[R-390] Official specs

Sun Oct 6 17:37:38 EDT 2024

Apparently a LOT of ham transmitters were leaking today.  I heard QSOs on 10, 14, 18, 21, and 28 MHz (California QSO Party).  Really nice to hear things on those bands for a change.

Barry - N4BUQ

> Hi
> 
> Signal generators leak as well. One of the pretty normal “drill’s” on a VHF
> generator was to grab a portable radio and see what you could detect as you
> waved it around the generator.
> 
> It was always a bit amazing to find two apparently identical generators that had
> very different leakage performance. Needless to say, the bad one headed back to
> the repair folks. Sometimes they could find the problem … sometimes they
> couldn’t. Home made “EMI probes” typically got used a lot in that process.
> 
> Bob
> 
>> On Oct 6, 2024, at 2:22 PM, Les Locklear <leslocklear at hotmail.com> wrote:
>> 
>> Well, the type of coaxial cable used makes quite a difference too.
>> Many years the R-390A "Guru" and e-mail favorite Nolan Lee stopped by my place
>> for a visit. We discussed problems he was experiencing with "leakage" of
>> signals on his coaxial cables he was using in his signal generators. I
>> suggested he might want to try RG-223 vs. the RG-58 he was using. I had a good
>> bit on hand and rolled out about 30 ft. for him to try along with a roll-around
>> rack and antenna material in exchange for a couple of pieces of test equipment.
>> Shortly after, he had a stroke or health event and wasn't to be heard from
>> again. So, I don't know if he found success with the RG-223. But the results
>> from this website should tell the tale:
>> https://www.awcwire.com/allied-university/this-vs-that/rg223-vs-rg58?srsltid=AfmBOopRQ3OqIMcBjxiwimtP8KuLE3GiI_HOTGjmFRK1HZVtIg8KTyed
>> If you are trying to get to "never,never" land on sensitivity specifications you
>> might want to check how much leakage you have from the standard coaxial cables
>> you might be using. "actual" measurements of 135 to 140 db are much more
>> realistic for a well aligned/tuned R390A/URR. I would suspect the same from the
>> older R-390/URR.
>> I'm too old and slow to be doing "detective" work for any of you regarding being
>> able to hear a "flea fart in Tahiti" on a particular receiver, but searching
>> the internet and reliable websites will prove me right regarding coaxial cable
>> used on "Test Equipment" or Signal Generators.
>> Les Locklear
>> Everyone has a photographic memory.
>> Some people just don't have film.
>> ..Unknown..
>> 
>> 
>> ----- Original Message -----
>> From: Bob  Camp <kb8tq at n1k.org>
>> To: Ing. Giovanni Becattini <giovanni.becattini at icloud.com>
>> Cc: <r-390 at mailman.qth.net>
>> Sent: 10/6/2024 7:37:04 AM
>> Subject: Re: [R-390] Official specs
>> ________________________________________________________________________________
>> 
>>> Hi
>>> There’s nothing wrong with the 80,82,84 generators considering when they came
>>> out. They still can be useful. However keeping them in “full spec” running
>>> condition  gets harder and harder as the years go by.
>>> Bob
>>>> On Oct 5, 2024, at 5:56 PM, Ing. Giovanni Becattini
>>>> <giovanni.becattini at icloud.com> wrote:
>>>> Hi Bob,
>>>> Thanks for the interesting links. By means of them, I could discover that the
>>>> model 80 is the civil version of my TS-497 which I bought almost for free
>>>> because nobody wants it. It has wonderful mechanics and a very good attenuator
>>>> which arrives down to 0.1uV.
