AM Radio Interference w/Ham It Up & NESDR SMArt

[hax0rwax0r]

Disclaimer:

I am completely new to this. I probably have no idea what I am doing here.

Issue:

I am hearing my local 700 kHz AM radio channel bleed into many other non-AM radio frequency bands. It's on lots of frequency bands but for sake of narrowing this down, I am trying to listen to 80 meter. I am tuned into 3.745.784 and am getting the AM radio channel. It has a hum and is fuzzy but it's very clearly there.

I have attached a screenshot. It's also audible up at the 3.900M seen in the screenshot (it's much clearer there, too) and down just below 80 meters at 3.495.974. It happens on other frequencies that aren't near the 80 meter band as well (e.g 2.996 MHz and 2.497 MHz).

This also happens when using a 25' piece of RG8U coax that I had running through an open sliding door to test it all out. All the other parts mentioned below were still in-line to test and only the main segment of coax was swapped out (and the CTC-50M was not shut in a window yet, but it was still attached).

Thoughts on what could be causing this and how do I resolve it?

Hardware:

Antenna - end-fed "random wire" HF dipole 9:1 antenna that is supposed to be good for 80-6 meters
SDR - Nooelec NESDR SMArt w/Nooelec Ham It Up v1.3 upconverter
Coax - 50' Jetstream 400FLEX ("LMR-400 flex equivalent")
Coax - 3' Jetstream RG213U
Other - Comet CTC-50M (feed-thru jumper for running through closed window)
Other - SMA male to SO-239 female adapter
Other - SMA male to SMA male RG316 jumper (15cm)

Software:

AIRSPY SDR# Studio v1.0.0.1909

Connectivity Chain:

Antenna -> 50' 400FLEX -> CTC-50M -> 3' RG213U -> SO-239/SMA Adapter -> Ham It Up -> RG316 SMA jumper -> NESDR SMArt SDR -> USB 3.0 extension -> PC

Additional Settings:

In SDR# my RTL-SDR controller is set to 3.2 MSPS sample rate and 2.7 dB RF gain.

 

[PDXh0b0]

Am filter, both rtl-sdr-blog & nooelec sell them on amazon.

 

[rabbit108]

Disclaimer:

I am completely new to this. I probably have no idea what I am doing here.

Hello, hax0rwax0r

I have days like that too.

Issue:

I am hearing my local 700 kHz AM radio channel bleed into many other non-AM radio frequency bands. It's on lots of frequency bands but for sake of narrowing this down, I am trying to listen to 80 meters.

Thoughts on what could be causing this and how do I resolve it?

PDXh0b0 is correct. You will probably need the RTL-SDR Blog Broadcast AM High Pass Filter if you are close to WLW. Also, the v1.3 upconverter might need to be in a metal enclosure. And you do know that the SDR needs to be tuned to 125MHz + the HF Freq you want to receive, don't you?

• Connect your antenna to the RF input
• Connect your SDR to the IF output
• Ensure your toggle switch is in the enable position
• Plug your USB power source into the USB-B USB jack
• Fire up your favorite SDR software. Tune to 125MHz + (+/- the tuning offset from the tuning procedure) + your desired frequency and enjoy!

 

[rabbit108]

The filter goes before the upconverter.

Buy RTL-SDR Dongles (RTL2832U)

RTL-SDR.com Broadcast AM Block High Pass Filter Now for Sale

 

[dave3825]

Disclaimer:

I am completely new to this. I probably have no idea what I am doing here.

Now thats funny. Definitely appreciate the up front honesty..

 

[hax0rwax0r]

Am filter, both rtl-sdr-blog & nooelec sell them on amazon.

RTL-SDR.com Broadcast AM Block High Pass Filter Now for Sale

I ordered the RTL-SDR Blog AM block high pass filter. It arrives Friday so we will see.

I also ordered some assorted size ferrite core clip-on chokes as somewhere else I read suggested they might help. I'm not sure, but they were cheap enough to roll the dice on. They apparently fit the diameter of the coax I have.

Now thats funny. Definitely appreciate the up front honesty..

Hah, I work in IT so I am pretty technical but yeah, I am pretty out of my realm here as a whole. It's all super fascinating, though.

You will probably need the RTL-SDR Blog Broadcast AM High Pass Filter if you are close to WLW.

Yep, the 700 WLW tower is about three miles as the crow flies. Apparently a local ham runs a tour of the facility where they have some of the old broadcast equipment still hanging around. I'd love to tour it as there's some neat history there.

Also, the v1.3 upconverter might need to be in a metal enclosure.

It's a pre-assembled unit in an aluminum enclosure from Nooelec.

And you do know that the SDR needs to be tuned to 125MHz + the HF Freq you want to receive, don't you?

Yeah, the attached screenshot shows the -125,000,000 offset enabled.

I think the AM block high pass filter is likely the fix here given my close proximity to the 700 WLW broadcast tower. Once it arrives and I get it installed, I will report back my findings.

Thanks everyone for the guidance.

 

[hax0rwax0r]

I ordered both the Nooelec Flamingo Broadcast AM bandpass filter and the suggested RTL-SDR Blog AM block high pass filter. I am using the RTL-SDR Blog AM block high pass filter currently.

I am no longer hearing AM radio voices on the 80 meter band anymore. That said, I still have high signal spikes similar to before and my ability to pick up 80 meter is still pretty awful.

