Re: Easy to make, low cost omni-directional antennae
I have just been involved with the sats since February and also wanted an omni for base station use. I started with a simple 1/4 wave ground plane (19" for 2m, 6 1/2" for 70 cm), later tried homebrewing Jerry's Eggbeater II, and then bought a second-hand M2 eggbeater and the ARR preamp. I noticed little or no difference between the 3 antennas, certainly not enough to justify the relatively high price of a new M2 eggbeater. The preamp helps a lot but, as Jeff says, SO-50 is still quite weak.
Have not tried the Lindenblad. Not many are using it or talking about it, so I doubt it is all that great. Same for the turnstile.
I do far better with a 5w HT and a handheld Arrow than I do with an IC-7000, ARR preamp, and any of the omnis I have tried. However, unlike some people, I don't really enjoy standing in the yard holding the Arrow antenna for 15 minutes. So I usually work from inside.
If you do go omni, get it high enough to be in the clear. And unless you get a preamp, use very good coax and keep the line as short as possible. You can get a 70cm receive-only preamp from Ramsey Electronics for $17, but with that you'll need a separate coax line for the 2m uplink, or a duplexer. The ARR is the cheapest RF switching preamp and it's over $125.
I also homebrewed one of Kent's dual band LEO cheap yagis, see http://www.wa5vjb.com/references/Cheap%20Antennas-LEOs.pdf. It can be built for $10 and it works as good or better than the far more expensive expensive Arrow, although it's not quite as portable. As Jeff mentioned, the Arrow unscrews into very small pieces and fits in a suitcase, very nice for air travel. The cheap yagi elements are glued to the wood boom, will fit into a car trunk but is not suitable for air travel, unless someone comes up with a different way to attach the elements to the boom that allows easy removal.
Have not tried this, but I'm almost certain that a cheap yagi mounted at a fixed 20-30 degree elevation and rotated with an old TV rotator will be less expensive and give substantially better results than any omni, even an omni with a preamp.
Good luck and 73, Bill NZ5N ********************************** Date: Thu, 27 Mar 2008 07:37:20 -0700 From: Jeff Mock jeff@mock.com Subject: [amsat-bb] Re: Easy to make, low cost omni-directional antennae To: Graeme Nelson zl2gdn@gmail.com, "'AMSAT-BB'" amsat-bb@amsat.org Message-ID: 47EBB120.30806@mock.com Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Hi,
I'm new to satellite stuff and I had essentially the same requirements as you. I live in a dense urban environment so I have more QRM problems than most, limited roof space, and I try to keep a low profile and not get the neighbors too excited.
I wound up purchasing two eggbeaters from M2, one for 70cm and one for 2m: http://www.m2inc.com/products/vhf/2m/eb144.html
They work well, they are well-built, and are great for AO-51, ISS-digital, and GO-32. I also wound up getting an ARR masthead preamp
for the 70cm eggbeater to compensate for my long feedline to the roof http://www.advancedreceiver.com/page10.html
To tell you the truth, the two eggbeaters are marginal for me working SO-50. It is just above the noise and I don't feel like I hear it well
enough to transmit. If you want to listen for weak signals you might go straight to a directional setup with more gain. I feel a rotator in my
not-too-distant future...
Eggbeaters aren't terribly portable. The copperweld loop is going to spring loose when you take it apart and poke someone in the eye, so I don't move them. For portable I got and Arrow-II handheld 70cm/2m yagi. It's great fun and seems to be popular. I used it with an old Icom-W32A HT on vacation and used it to work AO-51. It breaks down really small,
fits in a little bag, and I can put it together in less than 5-minutes: http://www.arrowantennas.com/146-437.html
jeff AD6EO
Graeme Nelson wrote:
Hi all,
I'm wanting to make an antenna for "talking with the
birds", mainly ISS and
LEOs. Thank you to Don ZL1THO and John KB2HSH for
the suggestions and
encouragement they have already e-mailed me.
