New tracker from Apogee?

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BLH said:
That is a good one!! I fly at basically four sites and have noticed the egg finder problem as have others.. Two of sites are far out away from life and two are closer and do have cell towers around... It seems the two closer sites are this issue makers and it takes a very long time to get a fix with my egg finder(s), if a fix is possible at all. I have had them never get a fix even after a couple of hours.

So being the inquisitive type, I wanted to know why and am still looking at this at different times and such so it is a work in progress. Using a cell phone analyzer and looking at the 737MHz, 751MHz, 800MHz, 1900MHz and 2100MHz bands, it is clear that the two issue sites have more 700-800MHz signals. Interestingly the second harmonic of these frequencies is right near the 1500MHz GPS band the trackers use!!!

Then I lugged a spectrum analyzer out and measured the 1500GHz GPS band and the two sites that cause issues do have a higher noise floor by around 10-13db's.

Then there is the fact that the egg finder starts transmitting data immediately after it is turned on and blast out allot of useless data just by virtue of how simple it is and how it works...

Working theory: It seems there is good correlation that with the higher noise floor from the cell towers and the egg finder beginning it's transmissions immediately on power up and every second sending allot of data out, I think the front end of the GPS chip is getting hammered and thus can't lock!! That poor automatic gain control circuit:(

From measurements made on my new simple tracker, it seems they do not turn on the RF transmitter until the GPS chip has a good lock. I guess they figured no need to transmit useless data. I haven't tested out my missile works unit yet.

So there you have it. Anyone building their own tracker - Don't turn on the downlink radio until the GPS chip has a good lock!! It seems those chips can keep a lock ok, once they get one! I guess good news about egg finder with SMA connector is one could put a "dummy" load onto it to prevent RF transmission until GPS locks... Bla
Click to expand...

Please tell me if I’m following your theory correctly.

You believe cell towers in the vicinity of the “problem” launch site are causing interference or intermodulation with the Eggfinder, causing difficulty establishing GPS lock. You believe this happens with the Eggfinder because it’s 915 mhz radio starts transmitting as soon as the Eggfinder is turned on.

You believe the Apogee product is better at avoiding interference because it doesn’t start to transmit until GPS lock is achieved.

Does that accurately restate your idea?


In my case - It does take longer for my Eggs to lock at home. I live a large metro area. My house is within a mile of 3 different high-watt TV and radio antenna farms, which also sport cell antennas. I also notice my Garmin Legend handheld GPS takes longer to lock at home as well.
 
Actually, the more I think about it, I think it's a theory NOTA and DOA; Because that whole theory is based on the "assumption" that the tower(s) I speak of are cell towers. It does kinda look like one and they are variant in construction, but maybe it's not. If it were something in the 400-600MHz range, then we could have a third high enough. Evens are hard to get in RF. What's odd is sometimes egg finder(s) work. That being said, sometimes simple trackers may not. There is something about that area and getting a GPS lock that is odd and transmitting less seems to help. Nonetheless, if I ever figure it out I will post answer:)

Never lost a rocket with either yet! So until then,

Happy flights,
GOD bless and Merry Christmas
Good night
 
BLH said:
That is a good one!! I fly at basically four sites and have noticed the egg finder problem as have others.. Two of sites are far out away from life and two are closer and do have cell towers around... It seems the two closer sites are this issue makers and it takes a very long time to get a fix with my egg finder(s), if a fix is possible at all. I have had them never get a fix even after a couple of hours.

So being the inquisitive type, I wanted to know why and am still looking at this at different times and such so it is a work in progress. Using a cell phone analyzer and looking at the 737MHz, 751MHz, 800MHz, 1900MHz and 2100MHz bands, it is clear that the two issue sites have more 700-800MHz signals. Interestingly the second harmonic of these frequencies is right near the 1500MHz GPS band the trackers use!!!

Then I lugged a spectrum analyzer out and measured the 1500GHz GPS band and the two sites that cause issues do have a higher noise floor by around 10-13db's.

Then there is the fact that the egg finder starts transmitting data immediately after it is turned on and blast out allot of useless data just by virtue of how simple it is and how it works...

Working theory: It seems there is good correlation that with the higher noise floor from the cell towers and the egg finder beginning it's transmissions immediately on power up and every second sending allot of data out, I think the front end of the GPS chip is getting hammered and thus can't lock!! That poor automatic gain control circuit:(

From measurements made on my new simple tracker, it seems they do not turn on the RF transmitter until the GPS chip has a good lock. I guess they figured no need to transmit useless data. I haven't tested out my missile works unit yet.

So there you have it. Anyone building their own tracker - Don't turn on the downlink radio until the GPS chip has a good lock!! It seems those chips can keep a lock ok, once they get one! I guess good news about egg finder with SMA connector is one could put a "dummy" load onto it to prevent RF transmission until GPS locks... Bla
Click to expand...

Very interesting phenomena. If anyone flying Egg Products at said site have the same problem, I suspect you're on to the problem. I have a couple of hacked EF's that use outboard GPS chips.
One uses a quadrifilar antenna as shown in this example: https://www.beyondlogic.org/fsa03/uBlox 5 GPS Breakout Module.pdf
Haven't had a chance to fly it yet. I kick myself every now and then for not picking up a couple of these: https://www.csgshop.com/product.php?id_product=108
Amplified Sarantel antenna would have held promise for keeping lock from inside an airframe. Kurt
 
scsager said:
(Snip for Brevity's sake)
In my case - It does take longer for my Eggs to lock at home. I live a large metro area. My house is within a mile of 3 different high-watt TV and radio antenna farms, which also sport cell antennas. I also notice my Garmin Legend handheld GPS takes longer to lock at home as well.
Click to expand...

Sheesh Scott, The Legend is ancient. Mine takes a long time to get a fix if it's been off for a long time. Once it's locked it does good. Actually, I stuck a serial cable on the end connector under that rubber flap and can pipe waypoints to an APRS tracking program or use a Kenwood D7, D72A or D74 along with a plethora of other APRS radios. The Blue Legend is a very simple cheap monochrome
GPS that can be read in sunlight and do navigation to a downed rocket. They are real cheap used too. If one gets a tech license, it's one thing to consider. Kurt
 
scsager said:
In my case - It does take longer for my Eggs to lock at home. I live a large metro area. My house is within a mile of 3 different high-watt TV and radio antenna farms, which also sport cell antennas. I also notice my Garmin Legend handheld GPS takes longer to lock at home as well.
Click to expand...

That's because in a populated area you don't get a 180 degree view of the horizon, you got buildings in the way. Any low azimuth satellites are going to be blocked or significantly attenuated. That goes for wooded launching areas vs desert or flat farm areas, too. All of the sites that I personally fly at are either desert or farmfields, flat as a pancake with typically 8 or 9 satellites in view at any point in time.

If you use an amplified helical GPS antenna like the Sarental one (yes, I know they got bought, but I don't know by whom off the top of my head) you pretty much can get around this because they are extremely narrow band and very high gain. They're also hideously expensive... like $150. That's just the antenna... compare that to maybe $2 or $3 for a GPS patch antenna... that's why almost everybody used patch antennas. And that's one reason why the Multitronix is so expensive compared to other units... they use the Sarental antenna.
 
Well - it's in stock with more than 10 available... being the "egg-head" that I am, I'm curious to see how it really performs. - If I only had an extra few hundred bucks...
I'm sure we will see some reviews pop-up in the next month or so.
 
Steveo said:
While this looks neat, I'm happy with both of my EggFinders. It is tedious work to solder yourself, but if you follow the directions (Cris spells it out for you step by step) it is doable. I wish it had a better LCD case - but BlackAero has kit that looks slick. Overall a great setup that is easy to use. I tested mine for the first time a couple of weeks ago and it was dead simple to use. Had it secured in a labratrocketry sled and GPS took me right to the rocket.
Click to expand...
Can someone direct me to Chris for soldering instructions on the Eggfinder please
 
BSNW said:
What will sell this is you put the darn thing in your rocket and walk in the direction of the arrow. Most folks simply want to know where to go and find their rocket. Many many times I have asked questions about one unit or another....how it works what to do and asked for replies in simple, common language. What I receive from vendors and electronics folk is advanced jargon. which leaves me confused. Some folks are into the radio/electronics/receiver/transmitter guru stuff.....that's cool. I simply want an arrow to show me where to go.

Amen!
Click to expand...
 
Has anyone that's actually purchased and used the Apogee Tracker have a review yet?
 
I have around 10 flights on mine and it seems to be working very well! Last flight 10,000' AGL Mach 1.43...
 
Side note: I have placed the transmitter on the top 2x4 rail of my cedar fence(behind the pickets) and then drove around and got good signals over two miles away in residential area!!! Seems like it would have worked much farther but terrain wasn't conducive...
 
I like the fact that they've come up with a product that makes me think it'd be more cost effective to actually lose an occasional rocket...
 
That is a stiff price. Had a ballistic flight with engine deployment FG tracker dog rocket that went in ballistic.
Received one position from the Egg Finder and got to dig the rocket out and fly it again. Somehow losing a $50.00 Egg finder didn’t bother me so much as I was elated to get the rocket and motor hardware back with a single position. The flight was totally unseen too. Kurt
 

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