Antenna Opinions?
Hi folks,
So, we had a swap meet a couple of weekends ago, and I found a bargain I couldn't refuse. Of course, now I need to decide what to do with it...
The Find was a 35 element 1296mHz antenna, well built and in excellent condition. Linearly polarized, horizontal; supposed to be 23dBi gain. Manufacturer, of course, is unknown. No markings, but it does not look home-built. By the mounting hardware, it looks like it was part of some sort of stacked array.
The problem is that I already have a 1296mHz antenna. Home-made, circularly polarized, 18 turns Helix. Should be something like 17dBic, if the calculations are correct.
In the shack, which is at the wrong end of 60' of 1/2" hardline and a total of about 15' of RG-213 or something like it, I have my Yaesu 736R and its 10 watts of screaming RF power. No preamps.
Which antenna should I keep up on the rotor assembly?
Last weekend I put up the new antenna. I've made one AO-51 LU pass with the new antenna, and I was not impressed. Several times I couldn't get into the bird, presumably because of the crossed polarization. But when I did get in, it was full quieting, even at low elevations. I don't recall having this much trouble with the Helix. I think AO-51 is the only current satellite on L-band, right?
For other uses, there's nothing terrestrial to aim at, repeaters-wise; they're all hiding behind one or more hills, or went off the air years ago. That leaves Weak Signal work (hence the horizontal mounting). I do have one shot into the valley, to the North West, but probably slim pickings for contacts. I haven't tried EME.
I'm leaning towards putting the Helix back up, and passing the new one on to someone more able to use it. What are your thoughts?
Thanks,
Greg KO6TH
Greg, I would keep the one that works the best. I have been disappointed in the performance of long boom Yagi's for UHF. Resistance loss in the elements often reduces the gain by several dB over calculated gain. Also they are very narrow band, the helix is good for an octave. Art, KC6UQH -----Original Message----- From: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Greg D. Sent: Tuesday, September 21, 2010 10:04 PM To: amsat-bb@amsat.org Subject: [amsat-bb] Antenna Opinions?
Hi folks,
So, we had a swap meet a couple of weekends ago, and I found a bargain I couldn't refuse. Of course, now I need to decide what to do with it...
The Find was a 35 element 1296mHz antenna, well built and in excellent condition. Linearly polarized, horizontal; supposed to be 23dBi gain. Manufacturer, of course, is unknown. No markings, but it does not look home-built. By the mounting hardware, it looks like it was part of some sort of stacked array.
The problem is that I already have a 1296mHz antenna. Home-made, circularly polarized, 18 turns Helix. Should be something like 17dBic, if the calculations are correct.
In the shack, which is at the wrong end of 60' of 1/2" hardline and a total of about 15' of RG-213 or something like it, I have my Yaesu 736R and its 10 watts of screaming RF power. No preamps.
Which antenna should I keep up on the rotor assembly?
Last weekend I put up the new antenna. I've made one AO-51 LU pass with the new antenna, and I was not impressed. Several times I couldn't get into the bird, presumably because of the crossed polarization. But when I did get in, it was full quieting, even at low elevations. I don't recall having this much trouble with the Helix. I think AO-51 is the only current satellite on L-band, right?
For other uses, there's nothing terrestrial to aim at, repeaters-wise; they're all hiding behind one or more hills, or went off the air years ago. That leaves Weak Signal work (hence the horizontal mounting). I do have one shot into the valley, to the North West, but probably slim pickings for contacts. I haven't tried EME.
I'm leaning towards putting the Helix back up, and passing the new one on to someone more able to use it. What are your thoughts?
Thanks,
Greg KO6TH
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M2 makes a 35 element 1296 MHz yagi, on about a 6' boom. individual elements are insulated "thru the boom" with keepers. Folded dipole driven element. I used 2 each stacked vertically for AO-40. Yes, they are pointy.
Stan, W1LE Cape Cod FN41sr
On 9/22/2010 1:52 AM, Art McBride wrote:
Greg, I would keep the one that works the best. I have been disappointed in the performance of long boom Yagi's for UHF. Resistance loss in the elements often reduces the gain by several dB over calculated gain. Also they are very narrow band, the helix is good for an octave. Art, KC6UQH --
I installed one of these a few months ago, in place of my 20-turn Wimo helix. Both are nice antennas, but I'll give the edge to the M2 yagi (more gain and it mounts balanced on the elevation boom). I have mine with vertical polarity. Since AO-51 is linear on L-band, it shouldn't matter--but putting that little antenna horizontal in line with my metal boom didn't seem to make much sense....
