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eHam Forums => Boat Anchors => Topic started by: 9A5BDP on September 07, 2013, 11:15:15 AM



Title: R390A vs Tentec VII
Post by: 9A5BDP 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!


Title: RE: R390A vs Tentec VII
Post by: N3QE 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


Title: RE: R390A vs Tentec VII
Post by: G3RZP 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.


Title: RE: R390A vs Tentec VII
Post by: K8AXW 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.



Title: RE: R390A vs Tentec VII
Post by: AC5UP 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.

(http://www.fernblatt.net/pic/390ACV.jpg)

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.


Title: RE: R390A vs Tentec VII
Post by: G3RZP 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.


Title: RE: R390A vs Tentec VII
Post by: KG8LB 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 .


Title: RE: R390A vs Tentec VII
Post by: KC4MOP 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.

(http://www.fernblatt.net/pic/390ACV.jpg)

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


Title: RE: R390A vs Tentec VII
Post by: KC4MOP 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


Title: RE: R390A vs Tentec VII
Post by: KC4MOP 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.


Title: RE: R390A vs Tentec VII
Post by: N3DT 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.

(http://i251.photobucket.com/albums/gg287/DogTi/R390A/filterapart_zpseb3e20cf.jpg) (http://s251.photobucket.com/user/DogTi/media/R390A/filterapart_zpseb3e20cf.jpg.html)

(http://i251.photobucket.com/albums/gg287/DogTi/R390A/filter4k_zps7bf4c9ec.jpg) (http://s251.photobucket.com/user/DogTi/media/R390A/filter4k_zps7bf4c9ec.jpg.html)

Of course it takes forever.


Title: RE: R390A vs Tentec VII
Post by: KC4MOP on September 12, 2013, 03:35:12 AM
gotta have a lot of patience to do that surgery. But worth it in the end.


Title: RE: R390A vs Tentec VII
Post by: G3RZP 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...


Title: RE: R390A vs Tentec VII
Post by: KG8LB 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.

(http://i251.photobucket.com/albums/gg287/DogTi/R390A/filterapart_zpseb3e20cf.jpg) (http://s251.photobucket.com/user/DogTi/media/R390A/filterapart_zpseb3e20cf.jpg.html)

(http://i251.photobucket.com/albums/gg287/DogTi/R390A/filter4k_zps7bf4c9ec.jpg) (http://s251.photobucket.com/user/DogTi/media/R390A/filter4k_zps7bf4c9ec.jpg.html)

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  ;)


Title: RE: R390A vs Tentec VII
Post by: G3RZP 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.


Title: RE: R390A vs Tentec VII
Post by: 9A5BDP on September 19, 2013, 01:59:49 PM
What is purpose of green socket near phone jack socket on the EAC version of 390 receivers?


Title: RE: R390A vs Tentec VII
Post by: VK3DWZ on September 19, 2013, 11:25:31 PM
This socket is a naval modification.  According to Navships 0967-063-2010, the socket is a Diode Load jack used to measure detector voltage.


Title: RE: R390A vs Tentec VII
Post by: 9A5BDP on September 20, 2013, 01:46:34 PM
But for what purpose they used that measurement? It is like checkpoint or for something else...?


Title: RE: R390A vs Tentec VII
Post by: W2RKJ on September 21, 2013, 06:35:56 PM
Concerning that diode load jack, I have a Collins R-388 (1962 Model) that has that jack. I connected that via a capacitor/resistor curcuit and connected that to a amplifier. The audio out of that connection is unbelievable. Very rich and bassy, unlike the pinched audio out of the R-388. Anyone who has that available that isn't using it is missing a whole lot!.


Title: RE: R390A vs Tentec VII
Post by: KC4MOP on September 22, 2013, 04:09:22 AM
Concerning that diode load jack, I have a Collins R-388 (1962 Model) that has that jack. I connected that via a capacitor/resistor curcuit and connected that to a amplifier. The audio out of that connection is unbelievable. Very rich and bassy, unlike the pinched audio out of the R-388. Anyone who has that available that isn't using it is missing a whole lot!.
A very nice secret that not many know about. Beautiful audio from the Diode Load
"Simply obtain an audio extension cable with an RCA plug on one end from Radio Shack. Place a 470K resistor in series with a 10uf, non-polarized (also available at Radio Shack) capacitor and connect it to one of the screws holding the jumper across the "DIODE LOAD" screws on TB-103. Do not remove the jumper. Connect the other end of the capacitor/resistor network to the center conductor of the RCA cable then ground its shield to the "GND" screw located on TB-103 immediately to the right of the "DIODE LOAD" screws. Plug your cable into the TAPE or AUX jack on your stereo receiver, adjust the tone controls as appropriate and enjoy."

