No the antenna is sma, 433mhz, not an omni-whip... pretty small and discrete, I got excellent reception. Mostly built for tracking devices(radio controlled inventory movement) or handheld radios. It was no bulkier than the stock antenna after you put in reinforcement to keep it strait. What I was suggesting eliminates the feed line from the board SMA to the antenna. so there are weight savings that may come to play. May actually be a net savings depending on how you breach the bulkheads...
There are also people here who make their own sma / coax antennas and they do wonders, I think Google has a lot of information on the bi-polar coaxial antennas. From: Scott Myers Sent: Thursday, April 13, 2017 14:08 To: 'Altus Metrum' Subject: Re: [altusmetrum] New Member Hi Clay, No, I'm not looking to do something like that. If I understand what you are calling a "whip antenna" and 3/4 connector, I think you are referring to a regular car whip antenna with a PL259 / SO239 connector junction. If that's what you mean, no, I would not use something like that. With respect, there is no advantage to doing that. Those antennas are designed to rely on the car's metal surface as the counterpoise in order to give the correct impedance and expected radiation pattern. Not to mention they have a lot of mass. Further, they tend to be tuned rather poorly out-of-the-box. I've been an extra class ham radio operator for many years and I've built hundreds of antennas over those years, some for very specialized applications. My goals are simple; Make sure I'm not detuning the built-in antenna or creating an odd radiation pattern due to interaction with the all-thread in the avionics bay. As BDale suggests, I may need to do nothing at all; just install it. I've had a mixed bag of success and failure over the years with various antennas next to other metal structures. Sometimes, it's as if the structure wasn't there. Other times, I've been less lucky. It is a difficult thing to predict. I've got a plan based on BDale's comments on Facebook. I'll get a Telemetrum installed in an avionics bay and then suspend it about 75' up in the air between my radio tower and a tall tree. Then, I'll move away by about 1/4-12 mile in 4 different compass directions and check signal strength in both horizontal and vertical polarizations. If I get relatively equal signal strength readings in all 4 directions, then I won't do anything else and just go with the on-board wire. (If it ain't broke...) But if I get significant variances, then I'll consider going down the SMA / external antenna path. If I do an external antenna, I'll probably try a simple dipole arrangement made of some fine 22 gauge wire fed by several inches of RG316, assuming the board will allow for the balanced antenna set-up. Otherwise, I'll just use the stripped back center conductor of the RG316 that I tune with my antenna analyzer while installed in the avionics bay. Thanks, Scotty From: altusmetrum [mailto:[email protected]] On Behalf Of Clay & Carly Sent: Thursday, April 13, 2017 2:05 PM To: 'Altus Metrum' Subject: Re: [altusmetrum] New Member I moved mine from a whip to an sma connector. I just bought a cheap one off eBay with a 3/4” threaded section, then I bought 7” whip antenna. I use G10 for bulkheads, so I drilled and tapped the bulkhead for the SMA connector. Think of it like panel mounting your telemetrum. Worked great but lost that rocket From: Scott Myers Sent: Thursday, April 13, 2017 09:22 To: 'Altus Metrum' Subject: Re: [altusmetrum] New Member Thanks Tim for the reply and thanks for the links. I've read all those links before. I think I have read nearly everything there is to read, including development history and the manual. Granted, I could have missed or skimmed over the details I am looking for. BTW- I'm a 55 year old mechanical engineer and an Amateur Extra class, AC8DE. My first question is on the uplink/downlink frequencies. It simply states 433 MHz. I assume this to be an approximate frequency in the 70 cm band and not the actual exact frequencies. Rarely is something right at 433.000 MHz. Are there separate uplink and downlink frequencies (full duplex) or does it switch on/off transmit/receive at each transceiver (Telmetrum and Teledongle) using the same exact frequency. Is the frequency(ies) movable in case of frequency conflict and RFI? How wide is the data bandwidth in KHz? I happen to have a commercial radio (HBC Radiomatic) in my launch system design that uses, yep... the 433 frequency range. I can select 4 discrete "channels" on it to help it avoid any conflict, but it would be good to know where the Telemetrum actually transmits and receives so I can shift the launcher away from that frequency as far as possible. Then there is the case of what if there is another Telemetrum or two around the launch site; a very probably scenario. (I think they are all coded and using "telegraph" messaging handshaking to avoid conflict with another Telemetrum, but I could be wrong.) I could figure most of this out with a spectrum analyzer, but I'd have to buy it first and then spend the time to test. Better to know these technical details before I buy. I see there is a starter "kit" that uses the Teledongle. But there is also the TeleBT, which seems to do everything the Teledongle does, PLUS adds bluetooth for use with the Android App. It seems that starting with the TeleBT would the better choice and don't even buy the Teledongle, but I wanted to make sure I wasn't missing something on this. I saw the history on older versions with the problems with pyro events and battery rail sag and that it is supposed to be solved now. (An age-old problem on many avionics packages.) I think I'd rather put a second LiPo on the Telemetrum and give the pyro events their own rail and simply avoid any potential rail sag issue. Just a small LiPo should do the job. I'm guessing others have done this and I read where that is an option on the board. I'd like feedback on that. I read where there is an SMA connector option for the Telemetrum. I've considered ordering the Telemetrum with that option and make the antennas a permanent part of the Avionics bays fed with a short piece of RG-316 or the like. Of course downside is mass of the connector soldered to the board and having to support the feed line to account for high-G conditions so the connector isn't broken from the board. I'd like some feedback and discussion on the use of the SMA connector. I can't figure out how to order the Telemetrum with that option anyway. Perhaps it is a field mod? Thanks, Scotty From: altusmetrum [mailto:[email protected]] On Behalf Of Tim Cubbedge Sent: Thursday, April 13, 2017 8:53 AM To: 'Altus Metrum' Subject: Re: [altusmetrum] New Member Have you looked here? http://altusmetrum.org/AltOS/doc/altusmetrum.html or here? http://altusmetrum.org/TeleMetrum/ What do you want to know? From: altusmetrum [mailto:[email protected]] On Behalf Of Scott Myers Sent: Thursday, April 13, 2017 7:11 AM To: [email protected] Subject: [altusmetrum] New Member I just joined this Altus Metrum mailing list. I'm trying to get a bit more information and learn more about the Telemetrum before I purchase one. Thanks, Scotty -------------------------------------------------------------------------------- _______________________________________________ altusmetrum mailing list [email protected] http://lists.gag.com/mailman/listinfo/altusmetrum -------------------------------------------------------------------------------- _______________________________________________ altusmetrum mailing list [email protected] http://lists.gag.com/mailman/listinfo/altusmetrum
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