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#1
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You still haven't explained how the tubes fiqure into this...
Of course it's a good receiver. It was pretty much a lab instrument. But it's the overall attention to detail, rather than the use of tubes that makes it good. If the one picking up the het couldn't get the audio, it's due to poor filter shaping in that radio.. The sensitivity pretty much means nada for him in Fla. You'd have to be on a frozen desert Isle to have quiet enough cdx to take advantage of that sensitivity on MW. Severe overkill for 99%...I'm sorta dubious of how those numbers were measured also, but thats another story... Doesn't really matter as even 1 uv for 10 db s/n+n is overkill in the MW band.. I don't dispute that it's a good radio. It's one of the best. But the same could be done solid state, if they still built radios like collins did 50 years ago... The sensistivity on my icom on MW-AM is way less than those numbers, and I still have way more sensitivity than I could ever use, unless I was waaaaayyyy out in the sticks , in the dead of winter...And even then, I probably have enough.. In his case in Fla, just having a R-390 alone is not the answer. His location is not quiet enough to take advantage of any great sensitivity numbers. The only thing he needs is good selectivity. Any half decent radio, tube or s/s, will have enough sensitivity if any kind of decent antenna is used. The station will either be there, or it won't, due to cdx. If it isn't, nothing he uses will likely help too much. On HF, the 706g does .15 uv for 10db.. .12 on six meters. ..11 on vhf/uhf.. Thats overkill for HF and six...I never use the preamp...It's *too* much sensitivity, so I actually use less than those numbers ..Those are with the preamp on. It's reduced on AM mode, how much depending on the band, but it's still never lacking for sensitivity. Not even close. And it's a fairly cheap radio, relatively speaking. Much less than the R-390 when it was new...About 1/20th the size and weight...:/ BTW, I do have both tube and solid state radios, so it's not like I've never used a tube rig before to compare... Receiving wise, there is nothing done with tubes, that can't be done with solid state. Now audio....That's open to real debate.. I don't deny many tube radios have great audio to the ears. But so does my 706 if I'm going into the sound card, and to my kenwood stereo audio amp, good speakers, etc... It's my best sounding radio for listening to the "rack" crowd, that run all the transmit audio gear. Way better than my old all tube Drake R4, which sounds thin in comparison, due to it's filtering. Not much low end on that radio... MK |
#2
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#3
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David wrote: The front end (tracking preselector, RF amp, Mixer) makes abig difference. As does the absolute silence of the circuitry. Still, no one mentions where the tubes come into play... All the above could apply to my old drake R4...Except I disagree about the absolute silence of the circuitry... Nothing is absolutely quiet... The front end (tracking preselector, RF amp, Mixer) of my kenwood TS-830 is very good, and it has no tubes... Are you telling me it would be better if I converted those circuits to tubes? Sorry, I just don't buy it... The R-390 is a great receiver because it was a *very* expensive, carefully designed radio made for commercial/lab and gov use. Not because it has tubes. I can list a whole slew of other all tube models that are fairly pathetic in performance compared to the collins. Why didn't the use of tubes help those models? MK |
#4
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#5
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Why didn't the use of tubes help those models?
MK Dynamic range. Overload immunity. ........... Because of tubes? I dunno...All of my radios have good enough dynamic range, and none overload...Tube, or solid state...That doesn't tell me too much... Only cheaper radios have poor dynamic range, and overload...:/ But, we ain't talking about R-390's. We are talking about tubes themselves vs solid state.. I'm still waiting to hear why the use of tubes didn't help some radios to avoid being pieces of junk... If tubes themselves are so great, *all* tube radios should be about on the level of a R-390. But they ain't... Not by a long shot. The old collins/R390's, etc, etc, and the collins A and S amateur line, and the older 4 line drakes are about the only tube radios that I still consider worth using. All the rest are basically junk, for my needs. I'm sure this will attract flames 0-plenty, but I'm picky. I demand *very* good stability. The collins and drakes basically used the same type of circuitry. A collins or drake is just as stable at 30 mc as it is at 3 mc. And the readout scale is the same also..You can't say that for many other old tube rigs. I can think of a few that are best used as doorstops...Unstable at higher freq's, and drifty as a Chicago snowstorm. Both my kenwood and icoms can be turned on dead cold, and never need to be retuned to clarify a SSB signal. Ever. I can sit on freq for weeks at a time, and never have to touch up my tuning..."Sure, they may microdrift with temp changes, but it's never enough to notice by ear" Most tube rigs can't do that. I know my drakes can't. They can come close, but after about a day, you will usually need to touch up the tuning a tad. I don't know how a R-390 fares in this regard, but if it's *rock* stable, it's the tube exception to the rule. And if it is, it's probably cuz it has a xtal oven, etc...Not cuz it uses tubes... I won't mention that most of my tube gear needed annual alignment tweaks and tube checks/changes to keep 100% up to par. My solid state rigs never change...Don't have to be fussed with every few months, if you leave them on all the time like I did/do. I still like tube radios, and still have a few, but I'm not blind to reality...There are not many tube radios that are up to R-390 standards. Tubes look warm, and may add slightly to the BTU rating of the heating system in the winter, but they ain't the magic answer to SW-MW nirvana... Heck, I hardly use mine anymore..Overall, I find them inferior for *everyday* use. IE: readout resolution, stability, tuning rates, memories, heck , I could go for days... The R-390 is a great radio, but not all tube radios can claim to be R-390's.....Quite possibly none can. The collins and drake ham radios are fairly close though. But neither of those were cheap radios when they were built either. MK |
#6
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#7
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David wrote: I think you answered your own questions, several times over. So, this still means you think everyone should go out and buy an old tube radio, even if it's not a R-390? FYI, a well maintained aligned R390A in a stable environment can be tuned within 300 Hz of a target frequency and will drift less than half that figure over 24 hours. Sorry. Not good enough...I used to get anal cuz my 830's internal VFO drifted 40 cycles with A/C cycling off and on.. Even thats enough to require retuning of a SSB signal. Thats why I went to the VFO-230 on the 830, which drifts nada.. My 706 will tune within 1 hz of a target frequency as far as readout...If you count slewing error thoughout the HF spectrum, the max error might be hummmm, 1-20 cycles depending on the freq being used...Being I calibrate the radio at 10mhz, and say I'm on 40 meters, the error will be under 5 cycles. And I don't even have the hi-stab xtal...It could be even better, if I wanted to spend a lil more $$$. Within 300 hz of a target freq? Man, that's pitiful for the year 2005... Drift? If the room temp is stable, the icom has no real drift. Not enough to ever require retuning SSB anyway. You'll be a long ways off from me, if you drift 150 hz in a day. Same applies to the kenwood using the external VFO. You may have dynamic range, but your readout and stability are fairly lame to my standards.. There ain't a $10 transistor made with the dynamic range of a tube designed for small signal RF amplification. Doesn't really matter if dynamic range is not a really much of an issue to begin with...MK |
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