I have done some more thinking since then and come
up with the following list
of criteria for the first antenna I make for
satellite work:
- easy to make
- lost cost
- omni-directional
- good performance, especially for satellite work,
without moving it
- portable enough that I can pack it into the van
when I go on holiday and it
won't take up much space (it needs to share the
space with all the stuff for
my wife and 3 children, as well as me). It would
also be nice to be able to
store it in the corner of my office at work if I so
desire.
When I started looking in earnest last Friday, a ham
colleague of mine did a
Google search an came across a turnstile antenna
that looked promising
evening, I noticed the
eggbeater on the web site of John KB2HSH
(http://kb2hsh.blogspot.com/), which
looks nice and easy to build. I then did some
searching and came upon the
Eggbeater II by Jerry K5OE
(http://members.aol.com/k5oejerry/eggbeater2.htm),
arguably a better fixed antenna for satellite use
than the original eggbeater.
A while later, I also found the EZ-Lindenblad by
Tony AA2TX
(http://www.arrl.org/qst/2007/08/monteiro.pdf).
I am currently leaning towards the EZ-Lindenblad
(for 2m) and a parasitic
Lindenblad (for 70cm ... when I get hold of the
design; I intend to e-mail
Tony about it if/when I go ahead with the
EZ-Lindenblad).
How do these antennae compare performance-wise? Am
I leaning in the right
direction (EZ-Lindenblad), or should I be looking at
something else? Your
input would be much appreciated.
TTFN., Graeme ZL2GDN
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At 06:17 AM 3/28/2008, Bill Dzurilla wrote:
Have not tried the Lindenblad. Not many are using it or talking about it, so I doubt it is all that great. Same for the turnstile.
The Lindenblad is said to be quite good, but requires a bit more mechanical work to build.
I do far better with a 5w HT and a handheld Arrow than I do with an IC-7000, ARR preamp, and any of the omnis I have tried. However, unlike some people, I don't
A directional antenna really does improve things on 70cm.
If you do go omni, get it high enough to be in the clear. And unless you get a preamp, use very good coax and keep the line as short as possible. You can get a 70cm receive-only preamp from Ramsey Electronics for $17, but with that you'll need a separate coax line for the 2m uplink, or a duplexer. The ARR is the cheapest RF switching preamp and it's over $125.
I wouldn't bother with a switching preamp, unless you're planning on using the omni for transmitting (e.g. for working the ISS repeater). You certainly don't need a switching preamp to work any of the Mode J birds, because the uplink is on a different band, and you want full duplex capability if you can have it. In any case, a good masthead preamp is a must for omnis.
I also homebrewed one of Kent's dual band LEO cheap yagis, see http://www.wa5vjb.com/references/Cheap%20Antennas-LEOs.pdf. It can be built for $10 and it works as good or better than the far more expensive expensive Arrow, although
I have had a lot of success with a homebrew directional antenna. Only reason I would consider an Arrow is for the portability as you mention.
Have not tried this, but I'm almost certain that a cheap yagi mounted at a fixed 20-30 degree elevation and rotated with an old TV rotator will be less expensive and give substantially better results than any omni, even an omni with a preamp.
I have heard this can work well, though I've never tried it. You will want to make sure that the Yagi only has moderate gain, as you will need a fairly wide pattern, so that the satellite can still be on the edge of the main lobe at high elevation.
73 de VK3JED http://vkradio.com
Good points, Tony.
I wouldn't bother with a switching preamp, unless you're planning on using the omni for transmitting (e.g. for working the ISS repeater). You certainly don't need a switching preamp to work any of the Mode J birds, because the uplink is on a different band, and you want full duplex capability if you can have it.
Of course, you can't use a receive only preamp if you use a dual band antenna with a single feedline, or if you want to use the 70 cm antenna for local repeaters, for working the ISS repeater, VO-52, or AO-7 mode B, or for any type of 70 cm transmission at all. But if you have an antenna that can be devoted exclusively to 70 cm reception, it will do fine and will be a lot cheaper than a switching preamp.
