What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

APRS antenna

Leland

Leland

Well Known Member
I just received a used RAMI AV-14 antenna from Avionics Unlimited (1-866-703-6388), located at KXCO, north of Houston. My antenna looks nearly new, but I asked for the best looking one they had. The "new" price is over $180. This is the correct antenna to use with an APRS system. These antennas were used briefly for the now defunct Garmin GDL49 Data Link Wx System. Avionics still has at least a half dozen. Their price is $24.95 each plus $10 shipping. They are an Ebay reseller (http://cgi.ebay.com/ebaymotors/RAMI-AV-14-COMMUNICATIONS-ANTENNA_W0QQitemZ260327646303QQcmdZViewItem).
Leland
RV9A
 
The AV-14 rocks!

Leland said:
I just received a used RAMI AV-14 antenna from Avionics Unlimited (1-866-703-6388), located at KXCO, north of Houston. My antenna looks nearly new, but I asked for the best looking one they had. The "new" price is over $180. This is the correct antenna to use with an APRS system. These antennas were used briefly for the now defunct Garmin GDL49 Data Link Wx System. Avionics still has at least a half dozen. Their price is $24.95 each plus $10 shipping. They are an Ebay reseller (http://cgi.ebay.com/ebaymotors/RAMI-AV-14-COMMUNICATIONS-ANTENNA_W0QQitemZ260327646303QQcmdZViewItem).
Leland
RV9A
Click to expand...

I replaced my home-made belly-mounted whip (which has worked well) with one of the Ebay AV-14 antennas and am impressed with the performance. At KMSL I have always lost packets below 400' AGL, but yesterday beacons from ground taxi made it to the network. The CHT and fuel flow indicators on the engine monitor previously bounced when the tracker fired but this has been greatly reduced with the new antenna. I suspect more RF is being radiated instead of having some of the energy reflected back up the coax into the cabin (lower SWR). This may be due to the antenna having a BNC connector vs the old coax pigtail termination.

The ground clearance of the antenna on my RV-6 is only a few inches, but guess that will be fine as long as I don't slam a landing!

Another change I've made is to turn off MIC-E encoding on the tracker. This is working fine and allows plain-language data of the beacon to be visible when looking at raw packet data. The main reason I turned off MIC-E is because it seems some digis corrupt data if translating MIC-E to text which causes problems on the aprs.fi server. The packet data now looks like this:

N399SB>APT311,WIDE2-1,qAR,WB5CON-1:!3437.43N/08736.76W'068/150/A=002578/KJ4CKK

Text displays path, little airplane symbol, lat-long, speed, altitude, and call sign respectively.

I also reset the text comments to "every packet" so nobody will have the opportunity to grumble about the FAA call sign not being included in every transmission. ;)
 
Last edited:
Only One Left

Leland said:
I just received a used RAMI AV-14 antenna from Avionics Unlimited (1-866-703-6388), located at KXCO, north of Houston. My antenna looks nearly new, but I asked for the best looking one they had. The "new" price is over $180. This is the correct antenna to use with an APRS system. These antennas were used briefly for the now defunct Garmin GDL49 Data Link Wx System. Avionics still has at least a half dozen. Their price is $24.95 each plus $10 shipping. They are an Ebay reseller (http://cgi.ebay.com/ebaymotors/RAMI-AV-14-COMMUNICATIONS-ANTENNA_W0QQitemZ260327646303QQcmdZViewItem).
Leland
RV9A
Click to expand...

I just ordered an AV-14 and it indicated that they only had one left after my purchase. One down and one to go.
 
