[Moon-net] 2.40m dish
wd5ago at hotmail.com
Fri Sep 26 15:37:32 CEST 2008
Hello Phil and EME Group I am re-posting some info I sent to Phil + other performance data. My dish is a commercial Andrews 2.4m Grid type (0.375 f/D) dish. It was given to me several years ago and was going to be use for sun noise demo's and 1420 MHz RA work for college students as I already had a HB 5.5m dish on 23cm. Moving locations in 2002 forced to sell large dish and stay ideal on EME. Then thought: what could be done on EME with 2.4m grid? With 0.25" hardware cloth placed for the reflecting surface we placed it on 6cm with 20 watts and worked W5LUA, heard F2TU and OE9ERC. That was a neat experiment then took dish down due to CCR's. Two years later I put 2.4m dish back up (4ft high) to see if anyone will say anything for RA work on 1420 MHz. Then a blessing came out of no were to the availability of 180 watt 13cm amplifiers. With that kind of power could the dish perform well on 13cm? The 13cm HB CP feed and HB LNA produced several contacts at the start and detectable echo's on 13cm. Calculated eff. was 56%. Then we experimented with higher efficiency scalar for deeper dishes. After dozens of multi-ring feeds designs built and CAd testing by W1GHZ, a 3ring was built that offered 64% eff. We also expanded the dish in 0.01 f/D steps to verify performance of feeds for deeper dishes down to 0.33 f/D for our paper. I left the dish at the expanded 2.7m and feed performance is ~60%. With other improvements like another HB LNA design change which is now running in the 0.3 dB n/f range we measure:13cm: 11.0 dB sun noise w/SFU at 66, 0.3 dB moon noise, 7.3 dB CS/G, ~28deg Dish Ta and echoes ~6dB above noise. 22 stations worked in 08' EME contest and 44 initial contacts on 13cm over 3 years. And there is no local RX problems of Wi-Fi on 2304, a little higher noise on 2320 and lots of pulse noise on 2424 but, is reduced with good noise blanker and HB higher IP Rx converter with interdigital filter for 2424 to work JA's. With the use of available, cheap, solid state power on 13cm, in my opinion, out weighs many of the other problems found on 13cm EME. We have also used the dish since the higher performance CP feed developed on 23cm, 9cm and again on 6cm. 23cm - two years ago, 2m-23cm EME contest..was board...built 3ring for dish (yes it was big in the dish!) worked 9 stations with solid state 120W in contest! 1 on SSB, Heard 28 stations, ~ 9.5 dB sn I think 9cm - sun noise about 1 dB less than on 13cm, worked 2 stations and heard 7 (only 40 watts), dish mesh a little big 6cm - sun noise also about 1 dB less than 13cm, worked 7 stations and SSB (only 20w at feed!) On 6cm I only illuminate 2.4m of dish due to outer ring not suitable for >4GHz
Contacts on all bands is CW only here
I hope this information will encourage you and everyone else to populate the moon with EME signals from small dishes (for starters).
Hope to see some of you at the Microwave UpDate 08, will present on above topic
> Date: Thu, 25 Sep 2008 18:59:18 +0400> From: fr5dn at izi.re> To: moon-net at list-serv.davidv.net> CC: moon at moonbounce.info> Subject: [Moon-net] 2.40m dish> > Hello All,> > I may have a possibility for a 2.40m TRVO dish, and wonder if it's worth > the effort to try on 23cm and/or above with it.> > My feeling is that it would be marginal on 23cms; and above 23cms the > efficiency would be too low?> 23cms activity is very nice but i need a bigger dish i guess...> > Just a note on the ZS-FR tropo qso mentionned in the NL. It was the > first between africa and reunion, and a record for ZS...and FR.> Longer paths have been worked on some other areas.> > Vy73 - Phil> FR5DN - LG78qs> > _______________________________________________> Moon-Net posting and subscription instructions are at http://www.nlsa.com/nets/moon-net-help.html>
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