---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Sat 07/18/20: 5 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 07:09 AM - Re: Re: IS a COM ANTENNA GROUND PLANE NECESSARY (Robert L. Nuckolls, III) 2. 07:11 AM - Re: Re: IS a COM ANTENNA GROUND PLANE NECESSARY (Robert L. Nuckolls, III) 3. 07:43 AM - Re: LiFePO4 friendly electrical system, was: Re: Premature EarthX death? (Rob Turk) 4. 10:06 AM - Re: antenna analyzer? (merlewagner2) 5. 06:51 PM - Re: DIY LOC/VOR_G.S. Antenna (Robert L. Nuckolls, III) ________________________________ Message 1 _____________________________________ Time: 07:09:45 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: IS a COM ANTENNA GROUND PLANE NECESSARY At 12:17 AM 7/18/2020, you wrote: > >At 3.8 SWR the transmitter is in danger of over heating to the point >of meltdown!!!!! This used to be the case back in the day. During the vacuum tube era, transmitters were a bit more tolerant of high swr especially given that two-way radio communications were very low duty cycle. Except for when you're reading your flight plan to the FSS, transmissions seldom lasted more than a few seconds. Early solid state radios were a bit more fragile given their thermal weak-spots in tiny junctions within the transistor's architecture . . . but even that vulnerability faded with improvements in transistor design. Further, it is not uncommon these days for a transmitter to have an SWR bridge BUILT IN to the antenna output pathway with REVERSE power signals looped back to the transmitter's power amplifier such that operating power is scaled down in response to high SWR. The most probable manifestations of the high swr . . . especially in a low conductivity airframe are (1) poor operational performance and (2) high levels of radio frequency energy in the cockpit during transmissions. This phenomenon has been observed countless times in OBAM aviation's 'plastic' airplanes. In the case before us, the coax is poorly terminated thus making the whole feedline a radiator of energy along it's entire length . . . which puts significant energy into the aircraft interior. RF interference with cockpit instrumentation is most often observed with products not designed with rudimentary DO160 qualification guidelines in mind. Bob . . . ________________________________ Message 2 _____________________________________ Time: 07:11:22 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: IS a COM ANTENNA GROUND PLANE NECESSARY At 07:54 PM 7/17/2020, you wrote: > >I took my SWR meter to the airport today and checked my friend's com >antenna. The SWR was 3.8 >Now he knows that his antenna installation will not work very well. >He is considering mounting a new antenna on top of the fuselage. Sounds like a plan . . . thanks for helping this builder out -AND- sharing the experience here on the LIST. Bob . . . ________________________________ Message 3 _____________________________________ Time: 07:43:17 AM PST US Subject: Re: LiFePO4 friendly electrical system, was: AeroElectric-List: Re: Premature EarthX death? From: Rob Turk Hi Rob, > > I'd never seen that brand before, so I looked them up. > https://www.aeroakku.com/LIGHT-SPORT-AIRCRAFT/-AEROAKKU-LiFePO4:::6_139.html?language=en&MODsid=3024acbfbb1e3575f16a62b009d3bb51 > 1st thing I noticed is that it costs 299 Euros, or $341 US dollars. I > pay around $40 for the SLA batteries I use. > 2nd thing I noticed is that it's a 7AH battery. No doubt it's fine for > starting, but it's about 1/3 the energy capacity of the SLAs that I > use. That means that if you're running electronic fuel injection, > it'll be good for about 15 minutes after the alternator dies. > > What I *didn't* see (at least on that website) was any info whatsoever > on the BMS. Since that company also sells the more common brands of > batteries, it leads me to believe that they are rebranding someone > else's battery, but there's no documentation. Which brings me back to > what I wrote, above. With the addition of, 'we don't know what we > don't know'. :-) > > Charlie Hi Charlie, They are selling in Europe only, and have been doing so since 2012 or so. I think that's even earlier than EarthX? The AeroAkku brand is their own development, and they started selling a couple of other brands as well over time. The AeroAkku BMS is embedded in the battery, no