Static Build up on external antennae

I have just had my third reported case of damage to a Micro-Trak AIO from what appears to have been static build-up on an external antenna. This has never appeared to be a problem with an antenna installed in a wingtip, or rubber ducks, so I surmise that it is charged particles of dust carrying stray charges that accumulate on antennae frying the MOSFET RF amplifiers in the AIOs ( which use the same amplifier as the MT-8000 and MT-8000FA)

I will be looking around to see if I can find a source of charge arrestors for through-hull mounted antennae, but if anyone is aware of one, I would suggest you use it on your installation to protect your radio. I would consider placing an NE2 neon bulb across the antenna connections at the antenna as a bare minimum precaution. FYI, if you do fry your amp, I charge 20.00 for parts and return shipping via US mail, so its not too serious or expensive if something bad happens to the amp, you just have to live with it being out of service for a while.

Allen
VHS
 
VHS said:
I have just had my third reported case of damage to a Micro-Trak AIO from what appears to have been static build-up on an external antenna. This has never appeared to be a problem with an antenna installed in a wingtip, or rubber ducks, so I surmise that it is charged particles of dust carrying stray charges that accumulate on antennae frying the MOSFET RF amplifiers in the AIOs ( which use the same amplifier as the MT-8000 and MT-8000FA)

I will be looking around to see if I can find a source of charge arrestors for through-hull mounted antennae, but if anyone is aware of one, I would suggest you use it on your installation to protect your radio. I would consider placing an NE2 neon bulb across the antenna connections at the antenna as a bare minimum precaution. FYI, if you do fry your amp, I charge 20.00 for parts and return shipping via US mail, so its not too serious or expensive if something bad happens to the amp, you just have to live with it being out of service for a while.

Allen
VHS
Click to expand...

Wonder why static build-up isn't a problem with our eight-watt communication radios? For whatever it's worth, my Micro-Trak has been running with an external antenna for nearly a year and a half. I hope the AIO problems eventually turn out to be non-antenna related because the external antenna really lets the trackers perform well.

At a loss as to how to connect a neon bulb across the antenna connection when it is terminated with a BNC connector...
 
Last edited:
Most production radios have some sort of built-in protection.

Allen - would a small capacitor in series with the output work? Kind of like a DC block? I'm thinking a between a 100pF-1000pF ceramic chip cap for low loss. On the antenna side of the cap, a big inductor (aka choke) to ground to bleed off any static build up. If done with the right parts & construction, this won't hurt power output over the narrow transmit frequency.

This might help if the problem is bascially too much DC (caused by a slow buildup of static). If the problem is more a big sudden voltage spike (like a lightning strike) then the neon bulb (or a transorb) might be better. I'm betting the problem is the slow build up kind.

Just random RF thoughts - could be way off base.

dave (ex radio designer)

PS If you want to send me a radio I'll put it in and report results, complete with output power and SWR test data, as long as I can keep it for an extended test period.... ;)
 
Last edited:
Antenna

I'm going to shorten an old stainless steel whip antenna, the kind with the ceramic insulators, to work at 144 mhz. Won't take much.

Would a round ball on the tip, similar to the ones on the cheap transponder antennas help with the static any??????
 
Questions answered in no particular order:

Your com radios were designed for airplanes, and have unlimited room for protective circuitry. The Micro-Trak's were designed for portable use, and no special precautions have been taken in the design to prevent the MOSFET amplifiers from being damaged by static. The neon in an NE2 bulb will Ionize when the static charge reaches 80 to 90 volts, and when it does, it will act as a nearly dead short for the static, discharging it to ground. A 10 K 1/4 Watt resistor would also probably be a good choice. When I googled "Static Arrestor" I found a bunch of them, from about 6.00 on up. most seemed to be of the gas discharge variety ( Neon or other noble gas discharge tube) but most had N or SO 239 connectors.

I don't think the chip cap in series will do anything other than messing up your feed point impedance. with a couple thousand volt potentials on a static charged antenna, the static will just arc across the cap anyway.

The ball end on antennas is a standard protection against Coronas.

As one poster stated above, his has worked fine for more than a year, and it appears to be a rare problem, but if a .50 cent or 6.00 part part can protect your system form total failure, I would consider it.

