I have done very limited EME on 2m using JT65. My one good QSO was with W5UN who probably has the best EME setup on the planet. I was using a Cushcraft 13B2 and 160 watts. I also almost completed with RN6BY using this same setup but he had moonset at his QTH before we got the final sequence completed. The 13B2 has 13 elements on a 15 foot boom and Cushcraft advertises it at 12DBd or something like that. I have tried with other big stations using that same setup and was unsuccessful. I did not have an external preamp.
To use a 3 element arrow would really be pushing it, even for running with W5UN. I would think you would need at least 300 watts if not more, and an external preamp to even have a shot. 73s JOhn AA5JG --- On Thu, 4/1/10, Edward Cole <[email protected]> wrote: > From: Edward Cole <[email protected]> > Subject: [amsat-bb] Re: Arrow and EME? > To: [email protected] > Date: Thursday, April 1, 2010, 11:46 AM > A few comments for accuracy (no > criticism intended on what WF1F > wrote). I have been on 2m-eme since 1998 and have > used digital mode > since 2003 when it first was made available. > Insertions (below) > > At 04:36 AM 4/1/2010, MM wrote: > >Arrow Antenna and EME: > > > >It is possible to work Earth Moon Earth with an Arrow > Antenna. > > > >Of course, it is. You just need to make a > schedule with someone on > >the other side of the link with enough Antenna > Gain. You also need > >to be running the new digital text messaging mode > called JT65B > > > >Link for JT65 > >http://www.physics.princeton.edu/pulsar/K1JT/ > > > >Definitions: > >In this document I will refer to all antenna gain > values based on > >the number of elements. > > > >Example: A Single half-wave Dipole = 0 dBd > >Elements 2 = 3 dBd > >Elements 4 = 6 dBd > >Elements 8 = 9 dBd > >Elements 16 = 12 dBd > > This is not entirely accurate. Yagi antennas increase > gain in direct > relationship to length of boom and not exactly a function > of number > of elements. I run four ten-element yagis with a > total gain of 17.6 > dBd (19.2 dBi). One such yagi has 11.6 dBd (13.2 > dBi). It is > 21-feet long (eme'rs usually refer to wavelengths for > boomlength, i.e. 3 WL) > > > >The Arrow antenna (Model 146/436-10) has 3 elements on > the 2-meter > >band, so its maximum theoretical "Element Gain" is 4.5 > dBd. > > > >With the invention of the JT65 protocols, thousands of > Amateur Radio > >stations running a Single Yagi 2-meter antennas, now > have access to > >the Moon and EME contacts. > > The rest of this pertains to 2-meter eme. 432-eme > will take more > antenna gain since the path-loss is higher at increase > frequencies. This means antenna gain requirements go > up > (approximately 6-dB more for stations working eme on > 432). The norm > for two CW EME stations is 18-dBi with 1000w on 2-meters > and 24-dBi > with 1000w on 432. (subtract 1.64 dB to convert > antenna gain to dBd). > > The requirements drop significantly for running JT-65 > instead of CW: > 144-eme: 13-dBi with 600w (min) > 432-eme: 19-dBi with 600w (min) > this is for two such stations working each other. > This not easy at > this level and may take several hours spread over several > days to > make one contact for stations so equipped. > > I ran my four yagis with 125w (at the antenna; 170w at the > amplifier) > and made contacts with single yagi stations running > 600w. I now have > 600w. This is on 2-meters. > > >To make a contact on Moon bounce, the "Total Antenna > Gain" from both > >stations is added up and will need to be in the > approximate range > >of 25-30 dBd. With this gain and the average > transmitter power of > >(100-400 watts) you will have a 10-20+ percent chance > of completing > >a 2-way EME JT65B link, with another station. > >Note: There are many other factures used in EME gain > >calculations. For simplicity, we will just focus > on the antenna Gain. > > > >The amount of Total Antenna Gain required depends on > the mode you > >wish to use. The wider the mode, the more gain > that is > >required. The mode JT65B is a very narrow mode > and requires less > >gain. I am not going to go over all of the > details of JT65 in this > >article, look it up. > > > >Gain required by mode: (All values are approximate) > > > >JT65 28-30 dBd (1-Yagi + 4-Yagi) > >CW 30-40 dBd (4-Yagi + 4-Yagi) > >SSB 40-50 dBd (8-Yagi + > 8-Yagi) > >FM 60-70 dBd (16 + 24) Guess > > Don't even give any thought to using FM for eme; it is too > wide in > bandwidth to get reasonable sensitivity in receive. > SSB has only > been done with one or two super-sized 2m-eme stations; it > is more > common with large stations on 1296-eme. I expect to > work 1296-SSB > with my 16-foot dish running 300w