Dave,
I would be suspicious of the construction. I can get a few minutes of good copy from AO-51 on a high pass with just a rubber duck on an HT. If you do get a preamp, the run between the antenna and the preamp is critical, so if possible keep it short and use good coax. Ed seems to be having success with 4' of RG-58U, but generally the use of any RG-58U at 70cm is not a good idea.
Here's a quick summary of my results with various antennas:
* HT and rubber duck or other antenna mounted directly on the HT - success only at high elevations * HT and Arrow or Elk antenna, no preamp - success from horizon to horizon, if no trees or other obstructions * base rig and dual band omnidirectional ground plane, no preamp, 40' of RG-213U - success on most birds only when elevation is above 25-35 degrees * base rig and dual band omnidirectional ground plane, ARR preamp, 40' of RG-213U - success on most birds when elevation is above 15 degrees * base rig and Elk antenna on 12' pole at 15 degrees fixed elevation, azimuth rotation with old TV antenna rotor, ARR preamp, 70' coax run (my current setup) - full success from horizon to horizon on all birds, except in directions where blocked by trees or roof.
The Elk is $135 shipped and the used rotor was $25, and this combo is by far the most effective I have used. My community has antenna restrictions, but so far no one has complained about the little 2' long Elk. The Elk could be replaced with a homebrew Cheap Yagi or tape measure yagi, which can be built for $10.
I am not aware of anyone who is able to work the sats at low elevations with any type of omnidirectional antenna, even with the best preamp. You can have plenty of fun working the birds at higher elevations, but you will be able to work more passes and better DX (e.g., Europe on AO-7) if you can catch them at lower elevations.
73, Bill NZ5N
Date: Mon, 08 Feb 2010 17:26:11 -0700 From: David Ek dave@eksfiles.net Subject: [amsat-bb] Re: New Lindy's QRV To: amsat-bb@amsat.org Message-ID: 4B70ABA3.9090908@eksfiles.net Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Question for anyone out there: I just built the parasitic Lindy from the Feb 2010 QST. What kind of performance (on receive) should I expect from it during, say, an AO-51 pass (max EL 83 deg)? I had my Kenwood TH-F6a HT connected directly to it (only a few feet of RG-8X coax to the antenna) with no preamp, and I only had good copy for a moment here and there. Just wondering if I need a preamp or if I need to be suspicious of my construction.
tnx & 73,
Dave NK0E
Edward Cole wrote: I forgot to add that these are patterned after Tony, AA2TX, designs (UHF version is in Feb. 2010 QST). My variation was to use pvc sched-40 plastic pipe (white).
The preamp is one of the older DEMI designs that uses a mgf-1302 GasFet with about 0.7 dBNF. I see about one s-unit of noise when I turn it on. There is 4-feet of RG-58 to the UHF Lindy and 60-feet to the FT-847 from the preamp. The VHF Lindy has no preamp and is fed with 60-feet of RG-213.
The VHF Lindy brings up repeaters 70-miles away with 50w, and the UHF Lindy hears repeaters that far away. So actually can make a nice general purpose antenna.
73, Ed
I can consistently copy the beacons on FO 29 and HO 68 down to the horizion using a larsen 2/70 mobile antenna with the larsen radial kit. The feed line is approx 60 feet of Belden 9913F. I typically connect the antenna to a comet duplexer to my mirage UHF amplifer which has a gasfet preamp and use my FT736 as a receiver, but the 736 can copy the beacons with the preamp switched off. I have an ARR gasfet preamp that works a bit better but is not TR switched and I usually don't bother with it. VO52 is also typically copyable down to the horizon with this setup.
I haven't been on the FM sats in a while but don't recall any issues copying them either.
I have been told by several people that my ears seem to do a better job than others at copying weak signals though (:
----- Original Message ---- From: Bill Dzurilla billdz.geo@yahoo.com To: amsat-bb@amsat.org Sent: Tue, February 9, 2010 6:23:18 AM Subject: [amsat-bb] Re: New Lindy's QRV
Dave,
I would be suspicious of the construction. I can get a few minutes of good copy from AO-51 on a high pass with just a rubber duck on an HT. If you do get a preamp, the run between the antenna and the preamp is critical, so if possible keep it short and use good coax. Ed seems to be having success with 4' of RG-58U, but generally the use of any RG-58U at 70cm is not a good idea.
Here's a quick summary of my results with various antennas:
* HT and rubber duck or other antenna mounted directly on the HT - success only at high elevations * HT and Arrow or Elk antenna, no preamp - success from horizon to horizon, if no trees or other obstructions * base rig and dual band omnidirectional ground plane, no preamp, 40' of RG-213U - success on most birds only when elevation is above 25-35 degrees * base rig and dual band omnidirectional ground plane, ARR preamp, 40' of RG-213U - success on most birds when elevation is above 15 degrees * base rig and Elk antenna on 12' pole at 15 degrees fixed elevation, azimuth rotation with old TV antenna rotor, ARR preamp, 70' coax run (my current setup) - full success from horizon to horizon on all birds, except in directions where blocked by trees or roof.
The Elk is $135 shipped and the used rotor was $25, and this combo is by far the most effective I have used. My community has antenna restrictions, but so far no one has complained about the little 2' long Elk. The Elk could be replaced with a homebrew Cheap Yagi or tape measure yagi, which can be built for $10.
I am not aware of anyone who is able to work the sats at low elevations with any type of omnidirectional antenna, even with the best preamp. You can have plenty of fun working the birds at higher elevations, but you will be able to work more passes and better DX (e.g., Europe on AO-7) if you can catch them at lower elevations.
73, Bill NZ5N
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At 05:23 AM 2/9/2010, Bill Dzurilla wrote:
Dave,
I would be suspicious of the construction. I can get a few minutes of good copy from AO-51 on a high pass with just a rubber duck on an HT. If you do get a preamp, the run between the antenna and the preamp is critical, so if possible keep it short and use good coax. Ed seems to be having success with 4' of RG-58U, but generally the use of any RG-58U at 70cm is not a good idea.
Agreed in general, but if you look at the antenna it requires small diameter coax. Loss at 450-MHz for RG-58 is around 9-10 dB (I didn't look it up so used the loss for RG-223). So for 4/100 feet the loss is 0.4 dB. This adds to the preamp 0.7 dB NF so it is not optimum, but a lot better than the typical 432 ham receiver that is, at best, 6 dB NF. My FT-847 with internal preamp on is 12 dB NF, so reduction to 1.1 dB is a good improvement. The cable length is for convenience and could be made shorter.
Using better coax from the preamp to the shack would also be better. I used 60-feet of RG-58, because I am "cheap". yet, it seems to be working pretty good.
When I get the connections completed on my tracking array, I can compare it with my 0.5 dB NF preamp and 436CP42. The latter is lower to the ground so may encounter some ground clutter limiting tracking to zero elevation. Let you all know when I get it QRV. When I had it roof -mounted at the old qth, I could track AO-27 down to a few degrees.
Here's a quick summary of my results with various antennas:
- HT and rubber duck or other antenna mounted directly on the HT -
success only at high elevations
- HT and Arrow or Elk antenna, no preamp - success from horizon to
horizon, if no trees or other obstructions
- base rig and dual band omnidirectional ground plane, no preamp,
40' of RG-213U - success on most birds only when elevation is above 25-35 degrees
- base rig and dual band omnidirectional ground plane, ARR preamp,
40' of RG-213U - success on most birds when elevation is above 15 degrees
So far, with the Lindy+4 feet RG-58+preamp I am seeing good signals to and a little below 10-degrees.
- base rig and Elk antenna on 12' pole at 15 degrees fixed
elevation, azimuth rotation with old TV antenna rotor, ARR preamp, 70' coax run (my current setup) - full success from horizon to horizon on all birds, except in directions where blocked by trees or roof.
The Elk is $135 shipped and the used rotor was $25, and this combo is by far the most effective I have used. My community has antenna restrictions, but so far no one has complained about the little 2' long Elk. The Elk could be replaced with a homebrew Cheap Yagi or tape measure yagi, which can be built for $10.
I am not aware of anyone who is able to work the sats at low elevations with any type of omnidirectional antenna, even with the best preamp. You can have plenty of fun working the birds at higher elevations, but you will be able to work more passes and better DX (e.g., Europe on AO-7) if you can catch them at lower elevations.
That is why my Lindy is set up only for the typ. mode VU FM birds. I will use the better directional antennas for the linear birds (when I get them connected).
73, Bill NZ5N
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 ======================================
participants (3)
-
Bill Dzurilla -
Edward Cole -
Mark Spencer