April 2011 - AMSAT-BB - mailman.amsat.org

Re: Arrow and ELK Comparative Antenna Tests
by K5OE 26 Apr '11

26 Apr '11

Patrick, I don't mean to quibble, but don't you think using a Large Capacity Filter could have biased the Arrow tests? 73, Jerry, k5OE

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Trying to find Specs
by Farrell Winder 26 Apr '11

26 Apr '11

Looking for specifications on old PBS Ch 24 amplifier. Originally mfg by Comark Southwick, MA. Believe Comark was sold to Thompson. Amplifier module is model # B400698 and has 2 TRW 5030 RF transistors. If anyone has specs or source for info please reply off line. Many thanks. Farrell Winder, W8ZCF.

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Arrow and ELK Comparative Antenna Tests
by John Kopala 26 Apr '11

26 Apr '11

On Saturday, April 23, Pat Stoddard (WD9EWK) and I did some antenna testing in an attempt to answer the questions about which is the best antenna for portable satellite operation. We only tested the antennas in receive mode to determine their relative gain. Time constraints prevented us from performing additional testing to determine if the transmitted output was consistent with the receive gain of the antennas. For the time being we will assume (and we all know the dangers of doing so) that the transmit performance closely matches the receive performance. The antennas tested were an Arrow (3 x 7 elements), an ELK (4 elements), a PortaFox configured for 145/435 operation (4 elements), and a Home Brew 4 by 9 element "arrow" antenna. The standard Arrow antenna was the only antenna equipped with duplexer, but not the basic duplexer which is installed in the handle. We did not measure the insertion loss of the duplexer on the Arrow antenna, but this was obviously not a significant factor in the overall performance. A duplexer could still be required depending upon the antenna chosen and the radio(s) to be used. Using the Arrow antenna as the reference antenna and 145.300 MHz as our test frequency, our measurements indicated that the Arrow and the ELK antennas had identical gain. The PortaFox antenna showed 2db less gain than the Arrow and the ELK. The Home Brew 4/9 element crossed yagi showed 2db more gain than the Arrow and the ELK. On 435.300 MHz, the Arrow antenna had 2db more gain than the ELK and 8db more gain than the PortaFox. The Home Brew 4/9 element had 3db more gain than the Arrow. Although the ELK antenna shows slightly less (2db) gain on 435.300 MHz, it does have one potential advantage over the Arrow antenna. With the ELK, transmit and receive are in the same plane. With any satellites that have linear polarized antennas, such as AO-27, SO-50, the ISS and maybe SO-67, a crossed yagis can maximize the performance on one band while minimizing it on the other. That does not mean the Arrow won't work, as has been demonstrated by the thousands of satellite QSO's that are made on a regular basis using Arrow antennas. It just means that when you rotate the antenna to maximize the downlink signal, you may be significantly impacting you uplink signal strength in marginal situations. Even though a satellite may have a circular polarized uplink and downlink, don't assume that the orientation of your station antenna as horizontal, vertical, or something in between won't have a significant effect on your signal strength. My experience operating portable with my home brew antenna has convinced me that my horizontally polarized Qagi should either be remounted vertically polarized or replaced with a circular polarized antenna. That is another ongoing project. In summary, unless you plan to build your own, the performance of the Arrow crossed yagi antenna and the ELK log periodic antennas are very comparable and should provide lots of solid satellite contacts. The overall results reflect the adage that bigger is better, but along with more gain, you also get a more bulky antenna that is harder to handle. The home brew crossed yagi I built for portable operation is tripod mounted, can be rotated on its axis, and disassembles for storage in a roll up case. But because of its size, it would be very tiring to attempt to use it hand held for an extended period of time. Pictures of the home brew crossed yagi antenna are on my QRZ page. John Kopala N7JK

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Re: 2m/70cm Quadrifilar Helix antenna Antenna Kit fromAntennas.us
by K5OE 26 Apr '11

