AMSAT-BB Digest

Freddy, ON6UG, has informed me that my indication of 5 W and a short backfire antenna will not be adequate for the 1.2 GHz P3D uplink. This is because the receive antenna on the satellite is not as capable as had been originally planned. I have asked him if he can explain this and update us on the 1.2 GHz uplink requirements. In short he has indicated that about 3 dB more will be required. Either 10 W at the antenna or a different antenna with 3 dB more gain.

For those who asked about the short backfire antenna, the original reference for this antenna is:

The Short Backfire Antenna by H. W. Ehrenspeck, Proceedings of the IEEE (USA), August 1965, page 1138. Also US Patent 3,122,745.

The short backfire as described by Dr. Ehrenspeck uses a "pizza pan" reflector of 2 wavelengths diameter and 0.25 wavelengths deep. It is fed with a centrally located dipole spaced 0.25 wavelengths above the reflector. There is a circular secondary reflector of 0.4 wavelength diameter above the dipole feed and spaced 0.5 wavelengths above the main reflector. The reported gain for this easy to build design is 13.1 dBd or 15.2 dBi.

Perhaps Freddy will update us on the results of recent amateur experimentation by himself, Stan Wood WA4NFY and others.

73 de ron w8gus.

Ron Long The Ohio State University 

Michael Herr (herr@ridgecrest.ca.us)

I am looking at omnidirectional (no rotators !) antennas for RS-10 up and downlinks. Has anyone tried making them or have any information/experiences that they can pass on?
Thanks, John G8DYK

John
I've only used omnidirectional antennas for RS10. My typical uplink antenna on 145 mhz is a J-pole. Simple and effective. For receive I mostly have used a dipole but lately a turnstile loop antenna. Actually, the turnstile was built for RS15 use and the dipole typically out performes the turnstile at low angles.
On RS12 I use a dipole, no rotor, for uplink on 15m and the dipole or turnstile for receive. Even on RS15 the same as RS10, except mypower output really limits my access. You see, I do all this at QRP, 5watt, level. On quite nights, I have heard my downlink on RS10 using 2 watts an, a 5/8 wave antenna inside the house. Sure, not strong but it's there.

73 Mike WA6ARA Thu, 3 Oct 1996 18:23:32 -0700 (PDT)

Re: Turnstile Antennas

AA2TX@aol.com Sat, 12 Oct 1996 22:26:22 -0400

Hi John, A few comments on RS-10 antennas:

For the Downlink:
I did an analysis of a number of different antenna's including verticals and turnstyles for receiving LEO satellites on 10 meters. I posted the highlights to this email list about a year or two ago but I didn't keep a copy of it The bottom line is that a 5/8 wave vertical with a 1db Noise Figure preamp is pretty close to the best you can do without a beam. A major advantage to the vertical is the low angle elevation pattern without needing much height. I use one at just 3 meters high and it works great. You can do slightly better (less than 1 dB received signal improvement) with two full wave loops fed in quadrature and at least 7 meters high at the bottom of the loops but if you have that much space available, you might as well use a beam.

For the 2 meter uplink: I also did an analysis of a number of different antenna types. None of the commercially available antenna's are great. A vertical will have dead spots in the pattern and a turnstyle will show polarization QSB. You can make contacts with almost anything but for best results, you want circular polarization, an omni-directional azimuth pattern, and an elevation pattern that is approximately the inverse of the satellite path loss.

Since I couldn't find one that did this, I designed one. It provides a constant uplink signal level at the satellite without deep fades or "hot" spots. It consists of two stacked Lindenblad sections, spaced 3/8 wavelength apart and fed in-phase.(I have made "across-the-pond" contacts with this running just 25 watts.) Each lindenblad section has 4 dipoles at 30 degrees to the horizon. If you make each of the dipoles out of 3/4 inch aluminum and cut them for 37 inches end-to-end, they will each be 100 ohms at 146 MHz (Sorry for the english units). You need to make a feed system for transforming 50 ohms unbalanced (coax) to eight, 100 ohm balanced loads. . I don't have the plans electronically but if you would like, send me an envelope and postage and I will send you a photocopy of the plans. In the US, the parts cost about $75 for aluminum and the feed harness cables.

If you have any other questions (antennas or otherwise) please feel free to contact me.

Good luck getting on RS-10. 73, Tony AA2TX@amsat.org
Anthony Monteiro
180 Hope Road,
Tinton Falls, NJ 07724
USA 

John DiStefano (ke3su@amsat.org) Fri, 11 Oct 1996 08:37:07 -0400

On Wednesday, October 09, 1996 4:41 PM Johnny Miller wrote:
> 1. I work Rs-10 alot.
> 2. I use STS-Plus for tracking.
> I bring up the STS-Plus program and it shows me where to set my tx and rx freq's. As soon as the bird goes to 5 degree's above elv. I start calling CQ. Each time I do this I hear my downlink signal. Then as the bird starts to pass I follow the program and use the freq's that it display's to use for tx and rx which is always changing. Using this method I have made about 70 to 80 contacts. ( Give or take the ones I talk to over and over )

John, You should adjust the higher of the two frequencies. The reason being that doppler is more significant on the higher frequency. It doesn't matter if it's transmit or receive. But always only adjust one frequency so you don't cause QRM to others operating the bird. 73 de John KE3SU 

Mike73@aol.com Thu, 17 Oct 1996 11:31:07 -0400

Hello all,

I've had a good time lately operating the new MIR/SAFEX II 70 cm repeater. However I've noticed that there seems to be some confusion about its operation. I hear quite a few people trying to access, but not making it. Here are a couple of ways that I use to operate RR0DL successfully.

