The uputronics LNA is a bugger for getting blitzed by signals nearby. I’ve seen the same effect in two different installations where 5W of 144MHz completely kills reception. If that is enough to desensitise it, I hate to think what other nearby signals are doing to it. It’s not just me, others in this forum have confirmed it happens to them as well.
The same effect doesn’t happen with the RTL-SDR-LNA. At the Martello Tower, we also have a slow scan TV relay on 144MHz and when it transmitted, the feeder lost everything. We replaced it with an RTL-SDR-LNA and that problem went away.
For that reason, I personally can’t recommend the uputronics amp at all.
I mainly use HF for Tx but the wire is well away so not worried about VHF Tx.
I may be putting up a 2nd one later this year so will look at the one you suggest.
So far ive been happier with the set up i have but time will tell.
Suppose im lucky as the only interference i get (Im in the UK) is on HF and its VDSL which wipes some bands out, another subject.
Is the one you mention this one?
Yup, that’s it. My full setup is described in detail from top to bottom here although it’s not looking quite so vertical as that after the last two weekends
Sorry didn’t put name and callsign against Essex feed, you recently asked me to feed, which i now do.
Impressive set up.
The more i think about my set up, the more i think it may be better to loose the coax and have the amp direct to the flightaware antenna and then the dongle below that, cutting out any loss, what waterproof box do you use? What made you update to a pi4?
No problem Les - You already cover a very decent area from there, your heatmap is very good.
I don’t know what the exact box is as it was given to me by a friend. It’s a box he uses for alarms and is very similar to to the one at the MTG site here.
I moved to the Pi4 simply so it can handle more traffic and run the Airspy at 20MHz. Plus, it’s new and shiny and we all like new, shiny stuff!
The beauty of running the system a week to test has paid off.
Short coax run > Flightaware blue dongle > Pi3 on its own over a week max distance 251NM
Short coax run > uptronics Amp/fliter > RTL-SDR V3 Dongle > Pi3 251NM
Both identical in distance - I did initially get slightly further with the RTL-SDR V3 set up but think i can put that down to conditions.
Ive ordered the other amp/fliter recommended and its on its way from China direct from RTL-SDR so will leave alone until it arrives and give that a weeks run.
Ultimately I will be putting the amp and dongle in a waterproof box up on the mast, doing away with coax and having a run of usb cable instead.
Keithma would be interested to see from your end if the heat map has changed since i took out the blue dongle?
just trying to find if im in a better state than before. Just looked on airnav and i have dropped 6th in the UK to 9th so not looking good overall. I may have to switch back to the blue dongle.
Is any of that down to the short period of downtime showing in the bottom left? With my reduced coverage at the moment, I won’t be surprised if I drop down their table a bit.
I’m Anthony from Uputronics manufacturer of the Uputronics LNA.
The out of band attenuation on the current 1090MHz SAW isn’t as much as the RTL LNA. So very powerful signals in proximity may cause an issue as you have noted. Our ceramic LNA doesn’t exhibit this issue and has better out of band attenuation than the RTL (at a significant cost premium).
The choice of filtering / SAW was design to maximise the NF of the unit to give the best possible signal integrity in “normal” scenarios. However for some people with strong local signals we wouldn’t recommend our SAW based LNA we would recommend the ceramic version or the RTL unit.
That said we are aware of the issue and the unit is currently undergoing a significant redesign to address both the out of band attenuation and we feel it could do with slightly more gain as well. However our primary goal will be to maintain the signal integrity.
Hi Anthony
Only just bought the Uptronics, I don’t have any nearby problems but for me more gain would have been better.
Initially disappointed as i hoped that replacing the flightaware blue dongle with a RTL-SDR V3 and the Uptronics LNA/Filter would improve my range, its actually gone down. I have tried messing with the gain on Flightaware but can’t get an improvement.
Initially it was suggested i use the blue dongle with the Uptronics but then i was advised it would not work, luckily I had a RLT-SDR V3 already.
I am driving the BiasT via the rap pi and did make sure it was working.
Without it on the day i tested it, plane count was 10 and then with it in 60.
To be honest im not sure which way to go as using HeyWhatsThat shows i should get more range.
I don’t know whether to ditch the Uptronics and go back to the blue dongle or wait until the weather improves and try to do away with coax all together and mount the amp and dongle at the mast head and run a usb lead down. There by hangs a problem in getting a very good waterproof box.
I have ordered the RTL-SDR LNA but its on the slow boat from China and i realise there maybe delays.
Hi Anthony, it’s really good to see you posting here.
In both cases I’ve described, we’ve been using the ceramic filter version of your LNA and experienced complete loss of signal with just 5W of 2m nearby.
That would be a most welcome redesign - currently using your SAW filtered units, but have found that in my location I have to use a cavity filter before the LNA otherwise my range drops to half with a large drop in numbers.
Do you have a time frame as to when these might become available?
This is the way we are going to have to go. We may also go with a very well designed high pass. I’ll keep people in the loop on this as I’d appreciate feed back from the community.
A few months for testing and we still have existing stock to sell (however anything brought from today will have the bias-tee LDO installed at no extra cost, much better SMA’s as I know some of you have had issues with those).
I’ve actually employed a proper RF Engineer who has 30 years experience on this one as I’ve exhausted my skills at this point, we are on revision 5 of the LNA and we’ve made small improvements over the last seven years.
The ceramic is still on the cards but its benefits maybe negated by the redesign. There are 2 issues with the ceramic. The Minicircuits CBP1090EC is REALLY expensive and although the out of band attenuation is good the skirts are wide and don’t quite kill the GSM bands @ 950MHz +
I strongly believe we are well within the realm of diminishing returns here but as you can see by peoples experiences RF is a funny beast. In some situations the RTL performs better, in some ours does. I like to think of the (with all due respect) the RTL is more a sledgehammer with all that filtering and high gain compared to our more “surgical” lower NF less insertion loss unit. Our design brief for the new unit is “surgical sledgehammer”
Oh we are going to put an LED on it so people can tell its powered (go us!)
