---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Thu 07/27/06: 12 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:03 AM - Re: Re: Antennas general (Robert L. Nuckolls, III) 2. 06:34 AM - Re: Re: Antennas general (sportav8r@aol.com) 3. 06:52 AM - Re: Re: Antennas general (Hopperdhh@aol.com) 4. 08:39 AM - Re: VHF antenna mounting (more hair splitting) () 5. 09:37 AM - Re: Antennas general (Robert L. Nuckolls, III) 6. 09:49 AM - Antenna Coax Routing (Todd Richmond) 7. 11:09 AM - Re: Antenna Coax Routing (Hinde, Frank George (Corvallis)) 8. 12:25 PM - Re: Re: Antennas general (sportav8r@aol.com) 9. 12:25 PM - Re: Re: Antennas general (sportav8r@aol.com) 10. 04:42 PM - Re: Re: Antennas general (Dale Ensing) 11. 06:35 PM - Re: Re: Antennas general (sportav8r@aol.com) 12. 07:18 PM - Off line for a few days (Robert L. Nuckolls, III) ________________________________ Message 1 _____________________________________ Time: 06:03:25 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Antennas general --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 04:58 PM 7/26/2006 -0700, you wrote: >--> AeroElectric-List message posted by: "europa flugzeug fabrik" > > > >brian wrote: > > A 50W transmitter shooting its signal at you using a directional > antenna when you are less than 2000' away does not require much from the > receiver and its antenna. > >I believe theyre as little as 2.5W, though as highly directional, the >moral equivalent of higher power relative to like a COM. Perhaps you are >referring to that. > >Also, the sensitivity of the receiver isnt good, maybe 200 times less >sensitive than a COM. So, the antenna has to be reasonably good. I >wonder if we could use wire or copper tape to fake an equivalent of a sled >antenna. One end to shield, center wire about 10 down or wherever, but >we need a ramp tester to tune it. Or rig it up in the car, and find a >marker shed we can drive up close to. A coax monopole w/o ground plane as >proposed will probably be OK. > >Fred F. Lets put some rough orders of magnitude numbers to this discussion. Assuming 2.5 W transmitter driving a corner reflector (lets assume 3db gain) for an ERP of 5 watts, let's plug into: http://www.megalithia.com/elect/fieldstr.html With an ERP of .005 Kw and distance of .2 KM. Leave the channel defaulted at CH44. This calculator is for UHF frequencies the the performance at 75 MHz would be only slightly different due to tiny differences in path losses. The calculator says we can expect a field strength on the order of 80 dBuV at .2 Km above this marker site. Go to: http://www.radioing.com/eengineer/rfcalc.html and enter 80 (dBuV) before punching the box in the lower right column for DbUv -> Volts conversion and we get: 0.01 volts, or 10,000 microvolts. Marker beacon receiver sensitivity is on the order of 1500 uV in the LO SENS position and 200 uV in the HI SENS position. So barring errors in data or logic it seems that there's a LOT of head-roon for loss of antenna efficiency. I've had a number of builders in glass/epoxy airplanes simply lay a 40" piece of wire out in the tailcone and run a coax to the marker receiver report excellent results. But the bottom line is that what ever one installs that departs from the installation instructions (hence departures from the manufacturer's expectations) the installation should be flight checked by overflying a marker beacon facility at various altitudes. Returning to http://www.megalithia.com/elect/fieldstr.html Enter 1.5 KM into the distance box (5x higher than anything we would expect to do in a real approach) and we get 62 dBuV field strength. Which converts to a potential signal level of 1200 uV to a receiver in an IDEAL installation. Hmmmm . . . one would probably not expect even the best of installations to function at 5,000 AGL in LO sensitivity but it should come back alive when you select the HI sensitivity. A little bit of flight testing is all it takes to see how much headroom your installation possesses. Data-in-hand trumps un-quantified supposition every time. The above exercise suggests that considerable degradation of gross antenna performance is tolerable and worthy of further exploration. Bob . . . ________________________________ Message 2 _____________________________________ Time: 06:34:43 AM PST US From: sportav8r@aol.com Subject: Re: AeroElectric-List: Re: Antennas general While we're discussing dB's, I note that the installation instructions for m y Garmin GMA 340 audio panel mention several times a feature provinding "10 times gain (20 dB)" for the entertainment channel input. I have labored all my life under the impression that 10dB was 10x gain, and 20 dB was 100x gai n. It seems unlikely that the people who design this stuff professionally k now more about decibels and power gain than a radio hobbyist does, so it's s afe to assume I'm the one who is missing something. What gives? Sorry to hijack an antenna thread for this, Bob. But I've just got to get t his straight before I go nuts ;-) -Bill B -----Original Message----- Sent: Thu, 27 Jul 2006 8:52 AM --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 04:58 PM 7/26/2006 -0700, you wrote: >--> AeroElectric-List message posted by: "europa flugzeug fabrik" > > > >brian wrote: > > A 50W transmitter shooting its signal at you using a directional > anten na when you are less than 2000' away does not require much from the > receiv er and its antenna. > >I believe they=C3=A2=82=AC=84=A2re as little as 2.5W, though as highl y directional, the >moral equivalent of higher power relative to like a COM. Perhaps you are >referring to that. > >Also, the sensitivity of the receiver isn=C3=A2=82=AC=84=A2t good, ma ybe 200 times less >sensitive than a COM. So, the antenna has to be reasonab ly good. I >wonder if we could use wire or copper tape to fake an equivalent of a sled >antenna. One end to shield, center wire about 10=C3=A2=82=AC =C2=9D down or wherever, but >we need a ramp tester to tune it. Or rig it up in the car, and find a >marker shed we can drive up close to. A coax monopo le w/o ground plane as >proposed will probably be OK. > >Fred F. Lets put some rough orders of magnitude numbers to this discussion. Assuming 2.5 W transmitter driving a corner reflector (lets assume 3db gain) for an ERP of 5 watts, let's plug into: http://www.megalithia.com/elect/fieldstr.html With an ERP of .005 Kw and distance of .2 KM. Leave the channel defaulted at CH44. This calculator is for UHF frequencies the the performance at 75 MHz would be only slightly different due to tiny differences in path losses. The calculator says we can expect a field strength on the order of 80 dBuV at .2 Km above this marker site. Go to: http://www.radioing.com/eengineer/rfcalc.html and enter 80 (dBuV) before punching the box in the lower right column for DbUv -> Volts conversion and we get: 0.01 volts, or 10,000 microvolts. Marker beacon receiver sensitivity is on the order of 1500 uV in the LO SENS position and 200 uV in the HI SENS position. So barring errors in data or logic it seems that there's a LOT of head-roon for loss of antenna efficiency. I've had a number of builders in glass/epoxy airplanes simply lay a 40" piece of wire out in the tailcone and run a coax to the marker receiver report excellent results. But the bottom line is that what ever one installs that departs from the installation instructions (hence departures from the manufacturer's expectations) the installation should be flight checked by overflying a marker beacon facility at various altitudes. Returning to http://www.megalithia.com/elect/fieldstr.html Enter 1.5 KM into the distance box (5x higher than anything we would expect to do in a real approach) and we get 62 dBuV field strength. Which converts to a potential signal level of 1200 uV to a receiver in an IDEAL installation. Hmmmm . . . one would probably not expect even the best of installations to function at 5,000 AGL in LO sensitivity but it should come back alive when you select the HI sensitivity. A little bit of flight testing is all it takes to see how much headroom your installation possesses. Data-in-hand trumps un-quantified supposition every time. The above exercise suggests that considerable degradation of gross antenna performance is tolerable and worthy of further exploration. Bob . . . ========================= =========== ========================= =========== ========================= =========== ========================= =========== ________________________________________________________________________ ________________________________ Message 3 _____________________________________ Time: 06:52:47 AM PST US From: Hopperdhh@aol.com Subject: Re: AeroElectric-List: Re: Antennas general In a message dated 7/27/2006 9:39:55 A.M. Eastern Daylight Time, sportav8r@aol.com writes: While we're discussing dB's, I note that the installation instructions for my Garmin GMA 340 audio panel mention several times a feature provinding "10 times gain (20 dB)" for the entertainment channel input. I have labored all my life under the impression that 10dB was 10x gain, and 20 dB was 100x gain. It seems unlikely that the people who design this stuff professionally know more about decibels and power gain than a radio hobbyist does, so it's safe to assume I'm the one who is missing something. What gives? Sorry to hijack an antenna thread for this, Bob. But I've just got to get this straight before I go nuts ;-) -Bill B Bill, You are correct for POWER gain. For VOLTAGE gain Garmin is right. Db=10 log (P1/P2) Db log (V1/V2) Dan Hopper K9WEK RV-7A ________________________________ Message 4 _____________________________________ Time: 08:39:54 AM PST US From: Subject: AeroElectric-List: Re: VHF antenna mounting (more hair splitting) Rumen: Excellent point, that is why this list is great, input from everyone and splitting hairs or not that is a GREAT IDEA. I have just made note of this and put it into my RV-7 builders instructions. Thanks Another hair to split, not that anyone on the list would ever do