[R-390] Official specs

Sun Oct 6 14:57:02 EDT 2024

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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