[amsat-bb] Re: Arrow and EME?
aa5jg at yahoo.com
Thu Apr 1 10:14:31 PDT 2010
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 <kl7uw at acsalaska.net> wrote:
> From: Edward Cole <kl7uw at acsalaska.net>
> Subject: [amsat-bb] Re: Arrow and EME?
> To: AMSAT-BB at amsat.org
> 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
> >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
> >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
> >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
> (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
> 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 +
> >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
> >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
> 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
> 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.
> >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)
> >A good SSB 2-meter Transceiver (the best ever made
> Yaesu FT-736R)
> >Good Coax (RG-8 coax is 11 Millimeter coax. That
> is ok for 50' EME
> >runs, for longer runs use 12+ Millimeter coax)
> >Sent via AMSAT-BB at amsat.org.
> Opinions expressed are those of the author.
> >Not an AMSAT-NA member? Join now to support the amateur
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> 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 dubususa at hotmail.com
> Sent via AMSAT-BB at amsat.org.
> Opinions expressed are those of the author.
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