73,
Mark N8MH
On Wed, Sep 22, 2010 at 8:50 AM, Stan, W1LE stanw1le@verizon.net wrote:
M2 makes a 35 element 1296 MHz yagi, on about a 6' boom. individual elements are insulated "thru the boom" with keepers. Folded dipole driven element. I used 2 each stacked vertically for AO-40. Yes, they are pointy.
Stan, W1LE Cape Cod FN41sr
On 9/22/2010 1:52 AM, Art McBride wrote:
Greg, I would keep the one that works the best. I have been disappointed in the performance of long boom Yagi's for UHF. Resistance loss in the elements often reduces the gain by several dB over calculated gain. Also they are very narrow band, the helix is good for an octave. Art, KC6UQH --
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
Okay, my 35 ele M2 is about 10 feet long: http://www.m2inc.com/index2.html
They do sell a 22 element version that is about 6' long: http://www.m2inc.com/index2.html
Mark N8MH
On Wed, Sep 22, 2010 at 9:10 AM, Mark L. Hammond marklhammond@gmail.com wrote:
I installed one of these a few months ago, in place of my 20-turn Wimo helix. Both are nice antennas, but I'll give the edge to the M2 yagi (more gain and it mounts balanced on the elevation boom). I have mine with vertical polarity. Since AO-51 is linear on L-band, it shouldn't matter--but putting that little antenna horizontal in line with my metal boom didn't seem to make much sense....
73,
Mark N8MH
On Wed, Sep 22, 2010 at 8:50 AM, Stan, W1LE stanw1le@verizon.net wrote:
M2 makes a 35 element 1296 MHz yagi, on about a 6' boom. individual elements are insulated "thru the boom" with keepers. Folded dipole driven element. I used 2 each stacked vertically for AO-40. Yes, they are pointy.
Stan, W1LE Cape Cod FN41sr
On 9/22/2010 1:52 AM, Art McBride wrote:
Greg, I would keep the one that works the best. I have been disappointed in the performance of long boom Yagi's for UHF. Resistance loss in the elements often reduces the gain by several dB over calculated gain. Also they are very narrow band, the helix is good for an octave. Art, KC6UQH --
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
-- Mark L. Hammond [N8MH]
Hi Stan,
No, it's for sure not an M2. The boom is about 9' or 10' long, and the driven element is a simple dipole. The reflector element in the back is split, with two dipoles, one above and one below the boom. Coax connector is at the rear of the boom.
The pointiness of the antenna is not too bad. My rotor is good to 6 degrees (that's the clicker increment), and the one beacon I can barely hear way off in the distance can be heard +/- about 2 clicks.
Greg KO6TH
Date: Wed, 22 Sep 2010 08:50:05 -0400 From: stanw1le@verizon.net To: amsat-bb@amsat.org Subject: [amsat-bb] Re: Antenna Opinions?
M2 makes a 35 element 1296 MHz yagi, on about a 6' boom. individual elements are insulated "thru the boom" with keepers. Folded dipole driven element. I used 2 each stacked vertically for AO-40. Yes, they are pointy.
Stan, W1LE Cape Cod FN41sr
On 9/22/2010 1:52 AM, Art McBride wrote:
Greg, I would keep the one that works the best. I have been disappointed in the performance of long boom Yagi's for UHF. Resistance loss in the elements often reduces the gain by several dB over calculated gain. Also they are very narrow band, the helix is good for an octave. Art, KC6UQH --
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
----- Original Message ----- From: "Greg D." ko6th_greg@hotmail.com To: amsat-bb@amsat.org Sent: Wednesday, September 22, 2010 7:03 AM Subject: [amsat-bb] Antenna Opinions?
Hi folks,
The Find was a 35 element 1296mHz antenna, well built and in excellent condition. Linearly polarized, horizontal; supposed to be 23dBi gain. Manufacturer, of course, is unknown. No markings, but it does not look home-built. By the mounting hardware, it looks like it was part of some sort of stacked array.
Thanks,
Greg KO6TH
Hi Greg, KO6TH
It is probably a Tonna 35 element yagi.
73" de
i8CVS Domenico
----- Original Message ----- From: "Greg D." ko6th_greg@hotmail.com To: amsat-bb@amsat.org Sent: Wednesday, September 22, 2010 7:03 AM Subject: [amsat-bb] Antenna Opinions?