>>>>> Il giorno 5 ott 2024, alle ore 17:00, Bob Camp <kb8tq at n1k.org> ha scritto:
>>>>> Hi
>>>>> I’m quite sure the engineers involved understood this and that. The gotcha is
>>>>> that these spec’s are written by a committee. Having sat for un-ending amounts
>>>>> of time on some of those committee’s, what gets said is not always what goes in
>>>>> the spec. This or that gets shoved off to some other process or document ( or
>>>>> maybe simply ignored). Often the “shoved off” stuff turns into informal notes
>>>>> that somebody using the spec very much needs to have handy. Welcome to why you
>>>>> spend all those hours sitting there …. :) :)
>>>>> While that app note is a fun read, it turns out that it’s not the full story.
>>>>> These generators do not always have a 50 ohm output impedance. Put a VNA on one
>>>>> and crank the attenuator …. not always 50 ohms. If you take a look at this
>>>>> manual from 1945 (for the 80, a cousin of the 82):
>>>>> http://bee.mif.pg.gda.pl/ciasteczkowypotwor/Boonton/Boonton_Model_80_Manual.pdf
>>>>> It includes an “optional 6 db pad”. Why? The output impedance was a bit wonky
>>>>> (even for that era) without it. The model 82 (and its cousins the 80 and 84)
>>>>> came out in the while WWII was still going on. They stayed in production for
>>>>> quite a while after that:
>>>>> https://www.worldradiohistory.com/Archive-Catalogs/Miscellaneous-
>>>>> Manufacturers/Laboratory-Standards-1949-Catalog.pdf
>>>>> It’s a generator that “covers the frequency range”. (it’s the only one in that
>>>>> catalog that does so). An equivalent would be another generator that covers the
>>>>> frequency range. By the 1960’s most outfits had moved on from WWII test gear
>>>>> (if the spec allowed them to do so). So: *Is* this a reason the sensitivity
>>>>> specs are a bit crazy? We simply don’t know. We *do* know that they are more
>>>>> than a bit off from what every example of the radio any of us have seen
>>>>> actually does. Given how tight the rest of the specs’s are, That’s pretty
>>>>> strange. *Could* it be the reason? …. it just might be. You certainly can
>>>>> confusion about that 6 db pad on the model 80 popping up in a lot of places.
>>>>> Bob
>>>>>> On Oct 4, 2024, at 11:13 PM, Jim Whartenby via R-390 <r-
>>>>>> 390 at mailman.qth.net> wrote:
>>>>>> BobI don't know why you are speculating "Since you can use any signal generator"
>>>>>> when MIL-R-13947B(SigC) on page 20 specifies the Measurements Corp Model 82
>>>>>> signal Generator, or it's equal.  Your concern with matched impedances between
>>>>>> the generator and the R-
>>>>>> 390 may appear to be valid but this seems to have been accounted for in the R-
>>>>>> 390 spec with higher input voltages to account for the mismatch losses.  Collins
>>>>>> and the Signal Corps specified the 125 ohm input impedance of the R-390 and
>>>>>> they were surely aware that the standard impedance of high end signal
>>>>>> generators was normally 50 ohms.
>>>>>> Check out http://hparchive.com/Boonton/BRC-The-Notebook-03.pdf which is a 1954
>>>>>> Boonton Radio explanation for the use of Dummy Antennas.  Everything you need
>>>>>> is in the first four pages.  It explains why the mismatch between 50 ohms and
>>>>>> the receiver input impedance reduces the loading on the receiver input tuned
>>>>>> circuits and recovers the Q of the receiver RF input tuned circuits.  This also
>>>>>> affects favorably the S+N/N measurement.  There is a reason for the apparent
>>>>>> madness.
