So just a quick update on the SB-313.  Yesterday I brushed off all the dust from the case and front panel and fired it up.  It seems I will have to open her up and do some repair work before I can get those sensitivity numbers.  No internal 25 kHz or 100 kHz calibrator signals and no over-the-air HF signals with ext antenna connected.  Will report back after I fix whatever went south in the last 20-30 years or no use.

W8BYA

I have seen these signals go up and down in frequency on my HP SA.  Have no idea what they are but the first thing that came to my mind was that someone modified their rig to xmt on all frequencies and was then tuning their VFO up and down in frequency checking the SWR of an antenna.

W8BYA

Maybe you can give us a freq of some of the signals that are stumping you and a description of what you heard.  Between those two sites I see the vast majority of schemes identified so if it is something different that would be neat to hear.

W8BYA

"I am realistic enough to expect that much of it is stuff that civilians will never get understanding of, but is there any web site that catalogues or discusses the known and the unknown?"

If I understand your question right, you are wondering what different forms of modulation & signal types you might find on HF?  I'm not positive of your question.....but, Google is your friend.  Just for starts see these two sites below.  In addition there were hundreds of others I found in just a few minutes.

http://wiki.radioreference.com/index.php/HF_Digital_Decoding

http://www.kb9ukd.com/digital/

W8BYA

I would like to know if the antenna can be directly coupled to the receiver, and if so, would there be any performance issues?

Gedas, W8BYA

Over the weekend I installed a full wave length, single element delta loop antenna for 40m between two self supporting towers.  The antenna is in a triangle configuration with the horizontal side at the top at ~70' with the feedpoint down at the bottom at about the 20' level.  The loop favors E/W on 40m and has a TOA of around 30 degrees and a gain of almost 8 dBi. The loop is matched to 50 ohms through a series section line transformer. My goal is to use the loop as a general purpose SWL antenna on the different bands.

Using the two receivers of the flex 5000A I thought it would be interesting if I fed one receiver with the new loop antenna and fed the 2nd receiver with a CC R8 reference vertical that is ground mounted with the feedpoint at about 10'. Both antennas are in the clear.

Along those lines, I thought some members might find it interesting to see the relative responses of both antennas for several HF bands like I did.  I took a snap shot of the 16m, 19m, and 40m bands during the daytime at about 14:30 UTC.  Below are the URL's for those 3 snap shots with the loop being the top trace in all 3 cases:

http://gedas.cc/v/Misc/HAM-1/16m+band+2-ants.jpg.html

http://gedas.cc/v/Misc/HAM-1/19m+band+2-ants.jpg.html

http://gedas.cc/v/Misc/HAM-1/40m+band+2-ants.jpg.html

I guess the thing that struck me the most was how little difference there was between the two antennas, overall.  For some reason I was just expecting the loop to clobber the small vertical every where.  In general, it seems on 40m, most of this signals were arriving at a higher angle of arrival and the loop provided a slight advantage, but not huge.  On the other bands, the R8 seems to have provided slightly higher levels on some signals, but again, nothing huge.  If there is interest I can run more tests on more bands and at different times.  One test I will be doing soon is to repeat the 40m tests at night when lower angle DX signals will be present.

73 Gedas, W8BYA

Hi there and thank you for the reply and information.  I like that description "Vulcan mind meld system" LOL. As I mentioned in my post above I will now (unfortunately) have lots of time on my hands and will be able get some actual sensitivity numbers for the different bands for comparison.  I do own several recently calibrated HP sig gens, and along with a true RMS reading HP-3400A volt meter getting the required numbers will be a snap.

73 Gedas W8BYA 

Hi Don, wow this is great.  I was wondering if I would ever find another SB-313 user.  Your report gives me important information about my rigs issue.  Thank you for taking the time to chime in.  Last week my employment status was modified for me after 30+ years in the defense electronics industry and I now will have plenty of time to take a good look at my radio.  The issue with the LMO is a common one for many of the Heath rigs like the SB-102 etc since they all used the same LMO.  A good friend of mine did an extensive investigation of his many years ago and traced the problem to an intermittent ground connection.  As I recall all it took was an added ground strap to supplement the existing connection from Heath that was not up to par.  I will get with him and ask for the details again and post them here if you are interested.

73 Gedas W8BYA

"This is my review old eham reveiw of SB-303, that was an amateur band version of SB-313.
Ignacy, NO9E"

Thanks for that Ignacy !
Man, I just realized it's been over 25 years since I did my last realignment on my 313.  I need to go dig up the manual but I seem to remember that all the bands used the same common amplifier/buffers along the entire chain.  If something was messed up on 25m it would sure seem to be an issue on the bands above and or below as well but that isn't the case.  Like I said, it's just one band thats down about 10 dB or so (by ear).  The rest of the bands were red hot !  No overloading ever, no blow-by, nice and stable and a joy to listen to.  All you guys have given me some good info to get me rolling....thanks for helping out and all the info.

