Scott,
1. I would recommend using standard connectors and teeing them rather than soldering to a lug. You'll find that if you want to move the array for portable work, it will be easier to set up and take down.
2. Although I'm no expert, I wouldn't think you'd even need the same length feedline, although it couldn't hurt.
3. LB gives the dimensions in inches, but try converting them to millimeters. Just multiply by 25.4 millimeters to the inch. I'd round to the nearest 1/2 mm and cut as close as possible. Then, that ".49 inches" dimension becomes 12.5 mm.
4. You could always use duct tape... they use it on the shuttle and ISS!
BTW, the 70cm version calls for #12 AWG wire, not #14.
73 de N8AU, Jim in Raymore, MO
Light travels faster than sound... This is why some people appear bright until you hear them speak.
Date: Tue, 31 Jul 2007 07:08:16 -0700 (PDT) From: Scott Wilson s.wilson@yahoo.com Subject: [amsat-bb] ARRL dual moxon turnstyle project questions To: amsat-bb@amsat.org Message-ID: 862339.97515.qm@web31810.mail.mud.yahoo.com Content-Type: text/plain; charset=iso-8859-1
I'm working on building the ARRL dual moxon antennas, but the article isn't very detailed where I'd like it to be and a little over detailed in some places I wish it weren't.
If you want to look, this is the URL (http://www.arrl.org/members-only/tis/info/pdf/0108038.pdf)
1. What are acceptable ways to terminate the paralled 75 ohm matching sections? I'm thinking now I'll just terminate them to a couple of ring terminals attached to the mast rather than terminating each one with a bnc and teeing them.
2. How do I feed the 70cm and 2m with the same feedline? should I just tee a 50 ohm line to two equal length 50 ohm sections?
3. This is more of a comment... I'm wagering the uhf version doesn't work at all... measurements are given to the hundreth of an inch - and then you solder a big ring lug to the end of it!
4. Are there any other good techniques for setting the distance between the reflector and driver besides heat shrink?
The 70cm antenna is using #14 galvanized wire, and I can't think of anything small enough to hold them in place well. I found that the 3/16 rod for the 2m moxon will work great with 1/4" nylon tubing.
Thanks for any feedback - I'll probably have more questions.. I'm sitting here with a half-made 70cm turnstyle, and am about to start on the 2m version.
Whew - I'm beginning to think that a $1000 investment in rotators and antennae isn't such a bad idea after all!
Scott Wilson NW2S
Quoting "Reicher, James" JReicher@hrblock.com:
Scott,
- I would recommend using standard connectors and teeing them rather
than soldering to a lug. You'll find that if you want to move the array for portable work, it will be easier to set up and take down.
- Although I'm no expert, I wouldn't think you'd even need the same
length feedline, although it couldn't hurt.
- LB gives the dimensions in inches, but try converting them to
millimeters. Just multiply by 25.4 millimeters to the inch. I'd round to the nearest 1/2 mm and cut as close as possible. Then, that ".49 inches" dimension becomes 12.5 mm.
- You could always use duct tape... they use it on the shuttle and
ISS!
BTW, the 70cm version calls for #12 AWG wire, not #14.
73 de N8AU, Jim in Raymore, MO
Light travels faster than sound... This is why some people appear bright until you hear them speak.
Date: Tue, 31 Jul 2007 07:08:16 -0700 (PDT) From: Scott Wilson s.wilson@yahoo.com Subject: [amsat-bb] ARRL dual moxon turnstyle project questions To: amsat-bb@amsat.org Message-ID: 862339.97515.qm@web31810.mail.mud.yahoo.com Content-Type: text/plain; charset=iso-8859-1
I'm working on building the ARRL dual moxon antennas, but the article isn't very detailed where I'd like it to be and a little over detailed in some places I wish it weren't.