The two biggest problems are CTCSS tone and doppler shift. First off, you need to use 141.3 CTCSS tone to be able to bring up the repeater. Secondly, you need to compensate for doppler shift on both the downlink and well as the uplink (unlike AO-27). This confuses some people.

The 70 cm doppler can be as much as +/- 10KHz. Standard downlink doppler for a pass starts high in frequency and ends low. On your radio, you simply tune high at the start and move down in frequency during the pass. On the uplink, MIR hears your signal the same way. i.e. high at the start and ending low. Since you can't tell MIR to adjust its receive frequency, you must compensate by adjusting your transmit frequency. You need to start the pass on the low side and increase the frequency as the pass progresses. It's the opposite of the receive doppler. This is where I think people are getting confused.

Here are a couple of ways I do it on my FT-736R. The first method is to program a series of memory channels. I programmed 9 memory channels for +/- 8KHz doppler correction. I used a sequence of standard memory channels (not Sat channels) set up as minus offset with tone encoding. First, program the downlink frequency, then enter the offset. Make sure you are set for negative offset and tone encoding (141.3), then save to a memory channel. I set the frequencies for each channel according to the list below.

MIR/SAFEX 70cm Doppler Correction

Dnlink Uplink Offset

(MHz) (MHz) (MHz)

• 437.958 435.742 2.216
• 437.956 435.744 2.212
• 437.954 435.746 2.208
• 437.952 435.748 2.204
• 437.950 435.750 2.200
• 437.948 435.752 2.196
• 437.946 435.754 2.192
• 437.944 435.756 2.188
• 435.942 435.758 2.184

The second method I use is full time automatic doppler correction via CAT utilizing NOVA. I posted how to use this method to the NOVA reflector a while back. There is a problem with the way NOVA works with CTCSS while doing automatic tuning, but there is a simple "work around". If you're interested, drop me a note and I'll send you a copy.

Good Luck!

Mike

N1JEZ 

John W Wilson (z004391b@bcfreenet.seflin.lib.fl.us) Sun, 3 Nov 1996 18:23:06 -0500 (EST)

Hi Jim, I use the PK96 for 9600 satellite work and find it very simple. I run WISP and the TrakBox by TAPR. The TNC is there just to modulate/demodulate the audio signals to and from the radio and to make the signals into digital so that the computer can understand. The TrakBox does the rig frequency setting and doppler correction, and the computer program WISP triggers the whole system off when a satellite comes into view.

By the way, I tell the WISP program that my TNC is a DSP2232. I haven't gotten the thing to work any other way.

73, John W. Wilson, KN4HX z004391b@bcfreenet.seflin.lib.fl.us

Ed Krome (71611.76@compuserve.com) 06 Dec 96 16:52:29 EST

Wow, a 12 foot dish?! That guy's beamwidth is so narrow it is going to be fun to point at P3D. Anyway; you definitly can put more than one feed in a dish. It's called clustered feeds and you would typically put them around the center of the dish, with the lowest freq feed the furthest from the actual dish center (since the lowest freq will have the lowest gain and therefore the widest beamwidth, easing pointing requirements). But another problem rears its ugly head. Of the bands you noted, 13 cm is up or down (most will use it for down only), 23cm is up and 70cm is up or down. Therefore, you will be pouring watts into one feed that is right next to a receive feed connected to a GaAsFET, which may not like the heat. Relays will be required to keep them isolated from each other, which leads to the problem of probably not being able to operate full duplex due to relay switching times, etc.. Isolation by duplexers has been suggested, but there aren't any readily available that operate on 13cm.

I think a better arrangement will be physically separating transmit and receive feeds, so one is not blasting another. Uplink requirements are pretty light, so small amplifiers and short, separate transmitting antennas may be the most satisfactory solution. Interesting problem.

Ed Krome KA9LNV ka9lnv@amsat.org 

Bob Houghton (houghton@cyberg8t.com) Thu, 01 May 1997 21:33:10 -0700

Mike,

> intermod. The Yaesu performs real well with very little interference. I'd > like to know how the ICOM 821H compares.

I use both the FT-736R and the IC-821 radios regularly. I have no numerical data but I have had both radios in mountaintop (read: near repeaters and paging transmitters) situations with no intermod problems. In these same conditions, my Yaesu FT-8500 and Kenwood TM-231 mobile FM radios were subject to considerable interference and my handhelds were useless.

I'm not sure, but I would guess that under the toughest conditions, the double and triple conversion 736R might have the upper hand.

Bob kc6lvg 

Franklin Antonio (ANTONIO@qualcomm.com) Fri, 23 May 97 10:21:45 PDT

> The rule of thumb is to maintain 1/4 wave separation between a beam and surrounding metal parts. That's only about 20 inches on 2M.

My rule of thumb goes like this... I'd like to keep metal out of the antenna's aperture. If the antenna were a dish antenna, this would be really obvious visually. You would try to make the dishes not overlap. Like a dish, a Yagi is trying to grab for you the energy that flows thru some area, even if the area isn't as obvious as it is with a dish. Interfere with that area, and you interfere with the antennas ability to do this job for you.

Now, how big is that area? Depends on the antenna gain.

A = G lambda^2 / (4 pi)

For a 2 meter band Yagi with 10dBi gain, that would be...

