Hi Alan,

I have heard of a passive repeater, but I wouldn't expect them to have much performance, much as it sounds like you have experienced. For what it's worth, there was a period of time where cell boosters were marketed as boosting cell phone performance in rural areas. I've never known anyone to try them.

In professional use, I have seen active GPS amplifiers used indoors, such as in a large conferences where many gps equipped systems were being demonstrated, but that is the limit of my experience in that arena. Unless I had multiple GPS units that had to work in an area indoors where there is poor signal, it is more cost effective to use an external amplified antenna to bring the signal in to the GPS unit. The position fix reported by the GPS will the t-e location of the antenna, not the location of the GPS receiver, if that is of concern.

Best,

Shane

On Oct 10, 2020 at 00:36, Alan G4ZFQ <alan4alan@...> wrote:

> Hense my assertion that the modern receivers are so sensitive that they

> may not need an amplified antenna in some situations.



Shane,



Yes, I've seen lots of reports here of reception in seemingly impossible

places.



But I've tried repeater antennas and they have only worked when nearly

on top of the RX antenna. Maybe I've not done it correctly and that's

not typical?



73 Alan G4ZFQ

On Oct 10, 2020 at 01:32, Hans Summers <hans.summers@...> wrote:

Hi Shane

Yes the modern GPS chips are very sensitive. However there's also magic in the QLG1 GPS kit antenna... the reason the QLG1 GPS PCB is so "big" compared to other GPS modules is intentional, the large groundplane under the patch antenna greatly improves the antenna performance and therefore overall sensitivity. The patch antenna is also custom-manufactured for QRP Labs and is sized and tuned to match the requirements of the PCB groundplane; I sent the factory assembled QLG1 PCBs and they figured out the exact size and tuning for the antenna to be perfectly resonant on 1575MHz. So the high sensitivity of the QLG1 GPS is due both to the sensitive GPS receiver chip and also the PCB design and antenna matching. 

Generally people should try the QLG1 with its own patch antenna. In my applications it will work well. I don't find any need to operate it with a clear sky view etc., it works fine indoors. 

I've never used an active external antenna with it but the PCB is designed to take an SMA socket for people who want to do that, and they also need to fit an inductor and resistor; note that the quoted 27nH inductance should be viewed as a minimum, not an exact requirement. So almost anything goes. Wind some wire around a high value resistor and you've done it in 30 seconds. No need to fuss over finding exact 27nH inductors. 

In Tokyo I used to have the GPS outside the window on the railings outside the window, and I ran about 10 meters of 4-conductor cable (shielded/screened cable) to the shack. It always worked fine. Even though since I was on the 3rd floor of 7, and with lots of tall buildings all around, there wasn't much sky view. I haven't tried more than 10 meters distance between QLG1 and U3S/QCX/etc. 

Note that when using common plastic food containers as an enclosure, be careful: the sun is a pretty harsh foe... several times I left things for 6 months, a year... then went back to check and as soon as I touched the plastic tub, it fractured instantly into hundreds of tiny fragments. Strong UV decomposes some plastics quite fast. Depends on where you live too... Tokyo has a lot of sunshine 80-90% of days and strong. Turkey too where I live now. The food containers would last longer in England :-)

73 Hans G0UPL 

http://qrp-labs.com 

On Sat, Oct 10, 2020, 06:00 Shane Justice <justshane@...> wrote:

Alan,

While I was waiting for the inductor to supply power to the active antenna, I hooked that antenna up to the QLG-1, and much to my amazement, the gps got a full 3D solution and this was inside my house with a 15 foot deep overhang over the full length patio.

Hense my assertion that the modern receivers are so sensitive that they may not need an amplified antenna in some situations.

On Oct 9, 2020 at 13:43, Alan G4ZFQ <alan4alan@...> wrote:

> GPS signal levels are quite low, but has anybody considered a "passive

> repeater" in the form of inside and outside tuned antennas connected by

> a low-loss coupler?



The problem is that the coax is not low loss. An active antenna is required.

So you may as well just use an active antenna.



73 Alan G4ZFQ

On Oct 10, 2020 at 00:36, Alan G4ZFQ <alan4alan@...> wrote:

> Hense my assertion that the modern receivers are so sensitive that they

> may not need an amplified antenna in some situations.



Shane,



Yes, I've seen lots of reports here of reception in seemingly impossible

places.



But I've tried repeater antennas and they have only worked when nearly

on top of the RX antenna. Maybe I've not done it correctly and that's

not typical?



73 Alan G4ZFQ

On Oct 8, 2020 at 22:24, Michael Greene <kn6ize@...> wrote:

BTW, I had great luck burning the coating off of the wire that came with the main kit assembly, but found it impossible even at high heat to burn off the coating on the band specific toroid wire (seemed darker and thicker). I had to desolder those and scrape the wire end coating off with sandpaper.

On Oct 9, 2020 at 14:16, Arv Evans <arvid.evans@...> wrote:

Apparently you missed the point of my suggestion.

_._

On Fri, Oct 9, 2020 at 1:57 PM Shane Justice <justshane@...> wrote:

Arv,

These modern receivers have such a low noise floor that an amplified antenna is not required in an open sky situation. The amplified antenna is just extra insurance for situations where the are sky obstructions, and/or limited sky views available (think urban canyons, tunnels, and the like).

All the good, current receivers take all this into account in their signal processing chains, and you get this for the cost of the unit. The external antennas all come with weatherproof cables with connectors installed, ready to be threaded onto the socket on the board. 

In contrast, putting the whole GPS in a tupperware box, to be mounted outside in the weather, and bring in TTL level signals in the "shack" through a cable, is putting a lot more effort into accomplishing the goal of getting GPS data into the U3S/QCX/etc. You'll have to deal with a thicker cable, additional connections, RF noise injection on the TTL lines, and the poor signal levels of TTL over 5 or more feet, for starters. Unless you just like fiddling with stuff, getting a pre-made external GPS antenna and cable is the fastest, least trouble-prone, most efficient way to get the GPS data into the receiver.

I suppose it all boils down to your personal tradeoffs between using your time, spending your money, and your perceptions of what provides you with the greatest sense of accomplishment.

I prefer conquering a problem and having it stayed conquered for many, many years. I care about establishing a capability and being able to build upon that capability toward some goal, then moving on to the next challenge, the next capability, the next function, not continuously fighting with problems created by missteps with earlier, suboptimal implementations that require recurring maintenance/repairs.

It all depends upon what you want from your projects.

73,

Shane

KE7TR

On Oct 9, 2020 at 11:44, Arv Evans <arvid.evans@...> wrote:

GPS signal levels are quite low, but has anybody considered a "passive repeater" in the form of inside and outside tuned antennas connected by a low-loss coupler?

_._

On Fri, Oct 9, 2020 at 11:34 AM N3MNT <bob@...> wrote:

I am thinking entire GPS outside ( in waterproof container ( even tupperware) and run 4 conductor shielded signal cable into shack.

On Oct 9, 2020 at 13:43, Alan G4ZFQ <alan4alan@...> wrote:

> GPS signal levels are quite low, but has anybody considered a "passive

> repeater" in the form of inside and outside tuned antennas connected by

> a low-loss coupler?



The problem is that the coax is not low loss. An active antenna is required.

So you may as well just use an active antenna.



73 Alan G4ZFQ

On Oct 9, 2020 at 12:50, Frank W1FRA <allenfr@...> wrote:

There are always more proper ways to do something. My inexpensive, ie cheap, Tupper ware from the recycling at the dump, and 40ft of twisted pair of the telephone service truck works fine. Is it perfect Darned if I know, its always worked and I'm on to other projects !