If you want to look, this is the URL (http://www.arrl.org/members-only/tis/info/pdf/0108038.pdf)
Scott:
L.B. is a constant and reliable source of wisdom when it comes to antennas. I've built many of his designs, most recently a 7 element version of the OWA yagi for 2m. However, I have read a cogent criticism of these moxons, and I feel I should share it here.
For a fixed satellite antenna, the ideal pattern should provide diminishing gain as elevation rises. It should not null out as quickly as a 1/4 wave vertical, but certainly should have less gain overhead, where the bird's signal will be many dB greater due to lower 'path losses' and where you will rarely encounter the bird anyway.
Note that these moxons do not fulfill this requirement: in fact, the greatest gain is right overhead. For this reason, I would not build these antennas, despite the imprimatur of QST. Tony's lindenblad published in August 2007 QST would be a *much* better choice. (A 435MHz sister antenna to it can be found from the same source in the 2006 AMSAT symposium publication.) I'll guess that even a 1/4 wave might make a more practical antenna.
You joke that a $1000 rotor/yagi setup starts to seem like a good idea. I know how you feel, but I think it is important that all newcomers to this field understand that such commercial solutions are really, really unnecessary, especially for today's LEOs. A cheap tv-duty rotor can effectively turn a small pair of yagis, say 4 elements on 2m and 6-8 on 435 MHz. The beamwidth of these is large enough that the rotor can be touched up every three minutes or so. Many, including myself, have found Kent Britain's 'Cheap Yagis' design to work well in this application. Total budget: $90, I'd say.
In fact, such a set-up is *better* for the newcomer than a full-up pair of long yagis with az/el rotor. Why? Well, if your yagis are not pointed dead at the bird, you'll have worse performance than with shorter ones. So you've got to keep making sure that the az/el rotors are well-aligned, etc. This is difficult and not particularly fun.
Secondly, with so much gain on uplink, you run the risk of swamping the receiver of a linear bird such as VO-52 or AO-7. This creates a sort of arms-race situation, where everyone else has to use equal effective power, or their signals don't get heard, and some QRP stations just fade away. We all make mistakes from time to time, but in my experience, the operators who consistently run many s-units over the beacon are also frequently in possession of long antennas, and perhaps simply can't turn down their transmitters sufficiently.
You might wonder why many people here, including myself, talk about our more elaborate stations. Well, I'm struggling to add effective elevation control (on a budget) and longer antennas because I'm attempting slowly to upgrade to a station that could operate the HEOs when they arrive. Others still have HEO-grade stations from those days and use them for the current LEOs. I've enjoyed the technical challenge of upgrading, but truthfully I worked way more satellite DX with the simple station described above than with my much-tweaked more elaborate one.
Finally, I'm going to run off and spend half of that $1000 you mentioned. The best use of it is on brand-name mast-mounted preamps. ARR or SSBUSA. Don't even think of receiving 435MHz without one. On 435MHz, I'd rather have a paperclip as an antenna and a preamp than the biggest yagi without a preamp. In fact, my first satellite antenna was a 435MHz groundplane soldered on a bnc connector. Hooked up to a good preamp, it hears LO-19 wonderfully, even while indoors!
73, Bruce VE9QRP
Thanks very much for the feedback everyone.
From what I was reading in the articles, I was under the impression that
a circularly polarized antenna was a step above linear polarized setups such as the Arrow (or any small yagi) and verticals. In practice, I'm having somewhat better luck with the linear setup. Until Bruce Mentioned the short yagi/tv rotator setup, I hadn't even considered my own similar setup as an option.
Here are my experiences so far:
My first attempt was with a 2m/440 mobile whip with a radial base. The antenna was tilted over about 30 degrees to be slightly more perpendicular to the predicted path of AO-51. From that pass, I could definitely tell that I was tracking a satellite, but couldn't copy anything that I was hearing. This was fed into my IC-7000 with about 15 feet of RG-8X.
Second attempt was receiving with just the 440 section of the dual moxon antenna system. The closest I got with that was perhaps a little less noise, but definitely no copy. Obviously, that's not inheriently a problem with the antenna, but likely a problem with my implementation which - which I can't really test. My antenna analyser only goes to uhf.
Bruce's email saying that a TV rotator and linear yagi's would be better than a full blown system for a beginner contradicted what I had convinced myself of - that I would be way too far down in the noise with the fact that I was linear polarized and had no elevation control, and with about 75' of less than stellar RG-58.
In fact, I have something usable right now on my roof: a cushcraft 2m/440 3 el vertical yagi on a tv rotator.
So far this has the best results to date. I've been able to copy at least parts of call signs on the latest AO-51 pass, and managed to get a pretty clear copy on a couple of CW beacon passes.
Now I'm considering incremental improvements.
I have a length of RG-213 that's been waiting to replace the radioshack RG-58 feed to the yagi, so that should give me about 2dB.
I am hearing that a preamp is an absolute requirement. I'm now researching the best method to feed the dual yagi.
If, after that, I can get a better copy on the passes, I'll try to make contact.
Thanks,
Scott NW2S
Quoting scott wilson s.wilson@yahoo.com:
Thanks very much for the feedback everyone.
From what I was reading in the articles, I was under the impression
that a circularly polarized antenna was a step above linear polarized setups such as the Arrow (or any small yagi) and verticals. In practice, I'm having somewhat better luck with the linear setup. Until Bruce Mentioned the short yagi/tv rotator setup, I hadn't even considered my own similar setup as an option.
Here are my experiences so far:
My first attempt was with a 2m/440 mobile whip with a radial base. The antenna was tilted over about 30 degrees to be slightly more perpendicular to the predicted path of AO-51. From that pass, I could definitely tell that I was tracking a satellite, but couldn't copy anything that I was hearing. This was fed into my IC-7000 with about 15 feet of RG-8X.
Scott --
I'm delighted to hear that these experiments are meeting with some success. I think one of the great things about AMSAT work is that it puts the fun into *listening* to the radio: it's amazing, the signals are coming from a box in space!
Some thoughts on the above: 0) What you describe above is what I think most of us would expect from the equipment you describe. I find something like this a very useful baseline from which to assess later experiments in antenna building.
1) when listening to AO-51's FM signal with a sub-optimal system sometimes it is interesting to switch your radio to the CW or SSB mode. You will hear the warbling note of the FM signal much better, though you won't be able to make out what people are saying.
2) Similarly, with a system such as you describe above, LO-19 might be a good bird to track. Its CW beacon is quite loud. You can either listen for it manually (start tuning several kHz above the nominal frequency) and observe the doppler effect or use it to test out a computer tracking setup.
Second attempt was receiving with just the 440 section of the dual moxon antenna system. The closest I got with that was perhaps a little less noise, but definitely no copy. Obviously, that's not inheriently a problem with the antenna, but likely a problem with my implementation which - which I can't really test. My antenna analyser only goes to uhf.
Bruce's email saying that a TV rotator and linear yagi's would be better than a full blown system for a beginner contradicted what I had convinced myself of - that I would be way too far down in the noise with the fact that I was linear polarized and had no elevation control, and with about 75' of less than stellar RG-58.
In fact, I have something usable right now on my roof: a cushcraft 2m/440 3 el vertical yagi on a tv rotator.
So far this has the best results to date. I've been able to copy at least parts of call signs on the latest AO-51 pass, and managed to get a pretty clear copy on a couple of CW beacon passes.
Now I'm considering incremental improvements.
I have a length of RG-213 that's been waiting to replace the radioshack RG-58 feed to the yagi, so that should give me about 2dB.
Replacing the RG-58 will make a *huge* difference. According to this online calculator http://www.ocarc.ca/coax.htm, your matched loss on 435 MHz is 7.2 dB, meaning that you've raised your noise floor by that much, too. That's brutal! Matched loss of the '213 will be 3.7 dB, still brutal if it is in front of a typical receiver. However, if you put the low noise preamp on the mast, the effects of the '213 will be mitigated. The math is interesting, and can be followed in M. Davidoff's book, which you really should get your hands on.
The fact that you could hear better with the yagi suggests that this is the way for you to go: it's apparently fighting better, even with both hands tied behind its back :-) You might want to permanently raise the elevation of the yagi about 20 deg. so as to fill in the pattern overhead at the cost of some gain at the horizon. Odds are, you'll still make local terrestrial signals (especially if you make the improvements described below). I would even consider getting someone to buy you a 75 foot run of LMR-400 for an up-coming birthday!
If the yagi has one input for both bands, I would, for now, get a 70cm preamp up there and do without on 2m, where one is somewhat less important. Have you tried using your yagi to listen to VO-52 or AO-7? Given the results you describe with AO-51, the former should be quite audible because it is closer to you, there's less of a penalty in 'path loss' on that frequency, and your feedline is not tearing up your noise figure quite as badly.
Do you have a second radio with which you can listen as you are transmitting? On FM birds, a crummy old HT will do fine for both purposes. Since birds hear better than they transmit, you could use your vertical with an HT to transmit 5w and the improved yagi set-up to listen. If you want to go all-mode and are on a limited budget, consider the FT-817 as a second radio. It takes some fiddling, but SATPC-32 does let you control two radios at once, one for up-link and one for down-.
Thanks for sharing your experiences with us, Scott. I, for one, am enjoying hearing about your progress. If you haven't yet had the opportunity, I strongly suggest joining AMSAT-NA. It's nothing short of amazing that you can be part of a club that is designing a satellite as cool as 'Eagle', helping university students with their low-cost satellite experiments and even ask really simple space physics and communications questions that will be answered by bona fide experts. Besides its support for all this, it produces a great journal, and building some of the projects in there has saved me hundreds of dollars and been great fun.
73, Bruce VE9QRP
Hello Bruce and Scott,
My experience and testing has shown me that small yagis, at a fixed elevation AND a preamp at the antenna will more than adequately work all the current LEOs. The preamp with a plastic food container over it will improve your receive signal more than changing coax. Obviously both are good, but the preamp is your best investment. RF switched preamps are better in the long run.
I also get a great deal of enjoyment testing other systems, once I have a reasonable system to compare it against.
Continue with the experiments, but have a good reference. You should be able to hear AO-51 analog horizon to horizon with a fairly minimal system.
73, Gould, WA4SXM ----- Original Message ----- From: "Bruce Robertson" broberts@mta.ca To: "scott wilson" s.wilson@yahoo.com Cc: amsat-bb@amsat.org Sent: Tuesday, August 07, 2007 10:10 AM Subject: [amsat-bb] Re: ARRL dual moxon turnstyle project questions
Quoting scott wilson s.wilson@yahoo.com:
Thanks very much for the feedback everyone.
From what I was reading in the articles, I was under the impression
that a circularly polarized antenna was a step above linear polarized setups such as the Arrow (or any small yagi) and verticals. In practice, I'm having somewhat better luck with the linear setup. Until Bruce Mentioned the short yagi/tv rotator setup, I hadn't even considered my own similar setup as an option.
Here are my experiences so far:
My first attempt was with a 2m/440 mobile whip with a radial base. The antenna was tilted over about 30 degrees to be slightly more perpendicular to the predicted path of AO-51. From that pass, I could definitely tell that I was tracking a satellite, but couldn't copy anything that I was hearing. This was fed into my IC-7000 with about 15 feet of RG-8X.
Scott --
I'm delighted to hear that these experiments are meeting with some success. I think one of the great things about AMSAT work is that it puts the fun into *listening* to the radio: it's amazing, the signals are coming from a box in space!
Some thoughts on the above: 0) What you describe above is what I think most of us would expect from the equipment you describe. I find something like this a very useful baseline from which to assess later experiments in antenna building.
- when listening to AO-51's FM signal with a sub-optimal system sometimes
it is interesting to switch your radio to the CW or SSB mode. You will hear the warbling note of the FM signal much better, though you won't be able to make out what people are saying.
- Similarly, with a system such as you describe above, LO-19 might be a
good bird to track. Its CW beacon is quite loud. You can either listen for it manually (start tuning several kHz above the nominal frequency) and observe the doppler effect or use it to test out a computer tracking setup.
Second attempt was receiving with just the 440 section of the dual moxon antenna system. The closest I got with that was perhaps a little less noise, but definitely no copy. Obviously, that's not inheriently a problem with the antenna, but likely a problem with my implementation which - which I can't really test. My antenna analyser only goes to uhf.
Bruce's email saying that a TV rotator and linear yagi's would be better than a full blown system for a beginner contradicted what I had convinced myself of - that I would be way too far down in the noise with the fact that I was linear polarized and had no elevation control, and with about 75' of less than stellar RG-58.
In fact, I have something usable right now on my roof: a cushcraft 2m/440 3 el vertical yagi on a tv rotator.
So far this has the best results to date. I've been able to copy at least parts of call signs on the latest AO-51 pass, and managed to get a pretty clear copy on a couple of CW beacon passes.
Now I'm considering incremental improvements.
I have a length of RG-213 that's been waiting to replace the radioshack RG-58 feed to the yagi, so that should give me about 2dB.
Replacing the RG-58 will make a *huge* difference. According to this online calculator http://www.ocarc.ca/coax.htm, your matched loss on 435 MHz is 7.2 dB, meaning that you've raised your noise floor by that much, too. That's brutal! Matched loss of the '213 will be 3.7 dB, still brutal if it is in front of a typical receiver. However, if you put the low noise preamp on the mast, the effects of the '213 will be mitigated. The math is interesting, and can be followed in M. Davidoff's book, which you really should get your hands on.
The fact that you could hear better with the yagi suggests that this is the way for you to go: it's apparently fighting better, even with both hands tied behind its back :-) You might want to permanently raise the elevation of the yagi about 20 deg. so as to fill in the pattern overhead at the cost of some gain at the horizon. Odds are, you'll still make local terrestrial signals (especially if you make the improvements described below). I would even consider getting someone to buy you a 75 foot run of LMR-400 for an up-coming birthday!
If the yagi has one input for both bands, I would, for now, get a 70cm preamp up there and do without on 2m, where one is somewhat less important. Have you tried using your yagi to listen to VO-52 or AO-7? Given the results you describe with AO-51, the former should be quite audible because it is closer to you, there's less of a penalty in 'path loss' on that frequency, and your feedline is not tearing up your noise figure quite as badly.
Do you have a second radio with which you can listen as you are transmitting? On FM birds, a crummy old HT will do fine for both purposes. Since birds hear better than they transmit, you could use your vertical with an HT to transmit 5w and the improved yagi set-up to listen. If you want to go all-mode and are on a limited budget, consider the FT-817 as a second radio. It takes some fiddling, but SATPC-32 does let you control two radios at once, one for up-link and one for down-.
Thanks for sharing your experiences with us, Scott. I, for one, am enjoying hearing about your progress. If you haven't yet had the opportunity, I strongly suggest joining AMSAT-NA. It's nothing short of amazing that you can be part of a club that is designing a satellite as cool as 'Eagle', helping university students with their low-cost satellite experiments and even ask really simple space physics and communications questions that will be answered by bona fide experts. Besides its support for all this, it produces a great journal, and building some of the projects in there has saved me hundreds of dollars and been great fun.