I know my antenna placement is not ideal. I have a sloped yard and one end of the antenna is maybe 10 feet off the ground and the highest point of the far end of the antenna is maybe 16 feet off the ground. Neither are ideal.

I bought a slingshot to try and shoot a weight with fishing line attached higher up into the tree. My plan was to use the fishing line to pull a rope with the antenna attached. Unfortunately, my best case scenario is probably 25 feet up as it's a pretty small tree and that 25 feet is from the bottom of the sloped back yard point, too.

I ordered a SDRplay RSPdx to see how it compares to my RTL-SDR and Nooelec NESDR SMArt dongles. I am also eyeing an Airspy HF+ Discovery, too. I was reading up on the Ettus USRP B210 but it appears to not be for HF and only specced out for down to 70 MHz and I suspect that using a Ham It Up with it would seem silly.

In other SDR news, I picked up someone on 40 meter SSB tonight that was apparently about 590 miles away and they sounded absolutely incredible so that was pretty exciting.

 

[hax0rwax0r]

One last post on this for anyone that comes across it in the future. As stated in the previous post, the AM bandpass filter helped a lot. It made it usable.

I caved and ended up buying a HackRF, an Airspy HF+ Discovery and a SDRplay RSPdx. I have yet to play with the HackRF but the other two are noticeably superior at filtering out 700 WLW without anything extra necessary and both get better/clearer reception across the HF band. Obviously YMMV but it's something to consider for others in the market. By the time you buy a RTL-SDR or Nooelec NESDR SMArt dongle + Ham It Up + AM bandpass filter you are half way to the price of one of these other devices that seems to outright outperform in all HF regards.

I just wish I could get my antenna a little higher but the tree isn't very tall and it's as high as it can go. I live in a HOA subdivision so I'm pushing my luck with the antenna strung up as-is. Thankfully it's mostly invisible as it's thin and black.

Related on the SDR front, now I want a FlexRadio. I got the radio bug bad. I love toys. I am scheduling my Technician license test next week. Unfortunately everything that interests me requires General class.

Thanks again everyone for the help.

 

[rabbit108]

I caved and ended up buying a HackRF, an Airspy HF+ Discovery and a SDRplay RSPdx. I have yet to play with the HackRF but the other two are noticeably superior at filtering out 700 WLW without anything extra necessary and both get better/clearer reception across the HF band.

Thanks for the update.
I'm tempted by the RSPdx.

Related on the SDR front, now I want a FlexRadio. I got the radio bug bad. I love toys. I am scheduling my Technician license test next week. Unfortunately everything that interests me requires General class.

I got the radio bug a few times too. First it was HF Mobile because my wife and I lived in an apartment. Then it was DXCC. Now it's SDRs as a Spectrum Analyzer.

Have fun with your hobby and good luck with your upgrade.

73,
rabbit

 

[merlin]

Try a high pass filter with a 2 Mhz cutoff. I just made one myself from spare parts.
Also, if you are using a preamp, turn it off and keep the gain way down on your SDR.

 

[merlin]

One last post on this for anyone that comes across it in the future. As stated in the previous post, the AM bandpass filter helped a lot. It made it usable.

I caved and ended up buying a HackRF, an Airspy HF+ Discovery and a SDRplay RSPdx. I have yet to play with the HackRF but the other two are noticeably superior at filtering out 700 WLW without anything extra necessary and both get better/clearer reception across the HF band. Obviously YMMV but it's something to consider for others in the market. By the time you buy a RTL-SDR or Nooelec NESDR SMArt dongle + Ham It Up + AM bandpass filter you are half way to the price of one of these other devices that seems to outright outperform in all HF regards.

I just wish I could get my antenna a little higher but the tree isn't very tall and it's as high as it can go. I live in a HOA subdivision so I'm pushing my luck with the antenna strung up as-is. Thankfully it's mostly invisible as it's thin and black.

Related on the SDR front, now I want a FlexRadio. I got the radio bug bad. I love toys. I am scheduling my Technician license test next week. Unfortunately everything that interests me requires General class.

Thanks again everyone for the help.

The airspy HF+ discovery is on my order list. A complement to my Kenwood and Barrett, both with general coverage RX.
A secret is don't skimp on the antenna department. An antenna tuner, especially for long wire.
Hey, a little extra study, the general class is not so hard to get, That would be my goal.
Today's M class solar flare about ruined SWLing.
Cheers

 

[merlin]

One note usung SDR#. I doubt you will ever get rid of ghosting, but there is a slide bar just below the spectrum display. By sliding this, signals that move opposite are ghosts.
You can slide your desired frequency to a place with minimum noise.
> maybe try with AGC on and tuner gain set to zero. It may help a bit.

 

[dickie757]

One last post on this for anyone that comes across it in the future....

.......on the SDR front, now I want a FlexRadio. I got the radio bug bad. I love toys. I am scheduling my Technician license test next week. Unfortunately everything that interests me requires General class.
Thanks again everyone for the help.

Not sure how much you have to study, or how much time, but I recommend

HamStudy.org: Cutting edge amateur radio study tools

Free ham radio flash cards, practice tests, and question pools as well as introduction to ham radio and explanations for questions.

hamstudy.org

I used that for Tech and General. I'm still on the fence about the Extra license, waaay too much to do besides radios, wait, did I just say that here?