external circuitry required. The Oddyssey it replaced costs about 100 over here, so 3x for LiFePO4 and 14lbs saved. Indeed 7Ah doesn't sound like much, but it all depends on your power budget. On my Rans S-6S with Jabiru 3300 using a gravity-fed carburator, my power draw is very low. I just tested with everything I have switched on (Funkwerk radio + xpdr, Stratux receiver, AvMAP UltraEFIS, LED strobes (own design, modified Kunzlemans), LED landing light, an MGL FF-4 and an Insight G2 engine monitor. Also powering a Samsung tablet and a phone. All this draws just 5A steady. I started with main bus measuring 13.1V. After 40 minutes at 12.8V and after 50 minutes this had dropped to 12.6V, everything still operating fine. It then took another 10 minutes to drop below 12V, after that things went pretty quick. But even after an hour I still had juice to operate my electric flaps. And this is on a battery that enters it's 8th year. So for my mission, this battery is perfect. For yours not so much. Rob ________________________________ Message 4 _____________________________________ Time: 10:06:18 AM PST US Subject: AeroElectric-List: Re: antenna analyzer? From: "merlewagner2" Bob, Just took a couple photos of my antenna. I did two calibrations, one for Glide slope and one for Localizer. Not sure how the photos will come out. These are attached. I don't remember the length I initially used for antenna. I bench tested and it looked OK. After install the freqs changed, most likely due to frame proximity. There are some wire and and ferrites between the connector and the foil. This will take up some length. I had to cut the foil to get in the freq range. Merle -------- KC1DNJ General Radiotelephone Commercial SEL A&P Building scale P51, rebuilding Tailwind W10 Read this topic online here: http://forums.matronics.com/viewtopic.php?p=497363#497363 Attachments: http://forums.matronics.com//files/ils_vna_738.jpg http://forums.matronics.com//files/loc_vna_639.jpg ________________________________ Message 5 _____________________________________ Time: 06:51:06 PM PST US From: "Robert L. Nuckolls, III" Subject: AeroElectric-List: Re: DIY LOC/VOR_G.S. Antenna At 12:04 PM 7/18/2020, you wrote: > > >Bob, > >Just took a couple photos of my antenna. I did two calibrations, one >for Glide slope and one for Localizer. > >Not sure how the photos will come out. These are attached. > >I don't remember the length I initially used for antenna. I bench >tested and it looked OK. After install the freqs changed, most >likely due to frame proximity. There are some wire and and ferrites >between the connector and the foil. This will take up some length. I >had to cut the foil to get in the freq range. Interesting. I'm wondering if the 'short' elements are not really functioning as resonant radiators, rather reactive elements that influence the uhf characteristics of the overall assembly. We know that the basic 1/2-wave dipole offers significantly effective performance at odd harmonics of the fundamental. If memory serves, LOC/VOR transmitters operate in the 108 to 118 Mhz range. 3x these numbers are 324 to 354 . . . more than the 328 to 336 bandwidth occupied by the contemporary GS transmitters. This means that your barefoot LOC/VOR antenna is quite capable of providing GS signals to your ILS receiver. For many years, GS receivers have been installed using band-pass couplers on the LOC/VOR thus allowing one STOCK, LOC/VOR antenna to service both VORNAV and ILS systems. The attached photo is one of what must be dozens of examples for this kind of device. I'm thinking that if you removed the little 'stubs' from the array, your swr plots over the two band widths of interest would not be significantly different . . . indeed both acceptable for the task at hand. Given the VHF antenna's propensity for acceptable performance at third harmonic, it is almost a certainty that the observably 'too small' size of these stubs is of no benefit to the antenna's performance. Bob . . . ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message aeroelectric-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/AeroElectric-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/aeroelectric-list Browse Digests http://www.matronics.com/digest/aeroelectric-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.