A = 10 * 4 / ( 4 * pi)

A = 3.13 meter^2

That would correspond to the area of a circle with about a 1 meter radius. By this line of thinking, you'd want the other antenna to be about 1 meter away from the 2m antenna.

The above formula corresponds to a perfectly illuminated aperture, so real dish antennas with this amount of gain would typically have about twice the area shown. Like the typical dish, the Yagi does not perfectly illuminate any aperture, so perhaps some additional factor of 2 or so should be thrown in. (making the estimated reasonable separation maybe a factor of 1.4 or so larger yet) On the other hand, this is just a back-of-the-envelope calculation, so I'll stop here.

Of course, there is no magic distance. The effects decrease with increasing distance. Effects also depend on the size and orientation of the metal in question. For example a horizontally polarized antenna is less sensitive to vertically oriented conductors nearby. Conductors whose size makes them resonant have a greater effect than nonresonant conductors. (So notice that the elements on your 2m antenna are about 3x the length of the elements on your 70cm antenna, and therefore near resonant at 70cm.)

Someday I'd like to see someone do a scholarly study on this. The computer modelling tools are getting good enough so that someone will be able to do this on a home computer. Ideally this study would show the beam distortion and gain loss as a pair of Oscar type yagis are operated at various distances apart.

JC Smith (JC_Smith@designlink.com) Fri, 23 May 1997 20:01:27 GMT

Hi Mike,
Based on the length of available fiberglass crossbooms I would say 6' would be a reasonable minimum (boom to boom distance), more of course is better. If you put up a X-polarized 435 antenna, try to use a non-conductive mast or you will ruin the circular pattern of the antenna. It effects 2 meters as well, but not as much. Or, you could use a rear mounted 435 antenna (or a pair of them) and then the mast material won't matter.

Why not give your antennas a little up-tilt? Fifteen or twenty degrees of up elevation would increase the number of passes you could work and have very little effect on your signal on the horizon (I assume you are using your 148-20T for terrestrial stuff.)

Good luck & have fun.

73 - JC,k0hps@amsat.org 

Lau, Zack, W1VT (zlau@arrl.org) Fri, 13 Dec 1996 10:37:00 -0500

Joe Steinmetz wrote:

> > My antenna site is approximately 100 feet away, I have 4 feedlines and 3 8 conductor rotor cables going to the tower. The feedlines are 9913 except for one which is aircom plus. I plan on locating 2m, 440, and 1.2g inside with only preamps at tower. I plan on using 9913 for 2m, 440, and S band 2m IF. The aircom for 1.2g. Two rotor cables will be used for A/Z, while the third will be used to power the transverter and any associated components. The 2.4g loss over 100 feet seems too great to locate the electronics inside, so I was thinking of locating it outside in a NEMA 4 type enclosure. This is a water tight enclosure and I can get the power, antenna feedline and IF feedline via conduit. How do I keep humidity down in the winter? Lightbulb with a thermistat?
>The lowest average temp is probably around 40F.

One way is to pressurize the box with dry air, possibly using air dielectric coax as an air hose--sure beats using it as a water hose.

> How do I keep the temperature below 100F? In the summer the external temperature will get to 100+F, plus the inside due to the heat disipated by the electronics. A fan and a vent might work, but then water
> might get in when it rains (and when it rains, it pours)....

Obviously, ordinary heat sinks aren't going to work. I suppose you might modify an old refrigerator. Is it really necessary to make that temperature requirement, given that semiconductors typically can work at a junction temperature of around 150C? A revised design might restrict physical access to hot surfaces, allowing heat sinks to be used.

> What other things should I be considering?
> What are others doing for S band UP and DOWN for P3D?

I plan to use surplus IMFETs to generate at least 10 watts on the uplink. I was planning to re-tune some 6 GHz devices, but was able to locate some S band devices. The RF design technique is quite simple. Put the devices on a board/heatsink with long 50 ohm microstriplines and add metal tuning flakes or capacitors for best gain/power. The built-in matching networks usually act as low pass filters (thats why they are called impedance matched transistors).

The S band converter in the ARRL Handbook is overkill for Phase 3D. It can deliver better performance than is commonly used for EME! Someone revising the design may consider the following:

Use a cheaper board, such as Rogers RO 4003. I've heard that this board is much more cost effective, since it processes just like glass epoxy. Unfortunately, parts suppliers don't offer it because there isn't a demand...

Use a VXO to tune the band. A cheap 24 or 25 MHz crystal ought to be able to cover the satellite subband. True, it can be a bit of work to build a multiplier to get to 96 or 100 MHz, but this is the same technology you need to get on 2 meters...

Consider using a cheaper PHEMT like the ATF36077.

Don't wait for me to design it--I plan to be busy answering lots of Phase 3D questions instead--Zack W1VT zlau@arrl.org 

Thomas L. McDaniel (TomMcD@ix.netcom.com) Sat, 14 Dec 96 18:02:40 GMT

pidoux@ccr.jussieu.fr> wrote:

> An AMSAT France member is asking for help in configuring WISP for using it with a PK96. Can somebody provide the proper settings informations for this TNC into WISP?

> For instance, should he declare it as a TNC-2 or a PK232 ? This question has probably already been discussed here, but...

> 73 de

Bernard, f6bvp

ADEL: [Adresse ELectronique]) f6bvp@amsat.org
AMSAT France Maelle microsatellite project:
http://ourworld.compuserve.com/homepages/amsat_f
"Forum AMSAT France" 

Hi Bernard,

I use the PK-96 with WISP. I've set WISP to recognize it as a TNC-2 and accepted all of the standard defaults. The terminal interface is set for 19.2K (TBAUD in the PK-96), and I set HBAUD for 9600. Also, you MUST set EXPERT ON!!! It will not recognize some of the commands that WISP loads if you don't.

I've used this with the old WISP16 and the new WISP32 with no problems. I hope this helps your friend. :-)

Let me know if I can answer any more questions.

73's Tom n0ntx

Ron L. Sparks (sparks@sccsi.com) Wed, 18 Dec 1996 22:00:50 -0600

>Somebody once told me that metal has low IR emissivity (like it does for visible light),so a bare metal box will get suprisingly hot under the sun, hotter than a white-painted box, which may absorb more visible light, but will re-radiate a lot more IR.

>Doug Braun

Doug, You are absolutely right. The IR emissivity and the IR reflectivity are the critical numbers.

Amid all the discussion about paints and such I think one real important fact is being bounced around and may be in danger of being lost. The important issue is whether the box is hotter than ambient or cooler than ambient and which way you want the heat to go. If the box is loosing heat in cool weather and you are seeking to keep it in then use a low emissivity coating with good IR absorbtion. If the box is gaining (or generating heat) and you want to get it out you need a high emissivity, at the same time you probably would want to keep out the solar heat so you need a high reflectivity too.

So if the box is too hot and in the sun use the white zinc oxide or titanium dioxide paint which has a high emissivity and good reflectivity. But, if the box is too cold and loosing heat you need to reverse the situation so a highly polished zinc coating (low emissivity, good absorbtion) would be the way to go.

If you have a real world situation where both of the above occur then it is all moot unless you want to keep running out and painting and polishing everytime the weather changes .

73
Ron Sparks
KC5ODM
MIR SAFEX ERP Experiment 

Howdy all,

I made my first attempt at running the MIR repeater with reduced power during the 12:30 EST pass. First I'd like to thank WB4FWQ and KB8TJX for monitoring my downlink. This was a 16 degree max pass for me. I started the test as MIR hit 10 degrees. MIR was heading towards me. Here are the results.

• 2.45 Kw ERP full quieting
• 1.23 Kw ERP full quieting
• 614 w ERP full quieting
• 307 w ERP full quieting
• 147 w ERP still full quieting
• 74 w ERP still full quieting
• 35 w ERP on the edge.....

I hope to try again on the next pass. 73
Mike
N1JEZ 

Philip Chien (kc4yer@amsat.org) Tue, 31 Dec 1996 17:16:53 -0500

I ran across the following web pages which may be of interest to members of the AMSAT community

http://www.arianespace.com/
This is Arianespace - the commercial firm which launches the Ariane 4 launch vehicles. It's important to note that our launch contract is with the European Space Agency (ESA) which is a different entity. (ESA is responsible for the launch vehicle development and test flights, then Arianespace takes over operations for the commercial for-profit flights).

Spectrum Inventory Table -- 137 MHz to 100 GHz
http://www.fcc.gov/oet/info/database/spectrum/Welcome.html every single band the FCC controls from VHF and UHF through microwaves. Very large file with all of the band allocations - including all of our satellite allocations.

Also on the FCC pages is the MEASUREMENTS OF ENVIRONMENTAL ELECTROMAGNETIC FIELDS AT AMATEUR RADIO STATIONS report, and http://www.fcc.gov/ib/srd/se/snspc/ a 600K compressed(!) PC program for parties interested in filing for geosynchronous satellite slots.

and for those interested in the novel/movie 2001: A Space Oddysey with Hal's upcoming Birthday ---

The 2001 Internet Resource Archive
http://www.design.no/2001/

Philip Chien, KC4YER
Earth News - space writer and consultant
note new E-mail address - pchien@digital.net 

Joe Spinosa (Spinosa@msn.com) Sun, 5 Jan 97 18:32:15 UT

) Do you prefer:
-22- [a] Mast mounted pre-amps.
- 4- [b] In shack varieties.
-14- [c] Both!

====== For "In Shack" users ======
2) How reliable is your current in-shack pre-amp?
-23- [a] Very reliable, never a problem.
- 2- [b] It has failed in the past.
- 1- [c] Piece of junk.

3) How would you describe the overall performance of your current in-shack pre-amp?
- 4- [a] Top notch.
-17- [b] Satisfactory.
- 8- [c] Mediocre at best.
- 0- [d] Piece of junk.

4) Can you recommend a particular brand/model of in-shack pre-amp or amplifier/pre-amp combination?
-9- Mirage
-7- RF Concepts
-6- Advanced Receiver Research (ARR)
-3- TE Systems
-1- SSB Electronics
-1- Landwehr
-1- Microwave Modules
-1- Industrial Communications Engineers (ICE)
-1- Home-brew

====== For "Mast Mounted" users ======
5) Have you ever fried a mast mounted pre-amp by the simple act of transmitting RF?
- 0- [a] All the time, *&^%&&!
- 5- [b] On occasion.
-29- [c] Never.

6) Do you power your current mast mounted pre-amp with dedicated DC leads?
-22- [a] Yes.
-13- [b] No.

7) Do you power your current mast mounted pre-amp with "DC on the coax"?
-13- [a] Yes.
-22- [b] No.

8) How reliable is your current mast mounted pre-amp?
-25- [a] Very reliable, never a problem.
- 6- [b] It has failed in the past.
- 1- [c] Piece of junk.

9) How would you describe the overall performance of your current mast mounted pre-amp?
-16- [a] Top notch.
- 7- [b] Satisfactory.
- 2- [c] Mediocre at best.
- 1- [d] Piece of junk.

10) Can you recommend a particular brand/model of mast mounted pre-amp?
-11- SSB Electronics
- 8- Advanced Receiver Research (ARR)
- 7- Landwehr
- 3- Down East Microwave (DEM)
- 3- Home-brew
- 2- Mirage
- 1- SHF Technik
- 1- SWAGUR
- 1- KP-2/440

11) Care to make a comment about pre-amps?

== Separate File == First things first: The way the survey was designed, each reply did not have to answer each question. So if the numbers don't seem to add up, it's because many replies only answered a few questions.

This survey is by NO MEANS scientific. For example, just because SSB Electronics got 11 recommendations whereas Advanced Receiver Research only got 8, DOES NOT mean we can go around saying SSB is better. Many people had several different kinds of pre-amps around. Whenever they mentioned one in a positive way in question #10, I counted that as a recommendation.

The questions on the survey were intentionally vague. I was not looking for

hard numeric data, as much as trends and opinions.

So what's the point?

I think the we can identify a few trends here:
- Most people prefer Mast Mounted pre-amps.
- Both types of pre-amps received high reliability marks. (This surprised me).
- The performance of most In-Shack pre-amps is less than "top notch".
- The performance of Mast Mounted pre-amps is mixed, but with many receiving "top notch" ratings.
- More people use dedicated power lines to power Mast Mounted pre-amps Vs "DC on the coax". (Almost 2:1)

The real meat was in the comments. I have all the survey replies in one text file if anyone is interested. The "un-zipped" file is nearly a 200K text file, but should zip up nicely since it is all text. Let me know if you want a copy.
Many replies were posted for all to see.

Personal Observations:

Many people were adamant about the difference between mast mounted Vs in- shack pre-amps as the difference between "night and day". I've asked each person I've communicated with recently whether mast mounts are really worth all the trouble: Answer, YES. One fellow described finally hearing all those signals across the state that the "big guns" were working but he was missing. I can relate.

A lot of people don't run "DC on the coax" because it's simply not an option. Many references were made to drawbacks with DC on the coax. Decreasing receive sensitivity, not a good idea above 144MHz, possible damage to radios, etc. Interestingly, the people who are using DC on the coax report mostly satisfactory results. I think this question deserves more attention. "DC on the Coax" would seem to be a real convenience.

The whole question of making a "fail-safe" mast mounted pre-amp system seems overly complicated to me. Much talk about sequencers ensued. Many mast mount pre-amps RF sense, but sometimes not quickly enough. Many amplifiers RF sense, sometimes too quickly, sending RF down the line to the unsuspecting mast mount pre-amp. The solution seems to be a sequencer. My understanding is that this is a series of relays and/or pin diodes that does just what its name implies: When you hit the PTT, the sequencer takes over who generates RF when, and also shuts things like mast mount pre-amps off to protect them -- in sequence.

At the risk of sounding like an appliance operator, to me a sequencer means yet another RF patch cord or two, more leads from the power supply, another box, and another point of failure when things aren't working right. Isn't there an easier way?

I know surveys are not everyone's cup of tea, (I'm no fan either). However, this kind of benign technical survey can be helpful, as long as you keep them intentionally vague and not try to read too much into them. Personally, the replies I received here were infinitely better than what I could have gotten out of a magazine review, especially concerning practical experience.

BTW -- I'm looking at the new SSB SP2000/SP7000. Thanks to all who participated!

Want to see another one about...????

Best Regards,
Joe Spinosa
KF6CWX
Concord, CA

Martin Davidoff (AA65@catmus.cat.cc.md.us) Mon, 30 Dec 1996 11:35:17 EST

30 Dec 1996 de K2UBC
Re: Eggbeater Antenna

My file on the eggbeater antenna contains the following:

1. D. Thornburg and L. Kramer, "The Two-Meter Eggbeater -- Onmidirectional Horizontal Antenna of Simple Design," QST, April 1971, pp 44-46.
2. S. Ford, "E2 Enterprises EB-144 Eggbeater Antenna," QST, Sept 93, p 75. Review.
3. S. Ford, "M2 EB-432 Eggbeater Antenna," QST, Jan 96, p 74. Review.
4. M2 Catalog 7560 N. Del Mar Ave., Fresno, CA 93711

None of these references contain information on the "vertical" pattern which is critical to performance. According to my understanding the antenna has an omnidirectional linearly polarized pattern in the plane perpendicular to the symmetry axis (horizontal plane) and a circularly polarized pattern only in the direction of the symmetry axis. M2 specifies 6 dB gain "improvement" in direction of symmetry axis when "reflectors" are added. They do NOT claim 6 dB gain.

If anyone has any solid engineering info on this antenna I would very much appreciate receiving a reference. I especially would like to see graphs of gain and circularity as a function of angle from symmetry axis with and without reflectors.

Martin Davidoff, k2ubc 

Anthony Monteiro (monteira@integnet.com) Tue, 07 Jan 1997 11:54:13 -0500
>If anyone has any solid engineering info on this antenna I would very much appreciate receiving a reference. I especially would like to see graphs of gain and circularity as a function of angle from symmetry axis with and without reflectors. Martin Davidoff, k2ubc >

I have generated elevation pattern plots of eggbeater-style antennas for a variety of loop shapes both with and without reflectors. I will see if there is some way for me to retrieve them and email them.