>>>>>> Jim
>>>>>> Logic: Method used to arrive at the wrong conclusion, with confidence.  Murphy
>>>>>> On Friday, October 4, 2024 at 07:23:24 PM CDT, Bob Camp <kb8tq at n1k.org> wrote:
>>>>>> Hi
>>>>>> Based on a *lot* of interaction with DOD source inspectors over the years … it’s
>>>>>> very much a “that depends” sort of thing. The guy you get this month may be
>>>>>> *very* different than than the guy who comes in next month. Since you can use
>>>>>> any signal generator, there is room for “trouble” with minimal specs. Typically
>>>>>> the way this works out is a request to clarify things. Unfortunately that stuff
>>>>>> does not get into the official specs. Yes, some of us have pointed that out as
>>>>>> a problem …. never got addressed AFIK. Bob
>>>>>>> On Oct 4, 2024, at 5:19 PM, Jim Whartenby via R-390 <r-
>>>>>>> 390 at mailman.qth.net> wrote:
>>>>>>> Bob
>>>>>>> You are over thinking the testing.  The generator is terminated but not in it's
>>>>>>> characteristic impedance.  Collins and the agency letting the contract agreed
>>>>>>> on a test method and wrote it down in the test procedure.  Anything that would
>>>>>>> affect the testing like VSWR has already been considered and accounted for.
>>>>>>> That Hams don't use the proper termination for the signal generator, according
>>>>>>> to the spec, which affects the perceived sensitivity is another issue.  Spec is
>>>>>>> spec as they say.
>>>>>>> Not all Government Source Inspectors are knowable about the equipment that they
>>>>>>> are reviewing and putting their inspection stamp on.  Not all Signal Corps
>>>>>>> equipment is inspected by Army GSIs.  Every once in a while, Army equipment
>>>>>>> will have an anchor stamp on it and vice-versa.  Sometimes certain specs are
>>>>>>> wavered if not considered critical, most often they are not.  Again, spec is
>>>>>>> spec.
>>>>>>> Regards,
>>>>>>> Jim
>>>>>>> Logic: Method used to arrive at the wrong conclusion, with confidence.  Murphy
>>>>>>> On Friday, October 4, 2024 at 02:43:36 PM CDT, Bob Camp <kb8tq at n1k.org>
>>>>>>> wrote:  Hi
>>>>>>> Ok …. but …..
>>>>>>> If it is simply a resistor, then the generator is unterminated. It’s designed
>>>>>>> and calibrated to run into a 50 ohm load. If all that’s there is a series
>>>>>>> resistor the generator is not properly set up (and thus not calibrated ….). Yes
>>>>>>> some generators deal with this better than others. My guess is that there’s
>>>>>>> more to the load circuit than just that resistor. Without a schematic …. who
>>>>>>> knows ….
>>>>>>> Bob
>>>>>>>> On Oct 4, 2024, at 12:53 PM, Jim Whartenby via R-390 <r-
>>>>>>>> 390 at mailman.qth.net> wrote:
>>>>>>>> Bob
>>>>>>>> But we do know what the interface is between the signal generator and antenna
>>>>>>>> input.  On document page 20, the balanced RF input is in series with a 125 ohm
>>>>>>>> non-inductive resistor and the unbalanced RF input is in series with a 50 pF
>>>>>>>> capacitor.  Both interfaces do not include the generator's output impedance.
>>>>>>>> As for the sensitivity not being what the R-390/URR or the R-390A/URR is capable
>>>>>>>> of, well there are perhaps 100's of tests that the receiver must successfully
>>>>>>>> pass before it is accepted.  Tightening any of the specs to exactly what the
>>>>>>>> receiver may be capable of passing will guarantee that no one receiver will
>>>>>>>> ever pass all of the acceptance tests.  Then there is the added problem of your
>>>>>>>> test equipment's error tolerance and being traceable back to the NIST
>>>>>>>> standards.  Is your 10 microvolts from the signal generator really 10
>>>>>>>> microvolts?
>>>>>>>> Unless otherwise stated, the specification calls out a value that the receiver
>>>>>>>> must do better than.  A sensitivity of just under 6.5 microvolts for a 10 dB
>>>>>>>> S+N/N with an audio power output of 10 milliwatts seems reasonable over the
>>>>>>>> range of 2 to 32 MHz for either balanced or unbalanced RF inputs.  This is
>>>>>>>> perhaps typical for just about all HF receivers built for the military, at
>>>>>>>> least for what I am aware of, but I am sure that there will be the rare
>>>>>>>> exception.