26 Apr '11

Zack, Any solution could have benefits, depending on your needs. These antennas would be very stealthy, if deed restrictions are an issue. Also, they are simple (as all omnidirectional antenna) and you would not have to worry about tracking (rotors, software, PC interfaces, etc.). >From a cost perspective, you could buy a brand new TV rotor, an Arrow or Elk (user's choice, or any similar-gain pair of antennas), and a AAR/SSB/Mirage preamp for less and have a system far superior (~6 dB) in both uplink and downlink capability. Besides just the obvious gain benefit, directional antennas also noticeably reduce local noise/IM exacerbated by a preamp--thus your S/N ratio is also improved dramatically. If you do want to go with an omni solution, I concur with Mark's suggestion a pair of Tony's parasitic Lindenblad's and a separate RF-sensed preamp would be a good choice. You could build a pair in an afternoon for about $25 in parts and find a used preamp for $75 or so. UO-14 and SO-35 you could hear easily with an omni antenna. AO-27 you can't. FO-20 was easy to hear, FO-29 not quite so loud. AO-51 when at high power you can hear above 25 degrees with an omni and good preamp, but you will be frustrated by the short pass time available (and when it is set to lower output power). The bottom line is there are no truly "easy-sats" in 2011 and omni antennas are a real compromise that makes operating with them only attractive if there is a good reason you cannot use directioinal antennas. I'll give you a personal example: after moving back to Texas late last year I wanted to get back on the birds, so I "threw" up an old omin antenna (Eggbeater II from a long, long time ago) and put a Landwehr preamp in the attic (it was easy and fast). See my comment above about being frustrated--I didn't operate much. When ND9M was at sea I got really frustrated! So I swapped out the Egg II with a slightly-less old antenna, a TPM II and pointed it due West (fixed, no rotor) and worked Jim a few times, mostly on FO-29, when he was in the Pacific Ocean. After he went through the Panama Canal, I went back on the roof and pointed the antenna to the SE and worked him a few more times in the Carrib and GoM. I worked him in 9 grids, but was not able to work much else. Last weekend I finally made the time to run the cables through the house walls for the rotor and quickly built up a small homebrew beam for 70 cm (3x3), installed a coaxial relay for polarity switching, and moved the preamp to just below the antenna: a world of difference, as you can imagine. Solid copy on all those birds now. Sorry for the long story, but my recommendation is borne out of experience--only use the omni if you can't use a beam. 73, Jerry, K5OE --- original message --- Interesting, Zack. I would ask them about transmitting through the one with the preamp built in. Can you do it? (i.e., is it RF-sensed/switched) Or does the preamp make it a "receive only" antenna, with the accidental transmission through it smoking the device :) It's bound to happen on a dual band radio... (I think you'd be better off building a pair of AA2TX style Lindenblads...) Mark N8MH At 12:01 PM 4/25/2011 +0000, vtnn43e(a)comcast.net wrote: >Antennas.us is selling a combo package of 2M and 70cm quadrifilar helix >antennas and a bias tee for $330.00. The 70cm antenna has a built-in 15db LNA >BTW. > >http://www.antennas.us/store/p/391-UC-AMSAT-KIT-2-m-70-cm-Amateur-Satellite… > > >The UC-AMSAT-KIT, 2 m / 70 cm Amateur Satellite Antenna Kit is a discounted >bundle combination of quantity 1 each of the following three antenna products: >UC-1464-433, VHF Amateur Satellite QFH Antenna, Passive >UC-4364-513, UHF Amateur Satellite QFH Antenna, with built-in LNA and SMA Male >connector >BIT-1500-385, UHF Bias Tee > >I was wondering though what some of you on the list think of these antennas >for FM LEO users that are looking for fixed outdoor antennas? > > >73 >Zack >N8FNR

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Re: Arrow and ELK comparative antenna tests
by John Kopala 26 Apr '11

26 Apr '11

One supplemental note on the testing of the Arrow and ELK antennas. I indicated that having both the transmit and receive antennas in the same plane with the ELK might have some advantages. I failed to mention that having the crossed yagi design of the Arrow isolates the 2 antennas from each other and may help to minimize UHF downlink desensing when transmitting on a VHF uplink. This can vary greatly with the configuration and the radios used, but certainly would provide significant isolation when separate radios are used for the uplink and downlink. Recent posts on the Alinco DJ-G7 also highlight the fact that the radio itself my desense on one band when transmitting on the other. In that case, all the isolation in the world might not make any difference. John Kopala N7JK

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Re: Arrow and ELK Comparative Antenna Tests
by John Kopala 26 Apr '11

26 Apr '11

Mark, The testing method for the antennas was fairly basic. The antenna range was my front yard, the only easy location free of obstructions, other than a public park. Our signal source was an IFR-1200S station monitor feeding an aftermarket dual band rubber duck antenna vertically polarized and about 3 feet above the ground. The antennas, vertically polarized for the band being tested, were supported one at a time at about 44 inches above ground by resting their boom on the top edges of a large cardboard box positioned about 93 feet from the station monitor across the front yard. The receiver for the tests was an IC-910. The signal level was set on the station monitor to produce a mid scale, S9 reading on the receiver S meter. An attenuator was used at the receiver input to reduce the signal so that the addition on 1 db attenuation would cause a single step reduction in the S meter bar length. We used the Arrow antenna to establish this reference level against which each antenna could be measured. Each antenna was then tested to determine how much attenuation was required to match the signal to the reference level. With the PortaFox, the signal strength was below the reference level on 435 MHz, so we had to create a new reference level for that antenna. We then used the Arrow antenna and measured how much additional attenuation was required to get down to the signal level of the PortaFox antenna. The difference between the amounts of attenuation required to match the reference level indicate the relative performance of the antennas. John Kopala N7JK At 08:34 AM 4/25/2011 -0400, Mark Hammond wrote: Thanks John and Patrick. Interesting results and a very nice study. Question---what was your testing method? I can't glean that from the information below. Thanks! Mark N8MH At 08:49 PM 4/24/2011 -0700, John Kopala wrote: > >On Saturday, April 23, Pat Stoddard (WD9EWK) and I did some antenna testing in an attempt to answer > >the questions about which is the best antenna for portable satellite operation. We only tested the > >antennas in receive mode to determine their relative gain. Time constraints prevented us from > >performing additional testing to determine if the transmitted output was consistent with the receive > >gain of the antennas. For the time being we will assume (and we all know the dangers of doing so) > >that the transmit performance closely matches the receive performance. > > > >The antennas tested were an Arrow (3 x 7 elements), an ELK (4 elements), a PortaFox configured for > >145/435 operation (4 elements), and a Home Brew 4 by 9 element "arrow" antenna. The standard Arrow > >antenna was the only antenna equipped with duplexer, but not the basic duplexer which is installed > >in the handle. We did not measure the insertion loss of the duplexer on the Arrow antenna, but this > >was obviously not a significant factor in the overall performance. A duplexer could still be > >required depending upon the antenna chosen and the radio(s) to be used. > > > >Using the Arrow antenna as the reference antenna and 145.300 MHz as our test frequency, our > >measurements indicated that the Arrow and the ELK antennas had identical gain. The PortaFox antenna > >showed 2db less gain than the Arrow and the ELK. The Home Brew 4/9 element crossed yagi showed 2db > >more gain than the Arrow and the ELK. > > > >On 435.300 MHz, the Arrow antenna had 2db more gain than the ELK and 8db more gain than the > >PortaFox. The Home Brew 4/9 element had 3db more gain than the Arrow. > > > >Although the ELK antenna shows slightly less (2db) gain on 435.300 MHz, it does have one potential > >advantage over the Arrow antenna. With the ELK, transmit and receive are in the same plane. With > >any satellites that have linear polarized antennas, such as AO-27, SO-50, the ISS and maybe SO-67, > >a crossed yagis can maximize the performance on one band while minimizing it on the other. That > >does not mean the Arrow won't work, as has been demonstrated by the thousands of satellite QSO's > >that are made on a regular basis using Arrow antennas. It just means that when you rotate the > >antenna to maximize the downlink signal, you may be significantly impacting you uplink signal > >strength in marginal situations. > > > >Even though a satellite may have a circular polarized uplink and downlink, don't assume that the > >orientation of your station antenna as horizontal, vertical, or something in between won't have a > >significant effect on your signal strength. My experience operating portable with my home brew > >antenna has convinced me that my horizontally polarized Qagi should either be remounted vertically > >polarized or replaced with a circular polarized antenna. That is another ongoing project. > > > >In summary, unless you plan to build your own, the performance of the Arrow crossed yagi antenna and > >the ELK log periodic antennas are very comparable and should provide lots of solid satellite contacts. > > > >The overall results reflect the adage that bigger is better, but along with more gain, you also get > >a more bulky antenna that is harder to handle. The home brew crossed yagi I built for portable > >operation is tripod mounted, can be rotated on its axis, and disassembles for storage in a roll up > >case. But because of its size, it would be very tiring to attempt to use it hand held for an > >extended period of time. Pictures of the home brew crossed yagi antenna are on my QRZ page. > > > >John Kopala > >N7JK

