Numbers Stations and CDAA's

Discussion in 'Ham Radio Discussions' started by K4PP, Jun 30, 2021.

ad: L-HROutlet
ad: l-rl
ad: Left-3
ad: abrind-2
ad: HRDLLC-2
ad: MessiPaoloni-1
ad: L-Geochron
ad: Left-2
ad: L-MFJ
  1. K4PP

    K4PP Ham Member QRZ Page

    Regarding the numbers stations, do you think all of them were really sending coded messages or is possible some were run for the calibration crew at the several CDAA installations? Used for checking the bearings.

    I have been reading a lot of information on the CDAA antenna's and come to the conclusion that much effort went into keeping them tuned and maintained for the direction finding mode. My understanding is they used a fixed delay in the goniometer, and the electrical line lengths from the antenna elements were critical in bearing measurement and read out on the CRT compass. That the lines had be exactly identical in e-length and there were slideable line tuners for adjusting the lengths.

    KK4NSF, KI5QMP and KA4DPO like this.
  2. W3WN

    W3WN Ham Member QRZ Page

    Maybe. Insufficient data.
    K4PP likes this.
  3. KK4NSF

    KK4NSF Ham Member QRZ Page

    I don't have the tech specs on the CDAA, but I am familiar with goniometer based RDF systems, which require matching electrical lengths to keep the patterns accurate.... and possibly delay lines to keep the signals from various elements in phase. The TCI Loop Arrays used for HF at the end of the cold war used three cabinets, each one containing 16 delay lines on spools.

    Most systems had balance adjustments to keep them accurate. A few were calbrated "on the dial" or used "AZ correction charts" much like compasses do for magnetic variation. The ones I've studied, and my own crossed loop system, can produce very accurate results once they are calibrated using a few targets of known AZ. I spend alot of my radio time working out LOD of all sorts of tranmissions. It's a lot fun, but something few hams appreciate.

    As far as numbers stations being generated for the purpose of calibrating the equipment goes: I don't think that was the case, or would be necessary. Enough of the Russian / Chinese / Cuban / non-Aligned States/ and our own transmitter locations were known, so using those for calibrating the antenna would not be difficult.

    My understanding is that the numbers stations back then were one-time-code-pad transmissions. Modern ones seem to be a combination of one time transmissions, combined with a computer handshake.... that sound like old computer phone modems. My guess is that the numbers portion is a code-pad cipher, which contains the key that has to be typed into their computer to access the message.... but that's just a guess based on listening to the signals.
    KA4DPO and K0UO like this.
  4. K8BZ

    K8BZ Ham Member QRZ Page

    Where is there a CDAA system currently in operation? All of them I'm aware of have been long abandoned, most dismantled. I worked inside the CDAA that used to be on Guam but it's now long gone. Do you know of one that is still in use?
    N2UHC and K0UO like this.
  5. K4PP

    K4PP Ham Member QRZ Page

    Interesting. Yeah, that's why I always wondered about it because there were so many CDAA antenna systems spread out and used by both sides of the cold war. I thought maybe numbers stations was one of those things each other knew you had to do but you made it look like spying anyway. A lot of that kind of thing occurred.

    Last edited: Jun 30, 2021
  6. K4PP

    K4PP Ham Member QRZ Page

    I am pretty sure they are all defunct now, all of them world wide used by any country. The last one I knew about was a FLR-9 in Anchorage, Alaska but I believe it is done now. Check Youtube "The Last Elephant Cage". It is strange that the numbers station slowed down about the pace of the CDAA mothballing.

    Incidentally, there were units used in conjunction with the Soviet over the horizon radar, woodpeckers. Most say they were used as ionosondes to determine the radar frequency operation needed. Seems to me they might be used for tuning the radar phasing. CDAA's are pretty damn accurate in measuring bearing/ azimuth.

    NL7W likes this.
  7. K4PP

    K4PP Ham Member QRZ Page

    BTW in case there is an interest, I list a few papers I found very interesting regarding the CDAA. CDAA is the type antenna system while FLR-9's, FRD-10,s etc. where something developed upon, with additional modes of operation.

    History of the technology "Aspects of the German Naval Communications Research Establishment"

    Research paper results of study for inductive coupling as opposed to capacitively coupled goniometer delay line network for purpose of increasing signal level intellegence.

    Study done in 1994 to determine if the lower cost "Plessey Pusher, Co." CDAA was as effective as the AN/FRD-10 model.


  8. K3DCW

    K3DCW QRZ Lifetime Member #212 Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    I believe that the Russian KRUG (КРУГ - "circle") systems are still somewhat in use.
    KK4NSF and K4PP like this.
  9. KB9BVN

    KB9BVN Ham Member QRZ Page

    Hi there...I need you to look at my pen....>>FLASH<<
    WZ7U, KK4NSF and N4CKC like this.
  10. W4NNF

    W4NNF XML Subscriber QRZ Page

    I doubt it. What's likely is they--The Lincolnshire Poacher, The Swedish Rhapsody, and all the rest--were transmitting messages to operators equipped with one-time pads. Nothing else really makes sense as an explanation.
    N2UHC, KA0HCP, KI5QMP and 1 other person like this.

Share This Page