From: "KR-net users group digest" To: "kr-net digest recipients" Subject: kr-net digest: February 20, 2000 Date: Monday, February 21, 2000 2:00 AM KR-NET Digest2 for Sunday, February 20, 2000. 1. Re: transponder antenna placement? 2. Re: Brakes and Wheels 5in vs 6in size 3. Re: transponder antenna placement? 4. Re: transponder antenna placement? 5. plane weight ---------------------------------------------------------------------- Subject: Re: transponder antenna placement? From: jscott.pilot@juno.com Date: Sun, 20 Feb 2000 07:06:39 -0700 X-Message-Number: 1 On Sat, 19 Feb 2000 18:53:42 -0600 "Mark Langford" writes: > AntennaHeads, > > > My antenna is the copper foil tape variety mounted to the leading edge of > the vertical stabilizer. The antenna coax runs down the left upper > longeron, right by the pilot's seat up to the panel, and then to the radio. > That's as far as I can get it from everything else. All other wiring is > located on the other side of the fuselage (trim tab and ELT). The strobes > are in the wing tips, and the shielded cable for them enters at the stub > wings, and I'm thinking about putting the power supply for them on the top > shelf of the firewall. I could put it under the seat, but that would be > right next to the fuel pump, which makes me a little nervous (BOOM!). The > transponder antenna (about 4" tall) is probably going right next to the > strobe p/s up on the firewall, mounted between the top and bottom shelves of > the firewall. I would think it's better to put that antenna closer to the > radio than the comm antenna, although it's awfully close to me. My foil comm antenna in the leading edge of the vertical stab works great. > > Has anybody had experience with interference between these devices, and if > so, what kind, how were yours located, and how did you solve it? One > obvious answer is to wire it all up and see what kind of noises I get in the > system, but I've got to start somewhere. I may just start soldering wires > together tomorrow... I would think that you might have a problem with the engine blanking out your transponder antenna in this location. Mine is mounted to a small round plate buried in the middle of the aft fuselage. It works great. Sometimes I do catch an occasional bit of noise on the comm radio from the transponder replying to radar. I bump the squelch just a bit and it is gone. My reception range at this point is still a hundred miles or so depending on the conditions. The biggest source of interference on my radio is my old Eiseman mags. As you may remember, we are using the same model radios. My stobe power supply sits under the right seat....not too far from the right fuel pump. One note on the strobe power supplies. It they have not been turned on in over 6 months, it is suggested that you run the strobes for several minutes hooked up to 6 volts to allow the electrolytic capacitors re-orient themselves. If the power supply runs multiple strobes, it won't switch back and forth, but will just flash one strobe while running on low voltage. When you hook it up to 12V, it will work fine. There have been some problems with the capacitors overheating and rupturing after an extended storage period. Jeff Scott - Los Alamos, NM mailto:jscott.pilot@juno.com See N1213w construction and first flight at http://www.thuntek.net/~jeb/krjeff.htm ---------------------------------------------------------------------- Subject: Re: Brakes and Wheels 5in vs 6in size From: AviationMech@aol.com Date: Sun, 20 Feb 2000 10:58:18 EST X-Message-Number: 2 I'm using Matco wheels and 5" lamb tires. I feel 6" is excessive. I have landed on semi smoth surfaces with no problems. The rougher the surface,The harder and more potential damage to the fuse/spar. If you really needed the 6" tires to handle the roughness then, you should probably use a rental 152 and leave the KR at home. When mine was a retract, I bent every bolt in the retract mech landing at a quaint little lunch spot. Hope this helps Orma Robbins AviationMech@aol.com ---------------------------------------------------------------------- Subject: Re: transponder antenna placement? From: AviationMech@aol.com Date: Sun, 20 Feb 2000 10:58:17 EST X-Message-Number: 3 Mark, NII0LR has a transponder antenna located on the bottom of the fuse aft of the aft spar. aft of that is the center of the copper foil nav antenna, which extends fwd (90deg) into the midsection. My comm antenna (aka shortened CBand stainless whip) is attached to a chicken wire ground plain which is attached to the botton of the baggage shelf aft of the seat. It extends thru the turtle deck. My Loran antenna (factory, came with Loran) sits on the baggage shelf and is bolted to the same ground plain, It also extends thru the turtle deck, just not as high as the comm. My arrangement works well and ATC has never complained about my tansponder/encoder performance, except one time I forgot to go from standby to on I opted to keep everything as close