that, is not to use stainless steel screws? Why? The base of the antenna is aluminum alloy. Aluminum and SS is far apart on the galvanic corrosion chart. Boeing uses passivated/cadmium plated fasteners not stainless steel. I think the engineers at Boeing and Cessna might have a clue. Dang engineers what do they know. :-) All those years in school wasted. Cheers George M., MSME, ATP/CFII-MEI >From: rd2@evenlink.com >Bob, >Speaking of the magic (grounding the base) - looking at the >Antenna_Installation.gif , I have seen toothed lock washers used >between the doubler plate and skin. > >This was on a Cessna. The doubler plate was not riveted to the >skin (it came with with the antenna replacement kit). The lock >washer assured better el contact (grounding). They used externally >toothed lock washers, as per attached. Maybe a better idea would >be to use the external-internal toothed type washers (also attached). >Opinions? > >Rumen --------------------------------- See the all-new, redesigned Yahoo.com. Check it out. ________________________________ Message 5 _____________________________________ Time: 09:37:07 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Antennas general --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 09:58 AM 7/26/2006 -0700, you wrote: >--> AeroElectric-List message posted by: "Hinde, Frank George (Corvallis)" > > > On my Vans kit they provided a wingtip NAV antenna which is just a >strip of copper foil. Do not suggest how one is supposed to ground it to >the airframe. > >I assume one has to ground the coax braid to the wing somehow?? How is the foil installed? Does it begin right at the edge of the tip fairing such that transition from coax to antenna is closely located to metallic portions of the wing? If so, ground the coax shield to the nearest practical wing-metal. >Also I intend to run my marker beacon antenna (40" lentgh of stripped >coax) in the bottom of my cowl. Assuming this will work do I need to >bond that coax to the firewall or similar? Here's where having access to a piece of test equipment is a real help! An MFJ-259 antenna analyzer (See: http://www.mfjenterprises.com/products.php?prodid=MFJ-259B ) would allow you to run say 10" of straight wire, coil 20" or so around a piece of plastic or wooden dowel, then extend the remainder out straight for an overall length of 20" or so. Then use the antenna analyzer to look at the characteristics of this shortened antenna. You'll find that it resonates lower than 75 Mhz. Trim the 10" extension beyond the coil to bring the antenna up to 75 Mhz then glass over what remains. Bob . . . ________________________________ Message 6 _____________________________________ Time: 09:49:59 AM PST US From: "Todd Richmond" Subject: AeroElectric-List: Antenna Coax Routing Folks, This might be a newbie question but I'm giving it a shot none the less. I have an RV-7A (or part of one at this point) in which I am planning on mounting my VOR and marker beacon antennas in the wingtips (one in each tip). Can I route my antenna coax in the same conduit with the nav, landing, and strobe lights or should I do a separate run some distance away to avoid any potential interference. The current set up has one transformer for the strobes mounted in the fuselage and a shielded wire running to the wing tips (the strobes ground back at the transformer). The nav, landing and taxi lights are grounded locally on the wingtips. My other concern is that at some point I would like to upgrade to a HID system for the landing/taxi lights which would require a local power transformer by the light. Has anybody had any experience with interference caused by these next to an antenna? Thanks for any input. Todd R. Richmond RV-7A ________________________________ Message 7 _____________________________________ Time: 11:09:44 AM PST US From: "Hinde, Frank George (Corvallis)" Subject: RE: AeroElectric-List: Antenna Coax Routing Todd Just a thought but.... If you mount a comm in one wingtip, Nav in the other and marker bacon in the bottom of the cowl you'll have no com attenna sticking out in the breeze (at least one less if you have more than one com) and you'll reduce the amount of coazxyou have to run out to the wings. Frank ________________________________ [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Todd Richmond Sent: Thursday, July 27, 2006 9:42 AM Folks, This might be a newbie question but I'm giving it a shot none the less. I have an RV-7A (or part of one at this point) in which I am planning on mounting my VOR and marker beacon antennas in the wingtips (one in each tip). Can I route my antenna coax in the same conduit with the nav, landing, and strobe lights or should I do a separate run some distance away to avoid any potential interference. The current set up has one transformer for the strobes mounted in the fuselage and a shielded wire running to the wing tips (the strobes ground back at the transformer). The nav, landing and taxi lights are grounded locally on the wingtips. My other