with stations running > dishes >25-feet. > > EME is done on CW or JT-65, predominately. Using an > Arrow you will > HAVE to use JT-65. > > > > > > >The Mode JT65B requires approximately 30 dB of Total > Antenna Gain > >for an EME contact. > >If we assume the average 12-element 2-Meter Yagi has > 10.5 dBd (round > >to 11 for easy math) of "Element Gain", then the > more Yagi's you > >stack, the more gain you will have. In EME lingo, > 1x12 means, you > >have One Yagi, with 12 elements, 4x12 means you > have a stack of 4 > >yagis with 12 elements each (48 elements total) and an > approximate > >gain of 17 dBd. > > > >1-Yagi = 11 dBd > >2-Yagi = 14 dBd > >4-Yagi = 17 dBd > >8-Yagi = 20 dBd > >16-Yagi = 23 dBd > >32-Yagi = 26 dBd > >64-Yagi = 29 dBd (W5UN) > > > > > >A Single-Yagi station (11 dBd) calling a 4-Yagi > (17 dBd) station > >will have approximately 28 dBd Total Antenna > Gain. The 4xYagi > >stations are very common on JT56B EME. > > > >Let's go back to the Arrow Antenna: > > > >We need 30 dBd of total antenna gain. > >The Arrow antenna has 4.5 dBd. > >The Arrow also has a Maximum power limitation of 150 > watts (10 watts > >if hand held). > > > >If you are running the maximum 150 watts on your > Arrow antenna, you > >should be able to work stations with 32 to 64 > Yagi's. There are not > >very many 64 Yagi stations out there, however Dave W5UN > has been > >active on JT65 EME recently. > > > >If you want more of a challenge, you can try QRP at 5 > watts and your > >Arrow antenna. > >Reducing you power from 150 watts to 5-10 watts, will > reduce your > >performance by 12 db. > >To compensate for the reduce power, you will just need > to find a > >station with a bigger antenna. > > > >There is another big gun on EME. Two weeks ago, > Arecibo was on EME, > >running CW, working EME stations on the 440 band. > The antenna used > >at Arecibo is a simple 1,000 foot dish. The > actual gain for > >2-meters is not known, however I will assume it is more > than 64-Yagi's. > > Arecibo will be doing 432-eme, NOT on 2-meters! > However, one could > try their 6-element UHF Arrow antenna with preamp > (absolutely > necessary) to try hearing Arecibo which has 58 dBi (56 dBd) > gain on > 432-MHz. In a recent test folks with small yagis 7-10 > elements were > able to hear Arecibo. Arecibo will be running 500w > (from last > reports). it is not known if they plan to run JT-65; > the focus is > using SSB with other large dishes around the world. > Average sized > 432-eme stations (8-yagi and up) are expected work > them (maybe > requiring the use of CW for smaller stations). If you > have 100w+ on > 432 you might try CW with Arecibo with a small yagi (ONLY > IF you can > hear them, first - DO NOT Transmit if you cannot hear > Arecibo). > > I will be using 100w with my 16-foot dish (24-dBi gain). > > BUT I REPEAT Arecibo will NOT be using 2-meters; ONLY > 432.045 MHz > (plus/minus for the expected QRM of stations wishing to > contact them). > > Arecibo will be doing eme on April 16-18 at times limited > by their > Moon view (they can only point down to 70-deg > elevation). I will > reprint the times once I find the e-mail that cited the > exact operating times. > > > >http://www.naic.edu/ > > > >So here is your chance. Make a schedule with > Arecibo and go for > >QRP, EME, with a held Arrow antenna, or if you know of > any good > >contacts at Arecibo, send me the data and I'll try to > arrange a > >schedule and try it from my station. > > > >Other Hardware: > >A good Receiver Preamp (similar to ARR) > >http://www.advancedreceiver.com/ > > > >A good SSB 2-meter Transceiver (the best ever made > Yaesu FT-736R) > >http://www.xs4all.nl/~ketel/ham/ft736.htm > > > >Good Coax (RG-8 coax is 11 Millimeter coax. That > is ok for 50' EME > >runs, for longer runs use 12+ Millimeter coax) > > > >73 > > > >WF1F > >www.marexmg.org > > > >_______________________________________________ > >Sent via [email protected]. > Opinions expressed are those of the author. > >Not an AMSAT-NA member? Join now to support the amateur > satellite program! > >Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb > > 73, Ed - KL7UW, WD2XSH/45 > ====================================== > BP40IQ 500 KHz - > 10-GHz www.kl7uw.com > 500-KHz/CW, 144-MHz EME, 1296-MHz EME > DUBUS Magazine USA Rep [email protected] > ====================================== > > _______________________________________________ > Sent via [email protected]. > Opinions expressed are those of the author. > Not an AMSAT-NA member? Join now to support the amateur > satellite program! > Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb > _______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