The reflector does not make a big difference but 4 to 8 radials can be used to improve the pattern a little. For LEO satellite use, you don't want to put them where M2 says to because you don't want the signal to just point UP, you want to maximize the horizontal pattern. With the radials properly placed, the radiation pattern is pretty good from 0 degrees all the way up to 90 degrees. (Much better than a vertical)

The eggbeater produces virtually all horizontal polarization up to about 60 degrees. Above that, its within a couple dB of circular.

Also, the best shape for the loops for LEO sat use is not circular but is a tall rectangular shape. This gives a little more horizontal gain and less straight UP. If you make the loops about 1/6 wavelength on the top and bottom and 1/3 wavelength on the sides and make one a little bigger than the other, you can tie them together at the bottom for a simple, self-phasing, 50 ohm fed antenna. You can either make a small coil out of the coax to make the 1:1 balun or use a couple of low-u ferrites "W2DU" style over the coax.

I use just such an antenna for receiving mode J.

73,
Tony AA2TX@amsat.org

(Ed. Note- Following text is from a followup message)

I re-ran a couple of "eggbeater" plots.

These are for 436 MHz antennas with the bottom of the loops at 40 feet over very good ground.

Using circular loops with no radials produces a max gain of 6.57dBi at the horizon dropping to about 3 dBci overhead.

Adding eight 1/4 wave radials (6.75" each at 436 MHz) about 1/3 wavelength (10" at 436 MHz) below the bottom of the loops increases the max gain at the horizon to 8.14dBi dropping to 0 dbci overhead.

Using rectangular loops with 8 radials, about 1/2 wavelength (13") below the bottom of the loops gives 8.64 dBi at the horizon dropping to -2 dBci overhead.

Note that the polarization changes from horizontal to circular in the range of 60 - 75 degrees. Note also that NEC based analysis tools tend to be a little bit optimistic about the gain!

I can send the EZNEC plots (.ent) plot files to anyone who wants them. You would need EZNEC to display or print them however (unless someone knows how to convert them to some other format?) I am also willing to send paper copies of the plots to anyone who sends me an SASE.

73,
Tony AA2TX@amsat.org

Christie Harper (harper@huntsville.sparta.com) Thu, 9 Jan 1997 10:47:31 -0600
I have posted on my son's webpage some simple instructions and drawings to construct your own eggbeaters (if you are interested). the address is

http://fly.hiwaay.net/~harperrc CliCK HERE

the views expressed here are the author's
Christie Harper (KD4QIO) EM64rp
harper@huntsville.sparta.com or kd4qio@amsat.org
(205) 837-5282 x1216 voicemail (205) 830-0287 FAX

Jim Sanford (jsanfor@exis.net) Fri, 10 Jan 1997 07:02:26 -0500

curtis overman wrote:
> Vincent Fiscus, KB7ADL wrote:
> > I purchased a Kenwood TM 733a and it is supposed to be 9600 bps capable.
Can I use this radio for 9600 bps satellite monitoring? The tuning step on the radio is 5 kHz. How close to the actual downlink frequency does one need to be to receive good data?
73 de KB7ADL
> > Vince

> good question vince! the radio is 9600 baud capable and there is a direct access to the radio via the front data port. I have found that u must be able to get within 2 or 3kHz to copy uo-22 and ko-25. I know that chas w4hfz is uing his kenwood on the birds, but i dont know with what success. I gave up and modified my ft-736r for 9600
73 curt ad4nj

Curt and all:
Chas did in fact make it work, but was less than thrilled with the results. With 5Khz resolution, you are going to lose some data. It's certainly better than not doing it at all, tho! And, you can improve it by replacing the IF filters, just like many have in the FM portion of their all-mode rigs.
this rig should be ok for terrestrial use, but has big limitations on satellites. Still better than nothing!
73, Jim
wb4gcs@amsat.org

Mike73@aol.com Fri, 31 Jan 1997 08:43:49 -0500 (EST) verticals"

Howdy,

Yes it is possible to work the MIR 70cm repeater with a vertical. I helped a friend set up the doppler offsets in his Kenwood dualbander mobile radio, and he has been making contacts with 35 watts (I think) into his dual band vertical on his truck.

One question, are you using a 141.3 CTCSS tone?????

73
Good Luck
Mike
N1JEZ 

laura halliday (ve7ldh@amsat.org) Mon, 3 Mar 1997 11:30:56 -0800 (PST)

People have been looking for a starting point for microwave stuff, and here are some suggestions...

It's not cheap, but it's money well spent. From the ARRL, buy the UHF/Microwave Experimenter's Handbook and the UHF/Microwave Projects Manual. A non-obvious choice from the RSGB is Practical Transmitters for Novices, which has very good chapters on 1296 MHz and 10 GHz. This was my primary reference for 10 GHz WBFM, BTW. The RSGB VHF/UHF Manual is due for an update but still worth a look.

Magazines? DUBUS, UKW-Berichte/VHF Communications. The Above and Beyond column in 73. The RSGB Microwave Newsletter. Microwaves and RF is a professional journal, both fascinating and heartbreaking (especially the test equipment ads - sigh).

Conference proceedings are nice to have, but the ARRL's always seem to go out of print immediately. Look for collections like DUBUS Teknik and the UHF Compendium.