Best regards,

Allen
VHS
 
VHS said:
Your com radios were designed for airplanes, and have unlimited room for protective circuitry. The Micro-Trak's were designed for portable use, and no special precautions have been taken in the design to prevent the MOSFET amplifiers from being damaged by static. The neon in an NE2 bulb will Ionize when the static charge reaches 80 to 90 volts, and when it does, it will act as a nearly dead short for the static, discharging it to ground. A 10 K 1/4 Watt resistor would also probably be a good choice. When I googled "Static Arrestor" I found a bunch of them, from about 6.00 on up. most seemed to be of the gas discharge variety ( Neon or other noble gas discharge tube) but most had N or SO 239 connectors.

Allen
VHS
Click to expand...

Allen, would the neon bulb still be effective as a static arrester if mounted on the tracker PC board at the SMA connector?
 
APRS external antenna

I recently installed a belly mounted RAMI AV-14 antenna for my 300 mW Byonics APRS transmitter. The results are dramatically better than when the unit used a wing-mounted antenna. Here is a link to yesterday's flight of N137LC along the California coast.
http://aprs.fi/?call=N137LC&mt=m&z=11&timerange=86400

I could not measure any decrease in the 162 knot top TAS with the new antenna.

It'll be interesting to see what coverage will be in eastern Utah and Montana when I fly back to OSH. Last year there was barely any coverage there with the wing-mounted antenna.
Leland
RV9A
 
Leland said:
I recently installed a belly mounted RAMI AV-14 antenna for my 300 mW Byonics APRS transmitter. The results are dramatically better than when the unit used a wing-mounted antenna. Here is a link to yesterday's flight of N137LC along the California coast.
http://aprs.fi/?call=N137LC&mt=m&z=11&timerange=86400

I could not measure any decrease in the 162 knot top TAS with the new antenna.

It'll be interesting to see what coverage will be in eastern Utah and Montana when I fly back to OSH. Last year there was barely any coverage there with the wing-mounted antenna.
Leland
RV9A
Click to expand...

Leland, I continue to be impressed with the AV-14, it is an outstanding performer! I painted mine black to match the bottom of the fuse so it can't detract from top speed. ;)

I know it goes against the sensibilities of many RVers to hang another antenna in the breeze, but I'm convinced an external antenna is the only way to extract maximum utility from an APRS tracker.
 
Last edited:
Smoked my MOSFET?

On my way to OSH I stopped sending APRS packets near Terre Haute. About the same location I had slipped between to cells of heavy precipitation. Thinking back I remember hearing precip static on the com radio thinking it strange. I couldn't remember that ever happening on a single engine aircraft in my past.
Now back at home, researching and reading this thread, I'm pretty confident it's my MOSFET amplifier that's been damaged.
I guess I'll be sending my unit back to Allen for repair while shopping for protection before reinstall.
 
Blown Mosfet

Randy,

FYI, I am routinely adding a static-bleeder 47K resistor across the output of any of my 10 Watt transmitters that come back for repair of any type. So far, no amps have come back blown twice, but I still like the idea of a gasesous discharge static/lightning suppresor for metal vehicles with external antennae.

Allen
VHS
 
AV-14 Antenna Troubleshooting

N42AH said:
I just ordered an AV-14 and it indicated that they only had one left after my purchase. One down and one to go.
Click to expand...

The issue...it doesn't work, no breadcrumbs dropped

Finally got around to installing the AV-14 antenna this last conditional inspection. Mounted on the belly. It is used in conjunction with the MT-RTG. Using a sma to bnc adapter to coax to the antenna. When I check the adapter and coax for a short, it ohms out OK. When I hook up a mag mount antenna from VHS, that works also. So my thinking is it might be this antenna. Since everone has had such great success with their AV-14's that they have installed. MY question is how does one test the antenna? And has there been any comparisons between the AV-14 and the modified loran antennas if the AV-14 is unservicable?

Thanks,
 
You must log in or register to reply here.
Back
Top