>>>>>>>> Regards,
>>>>>>>> Jim
>>>>>>>> Logic: Method used to arrive at the wrong conclusion, with confidence.  Murphy
>>>>>>>> On Friday, October 4, 2024 at 09:39:26 AM CDT, Bob Camp <kb8tq at n1k.org>
>>>>>>>> wrote:  Hi
>>>>>>>> The gotcah here is that we really don’t know what the interface between the
>>>>>>>> signal generator and radio looked like for these official tests. Despite the
>>>>>>>> document going into a lot of detail, they did not include a schematic or a part
>>>>>>>> number. (or at least not one that I could find). There are a *lot* of ways they
>>>>>>>> might have been doing things …..
>>>>>>>> Bob
>>>>>>>>> On Oct 4, 2024, at 10:19 AM, Ing. Giovanni Becattini via R-390 <r-
>>>>>>>>> 390 at mailman.qth.net> wrote:
>>>>>>>>> But when we perform the classical sensitivity test with a modulated signal, do
>>>>>>>>> we get the AM or CW value?
>>>>>>>>> Following the instructions I got a value of -104 dBm, i.e. 1.41 uV. Because I
>>>>>>>>> used the DA-121, the real value should be even better, far from 5 uV. And
>>>>>>>>> surely my R-390A is not as good as it could be .
>>>>>>>>> Is my reasoning correct?
>>>>>>>>>> Il giorno 4 ott 2024, alle ore 16:13, Barry <n4buq at knology.net> ha scritto:
>>>>>>>>>> I don’t think of 1uV as “bad” but most of these radios will beat that. Thanks,
>>>>>>>>>> Barry
>>>>>>>>>>> On Oct 4, 2024, at 8:55 AM, Ing. Giovanni Becattini via R-390 <r-
>>>>>>>>>>> 390 at mailman.qth.net> wrote:
>>>>>>>>>>> ?Wow, thanks!
>>>>>>>>>>> By the way, do you know why the sensitivity values were so bad? Are we the ones
>>>>>>>>>>> who are taking measures that are too lenient or are they the ones who were too
>>>>>>>>>>> conservative?
>>>>>>>>>>> Thanks again
>>>>>>>>>>> Gianni
>>>>>>>>>>>> Il giorno 4 ott 2024, alle ore 15:37, Larry Haney <larry41gm2 at gmail.com> ha
>>>>>>>>>>>> scritto:
>>>>>>>>>>>> Hi Gianni and Barry,  Tom Marcotte and Al Tirevold (SK) obtained and cleaned up
>>>>>>>>>>>> the specs for the 390A and put it on our website.  Here's the link:
>>>>>>>>>>>> mil-r-13947b– (r-390a.net) <https://www.r-390a.net/mil-r-13947b.pdf>.
>>>>>>>>>>>> Unfortunately, the entry in References page indicates it is for the R390(), but
>>>>>>>>>>>> it is also the the 390A.  I will be changing that shortly.
>>>>>>>>>>>> Regards, Larry
>>>>>>>>>>>>> On Fri, Oct 4, 2024 at 4:49 AM Ing. Giovanni Becattini via R-390 <r-
>>>>>>>>>>>>> 390 at mailman.qth.net <mailto:r-390 at mailman.qth.net>> wrote:
>>>>>>>>>>>>> Have ever been released official specs for the 390A?
>>>>>>>>>>>>> The manuals report few data and neither too correct, for what I can understand
>>>>>>>>>>>>> (e.g., sensitivity)
>>>>>>>>>>>>> Thanks
>>>>>>>>>>>>> ______________________________________________________________
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>>>>>>>>>>> ______________________________________________________________
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>>>>>>>>> ______________________________________________________________
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>>>>>>>> ______________________________________________________________
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>>>>>>>> ______________________________________________________________
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>>>>>>> ______________________________________________________________
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>>>>>> ______________________________________________________________
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>>>>> ______________________________________________________________
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