[NLRS] 2m Pager? noise

Sat Oct 28 20:21:53 EDT 2017

I sure appreciate all the information and ideas. Yes, Im sure its APRA as thats its freq.

Not sure there is anything now that I can do as they are operating within their rights though some seem awfully over modualted.

It would appear that my only hope would be to find some type of filter I can set for a freq up higher in band that can just catch .380 on its lower edge..a cavity that I can adjust perhaps? I dont know..so much of this VHF stuff is newer to and above my knowledge..HF Id have it solved already HI HI

I modified my 746PRO to accept a SDR RX as its RX...I use both the Funcube PRO+ as well as RTL dongles for 160m-2m utilizing the 746 as the TX radio. Amazed at how well the RX is now that Ive done this..but it appears to come at a price..the dongles have a bandwidth of up to 1mhz of RX and the FC at 196khz and fold under such strong local signals when coupled with WSJTX for EME.

If I use just th746PRO as the RX in its original configuration (Yes, I can switch back and forth the way I did the mod) it handles this noise up the band much better..though doesnt hear weak signal as well as the SDR using SDR console software.

Anyone that give me filtering ideas Im open to suggestions.

PAR electronics got back to me and said no way.

They did mention a HIGH IP3 LNA as an option though Im not familiar with those. I currently use the ARR 144 LNA.

Kirk, N0KK

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________________________________
From: nlrs-bounces at mailman.qth.net <nlrs-bounces at mailman.qth.net> on behalf of Mary Brown <maryalanab at gmail.com>
Sent: Saturday, October 28, 2017 2:38 PM
To: geraldj at netins.net; nlrs at mailman.qth.net
Subject: Re: [NLRS] 2m Pager? noise

You have KE0CRW-10 RX I-Gate in New Hope, KD0TLS-7 also on APRS, either
could be the source... https://aprs.fi/#!addr=New%20Hope%2C%20MN

Mary
W0AAT

-----Original Message-----
From: nlrs-bounces at mailman.qth.net [mailto:nlrs-bounces at mailman.qth.net] On
Behalf Of Dr. Gerald N. Johnson
Sent: Saturday, October 28, 2017 1:52 PM
To: nlrs at mailman.qth.net
Subject: Re: [NLRS] 2m Pager? noise

While intermod of out of band signals isn't impossible, its almost certain
the signal at 144.390 is APRS, 1200 baud packet.
http://www.twinslan.net/packet.html says listen on 145.01, 145.67 and
144.390 to hear packet signals. At least a couple should be 1200 baud AFSK,
145.67 might be 9600 baud FSK which sounds like noise. Around here
144.390 is still 1200 baud packet according to my ears. Other than APRS I
think there is very little VHF packet in Iowa now. And the APRS graphic
locator page shows several APRS stations close to N0KK.

73, Jerry, K0CQ

On 10/28/2017 11:40 AM, Chris Elmquist wrote:
>
>
> On Saturday (10/28/2017 at 10:56AM -0500), Dr. Gerald N. Johnson wrote:
>
> [... snip ...]
>
>> I have it on line at:
>> http://geraldj.networkiowa.com/papers/EME/Intermod2.pdf
>> Intermod from other band activity is not a new EME problem.
>
> If you determine it is actually intermod, I have had good success with
> a notch filter from PAR Electronics,
>
> http://www.parelectronics.com/amateur.php
>
> His approach is to notch one or more of the out of band signals enough
> that intermod is no longer an issue in your front end.
>
> I was playing with one of the super cheepy Chinese 2m FM rigs (a
> TYT-9000D) and found that two signals in the 152 to 157 range were
> mixing and ending up on 146.4'ish, plain as day.  I wasn't sure why
> W0GHZ was dispatching ambulances on our "intercom" frequency  ;-)
>
> After I determined the exact frequency of the real ambulance service,
> PAR built the filter to notch it out and the problem was solved.
>
> Now, these won't take 1500W EME transmit power so you would have to
> put this in your receive-only path somehow if you are transmitting
> with more than about 50W I think.
>
> PAR (aka W4OP) do a nice job and give you an insertion-loss&  SWR plot
> for the filter they build, showing in-band and out-of-band losses.
> Well done, IMO.
>
> Chris NØJCF
>
>> On 10/28/2017 7:31 AM, Kirk P wrote:
>>>
>>>
>>> Good morning,
>>>
>>> I recently installed a 4x7 array for EME and a SDR RX for all bands.
>>>
>>>
>>> I have some very loud noise that sounds like a pager system at 144.390.
>>>
>>>
>>> I have tried all measures I can think of to determine if it is my
network or something from within my home. I have disabled network, unplugged
wifi and router, inserted a 2m bandpass filter etc. No luck.
>>>
>>>
>>> If I move antennas there is no change in signal ...
>>>
>>>
>>> Stumped here looking for ideas. Can anyone else hear this locally or has
anyone experienced this at all?
>>>
>>>
>>> My main concern here is that it does at time seem to desense WSJTX
ability to hear and decode which of course isn't good if I want to succeed
at EME.
>>>
>>>
>>> Kirk N0KK
>>>
>>>
>>> Thank you
>
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