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Author Topic: Broadcast reception on 27 Mhz and other bands  (Read 499 times)

Offline IZS4

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Broadcast reception on 27 Mhz and other bands
« on: February 17, 2020, 2250 UTC »
This RSP2 seems to receive many broadcast AM stations on 27 Mhz as well as other areas. Never experienced this with my Icom transceiver?
Listening on an Icom-718 with a 135' OCF dipole or a RSP2.  Grundig G3 and MLA-30 when portable. When QRP I use a Hendricks PFR-3 I built. Coverage is 20,30 and 40 meters.

Offline nickcarr3151

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Re: Broadcast reception on 27 Mhz and other bands
« Reply #1 on: February 18, 2020, 0853 UTC »
This RSP2 seems to receive many broadcast AM stations on 27 Mhz as well as other areas. Never experienced this with my Icom transceiver?

There are no broadcast stations on 27 megs.  Crank down the receiver gain settings -- it's probably intermod.
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Offline ChrisSmolinski

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Re: Broadcast reception on 27 Mhz and other bands
« Reply #2 on: February 18, 2020, 1109 UTC »
Yes, these SDRs are prone to overloading & images. IIRC the RSP2 has a MW filter which can be enabled in SDRuno, it does help. Also watch your gain settings.
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Offline IZS4

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Re: Broadcast reception on 27 Mhz and other bands
« Reply #3 on: February 18, 2020, 1256 UTC »
Will do. Thanks, I have noticed overloading more lately even when the gain is set at the half way point or a bit less.
Listening on an Icom-718 with a 135' OCF dipole or a RSP2.  Grundig G3 and MLA-30 when portable. When QRP I use a Hendricks PFR-3 I built. Coverage is 20,30 and 40 meters.

Offline ChrisSmolinski

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Re: Broadcast reception on 27 Mhz and other bands
« Reply #4 on: February 18, 2020, 1337 UTC »
Will do. Thanks, I have noticed overloading more lately even when the gain is set at the half way point or a bit less.

I ran a quick test here with an RSPduo and SDRuno, I did see some images on 27 MHz even with the MW notch filter enabled, turning down the gain (eventually) eliminated them. This was with the 43m dipole which is not even particularly sensitive on MW. It's pretty obvious to know you have the gain low enough, they all disappear at the same time.
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Offline nickcarr3151

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Re: Broadcast reception on 27 Mhz and other bands
« Reply #5 on: February 18, 2020, 1948 UTC »
The trick is finding out what's causing it.  If the MW filter was enabled and that didn't help then you might want to try a FM notch filter.  This is mandatory for me on VHF or higher.  I usually don't have an issue on HF but the Perseus is HF only.  Those broadband SDRs are susceptible a wide range of RF.

27 megs (x 4) is 108 megs so it makes sense.

https://www.amazon.com/Broadcast-FM-Block-Filter-88/dp/B01LE9LRPM/

I should point out that if this fixes your issue then you might be able to crank up the gain. 
« Last Edit: February 18, 2020, 1950 UTC by nickcarr3151 »
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Offline IZS4

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Re: Broadcast reception on 27 Mhz and other bands
« Reply #6 on: February 18, 2020, 1956 UTC »
Excellent. Thank you!
Listening on an Icom-718 with a 135' OCF dipole or a RSP2.  Grundig G3 and MLA-30 when portable. When QRP I use a Hendricks PFR-3 I built. Coverage is 20,30 and 40 meters.

Offline Josh

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Re: Broadcast reception on 27 Mhz and other bands
« Reply #7 on: February 18, 2020, 2142 UTC »
Yes, reduce gain in front end and IF as needed, set the mode to low IF, and ensure the noise blanker is not the cause.
If the blanker is set to too sensitive, it will cause all sorts of hob.
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Offline nickcarr3151

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Re: Broadcast reception on 27 Mhz and other bands
« Reply #8 on: February 18, 2020, 2208 UTC »
I just noticed but it looks like the RSPdx has a FM notch built-in.  Actually, according to the SDRPlay web site, the RSP2 does as well. 
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Offline IZS4

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Re: Broadcast reception on 27 Mhz and other bands
« Reply #9 on: February 18, 2020, 2334 UTC »
I engaged the FM/MW notch filter and that seems to clear things up. I'm still learning all of the features. Thanks for the heads up!
Listening on an Icom-718 with a 135' OCF dipole or a RSP2.  Grundig G3 and MLA-30 when portable. When QRP I use a Hendricks PFR-3 I built. Coverage is 20,30 and 40 meters.

Online Ray Lalleu

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Re: Broadcast reception on 27 Mhz and other bands
« Reply #10 on: April 08, 2020, 1252 UTC »

I ran a quick test here with an RSPduo and SDRuno, I did see some images on 27 MHz even with the MW notch filter enabled, turning down the gain (eventually) eliminated them. This was with the 43m dipole which is not even particularly sensitive on MW. .
The typical SW dipole antennas are not good on MW, except when the line is acting as antenna (in common mode, with the dipole as a top hat). A coil on the line would only make it a better MW antenna. I would try this : no earth connection on the receiver (not even through connected devices), but connecting the outside of the coax (or the center of the primary coil of the balun ) to earth via some resistance - don't know what would be the best value.

Well, I have no MW problem here, only powerful FM broadcast nearby. And RFI on any frequencies...
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Offline Josh

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Re: Broadcast reception on 27 Mhz and other bands
« Reply #11 on: April 08, 2020, 1754 UTC »
If you're within a few miles of an ambcer, their sig will likely be the single strongest signal source at your qth. If you've more than one within say 30 miles you're fooked and have to take drastic measures. A friend lived a few miles from a disney ambcer, he had to disconnect all unused radios as the rf activated their unbiased front end diodes and created a huge swath of imd for any rig he was using at the time. A ambc filter helped until the station went dark.
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Offline chanito

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Re: Broadcast reception on 27 Mhz and other bands
« Reply #12 on: May 22, 2020, 0006 UTC »
For $10 each you can add one of the inexpensive Distill brand AM notch filters and the FM notch filter from Amazon. I have both and they work well in addition to the onboard RSPY1A radio filters. Don't turn on the Bias Tee into them. :-)  The AM one cleans things up well enough to allow me to pick up WWVB on 60Hz with a low wire and several NDBs.




For less than $20 each you can get the NOOElec filters with the nice enclosures, from Amazon as well. I use the FM Flamingo one to kill all the residual nearby FM broadcasters so I can listen to Satcom on 260MHz with the RSPY1.



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