73 Gedas, W8BYA

"Hi Gedas. Go to "qth.com" and join the Heathkit reflector. If you search the archives, you will probably find your answer. Or, you can just ask the nice folks there. There is always a lot of discussions about the 3XX receivers.....

ron
N4UE"

Hi Ron, that's really great news.  Thanks very much for that information......will check it out.
73 Gedas, W8BYA

Had to chuckle...."4) for a bunch of SWL types, makes house look like a CIA station
http://www.angelfire.com/rebellion2/sw_underground1/embassy/czechloops.jpg" Too funny.

But, like you, this is an area of interest for me.  I should have removed the word "resonant" from my text....I actually know better....I only included it as that was a direct quote from KB6RWX.  I too have non-resonant antennas, designed that way on purpose by me that work very well.  I am actually leaning towards a small active vertical antenna for my initial HF scanning around.  I have room outside and live in a quiet environment and could put up a loop or vertical.  Altough I must say, like this evening, I was floored at how seemingly well even my R8 worked as I tuned around on the various SWL bands.

The thing that is most intriguing for me is to be able maintain a nearly constant azimuth and elevation pattern across a very wide range of HF frequencies.  As long as I have the S/N I will be happy.  Just trying to get a feel from others before looking further or before home brewing something myself.  TU very much for the neat links earlier and thoughts most recently.

Gedas, W8BYA

The work and level detail by K8ZOA is most impressive.  After Jack provided a brief description of the available antennas he has at his disposal, I was drooling & hoping for some comparisons between all of them.  I looked for additional articles on his site but could find any. Now that would be interesting since many of us do have V's and dipoles and yagis for bands other than the SWL bands.  Do you by chance know of any such reports ?

Ref comments by KB6RWX, I think a more interesting part of his report was:
"Active antennas will generally not perform better than a full size (resonant) antenna or even a long wire. Even so, active antennas are useful to those desiring to achieve adequate performance, but do not have the space for a long wire or other full sized antenna. Another major advantage is that is that an active whip is omni-directional which a long wire is definitely not. In fact, long wire antennas are fundamentally bi-directional and can be extremely directional depending on its physical length with respect to the signal frequency involved."

This makes me even more interested since if the small active antenna can even get close to the performance of a full-sized or resonant dipole antenna for one of the SWL bands, then IMO it may be very usefull.

Gedas, W8BYA

Hello group.  I do not own nor have had the opportunity to play with any active omnidirectional HF SWL antennas.  My experience has always been with various random & monoband outdoor wire antennas, and yagi's cut for the various ham bands.

Nowadays, through modelling, I know that these antennas can start to have complex & very undesirable azimuth & elevation patterns once removed from their intended operating frequency.  Having an outdoor omnidirectional, yet sensitive active antenna seems like it would make a nice addition to the copper I currently use.  Has anyone here had an opportunity to try one against the other and be willing to share their experiences?  Or maybe someone can point me to a URL where I might find such information.  Thanks !

73 Gedas, W8BYA 

Thanks for the suggestion Chris I will certainly check it out.  The radio was like that the day I finished putting it together and aligned it.  Back then all the silver on the wafer contacts were nice and shiny but still, maybe something was dorked up for that one band segment and I didn't notice it.

73, Gedas W8BYA 

Hi Tony and thank you for the reply.  I checked out and have ear marked the Ontario DX site.  Thanks for passing along that information.  I like the nice clean layout of the world English summary and will give it a try.

Regarding the SB-313, I knew it was a long shot asking about it but you never know.  Fingers are still crossed.  I am positive all the alignments were done right and I had made numerous checks to make sure all the right parts where in the right places and yet that one lone band was always a little deaf.  Just trying to figure out if it was an original engineering deficiency or something unique to my radio.

I have really fond memories as well as a kid listening with that receiver and all the old wooden console radios I had salvaged earlier from the allies in Detroit as a punk.  I'll never forget my first poke of the B+ line going over to the magnet coil on the big speaker !  It is what got me into electronics and even my career I suspect.

Anyway, what sparked my recent SWL interest was when I connected this bit-bucket radio (Flex 5000) to my 40m dipole and took it for a spin on the SWL bands.  I was just floored at how nice all the stations sounded and how easy it was to tailor the bandpass to reject nearby stations and other interference.  Listening on a set of full fidelity speakers with the right IF bandwidth was a real thrill I had never experienced before.  Other than the old console radios I never had a radio that had nice wide filters.  The SDR adds nice steep walls to those wide filters making them awesome.  The SB-313 was very limited at 6 kHz since it's really a ham rig first (SB-303 clone).  First night out listening to All India Radio at 20 over S9 and sounding like a local AM station still has me in awe.  Even got a kick listening to Radio Iran rant about the west....made me think of ole PO Box 88 or Radio Havana LOL.

Thanks again for the reply Rick, take care.
73, Gedas W8BYA