Validate bias tee is on

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KL2LR
Posts: 16
Joined: Fri Dec 11, 2020 9:50 pm
Location: BO37tt

Validate bias tee is on

Post by KL2LR » Sun Dec 27, 2020 1:14 am

OK there must be a simple way to check and see if the bias tee is on. I was expecting to simply use a VOM on the coax. So that idea did not tell me anything when I tried it. :? :? :? After all the first trouble shooting information for the GPS project (page 169) says is the bias tee on?

alanzfq
Posts: 201
Joined: Thu Oct 04, 2018 11:18 am

Re: Validate bias tee is on

Post by alanzfq » Sun Dec 27, 2020 7:28 am

Why did the meter not confirm?
Alan

tim_rtd
Posts: 178
Joined: Fri Jun 30, 2017 11:34 am

Re: Validate bias tee is on

Post by tim_rtd » Sun Dec 27, 2020 4:37 pm

You should see about 3.5-4v dc using a dvm at the output of your SILVER v3 dongle's sma connector when the bias t is on.

KL2LR
Posts: 16
Joined: Fri Dec 11, 2020 9:50 pm
Location: BO37tt

Re: Validate bias tee is on

Post by KL2LR » Sun Dec 27, 2020 4:53 pm

I did what I would call a fundamental test.
With the computer off I used a VOM from the center pin on the antenna side of the RTL-SDR SMA to the housing.
Zero reading.

With the computer on I used a VOM from the center pin on the antenna side of the RTL-SDR SMA to the housing.
Zero reading

Ran the BT ON bat file and used the VOM on the same SMA connector -- center pin to the housing.
Zero Reading.

I expected there to be a voltage indicated during the test after running BT on.

The bias tee uses the coax shield as a conductor the coax. There should be a measurable amount of voltage indicated on a VOM. Is this a valid testing procedure. It would be nice if there was an led on the dongle to show the bias tee is on.

I'm trying to troubleshoot why I get no data from my GPS antenna. I feel confident all the software is configure as detailed in the GPS project in the Hobbyist's Guide

I'm hoping for any advice on this.

tim_rtd
Posts: 178
Joined: Fri Jun 30, 2017 11:34 am

Re: Validate bias tee is on

Post by tim_rtd » Sun Dec 27, 2020 5:10 pm

Are you using the silver v3 dongle or another nooelect smart dongle ?
There are china clones around that don't have the bias t circuitry. Also rtl-blog may chime in and mention you may have a defective unit from a bad batch.

KL2LR
Posts: 16
Joined: Fri Dec 11, 2020 9:50 pm
Location: BO37tt

Re: Validate bias tee is on

Post by KL2LR » Sun Dec 27, 2020 6:14 pm

I just repeated my "testing" after eliminating the USB cable from the computer to the dongle. No change in the results.

Maybe I should change to another computer just to validate my testing. I orignially was using a Dell 2-4-1 for this. I do have other computers available for this test.

KL2LR
Posts: 16
Joined: Fri Dec 11, 2020 9:50 pm
Location: BO37tt

Re: Validate bias tee is on

Post by KL2LR » Sun Dec 27, 2020 6:44 pm

I am sure this is a genuine RTL-SDR unit. I was very careful to inspect the unit against the information on the website describing the knock off units. I've been burnt before by knock off parts.

KL2LR
Posts: 16
Joined: Fri Dec 11, 2020 9:50 pm
Location: BO37tt

Re: Validate bias tee is on

Post by KL2LR » Mon Dec 28, 2020 12:10 am

After a lot more testing I noticed the slightest movement and the dongle will disconnect and reconnect. This happens when the dongle is plugged directly into any of three USB interfaces on my 2-4-1. It appears to be the USB connector on the dongle that makes and breaks the connection. :idea: I guess it is time to send this unit back as defective?????

I wonder if this will become a major PITA to return. The postage for a return is half the price of the dongle.

BYE THE WAY :D I did find one of my USB devices that has a led to indicate if there is power from the USB port to the device. It is nothing more than a USB hub. But it does the job. So I can eliminate a problem with power to the dongle as one of the possible issues. :) :) :)

Meanwhile I sure wish there was a way to turn the bias tee on and leave it on. The information on the V3 only give a way to do that in Linux.

alanzfq
Posts: 201
Joined: Thu Oct 04, 2018 11:18 am

Re: Validate bias tee is on

Post by alanzfq » Mon Dec 28, 2020 6:22 am

You need to look at Device Manager to be sure the dongle is recognised. Lights on hubs usually mean almost nothing.
The best way to be sure of power is to measure voltage under load. A T piece or load resistor at the antenna feed.
If it was bought from a reputable dealer and is truly faulty then any return postage should be paid by them.
Alan

KL2LR
Posts: 16
Joined: Fri Dec 11, 2020 9:50 pm
Location: BO37tt

Re: Validate bias tee is on

Post by KL2LR » Tue Dec 29, 2020 9:44 pm

OK I just shipped the dongle back to the Amazon seller. They paid the UPS shipping and provided a shipping label. So I'll move on from here.

I considered buying one of the AIRSPY SDR units. However I am concerned as all the listed seller on the Airspy site shown noting new posted on thier site since 2015. None of these sellers had units available. I wonder if there more to this than simply a supply problem. Is Airspy still a viable option or are they slowly going out of business? The indications are not good when the product is not available at so many differnt distributors in the US and out of the country.

I do not know if the Airspy units would work with all the projects laid out in the RTL-SRD manual. Plus many of the reference sites in the manual no longer exist.

Thank You to those who answered my initial post. :D :D :D

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