73, Bill NZ5N
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Tony Langdon wrote:
At 06:17 AM 3/28/2008, Bill Dzurilla wrote: I wouldn't bother with a switching preamp, unless you're planning on using the omni for transmitting (e.g. for working the ISS repeater). You certainly don't need a switching preamp to work any of the Mode J birds, because the uplink is on a different band, and you want full duplex capability if you can have it. In any case, a good masthead preamp is a must for omnis.
I like having a switching preamp because I'm an idiot. I'm always moving stuff around, I'll get a crazy idea to work a local 70cm repeater or whatever. I would have certainly blown up a receive-only preamp 5-times over by now, even though I rarely use the switching part.
jeff AD6EO
At 09:43 AM 3/28/2008, Jeff Mock wrote:
I like having a switching preamp because I'm an idiot. I'm always moving stuff around, I'll get a crazy idea to work a local 70cm repeater or whatever. I would have certainly blown up a receive-only preamp 5-times over by now, even though I rarely use the switching part.
For idiot proofing, the switching preamp is a good idea. :)
73 de VK3JED http://vkradio.com
At 03:17 PM 3/27/2008, Bill Dzurilla wrote:
I have just been involved with the sats since February and also wanted an omni for base station use
...
Have not tried the Lindenblad. Not many are using it or talking about it, so I doubt it is all that great.
Dear Friends,
I want to help remove any doubt.
You cannot buy a Lindenblad for the ham bands. That is a major reason why that they are not so popular.
In terms of performance though, a few data points may help illustrate. This snapshot is for 2m antennas mounted at 6' elevation (like I do for field day)
1. At 5 degrees elevation, a Lindy has about 5 dB higher gain to satellites with circular polarization versus an eggbeater. That is pretty significant if you want to work max DX. Of course mounting the antennas higher will also help.
2. At 15 degrees elevation, the Lindenblad is only about +2 dB higher gain than an eggbeater for circularly polarized satellites (mostly insignificant.) But...
3. at the same 15 degrees, on satellites with linearly polarized antennas, a Lindenblad will show only about 5 dB max fading from polarization mismatch versus nearly 25 dB max fading using an eggbeater. That is pretty significant.
So, the eggbeater is probably the best omni antenna you can buy for working DX on the LEO satellites.
But, in terms of performance, the Lindenblad is a better antenna if you are willing to build one.
73, Tony AA2TX
Hi,
I don't have the test data but confirm the excellent receive performance of the Lindenblad with the 70cm downlink satellites. The first one I made was using the classic 4x folded dipole method as shown in Satellite Experimenters Handbook by K2UBC. Made a wooden jig so that all the folded dipoles were the same. Worked well, but was tricky to build due to the phasing harness.
The second one was Tony AA2TX's design which he described as a Parasitic Lindy. No phasing harness and much easier to build. With a good pre amp (a kit from G0MRF) I could copy the 80mW cubesat beacons at 1 degree elevation.
LO-19 beacon was very strong at low elevation with no pre amp and just a 2 meters of co-ax into an FT817.
73
John G7HIA
At 11:17 AM 3/27/2008, Bill Dzurilla wrote:
I have just been involved with the sats since February and also wanted an omni for base station use. I started with a simple 1/4 wave ground plane (19" for 2m, 6 1/2" for 70 cm), later tried homebrewing Jerry's Eggbeater II, and then bought a second-hand M2 eggbeater and the ARR preamp. I noticed little or no difference between the 3 antennas, certainly not enough to justify the relatively high price of a new M2 eggbeater. The preamp helps a lot but, as Jeff says, SO-50 is still quite weak.