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GO-32
by jerry keeton 25 Apr '11

25 Apr '11

recieved this from GO-32 on 435.325 9600k 1:Fm 7-14 To Z-7 Via c8-10*,,-8,-8,-8 <RR P/F R1 [DAMA] [EAX25]>[18:06:01]

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amsat-bb
by nh6vb Scheller 25 Apr '11

25 Apr '11

I am always looking for a change amsat-bb this was absolutely flawless its brought me nothing but good fortune http://lnk.co/G2MCN now im finally standing on my own two feet hope that you consider it

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AO-51 update 25 April 2011
by Mark L. Hammond 25 Apr '11

25 Apr '11

Hi All, For now, it looks like the PL tone management (and changes to other settings) has helped to keep AO-51 running and supporting normal operations. We are now running around 475 mW of power out on 435.300 MHz. Over the last few days, some of you on the east coast of the U.S. have probably heard command stations downloading telemetry files on the 435.300 frequency. You can expect this to happen every few days; sometimes in the AM, sometimes in the PM. Because it's 9600 baud packet, it sounds like a carrier or open squelch with a "SSSSSHHHHHHHHHH" sound to it. If you hear that sound, there isn't much use in trying to uplink; it means we're collecting telemetry and the voice repeater is off for the moment. Wait for the "SSSHHHHHHH" sound to go away, and you'll know the voice repeater is active again. The current power budget makes it very hard to run both transmitters at the same time. Also, we are trying to keep the amount of commanding to a minimum, so using the single transmitter for both voice and telemetry is our current approach. We'll see how it goes. It does mean that it eats into voice operations a little, but the trade off is worth it-both for the short and long terms. In the meantime, keeping using our old bird when it's active! We don't want to take it for granted... 73 on behalf of the Command Team, Mark L. Hammond [N8MH]

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VUCC, grids, and a new QTH
by Zachary Beougher 25 Apr '11

25 Apr '11

Hi All, I have an “out of the blue” question that hit me the other day since I am a freshmen in college and will likely move away from home sometime in the next 5+ years... I know the VUCC rules say you can count any grid towards VUCC that was worked from two locations no more than 120km apart. Lets say I have 500 grids worked by the time I move out (which is a LOT of time, work and $$), and I decide to move to SC. Are those 500 grids that I worked/confirmed no longer valid towards VUCC (if I wanted to get an endorsement)? 73! Zack KD8KSN

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