concern is that at some point I would like to upgrade to a HID system for the landing/taxi lights which would require a local power transformer by the light. Has anybody had any experience with interference caused by these next to an antenna? Thanks for any input. Todd R. Richmond RV-7A ________________________________ Message 8 _____________________________________ Time: 12:25:24 PM PST US From: sportav8r@aol.com Subject: Re: AeroElectric-List: Re: Antennas general Aw, shoot! Make that P=E^2/R. I knew better than that. Hit "send" too quickly. -Stormy -----Original Message----- Sent: Thu, 27 Jul 2006 9:46 AM In a message dated 7/27/2006 9:39:55 A.M. Eastern Daylight Time, sportav8r@aol.com writes: While we're discussing dB's, I note that the installation instructions for my Garmin GMA 340 audio panel mention several times a feature provinding "10 times gain (20 dB)" for the entertainment channel input. I have labored all my life under the impression that 10dB was 10x gain, and 20 dB was 100x gain. It seems unlikely that the people who design this stuff professionally know more about decibels and power gain than a radio hobbyist does, so it's safe to assume I'm the one who is missing something. What gives? Sorry to hijack an antenna thread for this, Bob. But I've just got to get this straight before I go nuts ;-) -Bill B Bill, You are correct for POWER gain. For VOLTAGE gain Garmin is right. Db=10 log (P1/P2) Db log (V1/V2) Dan Hopper K9WEK RV-7A ________________________________________________________________________ ________________________________ Message 9 _____________________________________ Time: 12:25:24 PM PST US From: sportav8r@aol.com Subject: Re: AeroElectric-List: Re: Antennas general Ah, the old P=E^2*R ploy. I see now. Thanks. -----Original Message----- Sent: Thu, 27 Jul 2006 9:46 AM In a message dated 7/27/2006 9:39:55 A.M. Eastern Daylight Time, sportav8r@aol.com writes: While we're discussing dB's, I note that the installation instructions for my Garmin GMA 340 audio panel mention several times a feature provinding "10 times gain (20 dB)" for the entertainment channel input. I have labored all my life under the impression that 10dB was 10x gain, and 20 dB was 100x gain. It seems unlikely that the people who design this stuff professionally know more about decibels and power gain than a radio hobbyist does, so it's safe to assume I'm the one who is missing something. What gives? Sorry to hijack an antenna thread for this, Bob. But I've just got to get this straight before I go nuts ;-) -Bill B Bill, You are correct for POWER gain. For VOLTAGE gain Garmin is right. Db=10 log (P1/P2) Db log (V1/V2) Dan Hopper K9WEK RV-7A ________________________________________________________________________ ________________________________ Message 10 ____________________________________ Time: 04:42:27 PM PST US From: "Dale Ensing" Subject: Re: AeroElectric-List: Re: Antennas general Are you sure it is not E=mc2 ;<) Aw, shoot! Make that P=E^2/R. I knew better than that. Hit "send" too quickly. -Stormy DO NOT ARCHIEVE ________________________________ Message 11 ____________________________________ Time: 06:35:21 PM PST US From: sportav8r@aol.com Subject: Re: AeroElectric-List: Re: Antennas general Dale, you may have something there... ask the patent office ;-) do not archive -----Original Message----- Sent: Thu, 27 Jul 2006 7:13 PM Are you sure it is not E=mc2 ;<) Aw, shoot! Make that P=E^2/R. I knew better than that. Hit "send" too quickly. -Stormy DO NOT ARCHIEVE ________________________________________________________________________ ________________________________ Message 12 ____________________________________ Time: 07:18:23 PM PST US From: "Robert L. Nuckolls, III" Subject: AeroElectric-List: Off line for a few days --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" Dr. Dee and I are loading the van up with aunt Sally and uncle George tomorrow morning to go poke around in the mountains for a few days. Got tickets for a steam-powered narrow-gage ride on Saturday. After that we'll probably go explore New Mexico ghost towns . . . or something equally un-stressful. We'll be back Wednesday, August 2. By the way, Eclipse got their provisional type certificate issued at OSH a few days ago. As far as I know, that's the first instance of networked, multiple smart actuators being used on flap system of any GA aircraft. Yours truly had a role in the architecture and development of that system . . . I'm still hopeful of getting this technology onto Premier before I retire. It's about half the cost, 20 pounds lighter and best yet - works as advertised Bob . . . --------------------------------------------------------- < What is so wonderful about scientific truth...is that > < the authority which determines whether there can be > < debate or not does not reside in some fraternity of > < scientists; nor is it divine. The authority rests > < with experiment. > < --Lawrence M. Krauss > ---------------------------------------------------------