Fred


Title: RE: R390A vs Tentec VII
Post by: W2RKJ on September 22, 2013, 07:14:27 AM
Hey Fred, I bet we're blowing some heads up with those comments on the diode load connections if they love those receivers and haven't tried that yet.

Kevin/w2rkj


Title: RE: R390A vs Tentec VII
Post by: N3DT on September 22, 2013, 04:34:24 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.
Well, thanks, but it's just a lot of detailed and time consuming work. It's not rocket science. I still have a couple of filters I need to finish off to get the 390A finished.  After all, it's a hobby. Who else would do it?

The other thing you can do with the 390A is take the 455 if out, convert it to 12 KHz and use some soundcard software to decode it.  Like DReaM or HDSDR, but it's not like listening to the radio, there's a bit of delay which makes it hard to tune, especially in SSB and CW. But AM is pretty good.  And if you can figure out the DRM it should be real good.  I haven't been able to do that yet.


Title: RE: R390A vs Tentec VII
Post by: KC4MOP on September 22, 2013, 05:16:37 PM
I do not want to hijack the thread but DRM radio is a real Dream to listen to. Sounds like perfect FM radio over shortwave.
I have the DRM software in the Flex radio PowerSDR software. I bought the license to decode and build the dll files needed to operate the DRM.
There's a growing number of shortwave stations on the air several hours a day.
And Kevin you are probably very correct. Military audio out of the headphones and even the Line out amps built-in the 390A......UNLESS they were modified for hi-fi audio.
Hi-fi audio already available from the Diode Load terms on the back
Fred


Title: RE: R390A vs Tentec VII
Post by: AC5UP on September 22, 2013, 06:04:06 PM
...and speaking of exploding heads

From time to time a new thread will ask the question: What's the * BEST * external speaker for Hamateur radio use?

Invariably I'll say something to the effect of having good luck with thrift shop orphans (bookshelf stereo electronics gone kaput, speakers still good) as long as they're of the 4 Ohm persuasion and reasonably efficient. Translation: Single driver bass-reflex with a whizzer cone. Within hours a dissenting opinion will assert that only a proper communications grade speaker designed specifically for SSB / CW use is worth having. Even if they are in the $100.00+ price class. If the advertising specifies communication grade, that's whatcha' want. Like the $2.00 orphan is overpriced. Or the AF amp in the radio is broadband. And a mostly flat response curve is a bad characteristic for a speaker.

Then I wonder if these are the same folks running an All Band WonderTenna. You know what that is... Something that makes you wonder who'd pay $250.00 for an antenna made from $20.00 worth of wire and marketed by an eighth of a page advert in QST that features the word 'miracle'.   ;D


Title: RE: R390A vs Tentec VII
Post by: 9A5BDP on September 23, 2013, 11:24:09 AM
Hi guys/girls..

What will be best SSB detector project for the R390A receiver? My receiver finally arrived,I have one EAC maded unit on repair bench and after cleanup and repair/readjusting job I will need some decent SSB detector for ham activity..That will be best to build?
I would like to build some outside unit, not to mod receiver..
For only AM is not a problem, some kind of synchro detectors but with SSB reception..hm..any clues?

73! Dubravko from Croatia 9a5bdp


Title: RE: R390A vs Tentec VII
Post by: W2RKJ on September 23, 2013, 06:17:25 PM
I got a SSB adapter/ProductDetector for my R-388 from Treetop Circuits. Here's the model for the R-390,  http://www.ebay.com/itm/SSB-Adapter-for-R-390-and-R-390A-/321208516105?pt=US_Ham_Radio_Receivers&hash=item4ac984fe09#ht_249wt_1179.



I highly reccomend this company for their products and their tech support. I am not connected with them. I am just a VERY satisfied customer.

73's

Kevin/w2rkj


Title: RE: R390A vs Tentec VII
Post by: 9A5BDP on September 24, 2013, 12:52:14 PM
I know for existence of this product, nice piece of electronics but unfortunately this is not what I am looking for. I want to built detector by myself, using my knowledge and patience for homebrew electronics...Beside of this detector, and one from Surrey will be possible to find some other somewhere on the net or in drawer?