73, Bruce VE9QRP _______________________________________________ Sent via AMSAT-BB@amsat.org. 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
I will certainly second Gould's comments. I recently Elmered some locals to get on the birds for FD. They ended up with some ancient Cushcraft satellite antennas, an azimuth rotator, and a preamp. In descending order of improvement, they got the circular polarization set correctly, installed a 70 cm preamp, and understood how to set the correct fixed elevation. By the time they got done, they had a very respectable signal after climbing a very steep learning curve very quickly. The array is packed up now, and one op is using a set of M2 egg beaters. He still gets in, but not as well, and absolutely needs a preamp.
Alan WA4SCA
At 11:37 AM 8/7/2007, Gould Smith wrote:
Hello Bruce and Scott,
My experience and testing has shown me that small yagis, at a fixed elevation AND a preamp at the antenna will more than adequately work all the current LEOs. ...
Dear Friends,
Just a few comments on omni's.
The key to working the LEOs is really just a decent mast mounted preamp. A Yagi is nice but I have worked 49 states and around 40 countries using just omni antennas on the LEOs. It really isn't that hard, you just have to be able to HEAR the satellite and that means a mast mounted preamp. I have worked AO-51 even on Field Day with just an EZ Lindenblad on 2m and parasitic Lindenblad on 70cm.
The coax is not that important as long as you get at least 5 watts or so at the antenna for the uplink. On AO-51, of course, the more power the better because of the QRM but the satellite would be full quieting at 5 watts into an omni.
73, Tony AA2TX
I'll second what Tony says, especially if you use the omni antenna's he has designed (which I also use and highly recommend - and they're really easy to build).
While Tony is modest, you can get his design and construction details for both his 146 and 435 MHz antenna's in the 2006 AMSAT Symposium Proceedings (available on the AMSAT website - I know a callous plug!!).
What? No AMSAT Proceedings handy?? Then try the current August 2007 issue of QST where Tony describes his 2 Meter EZ-Lindenblad. (Tony - will the 70cm antenna be in next month's QST??)
Regards...Bill - N6GHz
Anthony Monteiro wrote:
At 11:37 AM 8/7/2007, Gould Smith wrote:
Hello Bruce and Scott,
My experience and testing has shown me that small yagis, at a fixed elevation AND a preamp at the antenna will more than adequately work all the current LEOs. ...
Dear Friends,
Just a few comments on omni's.
The key to working the LEOs is really just a decent mast mounted preamp. A Yagi is nice but I have worked 49 states and around 40 countries using just omni antennas on the LEOs. It really isn't that hard, you just have to be able to HEAR the satellite and that means a mast mounted preamp. I have worked AO-51 even on Field Day with just an EZ Lindenblad on 2m and parasitic Lindenblad on 70cm.
The coax is not that important as long as you get at least 5 watts or so at the antenna for the uplink. On AO-51, of course, the more power the better because of the QRM but the satellite would be full quieting at 5 watts into an omni.
73, Tony AA2TX
Sent via AMSAT-BB@amsat.org. 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
Bill Ress wrote:
While Tony is modest, you can get his design and construction details for both his 146 and 435 MHz antenna's in the 2006 AMSAT Symposium Proceedings (available on the AMSAT website - I know a callous plug!!).
The lindenblads are not only the most approachable DIY solutions that I've seen, they are also the only ones that seem like they'll work when you're done with them. I can't comment on them directly, but when it's time to try out an omni, those will be the ones I build. I appreciated the very detailed diagrams about how the matching coax should be cut. I felt that the other omni plans left out that very important detail - especially considering the importance the phasing and matching section play in their designs.
I would like to report some additional progress! During tonight's AO-51 pass over the central US, I managed to clearly copy a few call signs and portions of a few QSOs. It is a small step from last week's work, but it proves to me that the fixed elevation yagi is serviceable and that I am getting a return on investment. Yesterday I replaced the questionable RG-58 with RG-213.
I have planned a few changes to the existing feed line configuration which will allow me to work 2m and 440 with seperate transceivers. I've also ordered an SSB preamp for the 70cm band. I am considering LMR-400 flex for the 70cm feed and keeping the RG-213 for the 2m feed.
