so far for VHF I'm satisfied that I hear as well as I can on 6 and 2
>> and maybe 432 with my FT-857D. The DSP isn't all that much help in weak
>> signals except it rolls off high frequency audio noise on SSB. The
>> Collins 500 Hz mechanical filter does improve CW weak signal to noise.
>> And unlike the FT-726 and FT-736 that shifted the receiver frequency
>> when changing from SSB to CW and back causing loss of contacts from
>> going off frequency, it doesn't make that dastardly shift. It even works
>> CW while in SSB with one menu setting so that mixed mode contacts are
>> trivial. Want CW, start sending with the key. Its that simple. An having
>> worked WV and Florida last year on 2m, I think the sensitivity is
>> decent. I copy stations that can't hear me with it's 50 watts on 2m, 100
>> watts on 6m. I like the first 857 so well, I bought a second one at a
>> ham fest. I've not used the second one much, the previous owner did a
>> super master reset that upset the computer settings for alignment and
>> alarm thresholds. But it does work. I think SSB would be improved with
>> the optional mechanical filter, might acquire one someday. I've also
>> used it recently for RTTY PSK-31 with the simplest of interface, a mini
>> din cable in the radio jack split to stereo plugs to fit the sound card
>> interface. Having line level ins and outs made the integration super
>> simple.
>>
>> A few years back I studied how I was going to be on VHF and up and one
>> option was a HF rig with transverters or a 736 with 220 and 1296
>> modules. Turns out the 736 receiver on 2m is junk and has so little
>> front end gain that there's 30 dB between signal detection and AGC
>> threshold. That's hard on the ears with the audio gain cranked up to
>> hear weak signals and a local (within 100 miles) comes on. In the 220
>> module I put in a MAV11 mixer buffer to give it more front end gain and
>> to give the mixer a proper termination. The added gain makes it sound a
>> lot better, but I can't prove with signal or noise generator that I
>> changed its sensitivity and I still have to use a double 222 cavity to
>> hear anything but channel 13 hash on the band. Now that module's control
>> cable has broken again and I've not been successful at fixing the
>> connector. Same thing has happened to the 1296 module but I got
>> snookered on it from an epay purchase. The seller claimed it was
>> perfect. It seems to have a bad output module and when I opened it up,
>> ALL the RF cables were unplugged. It now receives but I broke its
>> control cable. Yaesu can't identify the cable assemblies by description
>> in the technical manual nor in the parts department. It may never work
>> for me.
>>
>> Last year I picked up an IC-R7100 "communications receiver." So far I've
>> heard no signals on 1296, not even from Des Moines. Its deaf too. But
>> then after being screwed with an IC-211, ICOM is a dirty four letter
>> word under this roof.
>>
>> Back on the transverters and HF rig. I was considering Omni V or VI but
>> I found they copied Icom and shifted to LSB for CW, even on 10m and that
>> makes cross mode VHF contacts impossible. So I bought a Corsair II that
>> hears great and doesn't do that stupidity. If the Omni V and VI do that
>> shift I'm suspicious the VII does it too. Probably can be cured with a
>> computer doing the control, but I prefer to hear ham signals, not my
>> computer's hash on VHF and up so I don't use the computer when working
>> VHF weak signals.
>>
>> I've not use an IC-746 on 6m but I have for FD a couple times. I like my
>> 857 better, though there are reports the 857 can't handle a strong a
>> batch of signals as the 746. One year with the stations close together
>> so we had to use headphones, I kept hearing the rumble of a train, even
>> though we were a couple miles from the nearest tracks (Isaac Walton). It
>> was envelope detecting the SSB stations in the shelter.
>>
>> One year at FD in my barn we used an IC-730 that acted like it had no
>> AGC. That the 211 have made ICOM not welcome here.
>>
>> 73, Jerry, K0CQ
>>
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>>
>>
>>
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