You can find pointers to all this stuff on the Web.

Laura Halliday VE7LDH "C'est une femme mutine, assez
lhalliday@creo.com
elegante, grave et legere, ayant le
ve7ldh@amsat.org
sens du confort et du plaisir
Locator: CN89mg en tout.
" - C. Deneuve

Jensen, Jens Henrik (topcat@post4.tele.dk) Sun, 09 Mar 1997 06:05:26 +0100

program for Windows and SB"

Hi there, if you need a really good Wefax program, try:
ftp://members.aol.com/hffax1/Software/INST222K.EXE

It is a Windows prg, and uses your soundcard for the demodulation. At last, no more weird A/D converters to build, after all, your soundcard already includes all the A/D converter you need, so why not use it?

I have already tried it with NOAA-14, and the results were watchable even though my scanner has a narrow filter.

Thank you very much to Rafael, EA4R, for mentioning the program here on this list, that is really "news you can use"

If anyone has a weather-satellite FAQ, why not post it to the list

Vy 73 de OZ1LRG

Rafael Garcia (rgarcia@hp433.cide.upm.es) Tue, 11 Mar 1997 20:21:21 +0100 (MET)

English version of WXSat now available at:

http://members.aol.com/hffax2/fax/INST230E.EXE or http://ourworld.compuserve.com/homepages/HFFAX (section software)

Charles Gooden (chgooden@postoffice.worldnet.att.net) Sat, 29 Mar 1997 23:01:06 -0600

Hi All,

I would like to thank those that responded to my antenna questions. A summery of the responses is below. Being an enginner I find that the book work is a good learning aid but leave out the practical application with the real world.

At 05:30 AM 3/24/97 +0000, Charles Gooden wrote:
>Hi All,
>I am considering purchasing a KLM 2M-22C or a 2M-14C circularized polarized beam as the first piece of my satellite station. I have a number of questions below that I would appreciate comments on.
>1. According to the specs the 22C has 3 db more gain than the 14C however it would also be more difficult to aim and mount. Is the extra 3 db worth it?

With the exception to working AO-10 out at 30000 - 40000 km most of the responses favored the 14C (or the equivelent M2). Most of the responses tended to favor the M2 antennas. I asked this question back a few months ago and most of the responses favored KLM. One reason for looking at KLM is that I have a gift certificate from a store that sells KLM. I have ruled out a few manufactures already and will be taking another look at M2.

>2. Eventually I will also be buying the 435-18C or the 435-40CX again there is about a 3 db gain difference and I wonder if the 3 db of gain is worth it? There is less of a problem with these antennas due to the shorter boom lengths.

Actually these antennas have a shorter boom length than the 2 M antenna so the question really isn't that important from the rotational aspect. From a balance perspective the 40CX boom is almost as long as the 14C so it may help to balance the load on the rotator. From a price viewpoint, AES catalog shows a 30.00 difference. With these factors I think I will be going with the longer boom in either a KLM or M2.

>3. Is it necessary to change from RH to LH polarization (ie is the switcher necessary or desirable)?

Mixed response here. Some responses said NO if you have the receive gain to compensate for the polarity shift. Others said absolutely for working FO-20 and possibly AO-10 when it at appogee (?).

>4. KLM also sells a 5' and a 7 1/2 ' fiberglass mast to mount these antennas on which one would >better. Or would a longer cross boom be better?? I am also looking at the possibility of adding >1.2Ghz yagi antennas eventually. These would be mounted between the 2 m and 70 cm antenna.

All response here suggested the longer cross booms and especially the ones sold by Bob Myers in AZ. A few suggested the cross boom sold by M2. From the descriptions they seem to be one in the same is this true?. Thanks for the info I will be contacting Bob Myers for details.

>5. How should I support these antennas?? Rohn limits there towers listed in the AES catalog for >boom lengths no greater than 10 feet. I am mostly in the clear for trees and am only looking to put these antennas up 30-40 feet.

Mixed bag of response here. Some are using ground mounted tripods and masts high enough so the 2 M antenna clears the ground. From a rotational viewpoint the longer 2 M antenna would require a tower at least 20 feet just so I could rotate the antenna and not worry about hitting someone standing under them. With the 11' long cross boom, and possibly some other mode L or S antenna, antenna work may be difficult.

>6 How do you align the antennas for azimuth and elevation?? Seems like a compass and a protractor would not be very accurate. I am planning to use a G5400B rotor.

Well it appears that alignment is not that critical and a compass and bubble level on the boom should suffice. One person suggested a photocell in a tube to sight the sun or moon with. Does this mean you can align the rotor from in the shack?

>7. Are these antennas and rotor necessary, or desirable for working P3D and AO-10, or can I get buy with a cheaper arrangement?? If so recommendations?

For AO-10 these antennas and rotors appear to be necessary although I could use standard rotors for AZ/El and move to a G5400B for computer control operation becomes necessary. For P3D We will have to wait until it flys and then verify the engineering data is correct.

>8. How many Coax feed lines are necessary?? I suspect I will need one for each antenna but am wondering if a diplexer will allow me to get by with one, or is this not desirable.

As I thought one per antenna, diplexers are not recommended here.

>9 Although preamps may be desireable, are they necessary??