to the front as possible to save wt. On the drag side of the equation I'm sure I loose a Knot or two, but at the time I completed N110LR I was concerned about getting airborn, not how fast or how pretty. Jim Weir (RST)who now writes an article for Sport Plane, once produced a pamplet called Plastic Plane Antenna's. It is worth the read time and can help prevent the barbed look I have. Orma Robbins AviationMech@AOL.COM ---------------------------------------------------------------------- Subject: Re: transponder antenna placement? From: "Mark Langford" Date: Sun, 20 Feb 2000 10:48:44 -0600 X-Message-Number: 4 Jeff Scott wrote: > One note on the strobe power supplies. It they have not been turned on > in over 6 months, it is suggested that you run the strobes for several > minutes hooked up to 6 volts to allow the electrolytic capacitors > re-orient themselves... ...along a lot of other very useful information, as usual. I did a lot of research last night on transponder antenna location, mostly using www.deja.com 's search for "transponder antenna" on rec.aviation.homebuilt. There was a lot of good stuff from Jim Weir, and I had just about decided to put the transponder in between the seats and vertical stab like Jeff did. Larry Howell also mentioned that he had a buddy who got sick everytime he flew his composite homebuilt, until he moved his transponder antenna and shielded himself from it. And then Troy called and said his was right where Jeff's was (mid fuselage behind the seat) and that he had no problems at all with it. I checked this morning and got this result from my RAH post from Jim Weir (RST electronics): ---------------------------------- ->yes, there are two elevator cables radiating from the center ->of the dipoles, and two rudder cables WAY too close to the end of the lower ->element, so shoot me!). NO!!!! That's just the point. You made an educated decision knowing all of the factors and chose the best engineering compromise. GOOD FOR YOU. I've lost count of the number of times I've told people that airplanes are just a collection of engineering compromises flying in loose formation. Antennas are the LEAST of the compromises you make. -> The cable situation is bad enough, but now I have ->to put my transponder antenna somewhere. Reproductive issues are a moot ->point , but I WOULD like to save what little brain I have left, so I'm trying ->to put it as far away from ME as I can get it. I"m so sorry. My condolences to your wife...{;-) -> So that leaves one of two places. ->Right behind the firewall (18 inches from the radio) or between the seat and ->the comm antenna (maybe 3 feet from each). My question is, which is worse? I'd do right behind the firewall, but remember that the transponder is going to radiate like a donut impaled on the antenna. Be sure that everyone that you want the transponder to "see" (like center, ATC, and all the rest) have a good optical sighting on where you put that antenna. Since the quarter-wavelength at the transponder is about 2.5", getting the antenna 5 or 6 inches away from any other antenna is all you have to worry about. Best of flying... Jim ------------------------------------ So, despite Jim's recommendation, I still think I'm going to put it in the rear, maybe even sticking through the floor, using the 5.5" aluminum "ground plane" as a backup plate for the plywood, and fair that little 3" antenna front and rear to reduce drag. That way ATC has a perfect view in all directions, and the radiation isn't going to be in the same plane as my body. So thanks for the input guys. That helps a lot. Oh, on the reproductive thing, I just meant that I already have two fantastic kids (5 and 7), but we weren't planning on having any more, and since I'm so happily married, and don't plan to create any more children, that's not a problem. Everything else works just fine, so no condolences necessary... Mark Langford, Huntsville, Alabama mailto:langford@hiwaay.net see KR2S project N56ML at http://home.hiwaay.net/~langford ---------------------------------------------------------------------- Subject: plane weight From: "Auburn Packwood" Date: Sun, 20 Feb 2000 15:18:07 -0800 X-Message-Number: 5 Hopefully someone can help me! I recently purchased a KR2 and have begun working on it . It supposibly has flown but upon weighing it I have found it weighs 740 lbs. I have looked it over inside and out and cannot figure out how it can be over weight. I have torn into the wings which weigh nearly 60 lbs. a piece but cannot find anything excessive. I know the Rand Robinson page says it should weigh 480 but mine weighs that without the engine. Are there many flying at this weight and what is the maximum weight for the KR? What is the average weight? Can someone give me good advice? I have a revmaster 2100D for a powerplant. --- END OF DIGEST --- You are currently subscribed to kr-net as: johnbou@ipinc.net To unsubscribe send a blank email to leave-kr-net-110995W@telelists.com