Hi folks,
The Find was a 35 element 1296mHz antenna, well built and in excellent
condition. Linearly polarized, horizontal; supposed to be 23dBi gain. Manufacturer, of course, is unknown. No markings, but it does not look home-built. By the mounting hardware, it looks like it was part of some sort of stacked array.
Thanks,
Greg KO6TH
Hi Greg, KO6TH
If your antenna is from Tonna it must be 3,07 meters long.
Tonna make two models one for DX and SAT and the other one for ATV By the way the gain is 20 dB isotropic.
20635 35 ELEMENTI 1260/1300 MHz dx,sat 20 dB 3,07 meters long
20636 35 ELEMENTI 1250/1260 MHz ATV 20 dB 3,07 meters long
73" de
i8CVS Domenico
Hi Domenico,
The length sounds about right (I didn't measure it, but it's longer than my garage 8 foot ceiling is high). But searching for pictures of the Tonna antenna, I'm not seeing one that matches. The Tonna antennas have a different mounting (a parallel bar below the boom), and elements above the boom, or so it seems. I have put some pictures of the mounting for this antenna, and the overall "array":
http://home.wavecable.com/~ko6th/dsc00319-800.jpg shows the mounting, and element style. There is another similar block of metal at the rear of the antenna; slightly smaller, but with the same type of pipe fittings going up and down. The PVC pipe mounting is mine. 1/2" pipe elbow, slathered with glue and tapped into place with a hammer. Seems to work.
and
http://home.wavecable.com/~ko6th/dsc00320-1024.jpg for the whole thing. You can barely see the back of the antenna in this image, with the split reflector. The coax cable is hooked to a 90-degree elbow, so that it hangs down without kinking (and so it can reach!). Left to right are a 2x15 element 70cm antenna (also unknown pedigree), 13cm BBQ dish, 23cm antenna, tower camera in box, and 8 element 2m antenna. The cross boom is a wooden closet pole, and yes, the weight of the dish is causing a bit of a sag... Hence my earlier thread about replacing it with a pair of flat panel Wi-Fi antennas. I haven't finished that project yet.
If the gain is more like 20dBi (the seller claims 23), then the difference between my 18 turn helix and the 35 element yagi is even less. For satellite use, the helix probably wins because of the circular polarization. In terrestrial work, I lose 3db going circular to linear, so the net difference is going to be about 6dB. Not trivial, but not "wow" either. The helix is a lot smaller of an antenna, too, thinking of wind load and such.
Greg KO6TH
From: domenico.i8cvs@tin.it To: ko6th_greg@hotmail.com; amsat-bb@amsat.org Subject: Re: [amsat-bb] Antenna Opinions? Date: Wed, 22 Sep 2010 15:17:15 +0200
----- Original Message ----- From: "Greg D." ko6th_greg@hotmail.com To: amsat-bb@amsat.org Sent: Wednesday, September 22, 2010 7:03 AM Subject: [amsat-bb] Antenna Opinions?
Hi folks,
The Find was a 35 element 1296mHz antenna, well built and in excellent
condition. Linearly polarized, horizontal; supposed to be 23dBi gain. Manufacturer, of course, is unknown. No markings, but it does not look home-built. By the mounting hardware, it looks like it was part of some sort of stacked array.
Thanks,
Greg KO6TH
Hi Greg, KO6TH
If your antenna is from Tonna it must be 3,07 meters long.
Tonna make two models one for DX and SAT and the other one for ATV By the way the gain is 20 dB isotropic.
20635 35 ELEMENTI 1260/1300 MHz dx,sat 20 dB 3,07 meters long
20636 35 ELEMENTI 1250/1260 MHz ATV 20 dB 3,07 meters long
73" de
i8CVS Domenico
Greg,
My two cents is that AO-51 seems to be very sensitive on the L band receive, so a decent antenna will get in fine. I have been using RHCP on my uplink, a 31 turn homebrew helix modeled after the VE3NPC, and I have not experienced any fading problems on uplink. My choice then is to opt for the circular polarization. I do feed mine directly at the antenna (about 5 feet of LMR-400 from the upconverter) but I think your helix with the power you are feeding it is probably quite capable and a better idea to avoid the fading.
73, Jerry N0JY
Hi folks,
So, we had a swap meet a couple of weekends ago, and I found a bargain I couldn't refuse. Of course, now I need to decide what to do with it...
I'm leaning towards putting the Helix back up, and passing the new one on to someone more able to use it. What are your thoughts?
Thanks,
Greg KO6TH
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
participants (6)
-
Art McBride -
Greg D. -
i8cvs -
Mark L. Hammond -
n0jy＠lavabit.com -
Stan, W1LE