The preamp was a concern for me in that since I've been working HF, I've found that I receive much clearer with the preamp disabled and the attenuator enabled and just pushing up the AF gain. I realize this is due to noise in the area and the fact that the IC-7000 preamp is a broadband preamp, and generally will just increase the noise floor and lower the sensitivity of the frequencies I'm actually interested in.
Tonight I confirmed that I cannot copy any AO-51 signal without the IC7000 preamp engaged. Hopefully this means that with a quality narrowband mast mount preamp from SSB, I'll be able to bypass the broadband preamp and increase overall sensitivity of the UHF receive band. I know that everyone's saying that a preamp is an absolute must, but I needed to clear that up before I could justify buying a preamp when in other situations, it only makes things worse.
Again, thanks for your help. I'll let you all know as soon as I get transmitting.
Scott NW2s
Scott, You point out an interesting difference between HF and UHF...
<quoted> The preamp was a concern for me in that since I've been working HF, I've found that I receive much clearer with the preamp disabled and the attenuator enabled and just pushing up the AF gain. I realize this is due to noise in the area and the fact that the IC-7000 preamp is a broadband preamp, and generally will just increase the noise floor and lower the sensitivity of the frequencies I'm actually interested in. <end quoted>
The main difference is the noise of the exterior environment. Without going into the gory mathematical details, essentially the noise figure of the exterior environment is on the order of 40-60dB on 40m, decreasing to roughly 5-10dB on 10m. Most radios have RX noise figures on the order of ~10dB. Basically the radio only needs to be a bit more sensitive than the external environment--which is why attenuators are more appropriate for 40m, and sometimes (but not always) a preamp becomes helpful up on 10m.
At 70cm the external noise is on the order of a couple of dB...but the coax and radio push the total up to ~12dB...so a low-noise amplifier at the antenna can make a LOT of difference. I once made a calibrated off-air measurement of the sensitivity improvement rendered by an ARR GaAsFET preamp on an M2 eggbeater (another omni antenna) and found 8-10dB improvement.
Scott Townley NX7U Gilbert, AZ DM43di http://members.cox.net/nx7u
At 09:48 PM 8/7/2007, Bill Ress wrote:
I'll second what Tony says, especially if you use the omni antenna's he has designed (which I also use and highly recommend - and they're really easy to build).
While Tony is modest, you can get his design and construction details for both his 146 and 435 MHz antenna's in the 2006 AMSAT Symposium Proceedings (available on the AMSAT website - I know a callous plug!!).
What? No AMSAT Proceedings handy?? Then try the current August 2007 issue of QST where Tony describes his 2 Meter EZ-Lindenblad. (Tony - will the 70cm antenna be in next month's QST??)
Regards...Bill - N6GHz
...
A "parasitic" Lindenblad?? Please fill me in! I just ordered all the aluminum tubing for the 2M version, and plan to build one soon after it gets here. Looking forward to comparing it to the M2 eggbeater I'm using now. 73, Jim KQ6EA
Hi Bill and Jim,
Thank you for the vote of confidence!
On 70cm, the dimensions are too critical to scale the EZ-Lindenblad. Instead, I developed a "Parasitic Lindenblad" antenna that uses just a single driven element along with a passive parasitic circular polarizer. This takes advatage of the small size of the elements on 70cm and is much easier to build.
I presented a paper on this at the last AMSAT Symposium but I have continued to work on improvements to make it even easier to build and to get rid of the ferrites that were needed. I hope to finish in time for this years Space Symposium.
73, Tony AA2TX
Sounds very interesting. Good luck getting it tweaked, and I look forward to reading about it. 73, Jim KQ6EA
participants (9)
-
Alan P. Biddle -
Anthony Monteiro -
Bill Ress -
Bruce Robertson -
Gould Smith -
Jim Jerzycke -
Reicher, James -
Scott Townley -
scott wilson