Tag Archives: RTL-SDR

Saturday’s Radio-activity

Had a good club meeting this morning and chatted on quite a few and varied radio topics. Will be starting the HF voice and Digital Nets next week on 40m at 1pm local time. Voice will be on 7.250 Mhz and MT63 1000L digital following shortly thereafter on 7.060 Mhz. There is a major geomagnetic storm going on now that has impacted the HF bands. Not much in the way of QSO’s going on right now except for JT-65. Good time to play with some other projects.

Tested the new 10Ahr LiFePo4 battery this afternoon with the solar charge controller and a non-radio load (5V USB charger on 12V lighter plug). Pleased to report this battery worked like a champ and is a drop in replacement for the lead Acid SLA batteries. It is half the weight of the 7Ahr SLA battery and can provide at least 80% of its capacity without shortening the life of the battery. So I am replacing two 7Ahr batteries that provided 7Ahr of capacity at about 10 pounds with a single 10Ahr LiFePo4 that can provide 8Ahrs and weights only 2 lbs! Nice!


I ordered a USB OTG cable from Ebay. This cable allows me to hook up and SDR dongle to an amazon fire with the SDRTouch Android app. The only downside is that you need an external power source to get enough power to the SDR dongle. I hooked it up to the USB charger I was testing with the new battery and it ran fine.


Installed the RA0SMS Recieve Antenna

Installation of the mini-whip antenna wa straightforward the nice I had all the proper connectors and adapters. I tie wrapped the antenna to a 4 foot length of dowel stick and stuck it between the roof and gutter. It is up about 12 feet. I am using a length of RG-6 TV cable as a feed line to the window feed panel. Inside the shack I have a short length of coax to the bias-t and another to the SDRPlay reciever. Rigged up a power cable to provide the 12V needed to power the antenna through the coax. Did it work?

Well yes! It works quite well actually. It is marginally better than discone on 20m thru 10m and significantly better on 160m thru 40m. I’ll likely try and get some more height outside and clean up the wiring a bit. It is now my dedicated antenna for my panadapter.

A little diversion

I have been working quite a bit on learning and improving my HF operating skills as well as building some antennas for portable use. I am still working on the buddistick but have not been able to get it outside for testing. It is a bit to windy outside today to set it up as I have not worked out the guy wire scheme yet. I decided to try and finish a little project I had started a while back to put together a scanner for the public service band frequencies here in Brownsville. I have two USB dongles with the 820T tuner chip in them and wanted to set them up to run Unitrunker software. I had tried this once before with no success.

My original plan was to do a three way split from the discone antenna outside to allow me to use one line for the panadapter dongle and the other two for Unitrunker. The wiring for this was a little messy so I decided to try and build a 1/4 wave vertical for 865Mhz. This turned out to be easy as the elements are about 3-1/4″ long. I soldered heavy gauge wire to a chassis mount SO-259 connector, one at each mounting hole for the radials and One to the center terminal. The radials are bend down by about 45 degrees to raise the feed point impedance. I am using 75 Ohm coax for a feedline with a SO-259 to F-connector adapter. Only issue building this is it takes some time to heat up the connector flange to get a nice solder joint.


I tested this little antenna using SDR# and it was picking up the signals quite well. I was surprised to even get a strong signal at 162.55 MHz weather radio frequency. I may have to try this out on the air bands as well just for grins. I had much better luck setting up Unitrunker this time. I think I was using the wrong control frequency before. 858.075 MHz did the trick this time. I am going to try a different configuration that uses a SDR# plug-in and see if it provides any better functionality. I think it will allow me to download the available talkgroups from radioreference.com so I can tell who is speaking.

RTL-SDR as a Panadapter

My Yaesu FT-450D is connected to my PC via a serial to USB cable I pulled off of Amazon. I am using Ham Radio Deluxe ver to interface the Radio with the PC. So far this is working well. I like the log capability built into HRD.

What I was really hoping to pull off was to use a RTL-SDR dongle to provide panadapter/SDR like features to operating the FT-450D. What I did not want to do was open up my brand new FT-450D and tap into the IF output. That would have been the highest performance method but would have voided my warranty. So I can’t:

  1. Access my Radio’s IF output directly
  2. Use the same antenna that I am using on the FT-450D as I have no way to switch for transmit using the dongle.

What I do have is the broadband discone antenna that I plan to share between an RTL-SDR setup and with my Baofeng HT as a 2m Base station (more on that later). The discone antenna is wired through a manual switch and uses an adapter to go from SO-239 to an f-connectors. I then use a three way splitter to feed three individual dongles.

One dongle is connected to an upconverter and provides DC-25Mhz reception. The other two are 25Mhz to 1.8Ghz reception. I plan to use two ultimately with Unitruncker to use as a scanner. For now I just have the one hooked up to test.

I am using HDSDR software with the HF dongle. HDSDR has a DDE feature which allows it to be controlled by Ham Radio Deluxe software. The result is that when I change frequency or mode on the radio it updates HDSR to match. Now when I see a signal on the waterfall I can click on it and it changes the radio frequency to match. This seems to work well down to the 20m band.

UPDATE: Works well down to 40m and takes some adjustment to the display to see anything on 80m.

I am running SDR# on the other dongle. This one tuned manually and lets me monitor VHF/UHF bands while using the HF radio. Here is a screen shot of the whole thing running:


Unfortunately, the wiring is a mess: