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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