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Receiving EME Signals, Which Receiver

Discussion in 'VHF/UHF - 50Mhz and Beyond' started by KS2K, Nov 26, 2021.

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  1. SM0AOM

    SM0AOM Ham Member QRZ Page

    Measuring solar noise may work for comparing receivers, the 8 x 21 element Tonna array at SK6AB measured about 9 dB of solar noise at quiet sun conditions,
    so a single Yagi may yield a dB or so of sun noise. However, drawing conclusions out of so small differences is difficult at best.

    However, this system used a very low-noise preamp at the feedpoint and the whole system was painstakingly optimised for sensitivity.

    A "trick" used by many UHF-ers of yesteryear was to make up a small battery powered transistor oscillator with harmonic output at some convenient spot in the band. Then an "assistant" was enlisted to walk away with the oscillator until the signal vanished.

    Longer distance = better receiver.

    Receiver optimisation using this method was time-consuming and cumbersome, so in the 70s homebuilt automatic noise figure meters became popular, with the G4COM design as one of the earliest. Here, a diode noise generator was loosely coupled to the receiver input with the antenna pointing to cold sky so the receiver could be optimised with the antenna connected.

  2. ZL1TKL

    ZL1TKL Ham Member QRZ Page

    Good to see someone has the guts to "have a go " never mind the crap this is better than that ? its what suits your pocket at the time , Tried the multi yagi approach but never better than the "normal" so deviated to a 10 ft spun andrews dish and never looked back . its a pity that the practically of using waveguide at 70cm is out of the question but really good coax and n type connectors is a must , I used a corner reflector for my feed at 90 degrees but I could rotate it with the armstrong method , dont place a great deal of reliance on the brand of receiver just have a go and persist never say die attitude is the best equipment to have when chasing eme , best of luck Don zl1tkl
    SWL37632 and K0UO like this.
  3. KS2K

    KS2K Premium Subscriber QRZ Page

    Thanks for your post. How much rf power were you running on the Yagi's. Did you make
    CW or SSB contacts on the Yagi's. I am a huge believer that you study a project in depth, come up with a plan and try it. It its not what you want correct the plan and try again.
    Never give up.

  4. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Very few can make SSB contacts via e.m.e. unless at least one station involved is quite a "superstation" with enormous antenna gain not possible for most of us to achieve.

    In the early days, it was 100% CW. My contacts in the 80s-early 90s were 100% CW.

    Today, the dominant mode is probably JT65B, which allows the system to dig deeply into the noise and detect signals that cannot be "heard" by a human ear. CW is still used, but I think less. SSB = rarely, although guys with big dish antennas and such can do it.
  5. SM6GXV

    SM6GXV Ham Member QRZ Page

    When still working at the Onsala Space Observatory, I was granted permission by the director to use the observatorys┬┤25M dish and do EME together with VMG (West Coast Microwave Group) back in 2011 with the callsign SK6OSO. (We did this several times). On 1296, 5760 and again 1296. The last time, we could use a PA designed and built by Hannes, SM6PGP. 400W RF. This fed into a 25M antenna with some 49dB gain returned 57-59 echos on FM (!) There are videos on Y-T if anyone is interested.

    We received nice reports from all over the world. It was great fun. Many very low power stations were able to work us.
    WD4ELG and K6CLS like this.
  6. KS2K

    KS2K Premium Subscriber QRZ Page

    SM6GXV, do you have the UTube Links

  7. ZL1TKL

    ZL1TKL Ham Member QRZ Page

    I had several p-a s of varying types the most fun was the 4cx250 with four tubes but the wife didnt like it reckoned it was dangerous ( used to smoke at times )!! sukkybub !! mainly i used a tokyo high power labs at 300w never got to be a cw op so ssb was the norm for me I did have a go at 1296 ssb but the feed horn was a bit ratshitand was soldered together during summer I come home from work to find it in a million bits laying in the dish , at first I thought that some one had shot it but later found out that its not a good idea to polish a spun dish , then tried to silver solder it but it was a loss as it would distort in the sun . 70cm was the answer and paint the dish green to hide from the neighbours , still got the dish but not in use now 73s Don
  8. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    The Arecibo radiotelescope dish has been used many times to make amateur e.m.e. contacts, including 70cm work that included almost anyone on the right frequency at the right time and capable of sighting the moon. That also included FM contacts!

    Unfortunately, that dish is now gone. But in 2010 they made hundreds of contacts on 70cm from there, and some stations worked were using almost nothing!

    There are some videos for that operation.
    WD4ELG likes this.
  9. KS2K

    KS2K Premium Subscriber QRZ Page

    smoking amps and shot dishes...its dangerous down there in NZ land hi hi

  10. SM6GXV

    SM6GXV Ham Member QRZ Page

    This was shot during the first event. At first, we did not get any echoes and discovered that the software that controls the telescope had an offset on a degree or so. I had to sit and manually control the antenna every minute to add the offset. This software "glitch" was fixed for the next to occasions. The moon, as well as all other large objects in our solar system was included into the control system menus. The next two times, the software worked flawlessly. The last time it took less than two hours to set up everything.

    The video is narrated by Bengt-Arne SM6CKU, one of the many operators that enjoyed the event.

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