the best was neither vert or horizontal, and continously changing, well slowly changing faraday rotation. plus why would you want to aste n extra 3 db if you have it to be used?
Joe WB9SBD
The Original Rolling Ball Clock Idle Tyme Idle-Tyme.com http://www.idle-tyme.com
On 4/1/2010 2:27 PM, Mark Lunday wrote:
Would this also be accomplished in "poor man's design" by simply having one yagi vertical and one horizontal?
Mark Lunday WD4ELG Greensboro, NC - FM06be [email protected] http://wd4elg.net http://wd4elg.blogspot.com
-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Idle-Tyme Sent: Thursday, April 01, 2010 1:53 PM To: [email protected] Subject: [amsat-bb] Re: Arrow and EME?
Another very important thing is polarity. the ability to change polarity can easily me a completed QSO or one where not a peep was heard.
In the late 80's early 90's I had a small station of 4 eight element 2 meter yagis. I think they were a W1JR design?
anyway I mounted them in a way that i could rotate them in polarity also.
It was amazing I never thought i could do moonbounce with them but just for kicks was listening down at the bottom of the band one day and heard someone CQing and wortking someone off he moon. of course it was W5UN. but a random call when he finished and we had a complete QSO in the log with no repeats solid exchange both ways!
what make this amazing was I was using a kenwood TS700 rig into a old KLM (remember KLM amps?) a 70 watt one that was tired and only putting out about 35 watts, into a run of rg 213 50 feet to the antenna, no pre amps at all. and on CW by ear! no filters either just the standard 2.XX whatever wide filter. But the polarity made all the difference! In horizontal mode i heard NOTHING. but somewhere inbetween H and V he wa solid copy and he had no problem hearing me too.
I eventually went on to work about 30 other stations as small as other 4 yagi stations. The ability to make polarity changes is a GIANT advantage!
Joe WB9SBD
The Original Rolling Ball Clock Idle Tyme Idle-Tyme.com http://www.idle-tyme.com
On 4/1/2010 12:11 PM, Mark Lunday wrote:
I have been doing some reading on this also. Although I have not yet made any EME contacts, I have been uncovered the following:
- Moonrise/moonset will enhance signals because of ground reflections,
something like 6 dB. Many folks intentionally use moonrise and moonset attempts for this reason.
Mast mounted pre-amp is essential
Higher frequencies need more gain (so I have been told). But the 440
MHz
part of the arrow antenna should have a LOT more gain than the 2 meter
part.
- Low loss coax is very important, esp at VHF. Keep the runs short and
use
something equiv to LMR 400 (50 foot of the good stuff is probably under $100, and worth it.
- Definitely try to set up a sked with W5UN. If you can hear him, then
you
are halfway there!
Monitor websites like http://www.chris.org/cgi-bin/jt65emeA
2010 appears to be a promising year for EME, here is a good calendar:
http://www.vhfdx.net/w5luu.html
Mark Lunday WD4ELG Greensboro, NC - FM06be [email protected] http://wd4elg.net http://wd4elg.blogspot.com
-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of MM Sent: Thursday, April 01, 2010 8:37 AM To: [email protected] Subject: [amsat-bb] Arrow and EME?
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
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.
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
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.
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
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
On Apr 1 2010, Idle-Tyme wrote:
the best was neither vert or horizontal, and continously changing, well slowly changing faraday rotation. plus why would you want to aste n extra 3 db if you have it to be used?
Joe WB9SBD On 4/1/2010 2:27 PM, Mark Lunday wrote:
Would this also be accomplished in "poor man's design" by simply having one yagi vertical and one horizontal?
Mark Lunday WD4ELG
Sure, with an Arrow or similar antenna, you simply twist the beast until the signal is the loudest, and you have your best polarity. On a fixed station, getting continuously-adjustable polarization is not a trivial task.
With one yagi vertical, one yagi horizontal, and appropriate phasing harnesses, one could accomplish a variety of specific polarizations. The number of different polarizations would be a function of the complexity of the phasing harnesses. If you use no phasing harness at all (or two random but equal lengths of harness) you can still select a phase by moving one antenna a fraction of a wavelength forward or backward relative to the other. But at best, if you had one vertical and one horizontal yagi, with equal cable lengths to the impedance transformer, and the driven elements lined up with one another, you would only end up with the equivalent of a single yagi oriented diagonally, so no big improvement. You would always be -3 dB from any signal that was polarized either vertically or horizontally, but could still be way down (-20 dB or more) from a signal that started out in one of those polarizations but got rotated by the Faraday effect.
With two crossed yagis, and two phasing lines, you could set up either right or left-hand circular polarization. With two crossed yagis, three phasing lines, and a SPDT coaxial relay, you could have switchable left-hand/right-hand circular polarization.
Another step up (in both complexity and in the number and quality of phasing choices) would be one yagi at upper left to lower right diagonal, and one yagi at upper right to lower left diagonal, four SPDT coaxial relays, and 4 specific lengths of phasing harness. This would give the following four choices of polarity, depending on the choice of one of two phasing lengths to one of the diagonals and one of two phasing lengths to the other of the two diagonals:
Diagonal One Diagonal Two Net Phase Net Polarity 1/4 WL 1/4 WL 0 horizontal 1/4 WL 3/4 WL 180 vertical 1/2 WL 1/4 WL -90 right circular 1/2 WL 3/4 WL +90 left circular
Note that at a net phasing of 0 and 180 degrees, the polarization is halfway between the two yagis, so if the yagis are oriented diagonally, that gives you horizontal or vertical choices with that degree of phasing.
This, of course, does not give continuously-adjustable angular polarization, only a choice of 4 specific polarities. But it is a nice choice of 4: horizontal for terrestrial SSB/CW, vertical for terrestrial FM, PLUS both right circular and left circular for satellites and EME.
If the other station is running circular polarization, in theory, ANY linear polarization will be -3dB from optimal, and there is no advantage to any in-between adjustability.
If the other station is running linear polarization, in theory, any random linear polarization on your end will be anywhere from 0dB (perfect) to worse than -20dB (horrible) depending on the amount of polarity mis-match; and because of Faraday rotation, his horizontal signal (for example) may not reflect back to you as horizontal, but rather somewhere else (probably NOT vertical either!).
If both stations run circular polarization, and at least one of them is switchable between right and left-hand circular, then you can always have an ideal polarization match no matter what the degree of Faraday rotation. So, that might be the best option if you have it available to you. Remember that if you expect to hear your own echoes, the reflection from the moon is the opposite circularity from what you transmit...
Of course, if you were trying to out-gun W5UN and build an array of 128 circularly-polarized yagis, that's a helluva lot more work than building 128 linearly-polarized yagis! OTOH, building 128 of ANY sort of antenna is an enormous undertaking, so there! :)
W0JT
participants (2)
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Idle-Tyme -
tosca005＠umn.edu