Most people agree that a pre-amp is necessary on AO-10. The location of the preamps seem to be some dispute though. Some suggested at the antenna, others suggested using hardline and mounting the in the shack where they will not be exposed to the elements. For 2 Meters I have considered using some lossy coax such that my signal at the base of the tower would be down by 3 db. Then if my transmitter was putting out 50 watts I would have about 25 watts at the base of the tower an I could use a 2 meter linear that requires 25 watts input to get 150 watts out at the antenna. A pre-amp in the amp would correct for any recieve loss due to the coax.

>10. What type of power and on what bands is necessary to communicate via P3D, AO-10, or some of the other digital birds.

AO-10 about 100 watts, P3D ???, digital birds 10-25 watts.

>Well that is enough questions for now. But I do have one more request. I would like to find someone near Rockford IL that would be willing to show me what is involved in satellite operations, and function as an elmer in guideing me in the selection of equipment and building and operating my station.

No responses here. What I would really like to do is to be able to visit a ham involved with satellite ops and possibly be able to work AO-10 and see how the equipment is configured. I am somewhat concerned that I will buy the equipment and set up my station and there will be no one to talk to. Primarily due to the time of day that I will beable to operate my station and what appears to be a limited number of people on the birds. At present I do not have any capability to receive SSB or CW on 2 meters or 70cm so I can not tune into the downlinks to listen.

>Thanks alot in advance for the replies.
>Chuck Gooden - N9QBT
>Email: n9qbt@amsat.org (alias)
> chgooden@worldnet.att.net (Personel)
> cgooden@snds.com (Work)

Chuck Gooden - N9QBT Email: n9qbt@amsat.org (alias)
chgooden@worldnet.att.net (Personel)
cgooden@snds.com (Work)

Hello again Gene,

I like the bazookas too (crossed double version, made of 100% RG-58, love it on 40 meters), but the antenna you want for the RS birds is the turnstyle. Build two dipoles. Mount them low (8 - 10 ft. at the center, 6 ft. or so at the ends) and at right angles to each other. Connect them together with 1/4 electrical wavelength of RG-213 (or whatever you like). This is a great receiving antenna for everything but low elevation passes (combine with a Yagi for those and you are SET).

If this isn't enough info, contact Bob Myers (w1xt@amsat.org) and see if you can get a reprint of the issue of his magazine that had the article about the turnstyle. He puts out both "Satellite Operator" and "Oscar Satellite Report" and I don't remember which it was in. "Operator" would me best guess.

73 - JC,k0hps@amsat.org 

Chris Hill (phillcr@ozemail.com.au) Sun, 27 Apr 1997 22:32:32 +1000

Hi Jim,

I don't have any figures for insertion loss to hand, however do have the following;

Type-N connector - Max freq 11 to 18GHz, SWR typ <1.07:1
SMA - Max freq 25GHz
SSMA - Max freq 38GHz
APC-7 - Max freq 18GHz, SWR typ <1.04:1

Amphenol is a manufacturer of coaxial connectors (amongst other things), so I suppose any connector they make could be called an Amphenol connector. The text I have calls the APC-7 a "precision Amphenol connector".

In my opinion, the Amphenol products are one of the better quality products... the 'no-name' brands vary quite a lot in quality... I even found one source of cheap PL259s which had a different pitch thread to every other series of PL-259s and SO-239s.

If you want more info, get a copy of; J.H Bryant, "Coaxial Transmission Lines, Related Two-Conductor Transmission Lines, Connectors, and Components: A U.S. Historical Perspective", IEEE Transactions on Microwave Theory and Techniques, vol MTT-32, pp. 970-983, September 1984.

73, Chris vk6kch 

brian.chad@juno.com Sun, 27 Apr 1997 21:45:37 EDT

1. If possible separate your computer from the power circuit your radios are on.
2. Spray paint the inside of your computer cover with a signal dampening paint. (Most computers now have a layer of mettalic covering the insides to reduce EMI.)
3. Check for any wires in your shack that might be making a nice antenna for that frequency.
4. Separate your computer as far away as possible from the radio in question.

Either one of these might provide some relief. Unfortunately computers and monitors are a significant source of EMI/RFI.

Brian O'Rourke
KC5BGQ

Tom Clark -- W3IWI (clark@tomcat.gsfc.nasa.gov) Fri, 28 Feb 97 17:17:05 UTC

Regarding N4BNE's question: > Is there a good way to test hardline and connectors other than the obvious way of hooking it up to a my dummy loads on the tower and seeing if the SWR/Power looks normal? The only test equipment I have is a DMM and a 75MHZ Scope.

With the tools you have, you can easily do one absolutely mandatory "necessary condition" test which involves using your DMM as an ohmeter:

a. Open the far end of the coax. Set the ohmmeter to its highest sensitivity position and measure the resistance from center conductor to shield. It SHOULD be infinite. If it is a low value (under ~1 kohm), then you have a short somewhere in the system. If it is a high value (megohms), then you probably have some water entrapped in a connector somewhere along the line.

b. Put a low resistance short on the far end. Your hardline has big conductors, so the resistance you measure at the other end should be very small -- like 0.1 ohm or so, hardly distinguishable from the resistance you see when you short the DMM's proble leads together. If it isn't low, then some connector is making marginal contact (poor soldering, corrosion, etc). [with a long run of smaller coax like RG58, you would see a few ohms when doing this test, since the resistance of the conductors is more].

With the 75 MHz scope, you could make a time-domain reflectometer with a few ICs and actually look at the detailed properties of the coax. But you'd have top spend an afternoon building something! Do the resistance tests first.

73, Tom 

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