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Author Topic: R390A vs Tentec VII  (Read 29197 times)
9A5BDP
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« on: September 07, 2013, 11:15:15 AM »

Hi..

For all the hams who have legendary R390A receiver on table beside of Tentec VII...

In terms of weak signal receiving capabilities, its tube type receiver R390A better for CW or narrow band digital modes in contrast to Tentec VII (I have Tentec)? For a some long time I want to acquire one tube R390A receiver and finally I got opportunity to do so...but until my receiver arrive I want how good is in present airwave situation on bands?

Thanks for info's..

73!
« Last Edit: September 07, 2013, 11:37:01 AM by 9A5BDP » Logged
N3QE
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« Reply #1 on: September 07, 2013, 12:59:03 PM »

I have two 390A's, and I own several Ten-Tec rigs (a Triton and an Eagle) and have regularly used Omni VII's in the past.

The stock 390A is pretty sucky for ham SSB/CW use. It has a BFO that can be used for SSB and CW reception but no true product detector. If you've used any ham rig from the past 40+ years, you had a true product detector.

A very common "upgrade" for the 390A is to modify it to include a true product detector.

The tuning rate of the 390A is IMHO very much on the "fast" side when used with narrow filters.

The stock R-390A 100 Hz IF filter (crystal) and the stock "sharp" R-390A AF filter setting work pretty nicely for very narrow bandwidth CW use. Most of the time I am not working that narrow. The stock 1kc IF filter is not bad for tooling around on CW.

You might miss the more typical 350/400/600Hz CW filters that you would expect a CW operator to have in a modern rig.

I prefer the modern Ten-Tecs in terms of CW comfort and usability. I prefer the 390A for AM or SWL reception. That should not be a surprise - the general coverage rigs generally are not optimized for CW use.

I also have a WJ-8716, a well respected modernish general coverage receiver, and again it is very nice for AM/SWL BCB type usage. It has a true product detector and designed-in CW and SSB bandwidth filters, but I do not think it is very optimal for CW use. It is pretty decent for SSB "utility monitoring" use.

I strongly recommend most any ham receiver for ham CW use, over a general coverage receiver for CW use. The ham receiver really has been optimized in terms of controls etc. for CW use.

I strongly recommend a good general coverage receiver (like the R-390A) for SWL'ing and AM reception.

Tim N3QE
« Last Edit: September 07, 2013, 01:02:33 PM by N3QE » Logged
G3RZP
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« Reply #2 on: September 07, 2013, 01:56:27 PM »

I think that, in general, when it comes to CW, very few designers in the last 50 years have ever actually OPERATED CW, and so don't understand the requirements. Certainly, as a professional designer, I found that to be the case - even in companies building ham radios. Figures published on the R390 series suggest that for IMD, there are many better sets available now.
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K8AXW
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« Reply #3 on: September 07, 2013, 08:16:34 PM »

BDP:  If you have an R-390 on the way.... congrats!  I was one of the first to use the R-390 in the military in, I think, 1956. At that time it was considered the finest receiver available and the price tag reflected it...... $2400.00 1956 dollars.  That was approximately double the costs of the other receivers the military used, like the Hammarlund SP-600.

I have no experience with the 390 on SSB but understand it's not the best but can be modified for that mode.

On AM, fine and on CW very good.  The only thing I didn't care for with the 390 was that you can't "spin the knob" to get to another frequency in a hurry.

At any rate OM, you will own a classic and even after all these years they are very much in demand and still command respectable prices.

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AC5UP
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« Reply #4 on: September 07, 2013, 10:20:00 PM »

Lest we forget, Unca' Sam had a solution for SSB reception with the R-390 and R-390A that worked remarkably well... The CV-591A/URR outboard converter.



By contemporary standards back in the day the combo was stable enough for 24/7 cold war spookery and today there are diehards who will tell you that for audio quality and lack of ear fatigue the two still work well together.
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G3RZP
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« Reply #5 on: September 08, 2013, 01:31:21 AM »

Aren't there some problems with the mechanical filters degrading? Considering the probable age of some them, not surprising.
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KG8LB
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« Reply #6 on: September 09, 2013, 03:28:03 AM »

Never cared for the trash can mechanical filters in Cow-rinz radios . The mechanicals were intended as a cost cutting measure as the L/C filters wee indeed a costly system to produce , even then .

      However , the R-390 (non "A") had absolutely excellent L/C filters that were among the very best ever made .  My personal favorite of that series radio was the R-725 , a very short run hybrid (only about 250 were built) . The R-725 had the fine RF deck of the R-390A mated to the R-390 style L/C IF deck  . This was a marriage "made in heaven ! I stumbled across 4 of the R-725 receivers at Fair Radio about 20 years ago and bought all 4 of them  .  And ,yes the TMC manufactured slop-bucket convertor already mentioned  is a superb solution for CW and those who must do SSB .
  I also own the TMC GPR-90 . The matching GSB-1 SSB adaptor works quite well for CW, SSB . The GSB-1 and the CV-591 Technical Materiel units are well made and work easily on other radios that employ a 455 KC IF system .  I use them on Super Pro 600 Hammarlunds with good results .

 BTW  , the degradtion of mechanical filters is a bit overblown . The R-390 / R-390A /R-725 series is still capable of outperforming the typical rice-box radio and are far more durable .  The R-390 series is also very easy to service / align thanks to the modular construction .
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KC4MOP
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« Reply #7 on: September 09, 2013, 03:38:13 AM »

Lest we forget, Unca' Sam had a solution for SSB reception with the R-390 and R-390A that worked remarkably well... The CV-591A/URR outboard converter.



By contemporary standards back in the day the combo was stable enough for 24/7 cold war spookery and today there are diehards who will tell you that for audio quality and lack of ear fatigue the two still work well together.
I remember that CV 591 box. The military was able to get 4 "channels", of audio using DSB with reduced carrier. It could be a combination of voice, or 12 teletype per sideband. The early comm centers were using HF for long haul comms and rhombic antennas. Viet Nam was the modernization of communications using Tropo scatter.
Fred
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KC4MOP
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« Reply #8 on: September 09, 2013, 03:41:31 AM »

May I ask where there is any info on modding an R390A to have a product detector. Hi-fidelity audio? I have an outboard box that takes the 455 i.f. Capable of SSB also, BUT not the full audio range. I listen to music on short wave. I presently listen from the Diode Load terms on the back of the set with a nice tube amp and speakers.
Thanks for any links...I'll be googling
Fred
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KC4MOP
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« Reply #9 on: September 09, 2013, 05:30:11 PM »

The CV 591 is a lot of electronics and must be a killer detector......it still commands a $700-995 price tag.
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N3DT
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« Reply #10 on: September 10, 2013, 12:35:56 PM »

It's easy enough to build a product detector for the 390A, just take the 455 if out and make your own audio chain.  All external to the radio too.

And yes, the filters do degrade.  I've got 2 390As that the filters are leaky and mess with the AGC, plus when they get really bad, the innards start falling around inside the case.  What ever foam stuff they used to hold them together has turned to a sticky mess by this point.  I've been in the process of taking them apart and repairing them using foam from hardline and it increases the leakage and will hopefully last longer than I will.





Of course it takes forever.
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KC4MOP
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« Reply #11 on: September 12, 2013, 03:35:12 AM »

gotta have a lot of patience to do that surgery. But worth it in the end.
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G3RZP
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« Reply #12 on: September 12, 2013, 05:56:38 AM »

N3DT,

Some popular rigs made over here were by KW Electronics. They used Kokusai mechanical filters, and had exactly the same problem with the foam deciding to die after 30 or so years. Some people managed to rebuild them.

Well done on the rebuild...
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KG8LB
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Posts: 240




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« Reply #13 on: September 17, 2013, 09:48:07 AM »

It's easy enough to build a product detector for the 390A, just take the 455 if out and make your own audio chain.  All external to the radio too.

And yes, the filters do degrade.  I've got 2 390As that the filters are leaky and mess with the AGC, plus when they get really bad, the innards start falling around inside the case.  What ever foam stuff they used to hold them together has turned to a sticky mess by this point.  I've been in the process of taking them apart and repairing them using foam from hardline and it increases the leakage and will hopefully last longer than I will.





Of course it takes forever.

   Didn't say not a problem , just a bit overblown .
  When you have the R-725  or original R390 with it's fine L/C filters you can avoid the tinny can filter  "problem" altogether  Wink
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G3RZP
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« Reply #14 on: September 17, 2013, 02:13:41 PM »

I regard myself as a relatively competent technician when it comes to radio - as well as being a Senior IEEE Member. Looking at what you guys have done with restoring mechanical filters, if I ever wore a hat, I'd take it off to you all. Congratulations - just don't let the chest swell enough to burst the buttons!

Seriously, I'm impressed.
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