Title: RE: R390A vs Tentec VII
Post by: WB6BYU on September 24, 2013, 02:52:43 PM
There was a circuit for a product detector for tube equipment published in the Technical
Topics
column of the RSGB journal RadCom perhaps 10+ years back, along with a
discussion of how to use some of the old boat anchors (including the R-390 IIRC) for CW
and SSB with the existing detector. 

Not sure just what box my books are in after our recent move - may take me a while to
dig it out, but if someone locally to you has old issues of RadCom it may be
worth looking for it.


Title: RE: R390A vs Tentec VII
Post by: G3RZP on September 24, 2013, 03:23:23 PM
A diode detector on AM wants around 10 volts rms carrier  to minimise distortion. Most product detectors curl up their toes at that. So I used a 6SJ7 (6AU6 will do) as a Hartley CIO  (screen grounded to RF, cathode on a top on the coil)and applied the last IF voltage through a 5 pF to grid 3, which has a low mu: grids 1, 2 and the cathode acting as the CIO. Output from the plate. This works fine: a Norwegian ham didn't like it but I don't think he appreciated that an AM detector needs a lot of volts to avoid distortion and produce enough AGC. Because of that, you can use a very low gain SSB product detector.


Title: RE: R390A vs Tentec VII
Post by: 9A5BDP on September 25, 2013, 09:40:33 AM
To WB6BYU...please if you have some spare time to help me..find this article...Thanx


Title: RE: R390A vs Tentec VII
Post by: G3RZP on September 25, 2013, 01:47:21 PM
There  was an input by me to Technical Topics in RSGB RadCom, but I can't remember when: probably after about 1997. That was using a 6SH7 (octal)/6AU6 (miniature) as a BFO/product detector.

If you really need to know how to make a Hartley oscillator with a cathode tap on the coil, the SSB signal fed in on g3 and the output on the plate, I guess I can find time to make you a circuit diagram.


Title: RE: R390A vs Tentec VII
Post by: WB6BYU on September 25, 2013, 01:57:03 PM
I was hoping you'd remember the article, Peter, and perhaps have a copy on hand, as all I have
are the Technical Topics Scrapbooks, and I'm not sure which box they got packed into.  It
did generate a lot of feedback on whether the old receivers actually needed a product detector
or not.  Many have marginal BFO drive for good demodulation at high signal levels, so backing off
the RF gain control was an important part of the process for CW.

I'm assuming that the R-390 has a BFO, but the injection level and detector linearity are not
optimum for clean SSB, which is why an external product detector is desirable.


Title: RE: R390A vs Tentec VII
Post by: N3DT on September 25, 2013, 06:48:42 PM
If I did an external SSB adapter for the 390A, I'd tap off the 390A bfo with a jfet, boost it with a simple amp and use a diode ring mixer (homebrew or otherwise) mix it with the 455 out and feed the audio into LM380 or similar and then into what ever audio amp you like, if you even need another audio amp.

Actually the radio will work pretty good in SSB if you will deal with the RF control while listening to SSB instead of the audio control.  Just turn the audio up about 60-80% and control the audio with the RF gain.  Of course your filters and AGC needs to be up to spec, or just turn off the AGC.

Only trouble with the 390A is the choice of filters for SSB.

You can use HDSDR with the 390A if you care to convert the 455 to 12KHz and use your sound card.  The AM is real good with that option.  I even use the HDSDR with my TS-2000 and pulled out the 12 KHz output for that.  AM is real great that way, you can have any bandwidth you like, as long as the signal is good.


Title: RE: R390A vs Tentec VII
Post by: W2RKJ on September 26, 2013, 08:05:41 AM
I know for existence of this product, nice piece of electronics but unfortunately this is not what I am looking for. I want to built detector by myself, using my knowledge and patience for homebrew electronics...Beside of this detector, and one from Surrey will be possible to find some other somewhere on the net or in drawer?



Pozar, Bob from Treetop Circuits wanted me to advise you of the following, maybe this could still help you with your request.

The circuits used in our products are (as you know) fully described in our instruction books, which can be downloaded from our website. We have no objection to folks copying them for their own use. If he replicates some or all of the SB-390 circuitry, and adds a BFO and a 24-volt AC supply, he'll have a good "outboard" adapter that will perform as well as the SB-390. I'd recommend a BFO with some range of adjustment, because the best results are obtained when it's adjusted to the right frequency relative to the mechanical filter.

I really like the 4-diode detector because it has a soft clipping action when overloaded. You can get quite good results even with no AGC. You have to "ride" the RF gain, but it's much more forgiving than the detector in the R-390.

Good Luck,

W2RKJ