For a simple omni the 19-inch ground plane works as a 1/4 or 3/4 wavelength vertical on either 2m or 70cm respectively. I used one with a P432 ARR preamp ($79.95) to record AO-51 telemetry very well. This is a plain GasFet preamp with 0.5 dB NF so do not transmit into it. The 25w switching ARR preamp is worth the piece of mind in that respect. I think you get much better low noise performance with ARR over the cheaper preamps.
Have not tried the Lindenblad. Not many are using it or talking about it, so I doubt it is all that great. Same for the turnstile.
I am thinking to build a set of these antennas for non-tracking use. Tony AA2TX design looks good. (http://www.arrl.org/qst/2007/08/monteiro.pdf).
I do far better with a 5w HT and a handheld Arrow than I do with an IC-7000, ARR preamp, and any of the omnis I have tried. However, unlike some people, I don't really enjoy standing in the yard holding the Arrow antenna for 15 minutes. So I usually work from inside.
If you do go omni, get it high enough to be in the clear. And unless you get a preamp, use very good coax and keep the line as short as possible. You can get a 70cm receive-only preamp from Ramsey Electronics for $17, but with that you'll need a separate coax line for the 2m uplink, or a duplexer. The ARR is the cheapest RF switching preamp and it's over $125.
I also homebrewed one of Kent's dual band LEO cheap yagis, see http://www.wa5vjb.com/references/Cheap%20Antennas-LEOs.pdf. It can be built for $10 and it works as good or better than the far more expensive expensive Arrow, although it's not quite as portable. As Jeff mentioned, the Arrow unscrews into very small pieces and fits in a suitcase, very nice for air travel. The cheap yagi elements are glued to the wood boom, will fit into a car trunk but is not suitable for air travel, unless someone comes up with a different way to attach the elements to the boom that allows easy removal.
Have not tried this, but I'm almost certain that a cheap yagi mounted at a fixed 20-30 degree elevation and rotated with an old TV rotator will be less expensive and give substantially better results than any omni, even an omni with a preamp.
For couple years I had the 2m portion of my Arrow installed on az-el rotator and it worked well. I would recommend the fixed elevation short yagi as next better than an omni for simplicity with Leo sats. Either an Arrow or home-built will work.
I have the full AO-10/13 long x-yagi's on az-el rotator for the next Heo, but for simpler Leo operation the small fixed rotator or Lindenblad are fine.
***************************************************** 73, Ed - KL7UW BP40iq, 6m - 3cm 144-EME: FT-847, mgf-1801, 4x-xp20, 185w http://www.kl7uw.com AK VHF-Up Group NA Rep. for DUBUS: dubususa@hotmail.com *****************************************************
On Thu, Mar 27, 2008 at 4:17 PM, Bill Dzurilla billdz.geo@yahoo.com wrote:
If you do go omni, get it high enough to be in the clear. And unless you get a preamp, use very good coax and keep the line as short as possible. You can get a 70cm receive-only preamp from Ramsey Electronics for $17, but with that you'll need a separate coax line for the 2m uplink, or a duplexer.
You can get such a preamp from Ramsey, but as one who has built their preamps in hopes that they will suffice for satellite operations, I do not recommend it. Remember that the improvement that a preamp makes (for a given position in the receiving system) is related to the gain and inversely to the noise figure. Gain is easy, low noise figure is not; but without the latter you will receive more noise on 70cm, not more signal. I would strongly recommend a ARR or SSBUSA preamp for any beginner. Since the marginal expense is not that great, you are much better off getting a switching model appropriate for out-of-doors use. Get switching also because you will want to diversify into mode-B operations, using VO-52 in particular.
I have enjoyed many Ramsey kits in the past, but my experience is that their preamps are not designed for improving weak-signal reception on either the VHF or UHF satellite bands.
73, Bruce VE9QRP
participants (7)
-
Anthony Monteiro -
Bill Dzurilla -
Bruce Robertson -
Edward Cole -
Jeff Mock -
john heath -
Tony Langdon