I have a pull wire in all of my conduits to make it easy to add new cables. But getting a 135 foot long cable can be expensive, I will buy a new one if I have to but would rather "fix" this one.
SUCCESS! I hope...I sprayed contact cleaner in ALL of the connections, even the ones inside, and put marine grease on them all. Hooked it up, and got 30 SV's...
Going to let it run a few days (it makes daily 24hr files and automatically uploads to my desktop.?ÿ
The Alloy has a spectrum analyzer...here is GPS L1, which looks like it did before the problems started
and the RTX signal from a geosynchronous SV:
If anyone has an alloy that they can check the C/No values on, I would appreciate seeing the values to see if these are comparable. If you can send me that same table, and also how long/what kind of cable is being used.?ÿ
That dielectric grease is the stuff most people just toss to the side not realizing how important it is for the lasting effects of the product you are depending upon.
Much of our issues with GPS equipment has been cables. Sometimes there doesn't seem to be any problem with connectors, the cable wire, or breaks, but put in a new cable and everything is fine.?ÿ
@mightymoe you would be surprised how thin of an invisible film of some kind of filth on the connectors will stop the connection.
Then sometimes it is the iddy biddy amount of wear that does it.
I wonder if you can rent equipment that will analyze the condition of the cable you have in place?
Good question. I did get a private message from a person who offered to do it if they had a tech in my area.
But now it seems to be fine after the careful cleaning and application of grease after several days of testing.
Way late to party John, but couple comments. 1st off, I hope that is something better than RG8 for use at GPS frequencies. Let's compare the loss to LMR600. RG8 has a 9.0 dB/100 ft loss whereas?ÿLMR600 has 3.3 dB/100 ft. LMR600 is stiff and hard to work with, there may be other choices. Loss was computed at 1500Mhz, the higher the frequency the better cable you need to offset losses. in the 6db differnce is signal attention/100 feet you loose about 1/4 of your received signal power. The dB loss or gain is logarithmic.
Yes, buried cables can often get water intrusion and not much to do but replace.
Cables can be had in various flavors including direct burial which have a better outer jacket. I wouldn't direct bury, but it would be a better quality.
Your learn a lot when you get your amateur radio license and a ton is applicable to surveying equipment, RTK antennas, etc. Only wished I knew what I have learned recently when first doing RTK in the early-mid 1990's, would of been a lot less head scratching I think.
@john-hamilton I made that decision in 2016, got my Technician and a month later my General. The Extra question pool changed on July 1st, so I got busy and passed that in mid June to avoid buying new study materials. That Extra kicked my tail, took a lot of study! (I finally purchased an online study course and that worked way better than the books for the Extra). From nothing to highest level in four years, all self study, although I do have some local amateur radio buddies.
6db differnce is signal attention/100 feet you loose about 1/4 of your received signal power.
Actually, your receiver gets 1/4 of the signal power; the cable loses 3/4.
But that is the signal after the preamp in the antenna assembly boosts it.?ÿ To know how much the cable loss really hurts, you need to know the "noise figure" of the preamp and receiver and the preamp gain. The effective cost will be less than 6 dB.
@bill93 you are correct, that is what I get for posting late at night 🙂
It is still a 6db loss in the cable, no matter the pre-amp gain. If the pre-amp has a 6db gain, then the cable just brings that back to unity gain.
Regardless, cable type and length really does matter at GNSS frequencies.
Connectors also add loss and that varies by type of connector.
Good stuff knowing all this.
