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.
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
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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@hotmail.com ======================================